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b
T>>yi*»**v/<<iyy'^ Ay
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^'
-C^ j4*.
^1^
7.SA^^0
SCIENCE DEr
^■. v-^ :
HEAT ENERGY AND
FUELS
PYROMETRY. COMBUSTION, ANALYSIS OF
FUELS AND MANUFACTURE OF
CHARCOAL, COKE AND
FUEL GASES
BY
HANNS V. JÜPTNER
PROFESSOR, IMPERIAL* AND ROYAL TECHNICAL INSTITUTE,
VIENNA
TRANSLATED BY
OSK\R NAGEL, Ph.D.
NEW YORK
McGRAW PUBLISHING COMPANY
239 WEST 39th STREET
1908
THE NEW YORK
PUBLIC LIBRARY
490217
AtrOf«. LENOX AND
TltOCN FOU'^DATiONt.
n 1910 L
Copyright, 1908,
BY THK
McGUAW PUBLISHING COMPANY
NEW YORK
SStanbope pwM
p. H. QILSON COMPANY
•OSTOM. U.8.A
-n
TRANSLATOR'S PREFACE
Professor Hanns von Juptner has divided the study of
chemical engineering into two groups, namely: energy and
matter ; and beginning with a general discussion of the various
forms of energy, has written four volumes covering the subject
both theoretically and practically.
The present volume deals with heat energy and fuels, and
contains a large amount of carefully tabulated data in conven-
ient form for use. A great deal of this data is new and will be
welcomed by chemists, metallurgists and engineers.
Although the book is intended for use in universities and
engineering schools it is of equal value to practising engineers,
since it gives not only the fundamental principles, but also the
latest experimental data and practice.
Among the topics of greatest practical interest are : Measure-
ment of high tempemtures and late data on the melting points
of various substances; discussion of incomplete combustion,
combustion temperatures and combustion at constant volume
and constant pressure, and an immense amount of data on solid,
liquid and gaseous fuels and their production. The chapters
on the gasification of fuels, which contain the results of the
author's own experiments as well as those of Strache and Jahoda,
are of especial value.
The book has been extremely well received in Europe, where
it is widely u^sed both in schools and in practice as a text-book
and handbook.
THE TRANSLATOR.
New Yo&k, J^Tovember, 1908.
iii
CONTENTS
INTRODUCTION.
CHAPTKB PAGE
I. General Remarks 1
II. Forms of Energy 11
VOLUME I. HEAT ENERGY AND FUELS.
Part I. Heat Measurement^ Combustion and Fuels.
I. The Measurement op High Temperatures (Pyrometry).. 37
II. Pyrometry (Continued) 53
III. Pyrometry (Conclusion). Optical Methods of Measuring
Temperatures 68
IV. Combustion Heat and Its Determination 91
V. Direct Methods for Determining the Combustion Heat 110
VI. Incomplete Combustion 117
VII. Combustion Temperature 127
VIII. Fuels (In General) 141 -^
IX. Wood 145
X. Fossil Solid Fuels (In General) 155 ^
XI. Peat 166
XII. Brown Coal (Lignite) 173
XIII. Bituminous and Anthracite Coals 178
XIV. Artificial Solid Fuels 188
XV. Charcoal 191
XVI. Peat-Coal, Coke and Briquettes 214
XVII. Coking Apparatus 230
XVIII. Liquid Fuels 241
XIX. Gaseous Fuels 243
XX. Producer Gas 246
XXI. Water Gas 268
XXII. DowsoN Gas, Blast Furnace Gas and Regenerated Com-
bustion Gases 287
XXIII. Apparatus for the Production of Fuel Gases 292
Index 303
HEAT ENERGY AND FUELS
INTRODUCTION.
CHAPTER I.
GENERAL REMARKS.
If we . consider the immense strides that technical science
has made in the second half of the nineteenth century; if we
observe how prosperity is increasing, especially in the coimtries
prominent in engineering; and how, as a natural sequence, the
standing and influence of engineers are constantly growing in
these countries, we are forced to ask by what means all this has
come to pass — in other words, to what circumstances are we
indebted for this remarkable progress?
A close study of the development of technical science shows
its close connection with the natural development of mankind.
At first, man had no other resource in his struggle with wild
animals and natural forces than himself, that is, the organs given
him by nature. Necessity taught him how to protect himself
from cold by means of clothes, to seek protection from expo-
sure to the weather, and led him to build dwellings. Nature
gave him a cave for his first home, but he soon learned to
construct artificial shelters.
In his struggles with wild animals he tried to increase his
efficiency. For this purpose he first tried to lengthen his reach
with a stick. Then he found that a thrown stone was able to
act far beyond the immediate range of his arm.
He soon found that there were expedients for using the
strength of his muscles to greater advantage, and he began to
devise primitive tools in the widest sense of the word. His
problem now was to select the material most adapted to his
purposes from the mineral, vegetable and animal kingdoms;
thus his knowledge of nature was considerably increased. As
1
- HEAT ENERGY AND FUELS
the material suitable for his tools and implements could not
always be found near at hand, man had to get it by barter,
and we have the beginning of commerce and traffic.
It was a great advance in the progress of civilization when
man learned to use fire; this discovery is of special inter-
est to us as chemical industry depends on it. In close
connection are the manufacture of burned clay-vessels (the
beginning of ceramics) and the production of metals, both of
which are of the greatest importance in the development of
civilization, as they furnish materials that are especially suited
for the manufacture of implements and anns of various kinds.
Herewith are connected other improvements, such as the prep-
aration of food by boiling, broiling, roasting and baking, the
preparation of alcoholic beverages, the use of fermentation in
baking bread, dyeing, tanning, etc.
At first man lived alone or banded in small families.
With increasing civilization, especially after the beginning of
agriculture and cattle-breeding, which enabled a number of
people to live together by insuring the necessities of life, clans
were formed by the union of families, and therefrom, grad-
ually, the nations. Thus division of labor was made possi-
ble; the individual members of such families or clans were
enabled to devote their time to the solution of certain tasks,
acconling to their individual skill and inclination. Gradual
evolution along these lines, in the course of thousands of years,
resulted in the differentiation of skilled labor into distinct trades
and professions, and on this foundation modern engineering and
the modern industrial system developed.
In the Middle Ages the skilled artisans were working by rule
of thumb, and frequently kept their methods of working secret.
At that time there was no engineering science in existence in
the modem sense of this word. This is but natural, since the
process of reasoning was hampere<l by insufficient and conflicting
data; and wa*^, moreover, entirely different from our modern
way of thinking, the base of which is natural science. This
interfered with the progress of the trades and the development
of progressive methods. The period of R(*naissance only brought
a change by guicUng us back to the observation of nature.
Tliis change, naturally, could take place only slowly and
gradually, as there is no more difficult task for a man, not
GENERAL REMARKS 8
accustomed to it from his youth, than to observe and think
accurately; on the other hand, the scientists formed at that time
an entirely separate class, just as did the trades and profes-
sions, and a long time was required before the gap between the
two was bridged over, so that science and the trades could work
together.
At first the sciences had to be developed, before being
utilized in the trades; but soon — at least in some directions —
mutual relations presented themselves, which decreased the
gap, at the same time advancing both science and the trades.
Thus the invention of the printing press made it possible to
communicate one's thought or word easily to all the world, while
the invention of the steamboat and railroad brought people
in different countries directly together. Commerce became a
world power and opened new markets. Competition started
and with it came the necessity of making improvements.
In this way in the course of the nineteenth century modern
engineering and the technical sciences originated, which now
represent one of the most influential factors in modem civiliza-
tion. But this enormous progress was directly based upon the
correct practical application of the natural sciences.
Whereas formerly science was the foundation on which modern
engineering developed, the reverse is now often the case. Every
new scientific invention is still carefully followed up by the
engineer and utilized for practical purposes, even more than ever
before. But it often now happens that the engineer promotes
science by making a scientific research in order to solve a
technical problem.
This indicates what must be demanded now of a good
engineer.
He must have a thorough scientific education and must be
able to work scientifically in unexplored fiekls; he must gain
practical experience, which necessitates highly developed powers
of observation, and he must have the faculty of utilizing the
results of science in practice. For this purpose he nmst be able
to think logically, scientifically and technically, for these two
requirements are by no means identical.
We have seen above how the trades were gradually trans-
formed to modem industries. Like all great changes, this
transformation involved serious complications; the conflict
4 HEAT EX ERG Y A\D FUELS
between capital and labor originated, capitalism and socialism.
Between capital, that makes the creation of large industries
possible, and labor, which first of all represents the producing
power in the industries, stands the engineer, the mental leader.
His is the task not only to keep up order and discipline in the
enterprise, but also to act as mediator between those two opposite
parties. This is not easy, nor pleasant, but it is a very important
duty. Its fulfillment requires energy toward both sides, and
sometimes even apparent harshness; but also a good heart and
the earnest desire to find out the causes that are at the bottom
of the endeavors on both sides.
Every worker, including the engineer, who works with his
intellect, is right in asking for reasonable wages, and it is per-
fectly right and proper that the capitalist, who lends his money
to the enterprise, should expect a profit out of it. This is the
main cause of the conflict. The industrial enterprise as such
must also earn something. It is necessary to put aside capital
for protection against unforeseen events and against menacing
competition, for making enlargements, etc. Every industry
must, therefore, endeavor to make a profit. If the management
of an enterprise is to remain in the hands of the engineer he has,
therefore, to be familiar with commercial questions and economic
problems.
Like all others the chemical industry needs buildings, appa-
ratus, machines, and means of transportation, and the chemical
engineer should kaow sometliing about these mechanical appli-
ances, not only in the interest of the industry', but also to iasure
him his position, as otherwise the business management will be
given into the hands of a business man, and the technical man-
agement into the hands of other (non-chemical) engineers.
This will be especially the case in places where labor is scarce
and wages high, as it then becomes necessary to rerluce the
operating expenses by the installation of mechanical appliances.
Attention has to be paid also to the welfare of the working-
man by the provision of baths, hospitals, schools, etc., which
also requires special knowledge.
Penally the engineer must have a very important faculty,
that is, to keep cool in danger. This faculty has its own com-
mercial value, since on it human lives often depend. Related
therewith is courage, which in moments of danger enables a
GEXERAL REMARKS Ö
man to be cautious and quick, to consider all possibilities, and
to act for the greatest good.
Much is, therefore, expected of an engineer, and the question
is, how shall the chemical engineer acquire all these qualities
and this knowledge?
Coolness and courage are traits of character that each must
acquire for himself; hence we cannot consider them here. Nor
can practical experience be taught in a school, by a teacher or
text-book, since practical experience is not the knowledge of
such facts as are stated in technical text-books, but rather the
faculty of making proper use of such facts in practice. This
faculty is best acquired in practice if the eyes are kept open.
Instruction, however, can help a man to educate himself in
correct technical thinking, as we will proceed to show.
It is the task of the school to give to its students a thorough
scientific education, i.e., to give them, as far as possible, a
thorough theoretical foundation. The school must encourage
original research and independent scientific reasoning; it must
increase the powers of observation and judgment, and must
show by concrete examples how scientific results are used in
practice.
But this is not so easy a task as appears at first sight. First
of all the data available for lectures on chemical engineering are
so limited that it is absolutely impossible to discuss and treat in
detail all the branches of the industry. Only such branches of
chemical engineering can be treated in detail as are either of
great industrial importance (like fuels, combustion, the industry
of heavy chemicals, iron and steel metallurgy, etc.) or those
branches which seem especially adapted to develop in an engineer
the faculties sketched above. Special stress is to be laid on the
discussion of the theoretical basis of the various processes, and
the discussion of apparatus is to be limited to the most important
types. It may frequently happen that such typical examples
are not taken from latest practice, but from older methods of
operation, if the latter show the fundamental process with
greater clearness.
While this principle also holds good for the writing of a text-
book on chemical engineering, we are permitted to cover a wider
field; for limitation in the selection of the various industries is
not as essential as in le&tures. However, even a text-book, the
6 HEAT EX ERG Y AXD FUELS
object of which is first of all to supplement lectures, should not
be too voluminous.
Compared to a book the personal lecture has a great advantage,
in that the teacher can observe from the attentiveness of his
students whether he is understood; and if not he can explain
his subject more in detail. A text-book can, therefore, never
entirely replace the lecture, but may be very useful in supple-
menting it.
However, neither lecture nor text-book alone can accomplish
the same ends as university or college instruction, since the latter
has two additional aids in excursions and laboratory work.
The latter should not be limited to analytical work; on the con-
trary the student ought to be a good analyst when he starts to
work in the chemical engineering laboratory. Naturally he has
to do analytical work also in this period, but this should not be
his principal work. In this stage synthetic work should be kept
in the foreground, with solutions of problems such as may
actually occur in practice; it is even advisable that the students
learn to design plants and to make critical reports on designs
which have been worked out.
This goes far beyond the ordinary limits of chemical engineer-
ing instruction and increases the work of the teacher; but it
brings valuable results. This kind of instruction, however, is
very difficult in the ordinary laboratories and necessitates the
installation of special technological schools. Their erection
would simultaneously amend another defect of present methods
of instruction. As above mentioned, instruction as given now
cannot but be encyclopedical and is very far from being a
thorough technical education. This, however, can be remedied
by giving the students in special schools an opportunity to
acquaint themselves more in detail with a limited field of chemical
engineering according to their choice — without changing the
present encyclopedic instruction in the whole engineering field.
Excursions are also an important means of instruction, as
the student has a chance to see actual industrial works, and to
observe operations carried out on a large scale. If they are to
be useful and profitable, a number of conditions should be
fulfilled. The number of the participants should not be too
great; if the number of the students is very large they must be
divided into several partias. At first only short excursions
GENERAL REMARKS
should be made to stimulate the faculty of observation of the
students. An excursion must not be made before the processes
used in the works to be visited have been discussed in the lectures.
Interest in excursions and resorption of the things observed
are increased by exercises in designing, and by working out
projects, as we have already mentioned. It would also be
advantageous if a professor of mechanical engineering would
participate in these visits. Such excursions should be aided and
facilitated by the government, railroads and manufacturers. It
hardly requires mentioning that a well arranged museum or
collection of things of technical interest is also of great assistance
in instruction.
If we now turn to our subject proper — chemical technology —
we find it difficult to define exactly the word "technology."
The name of our science, literally translated, means *' disci-
pline of the arts" (rexyv, Xoyo^). So we might conclude to
define as technology the mechanics of all possible arts, from all
the fine arts to the handicrafts. This, however, is not the case,
as neither the fine arts and handicrafts nor agriculture and
mining belong to the sphere of technology.
On the other hand, in various trades, which are not included
in engineering science, the same appliances and methods are
used as in engineering.
The problem becomes even more complicated if we keep in
mind that in technical processes not only substances are trans-
formed but also energies so as to assume a more useful and more
convenient fonn.
We could, therefore, define technology as the science of the
methods by which materials and forms of energy as we find them
are transformed so as to become more useful and valuable.
To what extent the value of a substance is increased by the
work of the engineer is shown by the following example, taken
from a paper of the English ironmaster, Lowthian Bell :
Scale of Iron.
Price per Kg.
Scale of Iron.
Price per
Kg.
Pig iron
0.01
0.014
0.02
0.02-0.025
0.3
Needles from same
Fine wire
1.3
Rail-steel
1.4
Gas-oioes
Fine needles from same .
Chronometer springs ....
Finest watch-springs
1.68
Bessemer steel
3.00
Bessemer steel wire
2000.00
8 HEAT ENERGY AXD FUELS
The transformation of substances and energies always requires
a certain amount of work and always involves the practical loss
of a fraction of the substance or energy.
To carry out the desired traasformation, it is necessary to
install a plant with buildings and proper appliances, such as
machines, furnaces, etc. The running (operating) expenses are
calculated as follows:
(a) First cost of plant (to be depreciated).
(6) The oi)erating expenses proper (wages, cost of raw
materials, transportation, taxes, etc.).
(c) Reserves for protection against all emergencies.
On the other hand, the unavoidable loss of material and energy
in every process means a loss of capital and an increase of the
operating expenses.
For effecting the greatest possible economy all these expenses
and losses have to be reduced to a minimum.
The reduction of the first cost and operating expenses depends,
first of all, on the methods used; and, generally speaking, the
method of operation will be the more economical
1. The lower the first cost (capital invested).
2. The cheaper the labor and the raw material used.
3. The quicker the working (which means careful planning).
4. The more convenient the location (with respect to labor
market and shipping facilities).
5. The smaller the loss of raw material and energy. In
this respect a method can be made profitable in many cases by
utilizing again the losses (at least partly) either by using them
again in the same process or by converting them into marketable
by-products.
6. The quality and the selling price of the finished product
are naturally also of the greatest importance.
The object of a process can be of two different kinds:
The object may be, for instance, a change of form (disinte-
gration, agglomeration into larger pieces, change of shape) or a
mechanical separation into products of different values. In the
case of energies the object may be to transform them into use-
ful forms. This is the case in utilizing the energy of a water-
fall or of the wind by means of water-wheels and wind-mills;
or in the change of certain forms of energies into others, as in
GENERAL REMARKS 9
electric generators. The science that treats on these subjects
is mechanical engineering.
Secondly, the object may be to transform raw materials by
chemical changes into substances of a different chemical com-
position, or to transform chemical energy into other forms of
energy (mechanical energy, heat, light and electricity). All
such processes are in the sphere of chemical engineering.
Both branches of technology, however, are so closely related
that it is impossible to draw a sharp line between the two.
The manufacture of paper, for instance, and iron-foundry work
is frequently treated in text-books of both mechanical and
chemical engineering, while the purification of sulphur occurring
in nature and of the native metals is often described only in
chemical works, notwithstanding the fact that only mechanical
and physical processes are involved.
The chemical engineer has to use frequently, besides chemical,
also mechanical means, and in many cases he has to be well
informed as to water-wheels, steam-engines, blowers, pumps, etc.
Mechanical and chemical changes are often so closely combined
(as in annealing sheet metals, welding of iron, hardening of steel,
etc.), that a correct idea of the respective processes can only be
formed from a chemical-mechanical point of view.
According to these explanations chemical technology can be
divided into two main groups:
1. Chemical technology of the energies.
2. Chemical technology of materials.
This book will treat of the first.
In the chemical technology of materials use must be made of
energy for forming the desired products, while in the chemical
technology of energies materials must be employed as carriers of
chemical energy. No strict division can therefore be made
between these groups, but it presents many advantages for
instruction.
We therefore comprise under "chemical technology of the
energies" the science of the change of chemical into other forms
of energy and will consider the transformation of chemical energy
into
•
(a) Heat (by combustion, generated or consumed by other
chemical processes; firing and refrigeration).
10 HEAT EX ERG y AND FUELS
(6) Mechanical energy (explosives and internal combustion
engines).
(c) Radiant energy (mainly light, i.e., chemical illumination;
transformation into heat-rays is considered under a).
(d) Electricity (galvanic cells and storage batteries).
Especially in the case of production of heat from fuel, and in
the case of explosives and illuminants, it is hardly possible to
separate chemical technology of energies from the materials
that furnish the chemical energy to be transformed, so that
we ^ill find it necessary to consider also the technology of these
materials.
CHAPTER II.
FORMS OF ENERGY.
Energy is the power to do work, if we call work a change
of state in general.
The performance of all our industrial operations requires a
considerable amount of energy, for instance, mechanical energy
in the working of metals, disintegrating of phosphates, cements,
and other raw materials for conveying and transporting
materials; heat energy for melting metals and burning of lime,
cement and ceramic products; electric energy for illimiinating,
refining of copper, production of aluminum and chlorine; light
energy for illuminating and photography; chemical energy in
the production of chemical compounds, as chlorate of potash,
explosives, etc.
Energy cannot be made from nothing, but has to be prociu^
from the natural reservoirs of energy in which it is accumu-
lated. We ß,re, however, enabled to draw from the accimiu-
lated energies of nature, and by means of certain machines to
transform them into other forms of energy, but without increas-
ing the total amount. This is, for instance, done in steam
engines, electric generators and batteries, etc.
Of the natural reservoirs of energy, the following are of
industrial importance :
1. Live motors (man, horse, etc.).
2. Falling water (waterfalls, creeks, rivers).
3. Moving air (wind motors and sailing vessels).
4. Substances in which chemical energy is stored. The
most important of these are the fueLs.
All these available sources of energy are actually only inter-
mediate reservoirs, their energy having been obtained from the
sun in a more or less direct way. The sun is, therefore, the
original source of all energy, of all heat, of all electric energy
and of all chemical phenomena on the surface of the earth.
11
12 HEAT ENERGY AND FUELS
The sun transmits energy to the waterfalls by heating and
evaporating sea water; transmits energy to all plants by decom-
posing the carbon dioxide of the air by means of its rays, trans-
forming the plants in the ground into fossil coal.
It is evident that by this transmission a large amount of solar
energy is lost. We have to add, for instance, to the water for
evaporation the total latent evaporating heat, which is again
liberated by the condensation to liquid water and a large part
of the water condensed in the mountains cannot be utilized,
partly on account of practical reasons, partly on account of its
seeping into the ground, and partly on account of the evapora-
tion on its downward way; therefore the experiments for
directly utilizing the radiant energy of the sun deserve our
most earnest consideration^ Precisely speaking, however, all
these losses are only losses to the industrial world and not
to the earth, as, for instance, by the condensation of water-
vapor, the air layers, in which this phenomenon takes place, are
warmed up.
The radiant energy of the sun is, therefore, the only source
from which the energy-content of our earth can be increased,
and the radiation of the earth is the only source of energy-
losses.
Before going into the details of the chemical technology of
energies it might be well to say a few words about the differ-
ent forms of energy.
All possible changes occurring in a system can be referred
to three fundamental quantities: The mass (M), the space,
which can be conceived as the cube of length or distance (L'),
and the time (T). All these changes can be reduced to changes
of energies and we can therefore measure all forms of energy
by using as units mass, distance and time.
If we allow a system to go through certain changes without
adding or deducting energy, so that it returns again to the
first state, then the system contains again the same form and
the same quantity of energy as in the beginning. Energy
cannot be lost or generated, but only transformed into other
forms.
The mathematical expressions for all forms of energy can be
divided into two factors, the capacity factor and the intensity
factor. The former is more or less imchangeable, while on the
FORMS OF ENERGY 13
latter depends the equilibrium. Equilibrium between two
quantities of energy is only attained when the intensities are
equal. If we indicate the energy, intensity factor and capacity
factor with JE, A and c, respectively, we have
E =ic,
I
and therefore dE =^idc + cdi;
if c is constant we have t^= ^J
ai
if i is constant we have -;- = i.
dc
This defines exactly the natiu^ of these energy factors.
The following are the known forms of energy :
1. Mechanical energy.
2. Heat.
3. Electric and magnetic energy.
4. Chemical energy.
5. Radiant energy.
1. Mechanical energy occurs in the following forms:
(a) Kinetic or actual energy.
(6) Energy of space, which can be
(1) Energy of distance.
(2) Energy of surface.
(3) Energy of volume.
(o) The mathematical expression for kinetic energy is
E =■ i mv\
According to the way by which this expression is split into
factors we get as capacity factor either m, which quantity is
absolutely unchangeable, or mv, which is only relatively
unchangeable, while as factor of intensity we obtain half the
square of velocity [— j or the velocity itself (v).
The unit of kinetic energy is the Erg (E), which is the
energy contained in the mass of a gram, when moving with a
i4 HEAT ES ERG Y AND FUELS
velocity of 1 centimeter per second. The dimension of the
ianetic energy (expressed by M, L and T), is
[£J = [ilf^]=[MLT-
'].
The energy of space occurs in three different forms in which
the capacity factor is represented by distance, surface and vol-
ume respectively. We have
Form of energy. Capacity. Intensity.
Energy of distance = distance X force
Energy of surface = surface (area) X tension
Energy of volume = volume X pressure.
The energy of distance acts between two points in the direc-
tion of their connecting line. If we indicate the length (dis-
tance) with / and the force with /, we have
^/ f ' /ä^i ^ ^ Vy s-nd therefore the force
is equal to the ratio of change of energy to change of distance
(length). If the energy of distance is transfomied exclusively
into kinetic energy (as in the ordinary mechanical and astro-
nomical problems) this equation expresses the acceleration, a,
and then corresponds to the ordinary definition of force.
The energy of surface is active on the surface of liquids and
solids. Its intensity of factor, the tension, is identical with the
^ ^ constant of capillarity.
^ The energy of volume appears in gases. Its factors are volume
and pressure.
We have, therefore, the follox^ing expressions for the dimen-
sions of the energies of space and its factors :
Capacity.
Intensity.
Energy.
distance (L)
force = [EL-']
E
surface (L*)
tension = [EL-']
E
volume (L')
pressure = [EL-^]
E
We know of two kinds of energy of distance, one of which
(called gravity) acts between two material points so that the
FORMS OF EX ERG Y 15
energy increases with the distance and reaches a niiniinuni
when the points are in direct contact. It is governed by
Newton^s law of gravitation. If we indicate the energy of dis-
tance with Edf the two masses acting upon each other with m
and mj, their distance with r, we can express this law by the
equation
hd = c^- h—r~'
r
in which c^ and j^ are constants. If r = oo and Ed = Cj, it
reaches a maximum. The diflferential of this equation gives
us the ordinary form of this law :
dr ~^ ~^' r' '
The quantity c^ is unknown; the second constant k^ is,
expressed in the centimeter-gram-second system,
j, = 6.6 X 10-«.
On the surface of the earth the force of gravity can be con-
sidered constant for moderate altitudes, and the energy of dis-
tance is directly proportionate to the altitude.
The second kind of distance energy occurs for instance in
electrically charged balls, and is distinguished from the former
by reaching its maximum value at infinitely small instead of
infinitely large distance between the bodies acting upon each
other. For this energy we have
E = In -~^f and for the force
r
dE . m,/;?.,
rfr^ " ~ ^' V'
This force has therefore the same formula as in the first case,
but is negative. While the gravity is an attracting force, this
force is repulsive.
AA'e have seen above that two masses acting upon each other,
under the influence of gravity, tend to approach each other;
whereby the distance energy is decreased, being partly trans-
formed into kinetic energy.
16 HEAT ENERGY AND FUELS
The decrease of distance energy, corresponding to a decrease
in Z of d/ is
JET . ^1^2 J
If we suppose
m^ = M mass of the earth and m^ = 7n mass of a falling
body, r = Ä the racUus of the earth and dr = dh is an incre-
ment of the fall-distance, corresponding to an infinitely small
change of distance energy, we have
,„ . M „ .... Mm ., . .
dEd == ^2 p2 ^^ "'^» ^^ expression wherem ]^ -^ =/ (gravity).
I'hence we can write
dEd = fdh.
As the lost distance energy is completely transformed into
kinetic energy of the equation dE^ = mv dv we can make both
expressions equal :
fdh = mvdv.
By integration between o and h and o and v respectively we
obtain
f J dh = m j V dv
or
fh = -— , as the fundamental law for the mutual transforma-
tion of kinetic and distance energ>\
If we put into fdh = mvdv for the acceleration the value
v = JT > ^'^ g^^ Gahleo's law of fall :
fdt = mdvy or
rfr ^/.
Equilibrium between kinetic energy and distance energy can
only exist if the two masses, acting upon each other, are moving
around their common center of gravity.
Analogous to the two kinds of distance energy we can
imagine two kinds of surface energy; however, we know only
one of them, t.e., the one that tends to decrease the surface.
FORMS OF ENERGY 17
The cause of this is called tension (y). a being the surface, we
have
which quantity is identical with the capillary constant. The
surface tension is, down to very thin layers, independent of the
thickness of same, is proportional to the surface, and is depend-
ent on the temperature and on the nature of the substances
separated by the surface.
A peculiar property of the surface energy is that changes in
its value are accompanied by changes of heat energy. If, for
instance, a soap bubble is increased by blowing, the surface
energy increases more than would corjpspond to the mechanical
energy used in blowing, the heat content decreases by a cor-
responding amount, or, if the temperature is kept constant, the
requisite heat has to be added from the outside. During the
contraction of the bubble the entire amount of the disap-
pearing surface energy cannot be transformed into mechanical
energy, since as much heat energy is again produced as was
tranformed into surface energy during the first process.
Phenomena of equilibrium between surface energy and energy
of gravitation occur in the rise of liquids in narrow tubes, g
being the weight of the raised liquid and dh the elevation to
which corresponds the infinitely small decrease of the surface,
we have for the equilibrium
y da- = g dh.
As the decrease of the surface (d<r) must equal the product of
the tangent-line (u) and the change of height (dh),
d<r = udhj
we have yu = g,
i.e., the weight lifted equals the product of surface-tension and
tangent-line.
For the intensity factor of the volume-energy we have the
expression
dE
d^^P'
18 IIKÄT EX ERG y AXD FUELS
Of the two possible kinds of volume-energy only that is of prac-
tical importance which decreases with increasing volume.
If a gas or vapor is given off from a solid or liquid substance
at constant temperature and constant pressure, we have
£, = C - p (y - Vo),
or, considering only the volume of the gas formed,
E, = C - pv.
In this eijuation for one mol of all gases C = RT, which
quantity is known from the gas-equation.
For an infinitely small change of volume of gases at constant
pressure we have ^
dE^ = - pdv.
From the equation
therefore
pv
= RT,
V
RT
V
'
-dE,
= RT
dv
V
an(
-E,. = R fr''-}-,
or, for (constant temperature,
- A-,. = RT ß
By integration Ixjtween i\ and i\ we g(»t
RTloy^^ -- E/ - E,
There is little known of the relation tetween volume-energy,
volume, and pressure, except in the case of gases.
For the equilibrium between volume and distance energy
such as takes place, for instance, in a cylinder filled with gas, in
FORMS OF ENERGY 19
which a pressure is exerted upon the gas by a piston working
without friction, we have
j dh = p dv.
The cross section of the cylinder being q,
dv = q dh,
then P9 =^ fy
i.e., the force equals the product of gas-pressure and cross-
sectional area.
Before mentioning the other forms of energy we want to
consider a few general important considerations.
If there is no equilibrium in a system between the forms of
energy present, the system is undergoing a change so that the
decrease of one form of energy is greater than the increase of
the other. Then energy goes over from places of higher inten-
sity to those of lower intensity whereby it is sometimes trans-
formed into other forms of energy; to what extent such a
transformation takes place depends on the nature of the system,
which — inasmuch as it effects a transformation of energy — is
called a machine.
In the above supposed case of unbalanced energy the neces-
sary change of state of the system can take place in various
ways. A lifted stone, for instance, can fall vertically to the
earth or can slide dowTi an inclined plane. It will select, in
fact, the way along which it attains in the same length of
time the greatest possible kinetic energy. The generalization
of this principle is: Of all possible transformations of energy
the one will take place that will produce in a given time the
largest transfer of energy from the original form to some
other.
2. Heat was the first form of energy to be recognized as an
independent quantity. In connection with this form of energy
two important laws were formulated, which laws also hold for
all the other forms of energy :
(a) Thermodynamic law: Heat can be transformed into
mechanical work and other forms of energy and vice versa.
This transformation takes place according to certain definite
20 HEAT ENERGY AND FUELS
laws. This law is based upon the fact that energy cannot be
made nor destroyed, but only transformed from one form into
another. Clausius has formulated this same law as follows:
the energy of the universe is constant.
(6) Thermodynamic law: Heat cannot go of its own accord
from a colder to a warmer body. Applying this law to all
forms of energy we can say : If two bodies are in equilibrium
with a third with respect to certain forms of energy, they are
also in equilibrium with each other as regards the same forms of
energy.
If we add to a body the heat dQ at the absolute temperature
Tf we have
/ — ^0 (= for reversible, < for non-reversible processes).
The second law has, furthermore, another important meaning.
In a reversible process, carried out between very narrow limits
of temperature (between T and T -}- dt), the heat quantity
added to the system being Q, the infinitely small part
of this added heat can be transformed into work or other forms
of energy. This is a law of special importance in the study of
energy. As, according to above explanation, we have for
/dQ dQ
— = 0,-j^ must be the total differential
of a quantity which — just as the energy — depends only on
the state of the body, but not on the way by wliich this state
was reached. Clausius calls this quantity "entropy," and it is
generally denoted by s, and by introducing this quantity into
the second principle we get
dQ = Tds.
Like all other forms of energy the heat can be decomposed
into two factors, one of intensity and the other of capacity.
The former is the temperature, while the latter, according to
circumstances, is represented by the entropy or heat-capacity.
FORMS OF ENERGY 21
The general equation of energy being
E ■■
= ä,
and the total differential
dE
= cdi + idc
we have for a constant c (dc
= 0)-;
dE
di
= c,
and for constant i (di
= 0)
dE
dc
= i.
For the heat we have i = T. If we add to a subetance the heat
quantity dQj so that no other form of energy is generated (with-
out being considered) and if we determine the relation between
the heat added and the increase of temperature effected
thereby, we have
dE = c dt,
wherein c stands for the heat capacity of the substance.
In melting and evaporation and solidifying or condensation
respectively, and also in many chemical processes taking place
at constant temperature we have
dE ^dcT
or analogous to the former equation
dE ^dsT.
The total values of the entropy being unknown we have to
transform these equations by referring them to two states
marked by index 1 and 2 :
(«1 — Sj) dT = (Cj — Cj) di.
We have, for instance, assuming equilibrium between heat
and volume-energy,
(Sj - s,) dT = (v, - Vj) dp,
or,
8^ — «2 ^P
V, -v^^df'
22 HEAT EX ERG Y AXD FUELS
If we indicate the latent heat of the process referred to
(chemical reaction, etc.) by / we have
/
»l - «2 = f
and therefore
I dp
T (r, - r,) (IT
which expression is correct for all changes of the state of aggre-
gation and all chemical changes of state, that are connected
with a change of volume. We can transform it into
—=^ = {v^ - v^ dp (Clapeyron's equation).
4. As coefficient of capacity of chemical energy the gram-
atom of the elements or the gram-molecule is generally used,
while as coefficient of intensity the '' chemical potential " or
simply '' potential " is used (J. Willanl Gibbs). For the latter
quantity we have, according to the general energy-equation,
. dE
The individual values of the quantities of chemical intensity
l)eing unknown, we can only consider their sum as appearing
in equations of chemical reactions. If, for instance, E^^ and E^
represent the total chemical energy-content of a system in the
beginning and end state respectively, q being the energy gen-
erated (liberated) in going from 1 to 2, we have
E.^E,^- q.
If we divide now both sides of the equation by the capacity
c of the system (c remaining coastant in the processes under
consideration) we get
9
or, 1, = »2 + -
FORMS OF ESERGY 23
As the capacity c is always a positive quantity we have,
if 5 = - i\ = i^'y % > ii if q > and tj < i^ if q < 0.
Thence chemical equilibrium can only take place if the inten-
sities of the forms of chemical energy before and aft^r the
transformation are equal; otherwise — if this is possible — such
a transformation will take place that the intensity decreases
(and on account of the equaUty of the capacities the total
chemical energy of the system will also decrease).
If instead of one single chemical substance, as in the case
above, there are several, it must be remembered that to every
one of them there corresponds a certain quantity of chemical
energy and also of intensity, so that we can write an energy-
equation for every substance. If we go back to the ele-
ments, i.e., to the individual kinds of atoms present, and
mark their number before and after the transformation with
n/, n/, n^' . , . and n/', r?/', n/', . . . , respectively, their
energy content with £/, E/, E/, . . . , E/\ £/', E/\ and the
energy of reaction connected with the transformation with
q^j g^', g"', we have, for every kind of atom,
n/E/ = < (£;/ -f g).
or, for every single atom,
E/ = E,' + q/,
(1)
(2)
We, therefore, get the following expression for the total
reaction:
I //
n/^/ + n/'E, ' + ...= n,'E,' + n,"E^
+ q' + g" + .... (3)
By an analogous method we get for the capacities
nX + n."c/' + . . . = n,V + W + ■■-, (4)
or, as according to the above explanation n,' = n/; n," = n,",
etc., «,'c/ + n/'c," + . . . = nX' + »/V- (4a)
24
HEAT ENERGY AND FUELS
If we divide each of the equations (2) with the correspond-
ing capacity value, we get the intensity-equation
and therefore for the total reaction
1/ + t," + . . . = rV -h i," + .
S!
(5)
(6)
It is necessary that for the equilibrium i/ + i/' + . . . «
i^^+i^"-\- . . . and this is only possible if 2) =0, i.e. if ^q = 0.
Now we can arrange the intensities corresponding to the
original and final systems so that they correspond to the dif-
ferent compounds appearing in the reaction-equation; if we
also sum up the quotients - and distinguish by index the sums
of intensities corresponding» to every substance, we get the
expression
X/i + S/'^* + . . . = S/^' + S/'^' + . . . +2-
For equilibrium
2':
0.
It could be thought from the above explanation that the
energy of reaction of a reaction represents directly the change
of the chemical energy of the system, when passing from the
original to the final state. This conclusion, however, would be
incorrect, since not only the chemical but also all the other
forms of energy contained in the system are undergoing a
change during the transformation. But we can go a little
further in the case of chemical equilibrium, since in this case
the intensities of the original and final system must have
become equal, and since the capacity of the system must
FORMS OF ENERGY 25
remain constant during the transformation, the amounts of the
various forms of energy also must be equal to each other. In
the case of the equilibrium, therefore, the heat-force of a
reaction measures the distance of the non-chemical energy
values before and after the reaction.
For ascertaining the changes of chemical energy of a system
when passing from one state to another, we can start from the
energy of reaction accompanying this change of state, consid-
ering also the changes that the other forms of energy are imder-
going. As such we find mainly the heat and the energy of
volume, which will be better understood by the following
example.
The reaction
H, + i (0,) = Hfi
takes place with generation of heat. The quantity of this
energy of reaction is calculated by means of Kirchhofes law as
follows :
Qr = 58,294.6 + 3.25 T ~ 0.002 T\
If the combustion is effected at constant pressure and at
constant temperature, the difference of the heat-content in the
ori^nal and final state is calculated as follows :
Heat content = spec, heat X abs. temperature
Original system = 1.5 (6.5 + 0.0006 T) T
Final system = (6.5 + 0.0029 T) T
Decrease of heat content = 3.257 T - 0.002 T^
If we deduct this decrease of the heat content (A W) from
the energy of reaction, we get
Qj,- AW = 58,294.6 cal.
We have to consider now the change of the volume-energy.
The combustion taking place at constant pressure, the volume
is decreased in the ratio 1.5 to 1, i.e., 1 mol steam is formed from
1.5 mols hydrogen and oxygen. The volume-energy of the sys-
tem is hereby increased by 0.5 RT. This increase of the
volume-energy, however, takes place under the influence of the
outside pressure, is therefore representing the addition (supply)
of foreign energy, and therefore has not to be considered here.
Hence we have, for the decrease of the chemical energy of
26
HEAT ESERGY ASD FUELS
the system in the complete transformation from original to the
final state, \E=^E,-E,,
= 9o
We get the same result if the reaction takes place at constant
volume. In this case both the energj' of reaction and the
decrease of the heat-content become less by \ RT, since c^ is
used instead of fp.
The change of the chemical energy is therefore independent
of the temperature and equal to the energy of reaction at
absolute zero.
TABLE I.
EXEROY OF VARIOUS REACTIONS.
K. -molecules.
H. + J O, -► H^O
CO + J O3 -> (X),
C + JO,->CO
C + (X -4 CCL
N, + O, -► 2 NO
2 CO -4 CO, + C
CO, + H, -4 CO + H,0
C + H»0 -♦ CO + H,
C + 2 H,0 -4 CO, + 2 H
K.-cal.
58294.6
68182.4
28674.5
96856.9
43000.0
39507.9
- 9887.8
-29620.1
-19732.3
As the direction of chemical reactions is not independent of
the temperature, the chemical changes of state do not neces-
sarily depend upon the chemical energy alone, but also upon
other forms of energy. When considering a measure of chem-
ical affinity the chemical energy alone is not sufficient, and we
have to use, therefore, the change of the free energy of the
system, in which the quantity q„ appears as independent of the
temperature (chemical energy).
We have seen above that chemical equilibrium can only take
place if the intensity of the chemical energy before the change
equals the intensity after the change. Otherwise such a change
of state should take place that the intensity of this energy in
the system decreases. If, notwithstanding, this transformation
does not occur, the reason for this can only be looked for in the
compensating effect of other forms of energy. This is of the
FORMS OF EX ERG y 27
greatest importance, as is shown by Ostwald in the following
explanation:
*^In chemical energy the possibility of compensating differ-
ences of intensity is apparently very general, as can be seen
from the fact, that in many cases it can be preserved without
loss, practically speaking, for an indefinite length of time.
The possibility of using chemical energy {i.e., of transforming
it into other forms}/ is necessarily connected with the pres-
ence of differences or chemical intensities, which can be kept
up (i.e., compensated) as long as desired.
*^The forms of compensating energy can only in rare cases
be observed. This is the reason why we know so little about
the presence of a function of chemical intensity. We see that
in spite of the possibility of transformation of the chemical
energy into other forms, for instance, in a mixture of oxygen
and hydrogen, no such transformation takes place as long as
the temperature remains below a certain point. In such
cases we speak of a 'passive resistance.' We can explain these
phenomena by supposing that a compensation of the differences
of chemical intensity, by other forms of energy, actually takes
place, and that between the stage of oxyhydrogen-gas and of
water at low temperatures intermediate stages are contained,
which for the transformation (the other energy-quantities
remaining constant) would at first effect an increase of the
intensity factor; afterwards a very considerable decrease of the
same, corresponding to the state of water, would take place.
Such states are called metastabile.''
3. Electric Energy. The magnitude of intensity of electric
energy is called electromotive force, or potential difference.
While, however, the intensity of heat, the temperature, is
counted from an absolute zero point, being therefore always
positive, no such point has been found for electric potential.
It is therefore necessary to use an arbitrary zero-point
whereby positive and negative potential-values are obtained.
The quantity of electricity is used as a factor of capacity.
If we denote the same with J5?„ the potential with t: and the
electrical energy with E^, we have
E = ^,
n
or, E^ = En.
28 HEAT ENERGY AND FUELS
For the quantities of electricity the law of conservation can be
expressed as follows: The total quantity of electricity is con-
stant, and equal quantities of positive and negative electric
energy are always present.
If two quantities of electricity, + E and - E, concentrated in
mathematical points at a distance r from each other, act upon
each other, the potential difference being r, they exert upon
each other a force /, which is given by the equation
K depends on the nature of the medium between the two
electric quantities, and is called its dielectric constant. If we
call the distance traversed by the two electric quantities imder
the influence of this force rfr, we have for the electric energy
and therefore for a change of the distance from r' to r,
If we make / ^ ^^ we have
E^-E =^M^,
or
E^E +*M^.
• r
If El and E^ are both positive or both negative, we see that
— —^ IS positive, I.e., the electnc energy mcreases with the
r
decreasing distance, or: the two electric quantities of like sign
repel each other. If, however, E^ is positive and E^ negative,
KE.E^ 1 . , . ...
or vice versa f — —^ becomes negative; electnc quantities of
unlike signs attract each other.
FORMS OF ENERGY - 29
If we have two infinitely large quantities of electricity of
opposite sign stored in reservoirs having a potential difference
7Ü, and we connect these two electricity reservoirs by means of
a conductor, electric energy will flow from both into the con-
ductor in the same way that heat-€nergy passes to a cold
body. Thereby the two electric quantities neutralize each
other in the conductor, the electric energy being transformed
into heat. This shows how the electric current is produced.
If the two quantities of electricity are not infinitely large
the generation of a uniform electric current (i.e. the preserva-
tion of the same potential-difference between two cross sections
of the conductor) will only be possible if the electric energy
consumed in the conductor in the time-unit is constantly
replaced at the source of the electric current. If we refer this
process to the time-unit, calling the ratio of quantity of elec-
6
tricity to time - = i, intensity of current, this intensity of
current must be proportional to the potential difference t: and
furthermore be dependent on a coefficient, the quantity of
which is determined by the quality of the conductor. This
coefficient is the conductance I; its reciprocal value r = - is
called the resistance of the conductor.
We thereby arrive at Ohm's law :
i =- Ik
We have seen above that in the conductor free electricity is
neutralized, or electric energy is converted into heat. If the
potential difference across the ends of the conductor is n and if
no other energy except heat is generated, we will have, if we
call the heat quantity formed from electric energy ''W,'*
W ^Qt:.
W
Considering also the time — = g,
we have a = — •
^ t
30 II EAT EX ERG y AXD FUELS
As — = t (intensity) and as according to Ohm's law n = /r,
t
we can write
q = iV,
I.e., the rate at which heat is generated in a conductor is pro-
l>ortional to the resistance and to the square of the intensity.
This is Joule's law.
Another important law of electrochemistry is Faraday's:
All motions of electricity in electrolytes take place only with
simultaneous motion of ions, so that with equal quantities of
(»lectricity chemically equivalent quantities of the various ions
are moved. This law is correct for every kind of electricity-
movement in conductors of the second class.
Of special interest for us is the transfonnation of chemical
into electrical energy as we find it in galvanic batteries. It
was thought at first that herein the chemical energy is per-
fectly transformed into electricity. This, however, is not
correct.
In general we can express these conditions by the equation :
wherein E^ means electrical energy, E^ chemical energy, Q the
(juantity of electricity transferred in the electrolyte, t: the poten-
tial difference and T the absolute temperature.
The radiant energy is the least known of any form of energy.
Ostwald says in regard to the energy of radiation :
'' The law of the conservation of energy shows a discrepancy,
as we know some phenomena in which energy present dis-
appears beyond the power of our senses and means of obser-
vation. It does not, however, disappear absolutely, as we can
get back a quantity of energy equal to the amount lost. But
in all these cases it can be proved that a certain (generally
very little) time has elapsed during which the energy has left
one part of the system under observation, but has not yet
appeared in the other part. From the fact that the energy
reappears after a ccilain time, we make the conclusion by
analogy that it existed during this interval in a different form;
as long as it was present in this form, it was imperceptible to
FORMS OF EXERGY 31
US until after its retransformation into one of the forms of
energy that we can perceive with our senses/'
This form, in which the energy has no connection with, and
no relation to our senses, is called radiant energy or energy of
radiation. By the regular relation between the disappearance
of energy from one place and its reappearance at another place,
we conclude that energy, if transformed into radiant form,
travels through the space with a velocity of 3 X W^ cm. per
second. This is called the velocity of transmission of light (ray) ;
it is correct, however, for radiating energy in general, from
which light may originate. Electric energy is easily changed
into radiant energy, which travels at the same speed, as energy
originated from heat and chemical energy, which is generally
called light. Based upon W. Weber's work Maxwell found, by
comparing the formula for the electro-dynamic effect (long
distance) and for the motion of light, that the principal con-
stants are identical, and Hertz lately demonstrated by means
of experiments that the periodical motions of radiant energy,
through space, generated by rapid electric oscillations, are
governed by the same law as the optical motions. To infer,
therefore, as is done generally at present, that light is an
electromagnetic phenomenon, is as incorrect as if one should
conclude, from the fact that burning phosphorus emits light,
that the light is a chemical phenomenon. We have, in all
these cases, transformations of other fornis of energy into
radiant energy, that follow their own laws and can be recon-
verted by proper means into every other fonn of energy.
Radiant energy can, as the other forms of energy, be pro-
duced from other forms of energy or changed into the same.
Its relation to mechanical energy is the least known. It cannot
be said with certainty at present whether direct change of the
latter into radiant energ}' takes place at all. I was not able to
find a single positive proof of this transformation. This is the
cause of the fact that the mechanical energy, which acts in the
movement of the stellar bodies, remains essentially unchanged,
while the other formations which contain other kinds of energy,
that are more easily transformed into radiation, do not show
such a constancy. The transformation from radiant into me-
chanical energy has also not been proved beyond doubt: possibly
such a transformation takes place in Crooke's radiometer.
32 HEAT ENERGY AND FUELS
Theoretically we should expect in every substance that 3delds
radiant energy, a mechanical counter effect in the form of a pres-
sure which works contrary to the direction of the radiation.
On the other hand a pressure in the direction of the radiation
corresponds to every absorption of radiant energy. This pres-
sure is equal to the radiant energy contained in unit volume.
At the very great velocity of the radiation this amount is gen-
erally very small.
Contrary to mechanical energy thermic energy is very easily
transformed into radiation. This change is so frequent and
so regular that the thermic energy is often called ''radiating
heat.'" This name is as misleading as the definition of heat as
a kind of motion; for the heat after transformation into radiant
energy is not heat, just the same as mechanical energy, after
transformation into heat, has ceased to e.vist as mechanical
energy; in the new state the energy follows new laws and
cannot be called by the old name.
The change of heat into radiant energy cannot be followed
up in an absolute manner, since we have no means of measuring
the radiant energy itself, being forced to convert the same into
another fonn of energy; we have to reconvert it in this case
into heat by placing in front of the radiant bodies, bodies
absorbing the rays and transforming them into measurable
heat. In other words the receiver has to be as sensitive a
thermometer as possible. The receiver has to contain a certain
heat of certain temperature,, and must therefore also radiate,
and the heat-quantity, which is perceptible on account of the
absorbed radiation, is the difference between the latter and the
emitted heat.
VOLUME I.
THE CHEMICAL TECHNOLOGT OF HEAT
AJXD FUELS.
VOLUME L
THE CHEMICAL TECHNOLOGY OF HEAT AND FUELS.
The chemical technology of heat treats of the methods used
in the industries for the transformation of chemical energy into
heat.
This transformation generally takes place by means of a
chemical process called combustion, which in all commercial
processes used up to the present time consists of oxidation.
The oxygen required is taken either from the atmosphere or from
oxides, the latter being thereby reduced. Lately experiments
that look very promising have been made to produce pure
oxygen on a large scale or to increase the oxygen content of the
air for obtaining an increased effect in the combustion.
The materials which are used commercially for generating
heat are called fuels. They are either used as they occur in
nature (natural fuels) or are made to undergo certain changes
before being used (artificial fuels).
The object of combustion, as above stated, is the trans-
formation of chemical energy into heat. It will therefore be
necessary to become acquainted with the methods of measur-
ing the generated heat and also with the methods that enable
us to determine the energy-content of the fuels.
Primarily, we are concerned with the measurement of the
intensity factors of heat energy, i.e. the temperature, since the
capacity-factors (the specific heats) are generally known, and
hence do not have to be determined in every case.
Second in order comes the experimental determination of the
calorific value. These determinations are of two kinds, depend-
ing on whether the quantity of heat yielded by the combustion
of a certain quantity of fuel is to be determined, or whether
the highest temperature that can be reached theoretically by
combustion, is to be ascertained.
Finally it will be necessary to study in detail the process of
combustion.
35
36 HEAT ENERGY AND FUELS
All these points are considered in Part I of this work. Part
II contains the science of firing, i,e, all the processes that favor
the utilization of the combustion heat, or reduce the unavoid-
able heat losses, and also the discussion of the different methods
of industrial firing.
Part III is added as an appendix, treating of the varioas
chemical methods of heat abstraction (refrigeration).
PART L
HEAT MEASUREMENT, COMBUSTION
AND FUELS.
CHAPTER I.
THE MEASUREMENT OF HIGH TEMPERATURES
(PYROMETRY).
The measurement of temperature is of the utmost importance
in the industries, because on the one hand certain processes and
reactions take place only within certain limits of temperature,
and on the other hand an increase of temperature above a
certain value means an increase of heat loss and a waste of fuel.
Instruments for measuring temperature are generally called
thermometers; thermometers used for measuring high temper-
atures, however, are called pyrometers. Widely different prop-
erties of certain substances which vary with temperature
have been used or proposed for the measurement of tempera-
ture: Change of length and volume of various substances,
variation in the pressure of gases and vapors, melting points of
different substances, heat given up by hot substances in cool-
ing, color of emitted light, change of electric resistance and
thermoelectric behavior, heat-conductivity, etc.
We are going to describe below the most important instru-
ments of this kind :
1. Ordinary thermometers, in which the apparent expansion
of a liquid (generally mercury, at low temperatures, alcohol) in
a containing glass vessel, is measured. Since the ordinary
thermometers can be used only up to the vicinity of the boiling
point of mercury (358° C. at atmospheric pressure), tempera-
tures up to about 500° C. require instruments that contain a
quantity of hydrogen or nitrogen above the mercury, instead of
a vacuum. When used they have to be heated up slowly, i.e.
gradually inserted into the medium or space, the temperature
of which is to be measured.
87
38
HEAT EX ERG y AXD FUELS
For exact measurements of temperature the following errons
have to be considered :
1. Reading error.
2. Graduation error.
3. Error due to pressure (inside or outside).
4. Error due to meniscus.
5. Erroneous determination of the fixed points.
6. Error due to time lag of thermometer.
7. Error due to glass-expansion.
We want to consider, in a few words, -the most important of
these sources of error.
To obtain correct readings the visual ray has to be perpen-
dicular to the graduation.
For exact measurements of temperature it is a disagreeable
fact that thermometers, after some time, show incorrect read-
ings, the freezing point being apparently moved upwards,
and returning to the original position only after being heated
to high temperatures for several months. This phenomenon is
called depression. This depression is in close relation to the
composition of the glass :
TABLE II.
DEPRESSION FOR VARIOUS COMPOSITIONS OP GLASS.
Depres-
sion.
SiOj
Al,03
CaO
MgO
PbO
K^O
Na,0
Degree
0.
50.83
72.04
65.42
69.04
56.74
65.00
72.09
69.52
64.48
70.29
75.65
74.72
66.42
66.55
63.47
60.56
68.30
70.29
72 44 1
1.04
2.42
0.93
0.89
0.66
2.04
1.45
3.86
1.48
2.29
1.34
1.35
3.35
1.31
1.77
1.14
1.28
2.49
1.60
0.52
8.20
13.67
12.21
0.18
13.58
11.20
9.13
5.68
9.55
6.11
9.10
10.70
13.37
10.10
10.21
10.41
8.68
9 23
27.98
11.08
1.63
19.46
18.52
12.48
19.51
1.88
3.07
3.55
14.51
5.68
5.86
14.55
15.50
12.24
3.52
8.27
12.06
11.29
0.08
15 32
0.09
0.09
0.10
29.86
11
07
0.12
0.15
0.20
24
0.12
0.71
12.71
13.41
13.77
12.81
2 48
31
...... ........
11.50
9.03
4.57
3 07
0.35
0.36
0.37
0.30
40
11.95
24.45
12.08
5.38
6.00
0.40
48
•••• 1
0.61
66
i
1
THE MEASUREMENT OF HIGH TEMPERATURES
89
TABLE III.
DEPRESSION FOUND BY WIRBK.
Depre».
sion.
SiO,
Decree
04
64.45
0.15
64.66
0.15
49.49
0.38
64.49
0.38
68.62
0.40
69.58
0.44
66.53
0.65
66.74
0.07
70.0
0.07
70.0
1.05
66.0
Fe,0,
Al,0,
0.81
0.53 I 0.24
0.35
0.61
0.53
0.46
0.43
0.30
0.42
2.37
2.09
2.18
0.21
CaO
MgO
Mn,Oa
A%0,
K,0
Na,0
12.36
0.22
Trace
0.89
20.09
86
13.38
0.27
Trace
PbO
0.87
18.89
1.4K
1.20
0.67
33.90
12.26
1 54
Mn,0,
11.56
0.38 0.77
0.35
17.14
3.75
7.36
0.36 0.34
Trace
3.56
16.89
7.90
0.30 Trace
0.27
3.97
15.35
9.44
0.21
Trace
0.74
3.95
16.15
8.68
0.22
0.08
10.57
12.72
16.5
13.5
15.0
15
6.0
■ ....
14.0
14
Other tests made by Abbe and Sehott also proved that lea<l-
potassium glass, potassium-lime glas'^ or srxJium-lime glass show
the lowest depression, which, however, increases if potassium
and sodium are present in a glass simultana)usly.
Acconling to these observations a standanl-thermometer
glass of the following composition is manufactured by Schott &
Genossen in Jena:
Silicic acid (i7 f)er r;ent
Boracic acid 2 f>er rM*nt
Alumina 2.5 fier cent
lime 7 per cent
Chdde of zinc 7 f>er cent
Soda (caastic) 14.5 per cent
This ^ass, after previously being heate^l U) i(%f C\ shows a
transient fall of the zero-mark of only 0.05 Ui O^O^)*^ C
The correction of the thennoraeter-rea^ling on account of the
meniscus is made by means of the equation:*
T ^i ^ 0.000148 nd - O,
wherein T meaas correctefl temfjerature.
t means ohf^rvcjrl temperature.
f means average temperature of the meniscus.
n meaxL« length of the meniwuft iii thennonieter-
degree«.
* 'Seie aiiio tiMf fcilknrüug uJtile gf TLofpe.>
40
HEAT ENERGY AND FUELS
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THE MEASUREMENT OF HIGH TEMPERATURES
41
0.000148 is an empirical coefficient that approaches the
apparent expansion-coefficient of mercury in glass (0.000154).
2. Graphite pyrometer and metal pyrometer. Notwithstand-
ing their defects these instruments are widely used. They are
based upon the imequal expansion of two different solid sub-
stances, and they measure the difference of expansion of two
different solid substances.
Especially the graphite pyrometer is largely used. However,
it is not at all reliable, as is shown by the following table, in
which t means the reading from the pyrometer and T the tem-
perature determined by the Weinhold calorimeter:
TABLE V.
COMPARISON OF GRAPHIC PYROMETER WITH THE WEINHOLD CALORI-
METER.
t
T
t
T
t
T
t
T
604
500
775
573
869
553
888
555
650
512
814
535
873
524
906
555
736
520
818
567
874
571
909
553
756
585
835
561
875
594
935
575
Furthermore, these pyrometers do not go back entirely to
air-temperature after cooling, but show a temperature 20°-
60° higher, which defect increases continuously, so that three
graphite pyrometers (examined by Beckert) that were only
exposed to hot blasts of less than 500° C. within two months
showed over 800°, and went to about 200° above the zero-mark.
Metal pyrometers show similar faults. With three of these
pyrometers Weinhold obtained the following rc(?orrectioas as
compared with air-pyrometers. (Table VI.)
A peculiar instrument of this kind is Joly's meldometer,
which is ased for determining melting points.
3. Wedgewood's pyrometer is based upon the contraction of
a clay cylinder, which, after being heated to the temperature
to be measured, is allowed to cool to oniinary temperature;
then the decrease of volume of the clay resulting from its change
at high temperature is measured; one degree corresponds U) a
contraction of y,V?F of the original dimension. The zero-point of
42
HEAT ENERGY AND FUELS
the pyrometer corresponds to a temperature at which complete
dehydration of the clay takes place, i.e, about 600° C. The
contraction of the clay cylinder is measured by locating same
between two graduated hnes, which form a certain angle.
(Fig. 1.)
TABLE VI.
COMPARISON OF VARIOUS METAL PYROMETERS WITH AN AIR
PYROMETER. (WEINHOLD.)
(a) Gauntlett's Pyrometer (Iron and Brass).
1
First Series of Tests.
After Continued Use.
Air Pyrometer.
Gauntiett Pyrometer.
Air Pyrometer.
Degrees
Degrees
Degrees
Degrees
507
325
407
310
13
-10
20
10
328
162
319
200
533
362
441
308
227
98
12
8
330
170
471
345
20
-10
348
220
12
6
-2
(6) Bock's Pyrometer (Iron and Brass).
Air Pyrometer.
Bock's Pyrometer.
Air Pyrometer.
Bock's Pyrometer.
Degrees
305
464
472
526
636
Degrees
125
245
250
298
352
Degrees
347
478
565'
716
Degrees
225
210
330
400
(c) Oechsle's Spiral Pjrrometer (Platinum-Silver).
Air Pyrometer.
Oechsle's Pyrometer.
1
Air Pyrometer.
Oechsle's Pyrometer.
Degrees
Degrees
Degrees
Degrees
277
325
257
275
272
315
15
- 7
273
310
316
336
311
338
362
381
352
372
494
475
404
401
-52
THE MEASUREMENT OF HIGH TEMPERATURES
43
These pyrometers are seldom used to-day, as they give widely
varying results even with slight variations in their composition
and method of manufacture; furthermore their results are not
proportional to the ones of the air pyrometer,
which at present is taken as standard ther-
mometer.
LeChatelier foimd, for instance :
Air pyrometer ° C.
900 1000 1100 1200 1300 1400
Wedgewood's pyrometer
20 30 70 130 152 160
In ceramic factories, however, where not
an actual temperature-measurement has to
be made, but only a certain temperature
has to be maintained, Wedgewood's pyrom-
eter can be advantageously used. In France
circular cakes 5 cm. thick, having a diameter of 5 cm., are
used for this purpose, being pressed out of the clay-mass
without moistening and then burned.
4. Gas or air thermometers are based upon Boyle-Gay-
Lussac's law, and are considered as standard instruments,
with which all others are compared. They are used either
with constant volume or constant pressure.
For a permanent gas, which at the absolute temperature T
and the pressure P, occupies the volume F, we have the law
PV = nRT
(wherein n stands for the number of mols of gas in volume V),
If we change the temperature of this gas to T,, while keeping its
volume constant, the pressure is changed to Pj, and we have
Fio. 1. — Wedgewood
Pyrometer.
or
or
P.F
= nRT„
T,
P.
T
~ P'
Ti
- T
P,-P
T
- P
44 HEAT ENERGY AND FUELS
By this method we can measure a change of temperature by
the corresponding change of the pressure.
If, however, we change the temperature of the gas from T
to 7",, keeping the pressure P constant, the volume of the gas is
changed to Fj, and we have
or
or
PV, = nRT„
T V
T V '
T,-T V,
T V
We measure here the change of temperature by the change
of volume.
As the active medium a permanent gas is used (nitrogen,
hydrogen, or air), which is enclosed in a vessel of practically
unchangeable volume. The Celsius-graduation is used, the freez-
ing point serving as zero-mark.
Temperatures between degree and 100 degrees are gener-
ally measured with a thermometer of constant volume. Above
100° C. however, the pressure increases so rapidly that the
strength of the pyrometer may be exceeded. Therefore for
such temperatures instruments with constant pressure are
used. If the pressure is measured in atmospheres we have for
the first method
/ = (P - 1) 273, I
and for the second method :
V - V
t = ^-y— 273.
Up to 500° C. the thermometer-vessel can be made of glass,
but for higher temperatures glass softens. Platinum vessels
were first tried for temperatures higher than 500° C, but not
successfully, since hydrogen (which is generally used) per-
meates platinum at high temperatures. Porcelain vessels, if
made impermeable for gas by glazing, can be used safely up to
10(X)° and even higher.
THE MEASUREMENT OF HIGH TEMPERATURES 45
For avoiding the error due to the change of the quantity of
the enclosed gas on account of the permeability of the vessel,
a method invented by Becquerel can be used. It consists of
forcing a further quantity of gas into the volume V of the pyro-
meter containing gas of the temperature (to be measured) T
and of pressure P and measuring the pressure required for this
purpose. Immediately before adding this quantity of gas we
have in the apparatus n mols of gas of volume F, pressure P and
temperature (to be measured) 7",
PV = nRT,
We now add the gas-volume v measured at t and p, for which we
have
j)v = n'Rt,
After pressing this gas-quantity in we have in the constant
volume V of the apparatus, gas of the temperature (to be
measured) T and of pressure P' :
P'V = (n + n') RT,
and therefore
PV pv _P^
T ^ ~t ~ T '
In this equation T is the only unknown quantity. We have
T _ jP' - P )V
t~ pv
or
pv
The applicability of this method is based upon the fact that
less than a minute is required for measuring and introducing
the additional quantity of gas so that the error caused by the
permeability of the vessel during this short period is very
small and negligible.
The only defect of this apparatus is the uncertainty of our
knowledge (exactly) of the expansion of the pyrometer-vessel
at high temperatures. An instrument of this kind, very con-
venient for practice, which, however, has to be handled care-
fully on account of the fragility of the porcelain vessel, was
46
HEAT ENERGY AND FUELS
constructed by T. Wiborgh. Figs. 2 and 3 show same in the
older construction. The thermometer-bulb F, having a con-
tent of about 12 cm., is prolonged into a porcelain tube of
20 mm. outside and 0.5 mm. inside diameter. This tube,
which is practically a capillary tube, and can be set upon the
other parts of the instrument, has to be very strong, and is
Fios. 2 and 3. — Wiborgh Pyrometer.
built with heavy walls. The tu\yo is cemented into the metal
shell i4,. which can be screwed ujxjn the metal cylinder H'y
whereby a connection is made between the tube and the mano-
meter BV'B\
The glass tube (manometer) is somewhat larger (1.5 to 2
mm.) at m for a length of 10 mm. ; then comes another enlarge-
ment containing the air volume F' that is to be pressed in the
thermometer-bulb when determining the temperature. At mf
the tube B opens into the longer manometer-tube B^, which is
THE MEASUREMENT OF HIGH TEMPERATURES 47
about 2 mm. inside and 8 mm. outside diameter. The latter
is prolonged downward and connects through a bend with the
iron vessel K, which is filled with mercury. A cover is screwed
upon this vessel, the cover carrying a nut for the screw S, by
means of which a second iron cover can be pressed directly
upon the mercury.
The screw S is turned by means of the metal disk S', which
sets loosely upon the pivotal end of the screw so that the disk
can easily be taken off. This is to prevent the mercury from
being forced through the manometer-tube B into the ther-
mometer-bulb by careless manipulation, which would injure
the instrument. As further protection against such an acci-
dent the tube B is provided with another very small enlarge-
ment right above m, that is filled with asbestos to prevent a
rise of the mercury beyond this point.
For protection the manometer-tube is enclosed in a little
rectangular metal box D, closed in front by a glass plate G.
The longer manometer-tube B' projects upward through the
box along the metal tube P. The metal tube P contains a
wooden cylinder 0, which can be turned by knob (7. The
scale is fastened to this cylinder, and is observed through a
slot in the metal tube P. By turning the cylinder the correct
scale, i.e. the scale corresponding to the barometric height, can
be brought into view. For preventing dust from entering the
open manometer-tube B', some cotton is put into the upper
end, above which a glass cap may be suspended. If the air-
volume V is at the same temperature as the thermometer-
bulb and the mercury is forced up to the mark m, and rises in
the manometer-tube B' to a certain height, it indicates the
zero-mark of the instrument corresponding to the barometric
height.
The correct scale is then brought into position by turning the
scale-cylinder until the scale, whose zero-mark coincides with
the barometric height, comes into view. If, however, the instru-
ment is so placed that V is warmer than V, it is not possible
to find the correct scale by this method.
For avoiding the necessity of using a special barometer in
this case, a third tube Q, terminating with a bulb Q', is
connected to the manometer-tube Ä. When the mercury is
pressed into the manometer it is also pressed into Q and rises to
48
HEAT EX ERG y AXD FUELS
the zero-mark of the instrument, at a certain height r, marked
on the glass. Here the same principle is used as in the pyro-
meter in general, i.e. a certain volume of air is pressed into
another; if we have the same temperature in the tube Q and
in the bulb Q\ the zero-point of the pyrometer can be deter-
mined by mark r, even if V is wanner than V\
For protecting the lower part of the porcelain tube A, which
contÄins the thennometer-bulb, from c^uick changes of tem-
perature and shocks, it is packed in asbestos. The upper part,
however, is free.
For cementing the pyrometer and manometer-tubes into
their respective metal shells, a cement obtained by mixing
finely powdered litharge with glycerin to a thick paste is used.
This cement gets hard in a few hours, and can be heated up to
about 2;>0 degrees without being decomposed. In order to
prevent the obstruction of the capillary tube during the cement-
ing process, a metal wire is passed through both tubes; then
the ends of the tubes are partially ^^ithdrawn from the metal
shells and coated with cement. About half an hour later the
superfluous cement is removed and the metal wire taken out.
Figs. 4 and 5. — Spring Manometer.
In order to render the instrument less fragile and to simplify
its manipulation Wilx)rgh replaced the mercury-manometer by
a spring-manometer (Figs. 4 and 5). The iastrument rests in a
round metal box with hesivy lx)ttom (a), to which the por-
celain pyrometor-tube (rV) is screwed, the same as in the other
instruments. In the interior of the box is a lenticular shaped
metal vessel V\ which can l^e pressed together, and will regain
its original shape when the pressure is releascil.
THE MEASUREMEXT OF HIGH TEMPERATURES 49
Facing plate a is a metal plate 6, held in position by a
cylindrical bearing; it is provided with a capillary tube. As the
lenticular shaped vessel contains openings corresponding to the
two capillary tubes, V and 7' are brought into communication
with each other and with the outer air.
A metal support, fastened to the box, carries a shaft e,
which serves to compress the vessel V^ through a short lever-
arm Ky which is connected to the rod s. By turning the shaft
the opening in the capillary tube Is closed and the plate b
pressed against the lenticular vessel F', compressing the air
and forcing it into the bulb V of the pyrometer.
The capillary tube in the hub d is connected with the
manometer-spring by means of a fine lead tube m. By means
of geared wheels the spring transmits to a pointer the motion
caused by the increased pressure.
The shaft e is turned by meaas of a forked lever-arm pro-
vided with a knob L.
If no measurement of temperature Ls being made the air-
volumes V and F'are in communication with the atmosphere,
and the rod s does not close the capillary tube. A spiral
spring (not shown in the figure) is arranged to hold the lever
in the position shown in Fig. 4.
The temperature-scale of the instrument is arranged for air-
temperature of 0° C. If the latter is t^^ the air-volume to be
pressed into the pyrometer-bulb is simply increased to
(1 4- «0 F', whereby the same value is obtained as if t were
0° C. A change of the barometic height H has the opix)site
effect, so that F' has to be decreased as the barometric pressure
increases if the scale Ls to give correct readings. Temperature
and barometric height, according to the law of Boyle-Gay-
Lussac, bear a certain fixed ratio to each other, so that, for
instance, to compensate for an increase of the barometic height
of 78 mm., the volume F' has to decrease as much as though the
temperature had fallen 30 degrees. Therefore one single scale
can be userl for re<^lucing the volume F'.
To accomplish this result the bearing d is provided with
a movable collar g, one end of which presses against a pro-
jection of/, while the opposite end is helical in form, and fits a
corresponding helix on the pivot plate b. By turning the
cover of the instrument, which is connected with the ring by
50 HEAT ENERGY AND FUELS
the rods n and o, the collar g is raised or lowered, whereby a
change of volume of the vessel V is effected.
In addition to the scale of temperature (0° to 1400° C.) , the dial
of the instrument is provided with a small aneroid barometer
Q, a thermometer P, a scale (from 690 to 790 mm.) for correct-
ing the barometric pressure, and a temperature correction
scale attached to a ring E. Correction for temperature and
barometric pressure (i.e. setting the instrument to the air-
temperature and pressure), is made by reading the thermom-
eter P and the barometer Q, then turning the ring E so that
the temperature and barometic readings on both scales coincide.
If a measurement of temperature is to be made, first of all
the ring E is turned into the right position, i,e, the instrument
is set to correspond with the air temperature and barometric
height. Then the lever C is drawn forward as far as possi-
ble, until the pointer Z stops moving and stands still. Then
the rod s is pressed down, the opening of the capillary tube
closed and the hub d pressed down with the metallic disk;
the vessel V is compressed so that the air is pressed into the
P3rrometer-bulb V, The air-pressure so obtained is trans-
mitted through the lead-tube m to the manometer-spring.
The latter then changes its position and sets the hand Z in
motion.
After reading the temperature the lever G is released.
It jumps back, partly on account of the elasticity of the vessel
V\ partly because of the spiral spring that is fastened to the
shaft e; and the pointer goes to the zero-mark. This meas-
urement can be performed in a few seconds.
The lever-arm G (which is forked and elastic) can easily be
taken off the shaft and removed, thus preventing the use of the
instrument by unskilled persons.
In order to render the porcelain tube less fragile, and to be
able to expose the tube directly to high temperatures without
danger of cracking and breaking, it is covered with asbestos
and packed into a sheet-iron tube, the latter being coated with
fire-clay, quartz and unbumed clay.
Both constructions of Wiborgh's air-pyrometer can be bought
from Dr. Geissler's successor in Bonn.
Of the other practical air-pyrometers we may mention the
pyrometer of K. V. Karlander (can be bought from Otto Meyer-
THE MEASUREMENT OF HIGH TEMPERATURES
51
son in Stockholm) and of A. Sieger and Walter Duerr (can
be bought from Alphonse Custodis in Düsseldorf).
The air-thermometer is not only used in practice, but also
to a great extent as a standard for calibrating other
instruments. For this purpose a number of very exact
temperature-determinations were made with the air-thermom-
eter, a number of which are given in Table VII :
TABLE VII.
ACCURATELY DETERMINED BOILING AND MELTING POINTS.
Substance.
Boiling Point.
Substance.
Boiling Point.
Naphthalin
Deg. Cent.
218
357
445
Sulphur (Regnault)
Zinc
Deg. Cent.
448
Mercury
Sulphur
921
Substance.
Melting Point.
Substance.
Melting Point.
Cadmium . . .
Deg. Cent.
321.7
326.9
419.0
630.6
657
Silver (in air)
Silver (pure)
Gold
Copper (in air)
Copper (pure)
Deg. Cent.
955
Lead
961 5
Zinc
1063.5
Antimony
Aluminium
1064.9
1084.1
The specific heat of platinum between 0° and 1200° C. was also
found by calorimetry :
Co'= 0.0317 + 0.000006 ^
I was determined by means of an air-pyrometer.
Daniel Berthelot has lately by an ingenious method elimi-
nated the error caused by the permeability and expansion of
the casting, by determining optically the density of the heated
air at atmospheric pressure, and therefrom calculating the
temperature by means of the gas-equation. By this method he
found
The melting point of silver to be 962° C,
The melting point of gold to be 1064° C,
which agrees exactly with the values ^ven above.
52
HEAT ENERGY AND FUELS
5. Klinghammer' s thalpotdsim^ter (Fig. 6). This instrument,
which can be used up to about 800 degrees, measures the vapor
tension of different liquids. It consists of a tube containing
Fio. 6. — Thalpotaöimeter (Klinghammer).
the liquid and a manometer. The following substances are
used as the active medium:
Liquid carbon dioxide. .
Liquid sulphur dioxide.
Ether (free of water). . .
Di8tille<l water
Heavy hydrocarbons. . .
Mercury
I>eg. Cent.
From - 65 to + 12.5
- 10 4-100
4- 35
+ 100
+ 216
+ 357
+ 120
+ 226
+ 360
+ 780
Mercury is especially suitable, since its molecules consist of
single atoms, which make the internal work very simple.
This pyrometer has to be gradually heated to the temper-
ature to be measured, in order to prevent injury to the appa-
ratus.
CHAPTER IL
PYROMETRY (Continued).
6. Pyrometers in which the fusibility of different substances is
uiilized for measuring temperatures. AH these pyrometers have
the disadvantage of only allowing the determination of con-
stant or rising temperatures or of temperature-maximums; but
they are not suitable for the observation of temperature-
changes (up and down), which are frequently of commercial
importance.
(a) Princep's alloys :
These are alloys of gold and silver, or of gold and plati-
num, the melting point of which was determined by Erhard
and Schertel by means of an air-pyrometer. These deter-
minations are shown in Table VIII.
The error of these determinations of the melting point is
generally less than 20 degrees, but in most cases it is very
much smaller. The above melting points were actually
measured up to 1400° C. by the air-thermometer; the higher
values were determined by graphic interpolation by using the
melting temperature of platinum as found by Violle.
An important requirement for temperature-determinations
by this method is the use of sufficiently pure metal for
Princep's alloys. It is, therefore, of advantage to prepare them
in a state of sufficient purity or to obtain them from a reliable
source. Erhard and Schertel obtained the pure' metals as fol-
lows : The silver was precipitated from diluted ammoniacal solu-
tion by ammonium-sulphide; gold was, after precipitation by
sulphate of iron, transformed into sodium-gold-chloride and
from the solution the pure crystals precipitated by means of
oxalic acid. For purifying the platinum, platinum-salammoniac
was treated (according to Claus) with sulphuretted hydrogen-
solution, for reducing iridium to sesquichloride. The sponge
obtained from the platinum-salammoniac (free of iridium) was
melted upon chalk in an oxyhydrogen-flame. The different
63
54
HEAT ENERGY AND FUELS
mixtures can advantageously be prepared by using wires made
out of the pure metals. A J mm. wire can be made even out of
pure gold or silver. Then the length of wire required for
each case is calculated. This is more convenient and more
correct than direct weighing, since only from tV to J gram of
an alloy is required for a determination, and even if a larger
stock of alloys is to be made, the preparation in small quan-
tities will yield a more uniform product.
TABLE VIII.
MELTING POINTS OF ALLOYS.
Gold-Silver-Alloys.
Silver.
Gold.
Melting Point.
Per cent.
Per cent.
Deg. Cent.
100
80
954
20
975
60
40
995
40
60
1020
20
80
1045
100
1075
Gold-Platinum-Alloys.
Gold.
Platinum.
Melting Point.
Per cent.
Per cent.
Deg. Cent.
100
1075
95
5
1100
90
10
1130
85
15
1160
80
20
1190
75
25
1220
70
30
1255
65
35
1285
60 "
40
1320
55
45
1350
50
50
1385
45
55
1420
40
60
1460
35
65
1495
30
70
1535
25
75
1570
20
80
1610
15
85
1650
10
90
1690
5
95
1730
100
1775
PYROMETRY 55
The alloys are made by melting the metals upon chalk by
means of a blow-pipe-flame, which gives sufficient heat for the
silver-gold alloys; for melting the platinum-gold alloys a gas-
oxygen flame or a flame obtained by blowing oxygen into a
burning mixture of 2 volumes ether and 1 volume alcohol has
to be used. For preventing the volatilization of gold, the
platinum-gold alloys are melted as far as possible with the
ordinary blow-pipe flame, and then for complete melting
exposed for a few seconds to an oxygen-blast.
The molten metal beads when quickly cooled show a fine
crystalline structure, and when slowly cooled a coarse crystal-
line surface of netlike structure. They have a remarkable
inclination for demixing (separating), which is accompanied by
the production of a yellow color, both after slowly cooling and
after heating for some time at a temperature near the melting
point. In this case the hammered surface is crystalline, and
shows a yellowish instead of gray color. The alloys with from
15 to 40 per cent of platinum show this variability frequently
to a marked degree ; they have then to be remelted in the oxy-
hydrogen-flame. The alloys of gold and silver also become
crystalline under these conditions, but their surface remains
smooth and shows only more or less brilliant parts.
After melting the alloys are beaten flat with a hammer and
exposed to the temperature to be measured in a cupola made
of fire-clay mixed with quartz. Direct contact with reducing
flames has to be avoided, otherwise a thin coating of slag is
formed which considerably lowers the melting point. Experi-
ments have shown that in such a case an alloy containing 47
per cent of platinum, that should melt at 1364° C, showed a
melting point of only 1247 degrees. This is probably due to
the absorption of silicon, and therefore it is necessary, if a
reducing flame is to be used, to use a cupola-base free of quartz,
Le. either of pure magnesia or pure clay.
(6) Seger-cones:
These are mixtures of quartz, kaolin, white marble and
felspar, and are prepared by moistening the dry mixture with a
solution of arable gum, forming it into triangular pyramids
6 cm. high, the sides of the base being 1.5 cm. long. For lower
temperatures part of the kaolin is replaced by ferric oxide.
The "cones," provided with a number at the top, are put into
56
HEAT EX ERG Y AXD FUELS
a chamotte-dish, which is brought into the room of which the
temperature is to be measured. The point at which the
"cone" begins to soften (at which the sinking apex touches
the chamotte-base) is taken as melting point. At higher tem-
perature the entire cone melts together into one mass.
TABLE IX.
COMPOSITION AND MELTING POINTS OF SEGERrCONES.
No.
10
11
12
13
14
15
16
17
18
19
20
Chemical Composition in Equiv-
alents.
3K,O(0.
7CaO(0.
3K,O(0.
7CaO(0.
3K,O(0.
7CaO (0.
7 CaO J "
3 K,0 ^
7 CaO r
3K,O^0
7CaOr
3K,0Jq
7 CaO r
3K,O^0
7CaOr
7 CaO j "
3K,0K
7 CaO r
3K,0)
7CaOr
3K,0K
7CaOr
3K,0K
7Ca0r
3K,0I
7 CaO S ^
3 K,0 )
7 CaO J ^
3K,OU
7 CaO S ^
3K,0)
7CaOr
3 K,0 )
7CaO('^
7 CaO f ^
3 K,0 U
7 CaO ( ^
05Fe,63)Ug.(.
45 Al A) )
.5Ala03, 4SiO,
.5AI3O3, 5 8102
.6AI3O,, 6SiO,
.7 AI A, 7Si02
.SAlaOa, SSiO,
.9A1A, 9SiOa
OAIA. lOSiO,
.2A1,03, 12 810,
.4Ala03, I4SIO2
.6A1A, 16 8 A
.8 AljO.,. 18 8 A
. 1 AlA» 21 SiOa
.4A1A, 24 8 A
. 7 AljOg. 27 8iO,
. 1 AlA. 31 SiOj
.5AI3O3, 35 8 A
.9 AlA, 39SiO,
Composition.
Fel-
si)ar.
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
83.55
Marble
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
35.00
Quartz.
66.00
60.00
57.00
54.00
84.00
108.00
132.00
156.00
180.00
204.00
252.00
300.00
348.00
396.00
468.00
540.00
612.00
708.00
804.00
900.00
Ferric
Oxide.
16.00
8.00
4.00
Kaolin.
12.95
19.43
25.90
25.90
38.55
51.80
64.75
77.70
90.65
116.55
142.45
168.35
194.25
233.10
271.95
310.80
362.00
414.40
466.20
Melt-
ing
Point.
Deg.
Cent.
1150
1179
1208
1227
1266
1295
1323
1352
1381
1410
1439
1468
1497
1526
1555
1584
1613
1642
1670
1700
PYROMETHY
The melting points given were found as follows :
No. 1 melts at a little higher temperature than the alloy
with 90 per cent gold and 10 per cent platinum (melting point
according to Erhard and Schertel 1130° C); its melting point
was therefore assumed to be 1150° C.
No. 20 melts at a lower temperature than platinum; the
melting point was therefore estimated to be 1700° C.
Assuming, furthermore, that the melting points of the 20
cones followed each other at equal intervals (which is actually
not correct) the interval between two melting points following
each other is calculated thus:
1700 - 1150
19
= 28.9 degrees.
Composition of the pyroscopes of higher numbers of Seger
are given in Table X.
TABLE X.
COMPOSITION OF PYROSCOPES OF HIGHER NUMBERS. (Seger.)
Nr
K,0
CaO
AI3O3
SiOj,
21
0.3
0.7
4.4
44
)
22
0.3
0.7
4.9
49
> Difference:
0.5 AljOa, 5Si02.
23
0.3
0.7
5.4
54
)
24
0.3
0.7
6.0
60
)
25
0.3
0.7
6.6
66
\ Difference:
O.6AI3O3, 6SiO,.
26
0.3
0.7
7.2
72
)
27
0.3
0.7
20
200
28
1
10
29
1
1
8
6
30
31
1
5
32
1
1
4
3
33
34
1
2.5
35
1
2.0
36
1
1.5
38
1.0
Cramer has made melting cones for measuring lower tem-
peratures in the brick industry. They can be bought in two
sizes (6 and 10 cm. high) from the Royal Porcelain Factory in
Charlottenburg or from the Chemical Laboratory for Clay
Industry, Berlin, N. W., Kreuz str. 6.
58
HEAT ENERGY AND FUELS
TABLE XI.
COMPOSITION OF PYROSCOPES FOK LOW TEMPERATURES.
Molecules.
Nr
K,0
CaO PbO
AlA
Fe,0,
SiO,
BaO,
01
02
03
04
05
06
07
08
09
010
Oil
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
Na-O
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
<6GGC>c>cic>e>&G
1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.8
0.75
0.70
0.65
0.60
0.55
0.50
0.40
0.30
0.20
in
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
3.95
3.90
3.85
3.80
3.75
3.70
3.65
3.60
3.55
3.5
3.6
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.5
10
012
3.5 1
013
3.4
3.3
3.2
3.1
3.0
2.8
2.6
2.4
2.2
2.0
1.0
014
1
015
1.0
016
1
017
1
018
1.0
019
1
020
1.0
021
1
022
0.5
1
C. Bischof, who thoroughly investigated these pyroscopes,
found even the highest melting point far below that of melting
platinum. The melting points of Nos. 13, 14, 15 and even 17
are only slightly above that of melting palladium (1500® C);
furthermore these pyroscopas show various irregularities among
themselves. However, notwithstanding these defects the Central
Association of German Manufacturers recommended the oflScial
adoption of the Seger-cones, March 28, 1904.
The table on following page contains some new data relative
to the melting temperatures of all these cones (measured with
Le Chatelier pyrometer).
Only the following of these melting points are correctly
determined : Nr. 022 melts at dark red glow, Nr. 010 at the
melting point of silver, Nr. 1 near the melting point of an alloy
containing 90 per cent gold and 10 per cent platinum, Nr. 10 at
PYROMETRY
59
the point where felspar begins to soften, and Nr. 36 at about the
melting point of platinum. The other temperatures are only
approximate.
TABLE XII.
MELTING POINTS
OF PYROSCOPES.
Nr.
Deg. Ont.
1 Nr.
1
Deg. Cent.
i
St.
Deg. Cent.
022
590
1
02
1110
1
19
1510
021
620
01
1130
20
1530
020
650
1
1150
21
1550
019
680
2
1170
22
1 1570
.018
710
3
1190
23
1 1590
017
740
4
1210
24
1610
016
770
5
1230
25
1630
015
800
6
1250
1 26
1650
014
830
7
1270
27
1670
013
860
8
1290
28
1690
012
890
9
1310
29
1710
Oil
920
1 10
1330
1 30
1730
010
950
11
1350
31
1750
09
970
12
1370
32
1770
08
990
13
1390
33
1790
07
1010
14
1410
34
1810
06
1030 •
15
1430 !
35
1830
05
1050
16
1450 1
36
1850
04
1070
17
1470 1
i 38
1890
03
1090 i
i '«
1490 '
7. Caiorimetric pyrometers. With these instruments the
temperature is derived from the quantity of heat that is
given off by a heated body when cooling off in the calorimeter.
This method was strongly recommended by Pouillet, Rfegnault,
Camelley, VioUe and others, and introduced into industrial
practice by Weinhold, Fiodier and others.
In order to reduce the radiation heat losses from the calo-
rimeter to a minimum, the instrument is so designed that it
becomes only slightly heated. In an apparatus to be used for
scientific purposes the temperature rise of the calorimeter is
measured by a mercury thermometer comprising 2 degrees
and divided into ji^r degrees.
At first an iron cylinder was used as the thermometric sub-
stance, i.e., the substance which gives off the heat to be measured
in the calorimeter. The use of iron, however, proved to be
60
HEAT EX ERG Y AXD FUELS
unsatisfactory on account of its easy oxidation and of its non-
uniform cooling. If we take the heat given off and the tem-
perature as co-ordinates, we obtain a curve with two points of
inflexion, corresponding to the allotropic change of state of
the iron. This shows that the temperatures calculated could
not be correct.
This is the reason why platinum substances and a mercury-
thermometer divided in xJ^ degrees are used in laboratories,
and in the industries a nickel-cylinder (the heating of this
metal is very regular) and a mercury-thermometer divided in
iV degrees whose scale, therefore, can be larger. A rise of
about 50° C. in the calorimeter-temperature is sufficiently exact
for practical purposes. The nickel-cylinder is put into a small
pipe of fire-proof material, fitted with a removable iron handle.
After the pipe with the cylinder has been in the furnace whose
temperature is to be measured for fifteen minutes, one can be
sure that equilibrium of temperature has been established.
The pipe is now taken out of the furnace, emptied into the
calorimeter, the calorimeter-water stirred and the increase of
temperature read and recorded.
The following tests made by the Compagnie Parisienne du
Gaze show the regularity of the heating law for nickel:
tC,' = 50.5 63.5 89.5
t = 400° 500° 700°
103 117.5 134 150 166
800° 900° 1000° 1100° 1200°
We ^ve below a few melting temperatures determined by
Violle and also by Holbom and Day.
TABLE XIII.
MELTING POINTS OF METALS.
Metal.
Violle.
Holburn and
Day.
Silver
Degrees
954
1045
1055
1500
1779
Degrees
961.5
CiO\i\
1064
Copper
1065
Palladium
Platinum
1500
1780
PYROMETRY
61
Below we describe a few pyro-caloriiiieters that were con-
i^tructed for practical use.
The latest type of Weinhold's pyrometer for determining
high temfH^ratures is illiBt rated in Fig. 7, The calorimeter-
vessel proper CC is made of thin sheet brass. It holdi? about
1 Kg of water, ig cylindrical at the bottom and conical at
Kmj. 7 — WeiiihfjJti'w PyrtKtieter
the top. The ratio of the height to the diameter is so chosen
a*4 to make the surface as small a.« p<:>s^ib!e. in order to n^dnce to
a minimum tlie los^ or gain nf heal by radiation or coniiuc-
lion. A cylindrical verti^el of tin-plate BB witii a loose conical
cover DD siirmumis the calorimeter-vessel, which is carried
by three cork -piece;*, eemente*! into BB^ and so arranges I as to
maintain a space of I cm. l>etween the walls of the containing
vessel anrl the calorimeter. BB is faf'tpncd in a wooden lx)X
HII. As woo<! and still air are very poor conductors of heat,
and aä bright sheet metal prevents radiation of heat» by this
methotl an excellent heat-inoculation is effected* The center
62
NEAT ENERGY AXD FUELS
one of the three cylindrical openmgs in the calorimeter
vessel servers for iiUrnducing the metal ball, w^hich is bor
through in three directions perpendicular to each other* Th|
thermometer T is inserted through a cork in the shortest neck
The shaft of the circulating device K is in&c^rte<l through th^
narrow neck. This device (Fig, S) consists of an im}ieller mth
inix inclined paddles which move in a slim brass tube, open at
the top and the bottom. Its shaft is rectangular at the topJ
Pifi. ». — (.'JrrulMiiig Dc-viL'<' yUir 7)*
It I*. H. — Uriir'> Wirc^ JWkH.
SO that the pulley S ean bc^ attached. By mean^ of a cord
paösing over thive guide-pulleys and a crank wheel, attached
to the outRi<le of the wooden hnx, R can be rapidly rotated.
The lively circulation of water r-auwed thereby facilitates th<
equaUzation of the temperatun.^ in the calorimeter. Thfl
thermometer T is provided witi» a ecale divided in 0.1 degree,** J
on which, however, 0>01 degrees can be estimated. The thin
cyhndrical mercurv^-reservoir of the theimoujeter (5Ü to fit)
mm.'s long) ext-ends nearly the entire height of the calorimeterJ
The hot metal ball is kept in the brass-wire basket (Fig* 9)1
Its cover ran be turned around a hinge, and is provided with »■
pin attached rectangularly downward. If the basket — with
^^
PYROMETRY 68
the cover open — is let down into the neck of the calorimeter,
the cover — and also the basket — remain hanging upon the
edge of the neck. If now the ball is allowed to fall through
the neck, it hits the pin and thereby closes the cover. This
causes the basket with the ball to fall upon the bottom of the
calorimeter, so that finally the cover almost touches the surface
of the water, which, before putting in the basket and the ball,
should reach to the lower edge of the neck. To assure the right
amount of water in the calorimeter, a pipette is used, which is
fastened to a disk of metal, wood, or cork, so that its lower end
is exactly flush with the entry of the neck to the calorimeter.
At first water is put in until it stands a few milUmeters high in
the neck, then the disk of the pipette is laid upon the edge of
the neck and the excess water sucked out.
By throwing the hot ball into the calorimeter not only the
water contained in the latter but also the calorimeter-vessel is
heated up. To determine the quantity of heat absorbed by the
instrument, the quantity of heat absorbed by the vessel has also
to be considered. This is done by ascertaining the quantity
of water that would be necessary to absorb the same quantity of
heat as the calorimeter, i.e., by determining the water-value of
the calorimeter. For this purpose the brass calorimeter-vessel,
together with the stirring arrangement and the basket K (but
without the pulley S and thermometer T with cork) is weighed in
a dry state. The weight found, multiplied by the specific heat
of brass (0.095), gives the water-value of the empty calorimeter.
The water-value of the thermometer is difficult to find, but can
be neglected on account of the small quantity involved. After
inserting the thermometer with the cork the apparatus is weighed
a second time, and finally after putting in the cooling water it is
weighed for the third time. The difference of the second and
third weight gives the water content of the calorimeter. The
water-value of the filled calorimeter is the sum of this water
content and the water-value of the empty calorimeter. If, for
instance, the empty calorimeter without thermometer weighs
210 g., with thermometer 236 g., with water 1240 g., we have:
Water value of the empty calorimeter = 210 X 0.095 - 19.95 g.
Water content of the calorimeter = 1240 - 236 - 1004.00 g.
Water value of the filled calorimeter = 1004 4- 19.95 - 1023.95 g.
64 HEAT ENERGY AND FUELS
The water- value of the empty calorimeter is more conveniently
determined by putting into the instrument a weighed quantity
of water, then throwing in a test ball of a certain temperature
(for instance 100° C.) and measuring the increase of temperature.
If we divide the heat given ofif by the ball by the increase of tem-
perature and deduct therefrom the weight of the calorimeter, we
obtain the water-value of the dry instrument.
The balls used weigh from 60 to 80 g. For introducing them
into the space, the temperature of which is to be measured, a
pair of tongs made of heavy iron wire or bar iron, provided with
cup-shaped jaws, is used (Fig. 10), or a spoon with cover, and fitted
Fig. 10. — Tongue. Fio. 11. — Spoon.
with a long handle (Fig. 11). The weight of the ball has to be
detennined before use. If the balls are of the size mentioned it
is sufficiently accurate to weigh to the nearest decigrams.
When using, the calorimeter is filled with fresh water, the wire
basket put in, and — immediately before inserting the ball —
the circulation device is started, and kept in motion until the
thonnometer shows a constant temperature, which is read and
recorded (initial temperature of the calorimeter). When intro-
ducing the l)all, care ha^ to Ix^ taken not to injure the thermometer
and the driving cord of the circulation device. Directly after
throwing in the ball, the circulation device is worked until the
thermometer be(;omes stationary when the temperature (final
temperature) is read and reconled.
The difference between initial and final temperature multiplied
by the water-value of the filled calorimeter — expressed in kilo-
grams — gives the lieat-(]uantity (in calori(»s) transmitted from
the ball to the calorimeter. Therefrom the quantity of heat
given off by a 1 Kg. ball is calculated, and by comparing this
figure with a table in which the heat (c. t.) is calculated from
the specific heat of the metal, the temperature is found.
Considerably simpler in construction is the calorimeter of Dr.
Ferdinand Fischer (Pig. 12). The cylinder A, which is made of
thin copper plate and has a diameter of 500 mm., is suspended
PYHrniKTHY
65
ill the wooden Im^^c H. The ^invue lietween both U lillc«! with
fibrous asljcfltos or iiLineral woo). The apparatus is closerl by a
thin bra>is or ropper plate, having a large opening H (20 ninu
diaui,) for the stirrer r ami for throwing; in the metal eyhnder,
and a small opening for the thennometer h, which it^ a normal
therniotneter built by Geissler
in Bonn, It has a very .small
merrury reservoir; it^ scale has
a range of from 0^ to TrfP t\, and
is di\ided into 0.1 dc^'ei's, ^o
that ÜJ)1 degrees can eai^ity be
estimated : a ^Xvivy n oi thin rnp-
per plate protects it from l>eing
Fic.
Kiü, VA
Sirnir-ii^ ^\ nitr l*vrüiiit*ter*
broken by the^^firrer- The stirrer consi^st« of a round copper disk,
j^oldered to a copper nj<L The latter tt raelte^l into a glass rod,
tliat ?ier\*es a-^ Imndle. If, for iastancCt the copper vessel weigh
^J5,0Ü5 g», the stirrer without gia.^^ rotl wei^h 6,440 g*, then the
water-value of the calorimeter ii= 0,094 (35,905 + G,445) ^ 3,98 g,,
including the thennometer alxiut 4 g. If the calorimeter water
weigh 240 g-, the water-value of the filled calorimeter 13 2*j0 g-
66
HEAT ENERGY AND FUELS
For measuring the temperature doubly bored cylinders of plati-
num, wrought iron or nickel are used. For the first case, i.e., with
platinum cylinders weighing 20 g., such a quantity of water is
put in that the total water-value amounts to about 125 g., with
the two other metals to twice that amount. In a manner similar
to that given above the cylinders are exposed in the medium
the temperature of which is to be measured and thrown into the
calorimeter through the cover opening d. The cylinder falls
upon the disk of the stirrer, and now by raising and lowering the
latter a uniform heating of the calorimeter-water is effected, so
that at the end of about one minute the thermometer reaches
the final temperature.
No corrections are made for evaporation of water or heat
transmission by radiation or conductivity, as the evaporation is
extremely small and the insulation of the calorimeter perfect.
If the calorimeter-water reaches a temperature of about 40 de-
grees it has to be changed. The calculation of the temperature
is made as in the former case.
TABLE XIV.
HEAT CAPACITIES OF PIJITINUM. ETC.
Platinum
According
to Violle.
Iron.
Nickel.
t»c.
Post.
Pion-
chon.
Eu-
chAniie.
Calculated
. from the
Average
Specific
Hmt.
Pion-
chon.
Eu-
ch^nne.
100
200
300
400
500
600
700
800
900
1000
1100
cal.
3.23
6.58
9.75
13.64
17.35
21.18
25.13
29.20
33.39
37.7
42.13
46.65
51.35
56.14
61.05
66.08
71.23
76 50
cal.
10.8
22.0
35.0
39.5
67.5
86.0
108.0
132
157.0
187.5
cal.
11.0
22.5
36.5
41.5
68.6
87.5
111.5
137.0
157.5
179.0
cal.
11.0
23.0
37.0
42.0
69.5
84.0
106.0
131.0
151.5
173.0
cal.
10.8
21.5
32.5
43.0
54.0
65.0
76
87.0
98.0
109.0
cal.
11.0
22.5
42.0
52.0
65.5
78.5
92.5
107.0
123.0
138.5
cal.
12.0
24.0
37.0
50.0
63.5
75.0
90.0
103.0
117.5
134.0
150
1200
166.0
1300
1400
1500
1600
1700
1800
PYROMETRY 67
One of the simplest and oldest but also most widely used instru-
ments is the water-pyrometer of C. H. Siemens (Fig. 13). It con-
sists of a copper vessel A holding 568 cu. cm. of water. In order
to reduce the loss by radiation it is surrounded by two vessels,
one being filled with felt, the other being empty. The mercury
thermometer is protected by a perforated metal-shell and has
besides the ordinary scale a movable brass scale c (similar to a
vernier), that ^ves the temperature directly without calculation.
After filling the calorimeter with water the zero mark of the
pyrometer-scale is set upon the temperature of water, as shown
by the mercury thermometer. A hollow copper cylinder of a
certain heat-capacity is now exposed in the medium, the tem-
perature of which is to be measured, and after remaining there
10 to 15 minutes is thrown into the calorimeter-water.
The temperature required is obtained by adding to the tem-
perature read off the pyrometer-scale c, the temperature of the
calorimeter-water. The manipulation of this instrument is there-
fore extremely simple, naturally at the expense of accuracy.
For calculating the temperatures the following data of the
heat capacities of platinum, iron and nickel from degrees to
/ degrees can be used.
CHAPTER III.
PYROMETRY (Conclusion).
Optical Methods of Measuring Temperatures.
The instruments used for this purpose are based upon the
relation between temperature and emission of light from heated
substances.
(a) If a substance is gradually heated up, it starts at a certaui
temperature to emanate light-rays, the brightness of the latter
increasing with the temperature. The color of the emanated
light changes in a definite manner with the temperature. In
many industries, after some practice, the approximate tempera-
ture of a furnace can be estimated with the naked eye without
any instruments, from the brightness of the glowing walls and
the heated substances.
The oldest data relative to the temperature of these so-called
glow-colors were given by Pouillet.
The temperatures of the glow-colors have been determined by
means of a Le Chatelier-Pyrometer, by Maunsel White and F. W.
Taylor, and by Howe. The table on following page contains the
results of these investigations.
The extreme rays of the spectrum show plainly the changes
of brightness and color; but the yellow rays in the center, on
account of their brightness, cover up all the others. The experi-
ment was therefore tried of absorbing the latter by means of blue
cobalt-glass. A glowing substance, viewed with such a glass,
appears at relatively low temperature very red, and at high
temperature strongly blue; thence with this method more
reliable results are obtained than with the naked eye.
(6) The optical pyrometer of Mesur^ and Nouel (Figs. 14, 15)
can be obtained from E. Ducretet in Paris.
The direct observation of the glow-colors is rather difficult
since it depends on individual qualification and momentary dis-
position. The eye can never determine the color shades with
68
PYROMETRY
BÖ
absolute exactness, being only able to estimate by comparison.
In a dark furnace-room the dark red of a melting metal can
easily be taken as bright red, and vice versa in a light room, so
Figs. 14 and 15. — Lunette Pyrom^trique (Pyroacope).
that the result of such observation varies according to observer,
light and time of observation.
TABLE XV.
TEMPERATURES CORRESPONDING TO GLOW COLORS.
Pouillet.
Howe.
White and Taylor.
Heat Color.
Deg.
Cent.
Heat Color.
Deg.
Cent.
470
475
550
to
625
700
850
Heat Color.
Deg.
Cent.
Beginning slow .
Dark red glow . .
Beginning
cherry red.
Cherry red
Bright cherry
red.
Dark yellow ....
525
700
800
900
1000
1100
1200
1300
1400
1500
to
1600
First trace C in dark
of visible <
red ( in daylight
[ Dark red \
Dark red
Dark cherry . .
Cherry red
Bright cherry. .
Orange
Bright orange .
Yellow
Bright yellow..
White glow ...
566
635
Full cherrv red
Bright re({
746
843
899
Bright yellow. . .
White glow
Full yellow ]
Bright vellow
950
to
1000
1050
1150
941
1079
Bright white.. . .
White glow ...
1205
I
Daazling white]
' ■■ :i 1
The object of the pyrometric tube of Mesur^ and Nouel is
the correction of this defect; it allows the determination of the
70 HEAT ENERGY AND FUELS
temperature of a substance by simple observation and enables
us to determine more distinctly the shade of the color.
The apparatus is based upon the phenomenon of circular
polarization and consists mainly of two Nicol-prisms, the polarizer
P and the analyzer A, Between these two prisms is arranged a
quartz-disk Q, 11 mm. thick, split perpendicularly to the main-
axis. At the zero position of the instrument the planes of inci-
dence of the two Nicol-prisms are perpendicular to each other.
The correctness of the position of the prisms can easily be
verified by taking off M, and removing the quartz-disk. Oppo-
site to the eye-piece L at the other end of the tube is the
objective G, consisting of a plane-glass or a well-polished diverg-
ing glass.
The following phenomenon can be observed by looking with
this apparatus towards a source of light. After passing through
the Nicol-prism P the light is polarized. Without a quartz-
plate, I.e. with the second (perpendicular to the first) Nicol-
prism following the first, this polarized Ught would be reflected
by the cut surface of the Nicol-prism, and the field of view would
appear dark. The quartz-plate, however, causes a turning of
the plane of polarization that is proportional (according to Biot's
law) to the thickness of the quartz-plate and approximately
inversely proportional to the wave length of the ray (light).
Thereby certain colors of the spectrum are extinguished by
interference, and a mixed color is observed in the apparatus, de-
pending on the temperature of the luminous body. By turning
the analyzer the mixed color is changed, and whenever the instru-
ment is set upon the same color-shade the temperature of the
substance under observation can be inferred from the position of
the polarizer. For this purpose the analyzer inside the tube is
made so that it can be rotated. For measuring the displacement
angle the instrument has a fixed mark / and is provided with a
scale that can be rotated with the eye-piece and the analyzer.
Since the length of the wave of the emitted Ught varies with the
temperature, by slowly turning the analyzer certain colors that
are changing with the temperature of the luminous body can be
observed. The change from one color to another corresponds to
a certain displacement-angle, varying with the temperature of
the glowing substance.
Hereby we arrive at a position where the color, by the sli^test
PYROMETRY
71
further rotation, changes quickly from blue to red. Between
these two colors is observed a purple- violet shade formed by the
most extreme rays of the spectrum; this shade is character-
istic for measuring the angle of displacement. (Another shade
[lemon-yellow], between green and red, can also be used for this
purpose.) The position of hand / on the graduated arc C gives
the angle from which the temperature is figured.
For determining the scale of temperature Pouillet's data on
glow temperatures and the melting point of silver (954° C.) and
platinum (1775° C.) according to Violle are used.
TABLE XVI.
GLOW TEMPERATURE OF SILVER.
Heat
Color:
Beginning cherry red
Cherry red
Bright cherry red
Orange
Yellow
Bright yellow
Bright white
Dazzling white
Dazzling white
Dazzling white
Sunlight
Displace-
Tempera-
ment.
ture. Cent.
Degrees.
Degrees.
33
800
40
900
46
1000
52
1100
57
1200
62
1300
66
1400
69
1500
71-72
1600
73-74
1700
84
8000
Below are given the results of some measurements with this
instrument:
TABLE XVII.
DATA ON POLARISCOPIC PYROMETERS.
(.4) Measurements by the Author.
Bessemer steel in the pan
Open-hearth furnace, empty
" " " after charging the above steel
** *' " middle of charge
" " " towards end otcharge
Heating furnace
Angle.
Degrees.
59
61.75
59.5
58.5
63.5
50.5
Tempera^
iure. Cent.
Degrees.
. 1260
1290
1275
1245
1340
1050
72 HEAT ENERGY AND FUELS
(B) Measurements of J. Weiler in the Bessemer converter:
Dcg. Cent.
While blowing 1330
At the end 1580
Slag 1580
Steel in pan 1640
Preheated block 1200
Block under hammer 1080
Blast furnace for gray iron :
Beginning of melting zone 1400
Steel crucible furnace 1600
Brick kiln 1100
Heat colors : red heat 525
Cherry 800
Orange 1100
Whit« 1300
Dazzling white 1500
(C) Measurements of Le Chatelier:
Angle.
Deg. Cent.
Sun
Degrees.
84-86
65-70
40-45
8000
Gas-flame
1680
Red glowing platinum
800
To keep out side-light it is of advantage to fasten a protecting
tube in front of the objective. For the determination of low
temperatures a convergent lens is placed before the instrument.
(c) Temperature can also be judged from the proportion of
the intensities of two certain kinds of rays (for instance red and
green) that are emitted from the heated substance.
Table XVIII gives the diflference of the emission- of red,
green and blue rays of different substances compared to a black
substance.
Crova has constructed a pyrometer based upon these data;
however, it requires very great care in manipulation.
(d) Analogously the intensity of a single ray of a certain wave
length can be used for measuring temperature. One would think,
at the first thought, that the intensity depends on the emitting
PYROMETRY
73
capacity of the glowing substance, this capacity varying widely
as is shown by the above figures. Actually, however, with most
substances the variation in the emission is equalized by the
capacity of reflection, which varies in the opposite sense. Fur-
thennore the capacity of emission of most of the substances used
in the industries is not considerable.
TABLE XVIII.
EMISSIVE POWER OF VARIOUS SUBSTANCES.
Magnesia
Magnesia
Lime
Lime
Oxide of chromium
Oxide of chromium
Oxide of thorium . .
Oxide of thorium. . .
Oxide of cerium . . .
Oxide of cerium . . .
Welsbach mixture. ,
Welsbach mixture .
Deg.
Cent.
Red.
Green.
1300
0.10
0.15
1550
0.30
0.35
1200
0.05
0.10
1700
0.60
0.40
1200
1.00
1.00
1700
1.00
1.40
1200
0.50
0.50
1760
0.60
0.50
1200
0.8
1.00
1700
0.9
0.90
1200
0.25
0.40
1700
0.50
0.80
Blue.
0.20
0.40
0.10
0.60
1.00
0.30
0.70
0.35
1.0
0.85
1.0
1.0
The Comu-Le Chatelier optical pyrometer is based upon this
principle (Fig. 16). The instnunent takes the form of a tube,
through which the glowing substance is viewed. A reflector
Fio. 16. — Optical Pyrometer (CJomu-Le Chatelier).
consisting of a glass-plate with parallel faces throws the image
of a small flame into the eye-piece. A red glass in front of the
eye-piece cuts oflf all but certain rays. Absorbing glasses can
be put in front of the objective glass, so that only ^^ of the
74
HEAT ENERGY AND FUELS
incident light is allowed to go through. Between these glasses
and the objective a transparent piece of onyx (Fig. 17) is inserted
by means of which the light can be reduced
at will. The observation is made by
reducing the red light of the glowing sub-
stance, whose temperature is to be deter-
mined, by means of the darkening glasses
and the onyx, until it is equal in brightness
lamp. The apparatus is calibrated by direct
By this method the follow-
Fio. 17. — Piece of Onyx
for Reducing the Light.
to the standard
comparison with an air-pyrometer.
ing intensities of light (red rays ^ = 659) were measured;
TABLE
INTENSITIES
XIX.
OF LIGHT.
Red-glowing coal (600°)
Melting silver (950'')
Stearine candle, gas burner
Piflreon lamo
0.0001
0.015
1
1.1
1.9
2.05
Melting palladium (1550)
Melting platinum
Incandescent lamp
Arc light
4.8
15
40
10000
Arffand burner with glass . .
Welsbach burner
Sunlight (noon)
Melting Fe^O, (1350°) ...
90000
2.25
By this method at first a thermo-element was calibrated, by
means of which the intensity of emission of black ferric oxide
at different temperatures was determined. It was found that
the law for the change of intensity of the red rays with the
temperature can be expressed by the formula :
3210
wherein T is the absolute temperature. The following intensities
(in candlepower) were obtained for different temperatures:
TABLE XX.
LIGHT INTENSITIES FOR VARIOUS TEMPERATURES.
Intensity.
Temperature in Deg.
Cent.
Intensity.
Temperature in Deg.
Cent.
0.00008
600
39.0
1800
0.00073
700
60.0
1900
0.0046
800
93.0
2000
0.020
900
1800
3000
0.078
1000
9700
4000
0.24
1100
28000
5000
0.64
1200
56000
6000
1.63
1300
100000
7000
3.35
1400
150000
8000
6.7
1500
224000
9000
12.9
1600
305000
10000
22.4
1700
PYROMETRY
75
As can be seen from this table the intensities increase rapidly.
Hence, if in the determination of high temperatures an error of
0.1 candlepower is made in the measurement, the error in the
temperature does not amount to more than from 2 to 3° C,
which error can be entirely neglected.
The flame in the furnace must be avoided during the obser-
vation as otherwise incorrect results are obtained. This method
is very good for measuring high temperatures, it is less exact,
however, for low temperatures.
Le Chatelier made the following measurements with this
instrument:
TABLE XXI.
TEMPERATURE DETERMINATIONS (Le Chatelier).
Open-hearth steel furnace
Glass furnace
Porcelain furnace
Porcelain furnace, new
Incandescent lamp
Arc light
Sunlight
Blast Furnace.
At the tuyeres
Pig iron, oeginning
Pig iron, end
Bessemer Process.
r
Slag
Steel flowing into pan
Reheating of ingot
End of forring.
Open-hearÜi steel :
Steel flowing, beginning
Steel flowing, end
Casting into form
Deg. Cent.
1490 to 1580
1375 to 1400
1370
1250
1800
4100
7600
Deg. Cent.
1930
1400
1520
Deg. Cent.
1580
1640
1200
1080
1580
1420
1490
Fery has made some changes in this instrument.
Wanner's optical pyrometer is based upon the same principle.
If we denote the intensity (of light) as /, the length of wave as
76 HEAT ENERGY AND FUELS
k, the absolute temperature as T and two constants as c, and c,,
we have, according to Wien :
c -^
As we have no absolute measure for the intensity, we can only
compare same mth another luminous body; for the latter we
have
c.
-Cj
and therefore
/o"
an equation containing only one constant. This equation is
perfectly correct only for absolutely black bodies, but can also
be used for measuring temperatures in a furnace — on account
of the reflection going in all directions in the interior of the
furnace.
When determining flame temperatures great care has to be
taken. If the flame temperature is the same as that of the
surrounding furnace- walls, this method can be used as it is; if,
however, only glowing gases are present, colored for instance by
sodium, correct furnace temperatures are not obtained except
when the flame allows the rays used in the measurement to pass
unabsorbed. Converter-gases are rather opaque to red (the
color used in the Wanner pyrometer), especially so when many
solid particles are burning in the flame. Hence too low a
temperature will be obtg-ined.
In the optical pyrometer the light is decomposed by a straight
prism, and by means of a small slit nothing but the light corre-
sponding to Frauenhofer's line c is allowed to go through. As,
according to above equation, the measurement of temperature
is based upon the comparison of two luminous substances, a
small electric lamp is used as the standard luminous body. The
lamp is attached to the front of the apparatus, and the light
enters the instrument by means of a comparing-prism, while the
light radiating from the glowing substance, whose temperature
is to be measured, enters directly. The two intensities are
compared by means of two Nicol-prisms, one of which (the
PYROMETRY 77
analyzer) can be turned with the eye-piece. The angle, that can
be read from a circular scale, serves as the measure of intensity,
while the corresponding temperature is read from a table. If a
luminous body is viewed through the apparatus, the field of
view appears divided into two halves of unequal brightness.
The eye-piece is turned until both parts show the same bright-
ness, the angle read and recorded and the temperature found
from the table.
The entire apparatus, whose optical parts are manufactured
by Franz Schmidt and Haenisch in Berlin, is about 30 cm. long,
is shaped like a telescope and is easy to handle. Three storage
batteries furnish the electricity for the little 6-volt lamp. Since
the light-intensity of this lamp depends on the e.m.f. of the
storage batteries, it is necessary to adjust the lamp from time
to time by means of amyl-acetate lamps.
On account of the increasing weakness of light at low tem-
peratures, 900° C. is taken as the lowest working point. The
upper limit can be selected at pleasure.
TABLE XXII.
TEMPERATURE-MEASUREMENTS WITH THE WANNER PYROMETER.
(a) In blast-furnaces.
Slag
Pig iron
Pig iron from mixer
Pig iron flowing into converter .
Steel when turning converter. . .
Slag when turning converter . . .
Slag, flowing out
Pig iron, starting of flow
Pig iron in a prismatic form. . .
Pig iron getting solid
Slag from mixer
Slag from converter
Pig iron from blast furnace
Steel from converter
Iron from cupola
Deg. Cent.
1402
1370
1317
1284
1260
1240
1460
1555
1424
1372
1384
1372-1330
1230
1012
1384
1330
1230
1225
1211
1239
(6) Thomas-process. (Temperature of converter-gases during
charge) 1310*^, 1381°, 1472°, 1310°, 1331°, 1472° and 1494° C.
The temperature of the converter is much higher. The tem-
perature of the slag, three minutes after stopping the blower,
was found to be 1700° C.
78
HEAT ENERGY AND FUELS
(c) Various measurements.
Zirconium in oxygen gas blast 2090® C.
Electric arc light with retort coal 3560-36 W C.
Of other optical pyrometers we mention the apparatus of
Holbom-Kurlbaum and of Morse, in which the intensity of the
electric standard lamp is varied.
The thermo-electric telescope of F6ry (Fig. 18) is based upon
the measurement of the total radiated energy of a glowing
substance.
Fio. 18. — Fury's Thermo-electric Telescope.
The total radiation of energy of a substance according to the
Stefan-Boltzmann law is:
E ^ K{T' - T,').
In this equation E is the energy radiated from a black body at
absolute temperature T® to a body of the temperature T^^ and
/C is a constant. The correctness of this law within the widest
temperature limits was proved by Lummer, Kurlbaum, Pring-
sheim, Paschen and others. The following table ^ves the
observations of Pringsheim and Lummer:
TABLE XXIII.
RADIATION OF ENERGY.
1
Black Body.
2
Absolute
Tempera-
ture Ob-
served.
3
Reduced
Deflection.
4
K 10^0
5
Absolute
Tempera-
ture Gal-
culated.
6
r Ob-
served- r
Calculated.
Boiler (kettle)
373.1
492.5
723.0
745
810
868
1378
1470
1497
1535
156
638
3320
3810
5150
6910
44700
57400
60600
67800
127
124
124.8
126.6
121.6
123.3
124.2
123.1
120.9
122 .^
374.6
492.0
724.3
749.1
806.5
867.1
1379
1468
1488
1531
Degrees.
-1 5
Saltpetre kettle
+ 0.5
Oo
-1 3
Do
Fire brick furnace
Do
-4.1
+ 3.5
+ 0.9
Do
— 1
Do
+ 2
Do
+ 9
Do
+ 4
Avera«:e 123.8
PYROMETRY
79
The temperatures given in column 2 are referred to the tem-
perature-scale of Holbom and Day, in which the thenno-electro-
motive force of the Le Chatelier-element (Pt + Platinum —
Rhodium) is calibrated with a nitrogen-thermometer. Under
column 3 we have the radiant energy of the black body at the
observed temperature, measured bolometrically (and the gal-
vanometer-deflection reduced to the vsame units). The bolometer
temperature was 290° absolute. The following observations of
Lummer and Kurlbaum show the anomalies that have to be
considered with other than black bodies. (See the following
pages.)
The radiant energy of ferric oxide is from 4 to 5 times as great
as that of polished platinum, but nevertheless considerably
smaller than that of a black body. With increasing temperature
however the radiation of non-black bodies increases faster than
that of absolutely black substances.
In Fury's thermo-electric telescope (Fig. 18) the image of the
glowing surface whose temperature is to be measured falls upon
the soldered joint of a copper thermo-element, a galvanometer
being inserted in the circuit of the latter. The solder becomes
heated, and the thermo-e.m.f. generated is measured by the
galvanometer. The image of the glowing surface is thrown upon
the solder by means of the eye-piece 0. The objective F is
made of fluor spar, which absorbs very little of the radiant
energy. Some instruments are made with glass objectives.
TABLE XXIV.
RADIANT ENERGY OF VARIOUS SUBSTANCES.
^ *'
T" - K
T
To
290.5
290
290
290
290
290
290
Black Botly.
Polished Plati-
num.
Ferric Oxide.
372 8
108.9
109.0
108.4
109.9
109.0
110.7 •
492
4.23
5.56
8.14
12.18
16.69
19.64
654
795
1103
1481
1761
33.1
36.6
46.9
64.3
80
HEAT ENERGY AND FUELS
The following table shows the close agreement of results,
determined with different optical pyrometers, used to measure
the temperature of the electric arc light.*
TABLE XXV.
COMPARISON OF PYROMETRICAL MEASUREMENTS.
Observer.
Absolute Tempera-
ture.
Method.
LeChatelier
4370
3870
3600
3700-3900**)
3600-4000
3750-4200
3760««)
Photometry: intensity of
Violle
red light.
Calorimetry : specific heat
Wilson & Gray
of coal.
Total radiation of cupric ox-
Wanner
ide (empirical equation).
(According to the coal used)
F^ry
photometry; Wien's law.
Wave length of maximum
Lummer & Pringsheim . .
F6ry
radiation (Wien 's law).
do
Total radiation; Stefan-
Boltzmann's law.
' Temperature of the black body.
Methods based upon the change of electric resistance. Tem-
perature can also be measured by the change in the electric
resistance of a spiral platinum wire, wound around a rod of fire-
clay and protected from the outside by a clay-vessel (Fig. 19).
UCCCCGCCCCCCCCCCQ
^^^^^^m^
.ss...^x-»»^V
Fig. 19. — Spiral Platinum Wire (protected).
The law governing the relation between resistance and tem-
perature is represented by a parabola. This principle was first
used by Siemens, but soon abandoned in practice as the plati-
num is affected by silicon, phosphorus and the gases of reac-
tion, whereby its resistance is considerably changed.
At first a platinum tube was put around the platinum wire,
which made the apparatus too fragile and too expensive. It
was soon found that a porcelain-tube would do just as well.
The apparatus therefore is very apt to break, and is hardly used
except for very accurate measurements in laboratories.
» Waidner A. Burgess: The temperature of the arc (Phys. Rev. 19, Nr. 4).
PYROStBTRY
81
COMPARISON
TABLE XXVI.
OF PYROMETRICAL MEASUREMENTS. (Flschw.)
Pyrometer of
Mercury Thermom-
eter (QelMlff).
Steinte A Härtung
(Graphite Pyrometer).
Pyrometer).
Fischer (Calori-
meter).
Degrees.
358
Degrees.
361
612
612
266
98
100
99
101
751
837
778
751
744
449
308
290
728
700
260
602
261
101
99.5
102
99.8
103
99.8
103
99.8
843
754
910
862
761
858
848
730
440
511
312
294
304
287
Upon the same principle are based the pyronicterH of Hart-
mann and Braun in Bockenheim-Frankfurt am Main, of Callendar
and others.
The results of some measurements with these instrumcntM
are given in Table XXVII:
TABLE XXVII.
MEASUREMENTS WITH HARTMANN AND BRAUN'S PYROMKTKU.
Df«, (U'tii.
Melting point :
Tin
Bismuth
Cadmium
Lead
Zinc
Zinc
Magnesium. 1% impurities
Antimony
Aluminium, 99.5% Al
Silver
Gold
Copper
K^.
K,SCX soljdifyini^ point
NajSO^ meltinc point
Na^SO« solidifyinc point
Na,CO,. meltinr point
232 rCallcmiar and OriffithN, lf#?y
cock and Nifvill«;)
270 CallemJar and Griffith«,
322 Do.
329 Do,
421 Do
410 Unyctfi'k ami Nuvillu,
«33
Do.
629 F,
Do.
fM h
Do.
wrn
Do,
um
Do
lOM) T,
Do
lOM
Do
UAl
Do.
'4tn
Do
hH%
Do
HfM)
Do
82
HEAT ENERGY AND FUELS
Henri Le Oiatelier^s therrno-electric pyrometer. This instru-
ment is based upon the measurement of the current
produced by heating the soldered joint of a thermo-element.
The solder immediately reaches temperature-equilibrium with
the body or space whose temperature is to be measured, and the
instrument can be set at quite a distance from the place to be
investigated, which is of considerable advantage.
The selection of the metals for the thermo-element is of impor-
tance. Iron or nickel cannot be used, as these metals, when
heated at one point, set up local currents. Generally one wire
is of platinum and the other of platinum containing 10 per cent
of iridium or rhodium.
For measuring the current Le Chatelier uses a Deprez
d'Arsonval aperiodic galvanometer fitted with a mirror and scale,
or a needle-galvanometer, built according to his instructions
by Pellin in Paris. Kaiser and Schmidt in Berlin and Siemens
and Halske use needle-galvanometers.
According to the investigations of H. Le Chatelier the relation
between the electromotive force and the temperature difference
between the soldered joint and the extremity of an element
consisting of platinum and palladium can be expressed by the
equation : y «
e = 4.3 {t - g +
1000
{i' - C).
He found i -t^ = 100° 445° 954° 1060° 1550P
e = 500 2950 10,900 12,200 24,030
By using a thermo-element consisting of platinum and a plat-
alloy, the equation takes a different form.
TABLE XXVIII.
MEASUREMENTS WITH THERMO-ELEMENTS.
Barus.
Le Chatelier.
Holborn and Wien.
Pt-Pt 90 + Ir 10
Pt - Pt 90 + Rh 10
Pt - R 90 +Rh 10
t
e
t
€
t
e
Degrees.
300
500
700
900
1100
2,800
5,250
7,900
10,050
13.800
Degrees.
100
357
445
665
1060
1550
1780
550
2,770
3.630
6,180
10,560
16,100
18,200
Degrees.
100
200
400
600
800
1000
1200
' 1400
1 1600
565
1.260
3,030
4,020
6,970
0,080
11,460
13,860
16.220
PYROMETRY
83
All these observations when plotted show similar curves. For
Le Chatelier's observation we have:
log e = 1.2196 log t + 0.302.
Wherein e is expressed in microvolts.
The best way is to calibrate the instrument by direct observa-
tions. For this purpose the data given in Table XXIX can be
used-
TABLE XXIX.
DATA FOR CALIBRATING PYROMETERS.
Boiling point of water
Boiling point of naphthaline
Melting point of zinc
Boiling point of sulphur
Melting point of aluminium
Melting point of salt
Melting point of silicate of sodium.
Boiling point of zinc
Melting point of silver
Melting point of gold
Melting point of palladium
Melting point of platinum
Deg. Cent.
100
218
420
445
655 (667)
800
883
930
960 (961.5)
1045 (1064)
1500
1780
(The figures in parentheses were determined by Holbom and Wien).
The boiling points of water, naphthaline and sulphur are de-
termined by heating the substances to the boiling point in an in-
sulated glass tube closed at the bottom; then the soldered joint
of the thermo-element is immersed in the vapor. The melting
point of zinc is observed by enclosing the thermo-element in a
porcelain tube (Fig. 20), and immersing it in the molten metal.
I +
Fig. 20. — Thermo-element in Porcelain Tube.
Fio. 21. — Crucible.
When determining the melting point of gold a few milligrams of
gold are placed under the thermo-element, which is put into a
crucible filled with sand (Fig. 21) and heated above 1000 degrees,
84
HEAT EXERGY AND FUELS
at the same time carefully watching the movement of the galvft-
nometer, WTien the gold starts to melt^the galvanometer remains
stationary until all the gold is melted^ when the temperature
continues to rise at a steady rate.
WTien measuring the temperature of öteel-fnma^'es, etc., the
thermo-element niust be enclosed in an iron pipe. For porcelain-
furnaces where temperature measurements are made constAntlyJ
the themio-element, wlüch is protected by a glazed earthenware
pipe, is permanently attached to the furnace but does not extend
into the interior of the furnace* It is heated by a specially
arranged circular receRs»
This instrument is made in Germany by W. C, Heraeus in
Hanau* and by Kaiser and Schmidt in Berlin, as shoi^Ti in Fig. 22
I
Fia, 23, — Holböfo-WiMi Pyrometer*
it is specially con^itructed for indu^itrial use. In the report
the ^* physikalisch-technische Reichsanstalt/' the advantage
the Holbom-Wien nuMÜfication of the Lc Chateher pyrometer ar
PYROMETRY
85
set forth ; the reading of the instrument is so simple that a fairly
intelligent workingman can learn, in a short time, how to use it.
Furthermore the instrument is durable, the accuracy is not
impaired by high temperatures, the reading apparatus can be at
quite a distance from the furnace and one indicating device can
be used for a number of thermo-elements.
The thermo-element consists of a pure platinum wire 0.6 mm.
in diameter and 1500 mm. long, one end of which is melted to-
gether with the end of another wire consisting of an alloy of 10
per cent rhodium and 90 per cent of platinum. The purity of
the metals used is of importance if the same thermo-electromotive
forces are to be obtained. The opposite ends of the wire are con-
nected to a circuit. By heating the solder a small e.m.f. is
generated (about 0.001 volt per 100 degrees temperature differ-
ence between the soldered end and the free end). This e.m.f. is
measured by means of a galvanometer provided with two scales,
one graduated in microvolts, and the other in temperature-
degrees. According to Holbom and Wien, the accuracy of the
instrument at 1000° C. is 5° C.
-JUIQl_S |^_iUUL.
Fia. 23. — Arrangement of Element.
When in use the \^ires of the element must not come in contact
with substances that react with platinum or its alloys. This is
prevented by suitably mounting the instrument in a porcelain-
86
HEAT EX ERG Y A.\D FUELS
tube, which at the same time provides the insulation of the wires.
These porcelain shells can stand temperatures up to 1600 degrees.
Fig. 23 shows how the element is mounted. A hard rubber disk,
having an opening in the center is slid from the bottom over the
outer porcelain-tube. This disk has a recess which fits about the
head B of the porcelain-tube. A layer of asbestos-cord is wound
in between A and B. The upper hard rubber disk is provided
with two small openings, through which the wires of the element
are drawn and a recess for the porcelain insulating tube. The
disk I is permanently connected with disk A by means of three
brass screws. Two binding screws, which serve as terminals, are
attached to C, Asbestos cord is wrapped around the outer
porcelain-tube, the latter being forced into the iron pipe D, D
is provided at the lower end with a removable cap and at the
upper end with a bell E to which the hard rubber-head of the
mounted element is fastened by means of three iron screws.
The temperatures of molten metals, slags, etc., are preferably
determined with floating pyrometers of spheroidal shape.
TABLE XXX.
TEMPERATURE DETERMINATIONS, OPEN-HEARTH STEEL FURNACE.
(Le Chalelier.)
Gas leaving producer
Gas entering regenerator
Gas leaving regenerator
Air leaving regenerator
Flue gases at bottom of flue
Furnace, beginning of puddling
Furnace, end of discharge
Casting-pan, beginning
Casting-pan, end
GLASS FURNACE.
Furnace, during rcflning
Glass, during refining
Glass, during work
Heating of bottles
Rolling plate-glass .,
ILLUMINATING GAS MANUFACTURE
Furnace on top
Furnace on bottom
Retort at end of distillation
Flue-gases
Deg. Gent.
720
400
1200
1000
300
1550
1420
1580
1490
1400
1310
1045
585
600
1190
lOM
975
680
PYROMETRY 87
The Hartmann and Braun pyrometer is based upon the same
principle. The thermo-elements, up to 1000° C, consist of plati-
num and platinum-nickel, up to 1600° C. of platinum and plati-
nimi-rhodium. The nickel element is twice as sensitive as the
rhodium element.
Ceramics.
Burning temperature of hard porcelain 1400° C.
Burning temperature of china porcelain 1275° C.
Burning temperature of bricks 1100° C.
WiborgKs Thermophone (Fig. 24).
This consists of a fire-
clay cylinder, containing
a small copper-cartridge
filled with dynamite. The
thermophone is brought
into the space, whose tem-
perature is to be measured, ^'°' ^^'
and the length of time observed until an explosion takes place
(light detonation). The temperature is then read from a table.
To ascertain the time required for heating the cartridge by
heat-conduction to the explosion-temperature (150° C), Fourier's
equation is used :
y-O = (t^0) 1- ACe-^^di^.
In this equation, t is the outside temperature; j/, the tem-
perature of a point in the interior, at a distance x from the
surface after a time, z, and 0, the original temperature of the
clay-body.
C is the heat conductivity of the substance;
c, the specific heat of the substance;
d, the weight of 1 cu.m. of the substance, in kg., and
z, time in hours;
Xj the distance of the point observed, from surface of test-body,
in meters.
88 HEAT ENERGY AND FUELS
Table XXXI can be used for ascertaining the temperature.
TABLE XXXI.
DATA ON WIBORGH'S THERMOPHONE.
I
II
HI
§
i
£
U
111
i
j
1
is
2
■5
S
\
i
1
^
J
S
1
30Q
3
33.0
46.4
1140
46.2
36.0
44.2
330
3
0.0
2
25,2
, . . .
. , . .
1160
45.6
35 6
....
43. 6
340
2
45 e
2
9.2
1 . * «
1 1 . .
1180
■ . , .
45,2
35,2
43.3
300
29
1
56.8
1200
44 6
35.0
42 8
380
17.0
I
46.8
1220
1 . . .
44.2
34 6
42.4
4O0
6 6
1
3S.6
1
P . .
1240
43.8
....
34.2
■ 1 . .
42.0
430
58.0
1
32.0
....
1260
43.4
33.8
41,6
440
50.6
1
26.2
1280
43.0
■ . . ,
33,4
41.1
460
44.2
I
21.4
1300
42.0
33.2
40. S
m
39.0
1
17.2
....
1320
. . , .
42.2
33.8
....
40 4
5O0
33. S
1
13,4
. . , .
1340
41.8
33.6
40.0
520
30
1
10.2
1300
41.4
32.4
39,6
540
26,4
J
7.4
■ * . .
1380
1 . . ,
41.2
. . , .
32 2
. . . ■
39.2
5^
23.0
1
4.8
■ » - .
1400
. . . .
40.8
....
32.0
38.8
580
20.
1
2.4
, . . .
1420
r . . .
40.4
....
. . • »
38 6
flOO
17.2
1
0.4
. « . .
+ * + ,
1440
....
40 2
38.3
630
14.8
53.0
1450
39.8
38.0
640
12,6
56 6
! '.'.
1480
.. /
39 4
[[[[
37.8
660
10.4
....
55.0
. , . .
. , . .
1500
, . . .
39.2
37.4
680
8.6
53.6
...
1520
....
39.0
, . . .
....
37.2
700
6.8
52.2
. K . .
1540
38.6
....
36.8
720
6.3
50.8
. . . .
. , . .
1560
38.4
....
. . ■ .
36.6
740
3.6
2.2
49.8
18,6
1580
1600
.. ..
38.0
37.8
34.4
760
* > . .
. > . .
36.2
780
1.0
47.6
r , . .
1620
. * . .
37.6
. » . .
36,0
800
59.8
40.6
, . . .
...
1640
. , . .
37.4
. . . ,
35.0
820
5S.4
45.6
1660
lt..
37.0
- t * r
....
35.4
840
5^4
44.8
. * . .
. < . r
1680
. . , .
36,8
....
* * . .
35.3
860
56.4
...
44,0
. » . .
. . . .
1700
. . . .
36,6
. * . .
. » , .
35.0
880
55.4
43.2
. * r .
...
1720
36 4
....
....
34.8
900
54 4
42 6
^ _
1740
. . . .
36.2
. « . .
34.6
920
53.6
41 8
. , . .
. . , .
1780
36.0
. T * .
34.4
940
52.8
41.2
. . . r
17B0
. . . .
35.8
....
* ,. * .
34.2
900
53.0
40.6
1800
. . . .
35.6
. « « .
. ■ T F
34.0
980
51,2
40.0
1900
34.6
33.0
1000
50 6
39.4
. . . .
. . . .
3000
33. S
33,3
lOJO
49^8
3fl!8
2100
33.0
!!!!
. . «4
31,4
lOlD
J031)
40 2
3S 2
220P
2800
32.3
SO. 8
4S 6
4S.0
37. S
37 4
. . . .
...
31 6
. 1 . >
30.3
103:
! !!
2400
!!!'
3LD
!!!!
W,6
1100
47,2
37.0
1110
46.8
36 *
....
44 6
PYROMETRY
86
The
rhoiie has to be kept in a dry place, and when used,
I
1
I'
mist have an initial tniiperature of from IS to 22*^ C,
When tleterniining the temperature in reverbatory- or
niuffle-fuTDaces, stack«, etc, ur in all cases where the themio-
Lphorie rests npon a soli^l ba.se and is sun-ounded by hot ga^ses,
^the time elapt^ing 1x4 ween the insertion of the thernuj phone and
the explosion i?^ rt^a^i and the temperature taken from Table I,
{b) When determining the temperatui'e of Htiuiti metak^ such
Ifiß zinc, leail, copper, silver or gold, an iron pipe^ olo&ed at the
'bottom, 30 mm. inside, 34 to 30 mnrj, outside tliameter, is inserted
in the molten metal; after a few minutes^ when tlie pipe has
|attaine<l the same temperature a.« the metal, the tliemidphone is
ßlid into the pif}e. In this case the temperature is reafl frcjm
Table IL
(e) When meaRuring high temperatures of molten metal and
elag, such a^ iron, j^teel, etc., the thermophone is thnnvn upon
the surface of the meta! and slag, and the temtJeraturc is taken
from Table II L The alx>ve table is made out for = 20° C\
If the air-temptTature differs from this a correction mu;st be made
I according to equation :
t'- 1 =
6-9'
y = im>,
y-f>
d = 20",
(( - y);
re have:
t' -i =
20 ~e'
150 - 20
{t - 150) =
20 -y
130
(t - 150).
If at an ^r temperature of 0' = 30 degrees a temperature of
2000 degrees is found, the correction is
k
f -t =
20 - 30
130
(( - 150) = - 142°,
and the measured temperature is f = 2000 - 142 = 1858° C.
y The results obtained nith the thermophone are very satis-
factory. Contact of the thermophone with basic slags has to be
avoided, since in such cases the explosion takes place too early,
which ^ves too high results.
90
HEAT ENERGY AXD FUELS
TABLE XXXII.
COMPARATIVE DATA ON WIBORGH'S THERMOPHONE.
Temperature-MeAsurements.
Heating furnace
Heating
Open-hearth steel upon acid slag .
upon steel
upon strongly basic slag
Air Pyrometer.
784.5
875.0
Therinophone.
De«. Cent.
772 764
888 878
over 2400
1812
over 2400
In practice automatic registering pyrometers are very useful
as they make a continuous control of the temperature-changes
possible. Because of lack of space they cannot be described in
this book.
Suggestions for Lessons.
Practice in handling various pyrometers;
Adjustment of same;
Determination of melting points, heating and cooling curves;
Comparative temiDerature-measurements with different pyro-
meters.
CHAPTER IV.
COMBUSTION HEAT AND ITS DETERMINATION.
Heat value, fuel value, thermal value, calorific value or ther-
mal eflBciency is the quantity of heat developed from a certain
quantity of fuel in complete combustion. It is generally
expressed in calories.
This quantity is called absolute thermal value, etc., if it is
referred to the unit of weights, specific thermal value, if referred
to the unit of volume.
Pyrometric thermal efficiency is called the temperature that
can theoretically be reached by combustion of the fuel.
We are going to speak first of the absolute thermal value or,
chemically expressed, of the determination of the combustion-
heat, which is generally figured in calories, sometimes however
given in per cents of the thermal value of pure carbon, or as
"evaporating-power," or in comparison with some other fuels,
or as the quantity of lead reduced by 1 g. of fuel.
The expression of the thermal value in calories is easily under-
stood as it means the number of large calories furnished by the
combustion of 1 kg. of fuel. If this quantity is divided by 8080
(the thermal value of 1 kg. of charcoal according to Favre and
Silbermann) the thermal value is obtained, expressed in terms
of the heat- value of pure carbon.
The expression of the thermal value of a fuel by its "evapo-
rating power" was first proposed by Karmarsch. It means the
quantity of water transformed into steam by 1 kg. of fuel and is
obtained by dividing the thermal value expressed in calories
with 652 (the heat-quantity, necessary, according to Regnault,
to transform 1 kg. of water at 0° C. into steam at 150° C).
For certain purposes the thermal value of one fuel is compared
with the value of another fuel, i.e, the fuel quantity equivalent
to the other is ^ven. Generally 1 cubic meter of soft logwood
is taken as unity which has a thermal value of about 900,000 cal.
Table XXXIII will be useful for transformations.
01
92
HEAT EX ERG V AND FUELS
TABLE XXXIII.
THERMAL TRANSFORMATION VALUES.
Thermal Value in
Evaporating Power.
CMbic Meter of Soft
LofTwood.
(Glories.
Referred to 1 Kg. of
Pure Carbon.
1
8080
652
900.000
0.00012376
1
0.080693
111.4
0.0015337
12.39
1
1380
0.000001111
0.00898
0.000724
1
In determining the thermal value account has to be taken of
the quantity of hydrogen present which is oxidized to water.
According as we assume that this water is completely condensed
or completely changeil to steam, we obtain the highest and
lowest calorific values, respectively.
The following methods have been propased for detenmning
the fuel value:
1. Direct determination of the thermal value.
(a) On a small scale, in calorimeters.
(b) On a large scale, in steam-boilers.
2. By meaas of empirical fonnula based on certain chemical
tests.
(a) Calculation of the thermal value from the chemical
composition (elementary analysis).
(6) Calculation of the thermal value from the quantity of
oxygen required for complete combustion (Berthier's method).
(c) Based on simple chemical tests.
(1) Direct determination of the thermal value. These methods
undoubtedly ^ve the best results. Several details have to be
considered; all losses or gains of heat have to be avoided. This
is easier accomplished in small than in large apparatus.
The determination of the thermal value on a small scale, how-
ever, has a disadvantage in that it is very difficult to get a good
average sample small enough to be burned in a small apparatus.
The only apparatus to be recommended are those in which a
single reliable determination can be made simply and quickly,
COMBUSTION HEAT A\D tTS DETERMIN AT lOS
93
.so that a great iiuiiiter of det-enmnations can l>e made on any
one sample \\Tthout difficulty.
We shall consider here only some of the most widely uscfi
calorimeter.
Of the calorimeters in which combustion with oxygen under
atmospheric pressure takes place we shall de^^oribe only the
calorimeter of F. Fischer (Fig. 25).
The oxygon for combustion is letl
(sometime?? after being washed with
caustic potash and dried) througli
the gas pipe a an^l the platinum
pipe r. The latter is fitted loosely
in the cover e of the combustion-
chamlwr -4 (ma^lc of ^5 per cent
silvcrl and reaches into the platinum-
cnicible ^ wliich contains about 1 g.
of the fuel to be tested. The com-
bustion ga^^es esca]>c through the
jjlatinuni-net u and then upwaiils
l^tween crucible and ring V through
«, i and € into the pi|)es r ant I Ik The
platinun>net li, u}Kin which some
soot ia depositetl, finally gets so
hot that the soot is biu'ntxh The
calorinjeter*vessel H, wfiicfi rotitaiiiö
1500 g. of water, is surnmuflal by
a lay(*r of mineral wo<»l (' and the
wooden case I). The twu thermo-
meters t serve for measuriti^ the
teniiwratnre of the en!* >ri meter
water ant) of tin* ewcajMUg gjt^es
reöiK?ctiveIy; nms a stirrer» o|K*nttetl
by m antl the silkHVinl o. By nieans
of a njagnif\ing glass one one-hundretlth of a degree can Ijc
oliserved and recortle*!.
Caiorinietersin which combnfJttion in oxygen takes place under
pressure, as for instance the apparatus of Berthelot, Maliler,
Stohman, etc., are very eonvenient. In all these methods the
combiistinn of the fuel takes ])Iace in a closed chamber, in which
the fuel is enclosed with a sufficient amount of compressed
Fio. 25. — risdior'ij Ca.lijrinu:tLT.
94
HEAT ENERGY AXD FUELS
oxygen. The increase of temperature of a certain mass of water
(calorimeter-water) into which the apparatus is immersed, is
observed and recorded.
The calorimetric bomb of Mahler is illustrated in Fig. 26 and
consists of the following parts: (1) A bomb B made of excel-
lent steel somewhat softer than gun-steel. This steel has an
Fig. 26. — Calorimeter Bomb (Mahler).
absolute strength of 55 kg. per sfj. mm. and 22 per cent elonga-
tion. The quality of the steel was carefully selected on account
of the strength and also on account of the enameling, of which
we ^ill speak later.
The bomb has a capacity of 054 cu. cm. and its walls are 8 mm.
thick. This capacity is much larger than that of Berthelot's
bomb, the object being to obtain an oxygen surplus even when
using a gas not entirely pure. Fuel-gases are also studied with
this bomb. The fuel gases often contain as much as 70 per cent
of inactive substances, which make it necessary to take con-
siderable (luantitics when testing in order to obtain a measurable
increase of temperature in the calorimeter.
The oval shape was selected in order to facilitate the forging
and enameling. The bomb is nickel-plated on the outside, and
coated with enamel on the inside to prevent any bad effects from
nitric acid, which is always formed by combustion. This enamel
takes the place of the platinum-lining in Berthelot's apparatus.
The bomb is closed with a threaded plug packed with sheet
lead. The plug is provided with a taper threaded cock, which
COMBUSTION HEAT AND ITS DETERMINATION 96
serves as inlet for the oxygen and through which is inserted a
well insulated electrode E, which is attached to a platinum
rod F that extends towards the interior. Another platinum
rod, also fastened to the plug, carries a platinum cap for receiving
the fuel to be tested.
(2) The other parts of the apparatus are the calorimeter Z),
the calorimeter-jacket A and the stirrer 5. They differ in details
from Berthelot's apparatus and are less expensive.
The spiral-shapecl stirrer of Berthelot is replaced here by a
simple and easily operated circulation ctevice which allows the
production of a uniform circulation.
(3) We may further mention: the thermometer, which is
divided in yj^j degree, the source of electricity P and a watch or
minute-glass.
(4) Mahler uses oxygen from an oxygen-bomb. Since the
most favorable pressure for burning 1 g. of bituminous coal is
about 25 atm., and since the bombs contain 1200 liters (120
atm.), one of these vessels is sufficient for about 100 determi-
nations. A pressure-gauge (manometer) inserted between the
oxygen-bomb and calorimeter-bomb allows the pressure of the
oxygen to be controlled.
The pressure used with solid and liquid fuels is 25 atm.; with
gases rich in carbon (illuminating gas, etc.) 5 atm., and with
poor gases (producer gas, etc.) 1 atm. To insure the complete
combustion a certain excess of oxygen must be present; too
great an excess, however, would lower the combustion tempera-
ture and thereby cause incomplete combustion.
The two insulated electric conductors which pass through
the plug are connected inside the bomb by a spiral made of
0.1 mm. iron-wire, that extends into the fuel and causes ignition
after the state of incandescence is reached.
The fuel is contained in a small vessel of platinum, which is
connected in the electric circuit. In a \yomh containing 650
cu. cm., 1 g. of fuel is used. Slightly volatile liquids can also be
used directly.
When measuring gases the bomb is evacuated and filled with
gas at certain temperature under pressure, which process is
repeated twice for removing every trace of air.
It is necessary that the calorimeter-water and jacket water be
in temperature-equilibrium with the air of the room. All the
96 HEAT ENERGY AND FUELS
apparatus is allowed to stand in the test room for 24 hours pre-
vious to the test, immersed in a sufficient amount of water. The
apparatus has to be protected from the sun and from draughts,
wluch will cause a variation of temperature.
The constants of the calorimeter are determined by burning
a known quantity of a certain substance of known thermal value,
for instance, 1 g. of naphthaline yielding 0.70 cal.
When making a determination, 1 g. of the powdered fuel is
weighed and put into the small vessel. The powder should not
be too fine, as otherwise it might be carried away by the current
of oxygen. If a fine powder is to be used it is wrapped up in
paper of known weight and known thermal value.
The bomb is closed and the oxygen allowed to enter slowly so
as to avoid blowing away the powder. When the desired pressure
is reached the cock is closed and the bomb cut off from the manom-
eter. The bomb is put into the calorimeter, five minutes being
allowed for equalizing the temperature. The vessel must be held
upright to avoid spilling the powder. The stirrer is moved rap-
idly and continuously for three minutes in order to obtain a uni-
form temperature of the water, and the temperature of the
calorimeter read and recorded.
The fuel is ignited by impressing 10 volts on an iron-wire; the
temperature is read and recorded every minute for six minutes.
The temperature equilibrium of the bomb and calorimeter is
generally perfect after three minutes. The readings during the
next three minutes are used to correct the heat lost by radiation.
It is generally sufficient to add to the increase of temperature
rcconled three minutes after ignition the (tecrease of temperature
observed during the two following minutes. This is not abso-
lutely correct, but sufficiently so for commercial purposes. The
exact corrections give results varying not more than ^i^ from the
correction mentioned.
A second correction relates to the combustion heat of the iron-
wire in oxygen, which amounts to 1.000 cal. per 1 g. iron, and to
the heat liberated by the formation of a small quantity of nitric
acid. The latter quantity has to l^e determined for very accurate
work, but can be neglected in commercial tests, the error amount-
ing to less than -iJ^ and being nearly compensated by the error
in the correction for cooling. 1 g. HNO^ yields by its forma-
tion 0.230 cal.
COMBUSTION HEAT AND ITS DETERMINATION
Example : One g. of naphthaline is used for combustion.
Water-content of calorimeter 2200 g.
Water-valvie of bomb, etc 480 g.
Total
97
2680 g.
Measurements of temperature:
Before Test.
Combustion.
Cooling.
O' 17.52°
r 17.52°
r 17.52°
3' 20.15
4' 21.06
5' 21.11
6' 21.09°
r 21.07°
8' 21.09°
Rise in temperature observed 3.59°
CJorrection for cooling 0.04°
Total ""3.63°
Quantity of heat, 3.63 X 2.68 - 9.728 cal.
Correction for iron, 0.025 X 1.60 ==- 0.040 ca l.
Difference 9.688 cal.
If a correction for the nitric acid formed had been nuuie the
result would have been 9.685 cal.
Mahler found in a lecture, i.e. under condition« which pro-
hibited the attainment of temperature-equiUbrium in the calorim-
eter, 8373 cal. as the fuel-value of a biturninoas coal, whih» in
the laboratory, when taking all precaution.s, he obtained a value
1.3 per cent lower.
If the coal contains con.siderable amounts of sulphur, .same ha«
to be considered. The sulphur is completely oxidizwl to sulphuric
acid and can be determined by well-known metho<ls aftcfrwa^^hing
the bomb with water. The other calori meter- U)mb, in which
combustion is effected with oxygen under pressure?, is arrangwl
in a somewhat similar maimer.
All determinatioas marie in surh apparatas have* two defect«.
They give a thermal value at constant volume while in prarrticc
all combustion takes place at coastant pressure; on the other
hand they pve the .so-calle<l upfx*r thennai value, a« the hygrrj-
scopic water of the coal, and the coal fonnwi by combustion i«
cooled to air-temperature, i.e. condea*^*fl. .s^) that the thennai
value detemained in the bomb inclufles the latent h^mt of eva[x>rar
98
HEAT EX ERG y AND FUELS
tion of the water, which can never be utilizal in firing. To
counteract this last defect Krocker proposes to put the bomb
after combustion into an oil-bath at from 105° to 110° C, and
to absorb the evaporated water in a calcium' chloride appa-
ratus ; finally, to pass dry air through the bomb. Since he use^
very exact corrections for the cooling of the calorimeter, we
give an example of his method.
Temperature of the room 20 degrees.
Water in calorimeter = 2100 g. ) ,^^.
Water value of the apparatus = 340 g. >
Weight of iron- wire and coal-brickette = 1.0959 g.
Weight of iron-wire alone = 0.0187 g.
Weight of coal-brickette alone = 1.0772 g.
Weight of the chloride of calcium apparatus:
(a) Before test 48.2169 g.
(b) After test 48.7605 g.
Weight of total water 0.5436 g.
Weight of water in 0^ 0.0250 g.
Weight of water in coal 0.5186 g. = 48%
TABLE XXXIV.
TEMPERATIR K CH AN( I K .
First Test.
Main
Te.st.
After Test.
Xo.
Heading.
Differ-
ence.
ReudiiiK.
Differ-
ence.
UearJinK.
Differ-
ence.
Note.
T =
17 =
1 =
18.759
19.170
20 530
18 759
r' =
0.002
0.003
0.010
0.009
0.007
0.006
0.003
1
2
18.750
18.753
oo.x
21 . 744
21.742
21.739
21.729
21.720
21.713
21.707
21.704
The coal
was burned
3
18.753 Ö ÖÖÖ
as furnish-
4
5
6
7
8
18.756
18.756
18.757
18.758
18.758
18.759
18.759
0.003
0.000
0.001
0.001
0.000
0.001
0.000
21 240
21 590
21.723
21 749
21 '749
ed without
being made
air dry.
9
Difference 2 990
10
Sum
187.759
n 000
173.798
0.040
1
Aver.
18.756
001
1
21.725 0.005
COM BUST ION HEAT AXD ITS DETERMINATION 99
The temperature of the calorimeter water rose 2.990° C.
For correcting the temperature the formula of Regnault-Stoh-
mami-Pfauneller is used :
Corn = -^—-^^^^ + ^-^ +2; W - nr j- (n - l)v.
V means herein average of temperature-differences of the
preliminary test.
T means herein average of temperature-readings of the pre-
liminary test.
t^,t^. .in means herein the temperature-readings of the main
test.
r' means herein average of temperature-ilifferences of final
test.
/ means herein average of temperature-readings of final test.
n means herein number of readings of main test.
For our example we have :
V -v' = 0.001 + 0.005 = 0.006°
, r" - r = 21.725 - 18.756 = 2.969°
h
9
0.411
9
=
0.(M6°
A
2
n— 1
40.488
2
=
20.244°
^ (t) = 123.002°
1
nr = 7 X 18.756 = 131.292°
(n - 1) V = 6 X 0.001 = 0.006°.
The correction therefore is:
Corr. = ?^ (0.046 + 20.244 + 123.012 - 131.292) - 0.006
2.969
= 0.012°.
Corrected increase of temperature = 2.990 + 0.012 = 3.002°.
Heat generated in calorimeter
3.002 X 2440 = 7324.8 cal.
\{\9\'7
100 HEAT ENERGY AND FUELS
If we deduct herefrom 2.92 cal. (that are developed from
0.0187 g. iron-wire in combustion) we get the thermal value
of the coal:
7324.8 - 29.9
1.0772
= 6772 cal.
For the acids formed Krocker deducts 8 cal. (as average), whereby
the thermal value of the coal becomes :
7324.8 - 29.9 - 8 ^^^, ,
7-;;==^^ = 6764 cal.
1.0772
Altogether 0.5436 g. of water were absorbed by the calcium
chloride. According to previous tests 0.025 g. of same come
from the compressed oxygen, so that for the coal burned we
have 0.5436 - 0.025 g. = 0.5186 g. of water (48 per cent of the
coal burned). The latent heat of evaporation is:
0.48 X 600 = 288 cal.
so that we get as useful thermal value of the coal (lower heat-
value)
6764 - 288 = 6476 cal.
Since the quantity of hygroscopic water in coal varies widely,
only dried coal should be used for the determination of fuel
values. Furthermore since the determination of the water
content of the calorimeter is a tedious operation, it is of advan-
tage to determine the hydrogen content of coal by elementary
analysis.
A calorimeter constructed by S. W. Parr, professor in the State
University at Champaign, 111., for determinating fuel values is
more and more widely used on account of its low cost. This
calorimeter is based upon the same principle as the calorimeter-
bombs, i.e. the combustion takes place in an enclosed space, so
that during the process no gases can enter or escape. The oxygen
is used in solid form and the products of combustion obtcdned
are transformed into solid compounds, therefore combustion
takes place at low pressure, and the expensive bomb is done away
with.
COMBUSTION HEAT AND ITS DETERMINATION 101
Fig. 27 shows the assembled apparatus, Fig. 28 the reaction-
vessel (the cartridge). The calorimeter proper consists of a
nickel-plated copper-vessel Ay which contains somewhat over
2 liters and a vessel C, made of wood fiber and surrounded by
Fig. 27. — Parr Calorimeter.
Fio. 28. — Reaction Vessel (for 27).
another similar vessel, B. The entire apparatus is closed by
the double-cover G, made of one piece. Thereby such an excel-
lent heat-insulation is effected that the maximum temperature
attained in the reaction remains constant for five minutes,
without falling even 0.001''.
The reaction vessel D is a heavy, nickel-plated, brass cylinder
having a cubic content of about 35 cu. cm. ; it is closed at top and
bottom with screw plugs and leather gaskets. The lower plug,
/, rests upon a pivot-step bearing, F, connected to the cylinder
E. The upper plug is provided with a tube H, which extends
through the cover, (7, and carries the pulley, P. The four blades,
Ä, A, are attached to D. If the device is set in motion (by means
of a Raabe-turbine) at sufficiently high speed f 150 rev. per min.)
the calorimeter-water moves in the direction of the arrows and a
perfectly uniform temperature distribution is obt£uned in the
calorimeter.
From Fig. 28, which shows the reaction vessel (cartridge) on
a larger scale it can be seen that the tube H contiuns a small
102 HEAT ENERGY AXD FUELS
tube L which is open at one side and ends at the bottom in a
conical valve K. The latter is kept closed by the spiral spring
M until pressure is applied to A^.
In the cover, G, a hole (8-9 mm. wide) is provided, through
which a thermometer divided at least in ^ degrees, but better in
liu degrees, is suspended. The scale of the thermometer goe,s
from 15 to 26 degrees and is 38 to 40 cm. long. It is of impor-
tance to have the graduated part of the thermometer absolutely
and perfectly cylindrical.
The manipulation of the instrument is as follows: After
putting the double-vessel, CJS, upon a solid table the calorimeter-
vessel, A J is filled outside of the wooden jacket with exactly 2
liters of water (preferably distilled water), care being taken to
keep the outside of A and the inside of C dry. The temperature
of the water should be about 2 degrees below the temperature of
the room. A is now put into the wooden vessel, CJ5, the reaction-
vessel, /), is dried perfectly by slightly heating on the sand-bath,
the lower cover, /, is tightly screwed on and about 10 g. of per-
oxide of sodium (sifted through 1 mm. mesh) put in. Next
0.5 or 1 g. of the fuel and other substances, to be mentioned later,
are introduced into the reaction-vessel, and the cover (whose
valve if it should have gotten wet, has to be dried) put on.
While pressing N upwards, the charge is well shaken, then
lightly tapped to settle the mass on the bottom, the valve K
tried to see if it works easily, hh attached and vessel D inserted
in A, The cover, G, is now put on, also pulley, Ey and the cord
put over the latter, then the thermometer, r, is arranged as shown
in the figure. The stirrer is o[)erated (about 3 minutes) until
the thermometer reading is perfectly constant, the reading
recorded but the motor kept going to the end of the test.
Ignition is effected by means of a glowing piece of iron wire
10 mm. in length and 2.5 mm. in diameter, weighing about
0.4 g. Such a piece can be used frequently until its weight is
considerably less than 0.4 g. At a temperature of 700 degrees
this wire carries 0.4 X 0.12 X 700 = 33.6 cal., which corresponds
to an increase of temperature of 0.016 degrees in the calorimeter.
As readings are made with an exactness of 0.005 degree, correc-
tion is made by subtracting from the temperature recorded 0.015
degree. The iron wire is seized by means of curved tweezers,
heated to red glow in a Bunsen flame, allowed to fall throu^ N
COMBUSTION HEAT AND ITS DETERMINATION 103
into the reaction- vessel; then A^ is pressed down with the tweezers
and quickly released, so that the iron falls out of A' without any
gas escaping at L. A noise is heard for several seconds, and the
temperature rises first rapidly then slowly. After 4 or 5 minutes
the maximum is reached, which remains constant for about 5
minutes, then the reading is recorded. The test now being
finished, the motor is stopped and the apparatus taken apart.
Cylinder, D, is put into a dish filled with warm water, wherein
its contents are dissolved accompanied by the generation of
heat. After neutralizing the solution with hydrochloric acid
it is easily noticed whether unburned particles of coal are
present, in which case the test is unsuccessful. This, however,
happens only with anthracite, when persulphate of potash has
not been added. With bituminous coal an addition of tartaric
acid is sufficient, while with lignite simply double the amount of
coal is used, without the addition of anything. Vessel, /), is
immediately washed and dried.
The water-value of the calorimeter is 123.5 g. (which should
be checked) ; we have therefore, including the calorimeter-water,
2123.5 g. According to numerous tests (with an increase of
temperature = f — t) 73 per cent of the heat generated is from
the combustion proper, 27 per cent from the reaction of the
products of combustion ^ith NajO and NajO, respectively.
If 1 g. of coal has been burned (lignite), 0.73 X 2123.5 (f - t)
= 1550 (<' — t) cal. are generated. We have therefore simply
to deduct 0.015 degree (for the heat introduced with the hot
iron-wire) from the recorded difference of temperatures tf — i
and to multiply the quantity obtained by 1550, to get the
thermal-value of 1 g. of coal.
With bituminous coals, of which 0.5 g. is used, the difference
of temperature recorded would have to be multiplied by 3100.
Previously however 0.85 degree has to be deducted for 0.5 g. of
tartaric acid and 0.4 g. of iron at 700 degrees.
With anthracite the following points have to be observed:
1.0 g. of persulphate and 0.4 g. of iron effect an increase of
temperature of 0.155 degree; on the other hand, 0.5 g. of tartaric
acid and 0.4 g. of iron effect, as we have seen above, an increase
of 0.85. Since only one piece of iron is used for ignition we have
to deduct the corresponding increase of temperature and we
therefore have as correction for 0.5 g. tartaric acid, 1.0 g. of
104
HEAT ENERGY AND FUELS
persulphate and 0.4 g. of iron, 0.85 + 0.155 - 0.015 = 0.99
degree.
If the sodium peroxide is too moist, the results obtained are
too high; in such a case a second test is made with 0.5 g. of
tartaric acid and about 7 g. of sodium peroxide. If now the
temperature of the calorimeter increases more than 0.85 degree,
this has to be considered in the main test by deducting 0.15
degree for every 0.1 degree of observed additional increase.
This correction however can be avoided if the peroxide is kept
in air-tight cans of 50 g. or 100 g. capacity.
Care must be taken not to throw the mixture of coal and
peroxide into water, as otherwise an explosion might take place.
This is also the reason why the interior of the valve has to be
kept absolutely dry.
Parallel tests made by Lunge and Parr with Parr's calorimeter
and Mahler's bomb gave the results shown in Table XXXV.
TABLE XXXV.
TESTS WITH PARR'S CALORIMETER.
Water.
Ash.
Thermal Value.
Differ,
ence.
Kind of Coal.
Mah-
ler.
Parr.
Additions.
Ruhr flaming
coal
2.6
7.1
7685
7688 ) 7fiQ.
7703 \ ^^^^
8075
+ 10
0.600 g. Tartaric acid
Ruhr coal —
1.3
6.6
8059
+ 16
0.5 g. Tartaric acid
1.000 g. Persulphate
Anthracite. . .
1.5
6.7
7981
7967 ) -QQjj
8013 \ ^"""
+ 9
0.600 g. Tartaric acid
Coke
0.6
13.0
6640
^tl\^^^
+ 47
0.500 g. Tartaric acid
Welsh
Anthracite. .
English
Anthracite. .
Belgium
Braisette. .
2.0
2.4
2.4
4.2
4.6
10.7
8049
8365
7409
^378 7394
7409 J '^*'*
-28
-39
-15
0.600 g. Tartaric acid
0.500 g. Tart, acid +
1.000 g. Persulphate
0.500 g. Tartaric acid
Saar coal ....
Cardiff coal..
4.9
2.2
11.7
7.2
6594
7872
6634
7936
+ 40
+ 64
0.500 g. Tartaric acid
0.500g. Tartaric acid
Saar coal ....
3.5
8.4
7146
71Ö1 UlRA
7207 \ 7^^*
^^^* \ 5076
5068 ] ^"^®
+ 38
0.500 g. Tartaric acid
Lignite
Briquette.
15.17
5037
+ 39
No addition but
1.000 g. of coal first
dried then burned
COMBUSTION HEAT AND ITS DETERMINATION 105
T^t-boilers used for determining the thermal value of fuels on
a large scale differ from ordinary boilers; the heat-losses in com-
mon boilers are not suflBciently uniform. Therefore an especially
constructed calorimeter-boiler has to be used (see Muspratt).
It should be kept in mind in all determinations of heating
values that these values vary with the pressure and the tem-
perature at which the combustion takes place. This is of
importance, as we can hereby calculate the thermal efficiency of
a fuel under different conditions, and in commercial work, where
combustion takes place at constant pressure, the figures obtained
in the bomb (constant volume) have to be corrected. These
variations of the combustion heat are based on the well-known
energy principle : the sum of the energy -quantities accumulated
in the interior of a system, when the latter changes from one
state to another, is exclusively dependent on the initial and
final state and independent of the intermediate state. In the
special case where the initial and the final state are alike (cir-
cular process), this sum is equal to naught.
In the following consideration the heat generated by the
system and delivered outside and also the increase of volume of
the system is taken as positive.
Relations between combustion heat at constant volume and at
constant pressure. The combustion heat at constant pressure is
greater than at constant volume. If combustion takes place at
0° C. the difference of the two combustion-heats is, in cal., 0.54
times the contraction of molecular-volume which takes place in
the combustion.
If we bum a gas-mixture at constant pressure we obtain a
heat quantity Q. At first the volume of the gas is increased by
the heat, then it decreases, while cooling off to the starting tem-
perature, to a volume which is smaller than the initial volume.
The difference of volumes corresponds to the contraction effected
by decrease of the number of molecules present during com-
bustion.
If we allow the combustion to take place in a cylinder (closed
at one end, and fitted \\ith an air-tight piHU)n which can move
up and down without friction), we can lift this \mUm after com-
bustion and when the gases have cooled down to the initial
temperature, so that the products of combustion occupy the
ori^nal volume. The work expended thereby is APV.
106 HEAT ENERGY AND FUELS
If, however, the combustion takes place at constant volume,
the heat quantity q is generated. According to the above
explanations we have
g = Q - APV,
or since
we have
«-^"428*
If the system contains n mols we have according to Boyle-Gay-
Lussac's law,
PV = nRT ^n?^T.
If we substitute for
T = 273,
Po = 10,333 kg. per sq. m.,
Y^ = 0.02242 cu. m.,
1033 X 0.02242 X 273
^ ^ 273 X 428
= Q -n 0.5411 cal.
We can obtain the same value much easier by considering that
we have for 1 mol of the gases
^ (Cp - O = 1.982 cal.
and that the gas-equation referred to absolute temperature rests
on the supposition that the gas laws are correct down to absolute
zero and that the gases at this temperature occupy no volume.
We have
q = Q-APY
= Q - M (Cp - O T
1.982 X 273
"■ ^ 1000
= Q - 0.5411 cal. per mol.
we have
COMBUSTION HEAT AND ITS DETERMINATION
107
This equation enables us to transform combustion heats obtained
(in the bomb) with constant volume into combustion heat of
constant pressure. Per mol. of the substance burned we have:
TABLE XXXVI.
Reaction.
H.+ O- H,0
CO + O = CO,
i (Ha + CO) + O - i (ILO + CO,)
CH, + 20, - CO, + 2H,0
J (2C,H, + 50,) - 2C0, + H,0 . . .
Oontrac-
tion
in Mols.
1.5
0.5
1
2
1.5
Combustion Heat
at Constant
Volunje. Pressure.
68.2
67.9
68.0
212.4
314.9
69.0
68.2
68.5
213.5
315.7
All these calculations refer to the case where water is formed
in the combustion (upper heat value). For getting the lower
heat value the latent heat of evaporation of water (10.8 cal. per
mol) has to be deducted.
It follows also from equation pv = RT that wherever 1 mol
of a gas at any pressure, p, is generated or disappears, the
external work pv = RT = 1.982 T cal. will be consumed or
generated. For the average air-temperature of 18° C. this
quantity of work therefore is 1.982 (273 + 18) = 582 cal. In
cases where, as in the bomb, the gases are actually generated or
disappear, this phenomenon is taken into account by the com-
bustion heat, which is measured directly. This, however, is not
the case in Parr's calorimeter, since here no gaseous oxygen is
ori^nally present and since the products of combustion formed
disappear again. The determination of carbon is here not
affected, the formation of COj taking place without change of
volume. It is different with hydrogen, since a contraction
takes place during its combustion, but not in Parr's calorimeter.
Therefore this calorimeter does not give the combustion heat
at constant volume, but at constant pressure, which accounts for
the fact that the results found with Parr's calorimeter are higher
than the results found with the bomb.
The following law can be derived directly from the energy
principle above mentioned :
The heat generated in a direct reaction is the sum of all
heat quantities that are generated, provided that from a given
108 HEAT ENERGY AND FUELS
initial state the final state is reached by various consecutive
reactions.
This law can be used for calculating reaction heats that cannot
be measured directly, for instance, the heat of formation of
carbon-monoxide :
C + 0, = CO, generated q = 94.3 cal.
C + = CO generated 9i = ^ cal.
CO + = CO, generated g, = 68.2 cal.
We have according to our law,
q-qi+ qr
Therefore
9i = 9 - 92
= 94.3 - 68.2 = 26.1 cal.
By this method the heat of formation of all organic compounds
is calculated by deducting from their combustion-heats the heat
of the elementary components, for instance:
C -f H* + 20, = CO, + 2H,0g = 94.3 + 2 X 69.0 - 232.3 cal.
C -f H* = CH* q, - X cal.
CH, 4-2 0, - CO, + 2 H,05, - 213.5 cal.
= 232.3 - 213.5 = 18.8 cal.
Vice versa we can calculate from the heats of formation of
organic compounds (which are found in the thenno-chemical
tables) their heats of combustion, for instance:
C,(Diamond) + H,=C,H* 9 = - 58.1 cal.
2 C, + 2 0, =2 CO, (/,= +188.6 cal.l ^.. ^
H, + = H,0 (Uquid) g, - + 69.0 cal.) ^''^
C,H, 4-5 «2 CO, 4- H^O (Uquid) g,= x
9i=9i + 92-9
= 188.6 4- 69.0 - (- 53.1) = 315.7 cal.
Relations between combustion heal and combustion temr
perature. The combustion heat changes with the temperature.
The change depends on the fact whether the difference of specific
heats of the system before and after combustion is positive or
negative. We will show this by an example:
COMBUSTION HEAT AND ITS DETERMINATION 109
We will calculate the combustion heat of hydrogen at 1000° C,
supposing that the water formed remains in form of steam. We
have then at IS"" C. :
H, + = H,0 (steam) . . . ^^ = + 69.0 - 10.8 = +58.2 cal.
If we bum the hydrogen at 15° C. and heat the steam formed to
1000 degrees, we have:
uooo
J'ViUUU
cctt = 58.2 - 11.0
15
= 47.2 cal.
If we heat hydrogen and oxygen to 1000 degrees and then bum
them at this temperature, we have
J ,100
(c, +c,)dt + q,^ = - (7.5 + 3.7) -f 9,000
15
= - 11.2 + q,^
and from this:
J'»1000
(c " c^-c^)(Ü = 58.4 cal.
15
In this case the difiference is small, in others much greater.
We have, for instance, for CO + O = CO,,
1000
68.2 - 12.4
cdt^
15
= 55.8 cal.
JrtlOOO
(c, -¥c^)(U + g,ooo = ?iooo - 11-1;
15
and therefore
9iooo = 66-9 cal.
If we indicate the heat-capacities of the system in the initial
and final state by c, and c„ we can express this (KirchhofiF's)
law by the general formula:
ft, = ft + (c, + O (t, - 0.
CHAPTER V.
INDIRECT METHODS FOR DETERMINING THE COMBUS-
TION HEAT.
(a) Ccüculaiion of the thermal value from the elemenlary
analysis. The fuels used in the industries are mixtures of
different, not entirely known, chemical compounds. As these
compounds have different thermal values it is evident that the
calculation of the thermal value from the elementary analysis
does not yield exact results. Furthermore the maldng of an
elementary analysis is more complicated and more tedious than
the combustion in a bomb, the difficulty of getting a good average
sample being the same in both cases.
For certain fuels, however, by using the proper empirical
formula a result can be obtained that is sufficiently good for
many practical purposes.
For bituminous coal the following formula is used (Dulong) :
8080C + 34600 (H -JO)
^ iöö '
while for lignite, peat and wood, the formula
8080C + 29633 H, - 637 (W + W^)
^ 100
is used.
In these equations
C is the per cent of carbon ;
H, the per cent of hydrogen ;
O, the per cent of oxygen, and
Hp the per cent of disposable hydrogen (H, = H - J 0).
W means the per cent of chemically combined water (W — J 0).
Wj means the per cent of hygroscopic water.
Note. — Every coal — even dry coal — contains carbon, oxygen and nitro-
gen. It was formerly thought that the with a part of H was present
as chemically combined water. The excess of H was called "disposable
hydrogen."
110
MEt HODS FOR DETERMISISG COMBUSTION HEAT 111
_^080 meanis the combustion heat of carbon (Favre ami Silber-
^^P maim),
34,600 means the combustion heat of hydrogen to water
^p29A^3 meaDß the combustion heat of hydrogen to steam •
|JK37 means the heat of evaporation of water.
If a coal contain« combustible sulphur, üe* sulphur in other
|fürm than sulphate^ some heat in the combustion is also generated
[jy the sulphur which is taken into consideration by adcüng to
the above formula the product of the percentage sulphur S by
Wrf^ cal,
(ft) Berihier'a ttiethod for determining the ikermnl valve*
Berthier's methwi is ba.sed on the determination of the oxygen-
quantity required for the complete combustion of the fuel and
on Welter's law, the incorrectness of w^hich w*afl proven long ago.
This method however is still in use on account of its extraordinary
simplicity. Wetter supposed that, by burning a certain and
constant quantity of oxygen with any other element, always the
same amount of heat w^ould be generated. Tliis however is not
the case, since 1 kg. of oxygen in combination with the following
substances generat-es the following amounts of heat:
^H Carbon to carbon {Uoxide . * 3030 caL
^m Hydrogen to water 4272 cal
^m Hydrogen to steam 4192 cal.
B As Berthier's calculation is based on the quantity of heat
corresponding to the combustion of carbon to carbon dioxide by
means of oxygen, it is evident that the results
will generally be too low and the lower the
more disposable hydrogen is contained in the
fueh Berthier proceetied as follows: 1 g. (of
graphite 0.5 g.) of the finely ground fuel
is weighed exactly and mixed with sifted
litharge, which is free of metallic particles.
The mixture is put into a testr-cup (Fig. 29),
coveretl with from 20 to 25 g. of htharge, care*
fuUy put into a red-hot muffle-furnace, covered
Fio.2i> — iwihiflr-H Ä^J quickly heate<l to red-glow;; in from
Coal Tester. three-fourths to one hour the operation is
led and the litharge according to the fuel quantity reduced,
^xidizing the fuel:
2 PbO + C = 2 Pb + COj.
J^
:^
112 HEAT ENERGY AND FUELS
From the weight of the metallic lead obtained, the quantity of
oxygen combined with the fuel can be calculated. The test-cup
is now removed from the muffle, shaken up several times to
combine the small lead-particles, that may be distributed through
the litharge, with the main lead mass and allowed to cool. The
cup is now broken, the piece of lead brushed clean, and the
litharge examined for particles of lead.
In calculating the thermal value, the hydrogen present is
not taken into consideration, i,e. it is assumed that only the
oxygen has combined with carbon. Since 1 kg. carbon re-
duces about 34 kg. of lead and yields by combustion 8080
cal., the weight of the lead obtained is simply divided by
34 multiplied by 8080 for getting the ateolute thermal
value of the fuel in question. Sulphur would have to be
determined separately and taken into consideration as explained
above.
Various modifications of Berthier's test were recommended.
Forchhammer suggested the use of oxychloride of lead in place
of litharge. Munroe uses instead of the test-cup a gas-pipe
provided with a plug at one end, while Strohmeyer oxidizes the
fuel by means of cupric oxide, treating the residuum with hydro-
chloric acid and ferric chloride and determining the ferrous
chloride formed by titration.
(c) Other empirical methods for determining the fuel value. An
important advance is the empirical formula of Dr. Otto Gmelin,
based upon a few simple operations, which gives very much
better results than Berthier's process.
Gmelin assumed that the coals are mixtures of various chem-
ical compounds, which compounds differ from each other not
only chemically, but also physically. He selected such a phjrsical
property, the ability of retaining hygroscopic water and based
his empirical formula upon this property :
q = [100 - (H3O + "ash^OlSO- C (6H,0),
in which equation Hfi means the hygroscopic water, "ash, " the
ash-content of the fuel in per cent and C a coefficient which
changes with the moisture of the coal and has the following
values :
METHODS FOR DETERMINING COMBUSTION HEAT 113
Hygroscopic water below 3 per cent C=- 4
Hygroscopic water between 3 and 4.5 per cent. . C = + 6
Hygroscopic water between 4.5 and 8.0 per cent C = + 12
Hygroscopicwater between 8.5 and 12.0 per cent C = + 10
Hygroscopic water between 12 and 20 per cent . C = + 8
Hygroscopic water between 20 and 28 per cent . C = + 6
Hygroscopic water over 28 per cent C=+ 4
Seven years later the author tried to utilize more simple
properties that would be more independent of accidental circum-
stances than the moisture, and also be related to the chemical
composition and therefore to the combustion-heat of the fuels.
He selected the behavior of fuels in dry distillation and the
determination of the oxygen required for complete combustion.
He proceeds as follows :
About 1 g. of the finely powdered fuel is weighed in a platinum-
crucible and — after determining the moisture W by drying
at 100° C. — is heated (observing ordinary precautions) until
combustible gases are given ofiF. The loss of weight in per cent
represents the gas-yield G. The residuum P per cent is now
completely burned in the open, inclined crucible whereby the
ash content A and the fixed carbon or coke-carbon K is found.
The latter however always contains negligible quantities of
oxygen, hydrogen and nitrogen.
The quantity of oxygen required S is most conveniently
determined with about 5 g. of fuel by Berthier's method.
The quantity of oxygen required for burning the fixed carbon
is found by the following equation :
The oxygen for completely burning the gaseous products of
distillation is :
The combustion heat of the fixed carbon was (as average)
empirically determined as 7630 cal. per 1 kg. of carbon, while
the combustion heat of the gaseous products of distillation varies
114
HEAT ENERGY AND FUELS
according to the quality of coal and composition of the gases oi
distillation.
The nature of a fuel is indicated by the ratio (weight) of
/C\
gaseous products of distillation and fixed carbon f—j; and even.
more so by the ratio of the oxygen required for the volatiler
matter to the oxygen required for the fixed carbon f ^ j . The^
latter ratio is used empirically for determining the thermal-
value of a fuel by means of the equation :
wherein C is a coefficient, the value of which depends on the
quality of the fuel (wood, peat, lignite, coal) and the ratio ^.
TABLE XXXVII.
RATIO OF Sg TO Sk.
Sg
Sk
Values of C for
Wood and
Pteat.
Lignite.
Bitum.
Coal.
0.25
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
6.00
6.50
7.00
7.50
8.00
5500
4300
3420
3350
3350
3360
3370
5600
3500
3250
3225
3210
3200
3180
3170
3150
3140
3130
3120
3100
3080
3070
3060
3050
4930
4830
4750
4660
4570
4470
4360
4255
4150
4045
3940
3830
3500
3700
3950
In order to make the formula Independent of the kind of fuel
and to base the calculation of the thermal value entirely upon
the content of moisture, ash, gas, fixed carbon and oxygen
required for combustion, the different fuels were divided into
METHODS FOR DETERMINING COMBUSTION HEAT 116
four groups according to their ability to give off gas when dry
and free of ash and the value of C calculated for each of the
groups according to the different values of ~ • The following
table — by means of which the thermal value can be determined
without any knowledge of the quality of the fuel — is easily
understood^
TAÖLE XXXVIII.
DATA FOR DETERMINING THERMAL VALUES.
GROUP
I
11
III
IV
Gas given off
by the Fuel
(dry and
free of ash).
- 33%
33-47.5%
47.5-75%
75- 100%
Sg
Sk
Values of the Coefficient C.
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.54
0.55
0.60
0.70
0.80
0.90
1.00
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
4900
4550
4230
3960
3730
3540
3380
3260
3150
3086
3070
3000
2900
2850
2850
2850
5100
4800
4500
4220
4010
3850
3710
3600
3512
3490
3400
3280
3210
3166
3130
2955
5250
4900
4600
4350
4170
4020
3932
3910
3820
3690
3600
3558
3550
3550
3550
5050
4815
4619
4480
4230
4170
4120
4070
4020
3970
3920
3870
3820
3770
The following empirical formulas have since been proposed :
By G. Arth:
34,500 {H -10) + 8080 C + 21625
9=
100
116 HEAT ENERGY AND FUELS
By E. Goutal (a modification of Jüptner's formula):
q = 8150 C + AM.
M is the quantity of volatile matter, A a coeflScient the value
of which is:
Volatile substances = 2 to 15 per cent A = 13,000
Volatile substances = 15 to 30 per cent A =^ 10,000
Volatile substances = 30 to 35 per cent A = 9500
Volatile substances = 35 to 40 per cent. . . . A = 9000
The international union of the steam-boiler-inspection societies
has adopted the following formula:
g = r8000C + 2900^^/^ -^W 25005 " 600 Tt] j^,
in which W means the quantity of hygroscopic water. The
differences against direct calorimetric determinations are (L. C.
Wolff):
For bituminous coal ± 2 per cent
For lignite ± 5 per cent
For peat ± 8 per cent
For cellulose - 7.9 per cent
For wood ± 12 per cent
By D. Mendeleeff : 5 = 81 C + 300 ^ - 26 (0 - S).
D. de Paepe has substituted for the value M in GoutaFs
... . 100 M
formula the expression 77 •
M + O
Suggestions for Lessons.
Practice in handling various combustion-calorimeters; deter-
mination of water-value and error-limit.
Comparative determination of the combustion heat by different
methods.
Calculation of combustion heat at constant pressure from the
combustion heat at constant volume and vice versa.
Calculation of combustion heats for given combustion tem-
peratures.
CHAPTER VI.
INCOMPLETE COMBUSTION.
The complete combustion of the fuels used in the industries
yields carbon dioxide and water. The chemical composition of
the fuel being known, the quantity of oxygen theoretically
required for complete combustion is easily calculated. This
quantity is called the theoretical quantity of oxygen necessary for
complete combustion. The average composition of dry air, free
of carbon dioxide, being
Oxygen 21 per cent vol.
Nitrogen 79 per cent vol.
23 per cent weight
77 per cent weight
it is a simple matter to calculate the theoretical qtumtity of air
required for complete combustion.
(In many cases it is sufficient to calculate approximately and to assume
the composition of air: 20 per cent vol. O and 80 per cent vol. N.) The
CO, content of the air varies from 0.04 to 0.06 per cent. In densely inhab-
ited buildings it can go as high as 0.5 and even 0.9 per cent vol. The
quantity of moisture in the air varies considerably. Air saturated with
moisture contains per 1 cu.m.
Degrees C
g. H,0.
Degrees C.
g. H,0.
-10
+ 5
+ 10
+ 15
+ 20
2.284
4.871
6.795
9.362
12.746
17.157
+ 25
+ 30
+ 35
+ 40
+ 100
22.848
30.095
39.252
50.700
588.730
The moisture of the air is generally below saturation and above /g ^^^
quantity required for saturation.
In heating tests the moisture of the air has to be determined by means
of a hygrometer or Psychrometer.
In practice, however, this theoretical quantity of air is not
sufficient for complete combustion and therefore an excess of air
has to be used.
117
C +
CA + O4
CÄ + O
118 HEAT ENERGY AND FUELS
The reaßon for this is the difficult and incomplete mixture of
the gases to be burned with the combustion air and the occurrence
of incomplete reactions.
The incomplete combustion can therefore furnish various
products, as follows:
CO, or
iCO, + iC
2 CO, + 2 H„ or
2 CO + 2H,0
CO + CH„ or
CO + C + 2H„or
CjH, + H,0, etc.
The number of different reactions that can take place simul-
taneously and in parallel is frequently very great. The number
of reactions and the quantity of products depend on the pre-
vailing conditions.
In all these cases we speak of a chemical equilibrium which
depends on the so-called equilibrium-conditions. Such condi-
tions are: Temperature, pressure, electric state and the mutual
relation of the elementary components present, i.e. the concen-
tration. By a change of the conditions, the state of equilibrium
is changed as follows (Henry Le Chatelier) :
Any change in an equilibrium factor causes a change in the
system which is directly opposite to the change in the factor.
This law is best explained by an example :
1. Any increase of temperature causes a change, which tends
to decrease the temperature of the system and vice versa.
Example :
(a) Dissociation:
CO, -♦ CO + - 68.2 cal.
H,0 -♦ H, + O - 58.2 cal.
In both reactions heat is absorbed and therefore both are
caused or facilitated by increase of temperature.
The reaction
2 CO -♦ C + CO, + 42.0 cal.
in which heat is liberated, is facilitated by decrease of tem-
perature. Carbon monoxide is therefore more stable at high
INCOMPLETE COMBUSTION 119
than at low temperatures. In the presence of platinumi iron or
especially nickel in fine, spongy form this reaction takeB pluoa
completely at about 300^ C.
(6) Incomplete reactions:
CO, + H, -♦CO + H,0 - lOcal.
CH, + CO -* C,H, + H,0 - 39 cal.
In both reactions absorption of heat takes place; they are
therefore caused and facilitated by increase of tciniKsrature.
At low temperature more CO, + H„ or CH^ + CO; at high
temperature more CO + H,0 or C,H, + H,0, will be present.
The reaction
CO + H,0 -> CO, + H,0 + 10 cal.
will naturally be facilitated by lowering the temperature.
2. Any increase of outside pressure causes a change of equi-
librium, by which the pressure is decreased and vice verm.
Examples:
(a) Dissociation:
2C0, ->2C0 + 0,
2H,0->2H, -hO,.
By the dissociation of CO, or H,0 the volume, or (at coniitont
volimoe) the pressure is increased 50 per cent The dimomüim
will therefore increase with decreaidng pressure and (kereeme
with increasing pressure.
(b) Incomplete reacticMis:
The vohime of boM OLihfm, midch hi exr;^iri|^y muäl, tmnA
not be considered. TIm; volume, Yttrnt^t^ <tn at i*ßHi0^Jiuia
vcrfume the presRnej.of Ukt CH^ UmttfA hi fmly laiU ^A i\0tyfAm$m
of the mgiDal mixture of C^ a/jri H^ IV f*3ji/rti/>ri i* iJ^0^^
explosion in doeed vesdb, ifhtrttßy iht tfmutiiy *A Cif ^ mA C
in crcLMca mitfa the pragaw?.
Tbe exfSBonsBSk
is Qf tiie «alcr if m Uxm ^A t^Mu^, \sjA^!H^%jA^xA ^A tJ«; ynmmt^,
120 HEAT ENERGY AND FUELS
The reaction
2C0 = C + CO,
is decreased by decreasing the pressure because the volume and
therefore also the pressure of CO, is only half that of 2 CO.
3. Any increase in concentration of a substance in a system
causes a change in the state of equilibrium, in which a certain
quantity of this substance is removed and vice versa (mass-
action). The quantitative expression for the relations between
chemical equilibrium and equilibrium-conditions is different if
the equilibrium at a certain temperature or the equilibrium at
any temperature is considered. In the first case, i.e. for the
isothermic equilibrium, the law of mass-action; in the second,
general case, van't Hoff's or Le Chatelier's equation has to be
applied.
For gas-mixtures the latter equation is preferable as the
numerical concentration results directly from the volumetric
composition of the gases.
We want to consider now an example of great importance in
the industries.
Dissociation of Carbon Dioxide.
At high temperature carbon dioxide is decomposed according
to the equation :
CO,^CO + HO,).
Le Chateüer's equation in general form is:
I /^^ + (iV'' - ATO / P + 2 n,Z C3 - X^,l C, = constant.
In this equation Qj^ stands for the total heat of reaction (sum
of heat generated and external work performed by the reaction,
both expressed in cal.) at the temperature T, P is the pressure
of the system, N'' and N' the number of molecules on the right
and left side of the equation, n^ and n^ the number of molecules,
C^ and Cj the concentrations of the different substances taking
part in the reaction, index 1 meaning the initial system, and 2 the
final system.
INCOMPLETE COMBUSTION 121
If we use the common instead of the natural logarithms and
if we make ~ = 500, we can write our equation :
JtC
500 J^^ + 2.3026 (AT"- N') log P + 2.3026 (Xn, log C,
— 2)n, log CA = constant.
N" - AT' = 1.5 - 1 =0.5,
therefore
S»,log C,-2n, log C. = log X = log ^^4£^'.
If we make the total concentration of the system after the
establishment of equilibrium = 1, we have
C^ + C,, + 0, = 1. (1)
Assuming that no surplus-oxygen is present, we conclude
from the reaction equation :
Co. = iC«,. (2)
We call X the ratio between the dissociated carbon dioxide,
(i.e. the carbon monoxide formed) and the quantity of CO,
that would be present if no dissociation had taken place, i.e.
Ceo + Cco^, the coefficient of dissociation, and we have
X = - ^"- • (3)
There can be deduced from (1) and (2) the following equations :
and therefore
— >
i-iCco + c^ i-ic«
122 HEAT ENERGY AND FUELS
from this
or
and
" X 2 + x "^ 2 + X
2x 2 (1 - x)
"^ (2 + x) (2 + x)
By substituting these three values, we have
^ ^ (Coo.) (l-x)(2 + x)»
For finding the constant the following observations of Henry
Sainte-Claire-Deville are used :
P = 1 at.
T = 3000 + 273 = 3273.
X = 0.40.
If we assume (in accordance with Le Chatelier) the total heat
of reaction of the reaction CO + O — > CO2 to be independent of
temperature, and taking Q = 68.2 cal., we have
SOo/ ^^yf^ + 11513 log P + 2.3026 log
X'
4
(1 - x) (2 + X)*
= Constant;
or as for P = 1 at., log P = 0.
therefore
-34100
+ 1.1513 log P + 2.3026 log X = - 11.7194,
or
log K = m9- 11.7192 - 1.1513 log p)-l—^l^
* \ T * 7 2.3026 7
- 5.0895 - 0.5 log P.
INCOMPLETE COMBUSTION
123
From this Le Chatelier has calculated the values of z given in
Table XXXIX.
TABLE XXXIX.
COEFFICIENTS OF DISSOCIATION.
(Le Chatelier).
Pressure in Atmospheres.
Temperature
Decrees C.
0.001
0.01
0. 1
1
10
100
1000
0.007
0.003
0.0013
0.0006
0.0003
0.00015
1500
0.07
0.035
0.017
0.008
0.004
0.002
2000
0.40
0.125
0.08
0.04
0.03
0.025
2500
0.81
0.60
0.40
0.19
0.09
0.04
3000
0.94
0.80
0.60
0.40
0.21
0.10
3500
0.96
0.85
0.70
0.53
0.32
0.15
4000
0.97
0.90
0.80
63
0.45
0.25
The results of these calculations agree with the observations
made at 1500° C. on the density of carbon dioxide.
If we keep in mind that it is the partial pressure of carbon
dioxide that is dealt with here, we can make from the above
table the following conclusions, which are of importance in
practice:
1. Smelting furnaces. In smelting furnaces the maximum
temperature reached is 2000° C, and the maximum partial
pressure of carbon dioxide is about 0.2 at. There is therefore
about 5 per cent of the latter dissociated, which decreases the
capacity of the furnace to a small extent (maximum yV, but
generally much less on account of the excess of air used, which
diminishes the dissociation of carbon dioxide).
2. lUuminaling flames. The luminous fiame-zone, in which
the separated carbon is burned, seems to have in ordinary
flames a temperature of about 2000° C. ; in regenerative-burners
the temperature is higher. On account of the high percentage
of hydrogen in illuminants, the CO2 — partial — pressure falls
below 0.1 at. Therefore the dissociation can go above 10 per
cent, the flame-temperature decreasing accordingly. The illu-
minating power, which increases much faster than the temper-
ature, decreases to a much larger extent, which shows that the
dissociation is an important factor in illuminating flames.
124 HEAT ENERGY AND FUELS
3. Explosives, Their combustion-temperature is in most
cases below 2500° C. and always below 3000° C. As the pressure
of carbon dioxide herein goes into thousands of atmospheres,
the dissociation does not have to be considered.
On account of the very high pressures, in using the equili-
brium equations for explosives, the law of Boyle-Gay-Lussac
(PV = nRT) must not be used ; it is necessary to introduce into
the equation a constant b :
P (F - 6) = nRT,
Similar conditions prevail in the dissociation of water. As
we have seen above, we have (if no excess of oxygen is present) :
— 2 X X
Ceo = irT~~ ' quantity of oxygen =
X X
and
"» 2-h X 2 -hx
- 2 (1 ~ X) _ 2 (1 - X)
"^ 2-\-x 2 4- X
Sum =
2 -f X
If we have (n + 1) times the quantity of oxygen, the equation
for the reaction reads as follows :
CO^ + (n) O^^CO + {n + J) 0,
and we have, after the equilibrium has been established,
x' mols CO
(1 - xf) mols CO,
f — + n j mols Oj
X
]£ = 1 + - + w mob
INCOMPLETE COMBUSTION 125
and therefore
C ^ 2x^
* ,^a/^ 2 + x' + 2n
1+2 + »
— + n
■^ a:' . 2 + x' + 2n
l + -+n
^ ^ 1-x' 2 (1 - 0/)
, , x* , 2 + a/ + 2n
l + 2- + n
Therefore
2j[f / xf + 2n \i
2jf / 3f + 2n Y
(CJ (CJ* 2 + j/ + 2n b + x^ + 2n/
(Co,) ^1 - ^)
V2 + a/ + 2n/
2 + x' + 2n
a/ + 2 n \»
a/» + i' (2 n)»
1 - a:* (1 - a^) (2 + x' + 2 n)*
As K necessarily has the same value as in the former case,
we can say:
X« x^« + x^ (2 n)* ^
(1 - x) (2 + x)* ~ (1 - x') (2 + x' + 2 n)* '
If we had used twice the theoretical amount of oxygen, n
would have been equal to one (n = 1) and we would have
3* x" + x' v/2 x'« + x' v/2
(1 - X) (2 + X)» (1 - x') (2 + x' + 2)» (1 - X') (4 + x')*
^ x^«.+ 1.4142 x^
~ (1 - x') (4 + x')» ■
126 HEAT ENERGY AND FUELS
We found (see above) x = 0.05 for CO, at 2000° C. and 0.2 at
partial pressure. Substituting this value, we get:
0.95(2.05)"* " ""^^^^ " (l-:c')(4 + x')*'
an equation from which jf can easily be calculated. We see at
a glance that x' is smaller than z.
CHAPTER VII.
COMBUSTION-TEMPERATURE.
The maximum temperature that a fuel could produce if
burned completely, without any loss of heat, with the theoretical
quantity of air, we call pyrometric heating-effect. It is gener-
ally calculated from the equation :
2äcp
wherein q stands for the quantity of heat generated by com-
bustion, and c and p for the specific heat and the quantity of
components contained in^the products of combustion respec-
tively. This temperature however can never be attained in
practice.
The temperatures of industrial fires and fire-places depend on :
1. The quantity of heat furnished by the fuel, which consists of
(a) The heat of combustion proper and
(6) The heat previously stored, i.e. the heat-content of
the substances used.
2. The heat carried away by the products of combustion
which may be latent (for instance, CO leaving a blast-furnace).
3. The heat lost by radiation.
4. The heat getnerated or absorbed by the substances to be
treated.
5. The quantity of heat used for forming and expanding the
gases generated in the fire.
There is a relation between all these quantities, which can be
deduced from the principle of conservation of energy.
Proceeding from the fuel, air and substances to be worked, in
the first stage, the sum of all heat-quantities introduced into or
generated in the fire, is independent of the order in which the
transformations take place, depending only on the first and last
stage.
127
128 HEAT ENERGY AND FUELS
We therefore can say that the quantity of heat introduced
into the furnace is equal to the quantity taken out of the furnace.
The heat introduced into or generated in the furnace equals
the heat taken from the furnace.
These quantities of heat consist of:
1. Heat introduced into the furnace by fuel, air and sub-
stances to be worked (by their own temperature).
2. Heat of combustion.
3. Heat of reaction of the substances to be worked.
4. Heat content of the combustion gases.
5. Heat content of the finished products.
0. Loss of heat by radiation.
Since the absolute heat-content of the substances as they
enter or as they leave the furnace cannot be determined, we have
to be satisfied with a relative detennination generally referred
to a certain normal condition, which serves as a base for the cal-
culations. As such the temperature of melting ice is generally
used.
Let us imagine an ideal furnace which perfectly insulates the
heat and in which no working products are present. If we
introduce into this furnace fuel and air of a certain temperature
(say 0°C.), allow combustion of same and then cool the com-
bustion gases to the initial temperature (0°C.), we have the
equation :
Heat of combustion = Heat of cooling.
A. The heat of combustion is a known quantity. The heat
of cooling is the difference of the heat-content of the combustion
products at the temperature at which they leave the furnace
and at the starting temperature (here 0° C), to which we imagine
them cooled again in the end. In our ideal furnace, the heats
of combustion and of cooling are equal. The products of com-
bustion leave the furnace at the combustion temperature, which,
as we will see, is easily calculated.
The heat content is equal to the weight of the combustion prod-
ucts multiplied by their specific heat and their temperature. If
we use the absolute temperature, we obtain the total heat con-
tent; if we use the temperature in centigrade we obtain the heat-
quantity, by which the substance in question is richer than at
COMBUSTION ^TEMPERA TÜRE
129
In calculating the pyrometric heating effect, formerly the'
specific heat was taken as constant, i,e. independent of tem-
perature. The following are the figures used :
TABLE XL.
SPECIFIC HEAT OF GASES AND VAPORS AT CONSTANT PRESSURE
(Refored to Unit Weight.)
Name.
Air
Air
Oxygen
Nitrogen
Hydrogen
Carbon monoxide
Carbon monoxide
Carbon dioxide .
Carbon dioxide . .
Water Vapor
Methane
Ethylene
Interval
of Tem-
Specific
Observer.
|)erature.
Heat.
Degrees.
0—100
0.23741
Rögnault
0—200
23751
ti
13—207
0.21751
(<
0—200
0.2438
*'
12—198
3.4090
<<
23— 99
0.2425
Wieiiemann
26—198
0.2426
(<
15—100
0.20246
R^^gnault
11—214
0.21692
•(
128—217
0.48051
((
18—208
0.59295
«<
24-100
0.3880
Wiedemann
By means of these figures the teinf)erature of combustion of
carbon in pure oxygen is calculated as follows:
i =
v8080
= 10201° C*
3.667 X 0.217
The combustion of coal in the theoretical amount of air should
give:
i =
8080
= 2719° Ct
3.667 X 0.217 -f 8.929 X 0.244
while the combustion of carbon with double the volume of air
would yield %
8080
3.667 X 0.217 + 8.929 X 0.244 -h 11.596 X 0.238
8080
t =
0.792 -f 2.179 -f 2.760
= 1410° C.
♦ By the combustion of 1 kg. carbon to CO, 8080 cal. are generated;
3.667 kg. CO, are thereby formed, having a specific heat of 0.217.
t 8.929 kg. nitrogen are present in the air of combustion besides 2.667 kg.
oxygen.
{ 11.596 kg. is the weight of the surplus air.
180
HEAT ENERGY AND FUELS
TABLE XLI.
COMBUSTION DATA ON VARIOUS UNITS.
•
Combus-
tion Heat
inCal.
Combustion Temperature in
Degrees C.
Combustion of
With Pure
Oxygen.
With the
necessary
air Volume.
With
double the
air Volume.
fTvHroi?en to stGam .
Of 1 unit
(weight)
28780
8080
2400
3600
2750
6860
Of 1 Liter
6.0
Of 1 Moi.
191930
313200
68370
125930
773400
1
Degrees
6670
10201
Degrees
2665
2719
1400
2500
1900
2400
2530
2440
2750
3040
2860
2790
Degrees
Carbon (amorphous) to carbon
dioxide
1410
Carbon (amorphous) to carbon
monoxide
Wood dried at 120^
1300
Wood ordinary with 20 per cent
hygroscopic water
Coke
HOC
1340
Illuminatincr eras
7500
7160
8620
7180
6940
Methane CH^ to C(X and H,0
Ethylene C^ H, to CO, and H^O
Carbon monoxide CO to CO«.
Water gas CO -f H, to CO, 4- H^O
Benzole CeH« to CO^ and 0,0 . .
If the combustion of fuel and air takes place at any other
temperature than degrees, proper allowances must be made.
If we had to burn, for instance, 1 kg. of hydrogen of 50® C. with
exactly the theoretical amount of dry air of 20° C, the quantity
of heat available after combustion is figured as follows:
1 kg. of hydrogen of 50° C. contains 1 X 3.409
X 50
8 kg. of oxygen of 20° C. contain 8 x 0.217
X20
26.64 kg. of nitrogen (which are present in the
combustion-air besides the oxygen) of
20 degrees contain 26.64 X 0.244 X 20. .
Sum of the heat supplied before combustion . . = 270.33 cal.
The combustion of 1 kg. of hydrogen to steam
yields 28,780.00 caL
Heat quantity available after combustion .... = 29,050.33 cal.
= 170.45 cal.
34.88 cal.
65.00 cal.
COMBUSTION-TEMPERA TÜRE 181
On the other hand the heat capacity of the combustion pro-
ducts is :
Steam (1 + 8) X 0.4805 = 4.325 cal.
Nitrogen 26.64 X 0.244 = 6.500 cal .
Total 10.825 cal.
The temperature of combustion therefore is :
29,050.33
' " 10.825 - ^^ ^-
If the temperature of hydrogen and air before combustion
had been 0°C., the temperature of combustion (according to
Table XLI) would have been 2665 degrees. The heating of
the hydrogen to 50 degrees and of the air to 20 degrees therefore
increases the temperature of combustion by 2683 - 2665 = 18° C.
The results of these methods of calculation are too high, as
the specific heat of substances increases considerably with the
temperature. The law governing the relations of sf)ecific heat
and temperature (for gases) can be expressed according to Le
Chatelier by one of the general equations
Cp = 6.5 -h aT
or C, = 4.5 + aT.
Cp and Cv stand for the average specific heat of 1 gram-
molecule at constant pressure or constant volume respectively,
T is the absolute temperature, a has the following values for
different gases :
for 2 atomic gases (H,, N^, O^, CO) a = O.OOWi
for CO, a = 0.0037
for H,0 a = 0.(X)2(^
for C^. a = 0.0068
The total heat content of a gas at the temperature T ^ CpXT
or C„ X T and the difference of the heat content of a gas between
r and To is Cp {T - T^) and C. (T - To) respectively.
For simplifying the calculation the following table gives the
values of Cp {T - T.), also the difference (C^ - C,) (T - T.)
= il X P (F - Fo) = nAR (T - To), i.e. the external work
acooiding to H. Le Chatelier.
132
HEAT ENERGY AND FUELS
TABLE XLII.
DATA ON EXTERNAL WORK.
Tempereiure ° C*
200
1.4
L8
1.9
o.i
.00
«00
800
1000
1200
1400
10OU
CO,N,,0,.H,
ILO
cA
Work
AR(T — T^>)
2.8
3.7
OB
4 3
...
5.8
li
i.e
7*
11,0
12. A
2.0
»0
u.o
15.5
2.4
10 7
17.0
19 2
2.8
12. B
20.3
23.1
3 2
TeinfjHiitiire ^ V,
ISOO
2000
2:200
2400
2600
3800
300t^
CO,N„0,.H
U.2
16.0
17 3
19 1
2t.O
22.9
24 8
cT:
24
28.3
32.5
36. S
415
46,4
513
27.3
32.0
38 2
43.7
49 6
55 4
61.7
Work
AR<T
-T„)
3 fi
4
4 4
4.8
5 2
5.6
6.0
Example: Calculation of the combustion heat of hydrogen
in air. Pure dry air contains in 100 mols.
20.8 0, -f 79.2 N^, or about
20 Oj + 80 N^, or about 4 mols. A^ for every mol. 0.
The combustion of hydrogen with the theoretical amount of
air therefore corresponds to the equation:
H,+i (0,) + 2 iV, = Hfi -f 2 N,,
In this equation we have at constant pressure a combustion heat
of 58.2 cal. = 58,200 cal. for every mol. of burned hydrogen.
The products of combustion consist of 1 mol. steam (HjO) and
1 mol. nitrogen. Since the combustion heat is equal to the
cooling heat, we have :
58,200 = 6.5 {T - To) -f 0.0029 {r - To') + 2 [6.5 {T - To)
+ 0.0006 {r - To')] = 19.5 {T - To) + 0.0041 (^ - To").
If To = 0° C. and x the temperature (in ® C.) to be found, we
have
To = 273 and T = 273 + x and
58,200 = 19.5 X + 0.0041 (546 x + x').
COMBUSTION-TEMPERA TÜRE
183
This is a qua(^lratic equation the solution of which is not at
all difficult, but most conveniently obtained by graphical con-
struction. We know that the combustion-temperature is in
the neighborhood of 2000° C. Calculating the cooling heats for
temperatures in this neighborhood we have, using Table XLI :
1800°
2000° C.
2200° C.
2400° c.
ELO
24.0
28.4
28.3
32.0
32.5
34.6
36 8
is,.:
38 2
Total..
52.4
60.3
67.1
75
The combustion temperature in question therefore must be
between 1800 and 2000° C. By taking the cooling-heats as ordi-
nates and the temperatures as abscissas we obtain the curve
shown in Fig. 30. By marking on the ordinate-axis the heat-
jp^ff»
SflOO'P
Fio. 30. — Diagram for Combustion Temperatures.
generation (58.2 cal.) drawing from here a horizontal line to its
intersection with the curve, and a vertical line through the
intersection point, we see that the vertical line intersects the
axis of temperature at a point corresponding to the required
combustion-temperature (1960° C). An analogous calculation
is applied if the combustion takes place at constant volume (for
instance, in Mahler's bomb). The combustion heat at constant
volume (taking the water as steam) is 58 calories. The heat
134
HEAT ENERGY AND FUELS
necessary for heating is obtained by deducting the external
work 3 Aß (r - T,):
1800°
2000°
2200°
2400°
Heat reauired at constant pressure
Gxtemal work
52.4
10.8
60.3
12.0
67.1
13.2
75.0
14.4
DiflFerence
41.6
48.3
53.9
60.6
From Fig. 31 we see that the combustion-temperature is 2320° C.
In this calculation the dissociation is not considered; therefore
•^c
58-
.-^
^
606
^
53d
^
^3
^^b
40-
1£
00»
^0
00-
U
«•
.0-*^
M*
Fig. 31 . — Diagram for Combustion Temperatures.
the calculated temperatures are slightly too high. The dis-
sociation however can be taken into consideration by inserting
in the temperature equation the coefficient of dissociation as a
function of the temperature. Generally, however, a different
method is pursued.
As an example we will discuss the combustion of carbon
monoxide. Calculating the combustion-temperature without
considering the dissociation, we find as the result 2100® C. We
know from the preceding chapter that the coefficient of dissocia-
tion of carbon dioxide at this temperature and at a partial
pressure of 0.20 atm. is 0.06. The heat-generation resulting
from combustion therefore is 68 (1 - 0.06) «- 64 cal.
COMBUSTION-TEMPERATURE
186
In calculating the cooling-heat of the combustion-products
we have to take 0.06 less CO, (the amount dissociated at this
temperature), and we have to add 0.06 CO + 0.03 0„ whereby
the heat required for heating is decreased by
0.06 (33.8 - 1.5 X 16.6) = 0.6 X 8.9 = 5.34 eal.
The heat of combustion is therefore 2050 instead of
2100^0.
Analogous calculations show the following values for the
combustion-temperature of different gases with air containing
20 per cent of oxygen at an initial temperature of 0° C, without
considering the dissociation:
TABLE XLIII.
COMBUSTION-TEMPERATURE OF VARIOUS GASES.
a::.::::.::::::::
HCO+H,)
CO, to CO, + 2H,0
CH, to CO + 2H,0.
2320*» C
2430*» C
2370** C
2150° C
1860° C
By comparing these with the previously calculated tempera-
tures of combustion (which were obtained by assuming the
specific heats to be constant) the excess of the latter can be noted.
(ÜOMBUSTION-TEMPERATURE OF SOLID SUBSTANCES.
The same method of calculation can be applied to the com-
bustion of solid substances as carbon, coals, etc. We suppose
again the air to contain 20 per cent volume of oxygen. For sim-
plifying the calculation such quantities of the solid fuel are used
that the volmne of the gases of combustion (reduced to 0° C. and
760 mm. pressure) is 22.42 liters, i.e. corresponds to a moL,
because the volumetric composition of the combustion gases
then shows directly the number of mols of the different gas-
constituents present.
136
HEAT ES ERG Y AXD FUELS
We will now coasider the combustion heat of * amorphous
carbon, which differs from that of diamond or graphite.
12 g. diamond yields 94.3 cal.
12 g. graphite yields 94.8 cal.
12 g. amorph, carbon yields 97.6 cal.
According to the equation
C 4-0, 4-4N, = C0, +4N,;
the composition of the combustion gases is :
COj 20 per cent volume
Nj 80 per cent volume
In order to obtain a molecular volume (22.42 liters) of com- ^
bustion-gases 0.2 gram-atoms of carbon must be burned, whieb^
yields by the combustion :
Q = 0.20 X 97.6 = 19.5 cal.
The heating of the combustion-products requires :
2000° C.
2200° C.
For CO,
6.40
12.80
7.64
For 4Na
13.84
Total
19.20
21.48
The combustion-temperature in question therefore is 2026° C.
Actually, however, not only CO, is formed by the combustion,
but also, according to circumstances, either free oxygen (dis-
sociation), or carbon monoxide or steam (from hygroscopic
water). Accordingly we get the following results:
Combustion of Amorphous Coal.
Theoretically, if CO, Ls formed exclusively. . . 2026° C.
With 5 per cent oxygen 1950° C.
With 5 per cent carbon monoxide 1930° C.
Theoretically, with 25 g. of water per 1 kg.
carbon 1950° C.
Combustion to carbon monoxide 1250° C.
COMBUSTION-TEMPERA TÜRE 187
COÄiBüSTION-TEMPERATURE OF A NATURAL COAL.
The combustion-temperature of a natural coal is figured by a
similar method. As an example we take bituminous coal of
Commentry showing the following composition :
C 75.2 per cent
H 5.2 per cent
8.2 per cent
N 1.0 per cent
Hygrosc. H,0 3.4 per cent
Ash 7.0 per cent
Total 100.0 per cent
The composition of the combustion gases is calculated as
follows:
CO, = 752 : 12 = 62.7 (1)
H,0 hygroscopic - 34 : 18 = 1.9 ^ ^7 ^ .ox
from coal = 52 : 2 = 26.0 J "^ ^ ^
N: By the combustion there are formed:
CO, with 62.7
H,0 with 13.0
Total 75.7
From the coal 2.5
Difference 73.2
This 73.2 corresponds to
4X73.2= 292.8N)
N from coal 10 : 28 = 0.4 NJ ^"^"^ ^^^
Total from (1), (2), (3) 383.8 volume.
The volumetric composition of the combustion-gases therefore
is:
1 00 V ß2 7
CO, OQOQ = 16-34 per cent voL
„ _, 100 X 27.9 ^ ^ ^ ,
H,0 — gggg 7.27 per cent vol.
„ 100X293.3 _,„ ^ ,
N — =» 76.39 per cent vol.
Total 100.00 per cent vol.
138
HEAT ENERGY AXD FUELS
From this we can figure the heat of the combustion gases:
1800° C. 2000° C.
2200° C
17.053 19.508
21.820
The combustion heat is
Q = 19.888 cal.
and the combustion-temperature 2034° C.
Combustion-temperature of Producer Gas.
As we shall see later there are frequently used in the industrie^-^
gaseous fuels, which allow a better utilization of heat. Th^^
ideal composition of such a producer gas is :
CO + 2 N^.
Theoretically, this gas requires for combustion
H0,)+2N,
and yields
CO, + 4 N,.
The combustion of CO + J (O,) + 4 N, gives 68 cal.
If the gas is heated before combustion to 1000° C, 5.5 X 7.3
= 40 cal. are required. The total amount of heat, therefore, on
which the calculation of the combustion-temperature has to be
ba^sed is 68 + 40 = 108 cal.
TABLE XLIV.
HEAT OF THE COMBUSTION PRODUCTS
2000**.
2200** C.
2400* C.
CO,
4N,
32.0
64.0
38.2
69.2
43.7
76.4
Total
96.0
107.4
120.1
Combustion-temperature = 2220° C.
, The same gas gives under different conditions :
Theoretically, cold ISOO"" 0!^; cold, 5 per cent 1210° C.
Gas + air 500° 1860° C. ; cold, 5 per cent CO 1320° C.
Gas +air, 1000° 2220° C.
COMBUSTION-TEMPERATURE 139
The air used for the production of producer gas always contains
varying quantities of water vapor or steam, which is decom-
posed by coming in contact with glowing coal, so that the gas
contains less nitrogen. With an average content of 250 g. of
water per kilogram of coal, the gas obtained contains per gram-
atom of carbon:
CO + i (H,) + i (N,).
The combustion-temperature of this gas is :
Gas + air: cold . 1550° C.
Gas + air: 500° 1930° C.
Gas + air: 1000° 2230° C.
In practice however the composition of producer gas differs
from the above, since it always contains some COj and Kfi and
also (if bituminous coal or lignite is used) gaseous hydrocarbons.
As an example the following analysis of such a gas is given
(referred to 1 mol. of gas mixture) :
CO 0.20 vol.
H, 0.10 vol.
CO, 0.05 vol.
Bfi 0.02 vol.
N 0.63 vol .
Total 1.00 vol.
The combustion of this gas yields :
TABLE XLV.
COMBUSTION OF PRODUCER GAS.
Combustion Products.
Combustion Heat.
CO. 0.25
H,0 0.12
Nj 1.23
13.6 cal.
5.8 cal.
19.4 cal.
Total 1.60
The calculation shows the following combustion-temperature:
Gas and air: cold 1350°C.
Gas and air: 1000° 2150° C.
140 HEAT ENERGY AND FUELS
Suggestions for Lessons.
Calculation of the combustion-temperature of a fuel of known
composition and combustion heat, using different quantities of
combustion air, at diflferent temperatures of fuel and air.
Calculation of the combustion-temperature if the composition
of the combustion gases (at different temperature of fuel and air)
is given, besides the composition and the thermal value of the
fuel.
CHAPTER VIII.
FUELS. (IN GENERAL.)
We call "fuel" any substance which combines with oxygen
accompanied by the generation of heat and therefore can be
used in practice as a source of power.
Under the term "fuel" in the widest sense of the word we
include solids and liquids containing carbon (wood, peat, coal,
coke, oil, tar, alcohol, etc.) and gases containing carbon or hydro-
gen (iUuminating gas, natural gas, producer gas, water gas, etc.)
and also various other substances, the oxidation of which is used
in the industries as a source of heat. Some of the latter sub-
stances are:
Sulphur, which is used in southern Italy for smelting crude
sulphur (the reason being that no other fuel can be obtained
as cheaply).
Sulphides (FeS,) are used as fuel in the roasting of ore. In
the Bessemer process the silicon of the crude iron (acid process)
or the phosphorous (basic process) is used as fuel.
TABLE XLVI.
CLASSIFICATION OF FUELS.
Kind of Fuel.
a) Natural.
b) Artificial.
A. Solid
Wood, peat, lignite, bi-
tum, coal, anthracite.
Oil
Charcoal, coke, (bri-
quettes).
Tar. tar oil. alcohol, etc.
B. Liquid
C. Gaseous
Natural gas
Illuminating gas, pro-
ducer gas, water ffas,
Dowson gas, blast
furnace gas, acetylene,
etc.
141
142
HEAT ENERGY AND FUELS
Lately Goldschmidt has introduced aluminium as a fuel (ther-
mit). A mixture of fine-grained aluminium and certain oxides
(FejO,, etc.), when ignited, continues to bum and generates
considerable heat: Fe203 + 2 Al = A\fi^ + 2 Fe. This process
is used for the reduction of metals, preparation of metals and
alloys, free of carbon, generation of high temperatures for weld-
ing, melting, casting, etc.
In this work we will treat only the first two groups given
above, which are commonly called fuels in the true sense of the
word.
A. Solid Fuels.
(a) Natural Solid Fuels, Wood, Peat, Lignite, Coal and
Anthracite.
All these fuels contain:
1. Ash, which remains after combustion.
2. Hygroscopic water, sometimes called moisture.
3. A substance containing the combustibles and consisting
mainly of carbon and variable quantities of hydrogen, oxygen and
nitrogen. The composition of this substance free of water and
ash is as follows for the different fuels:
TABLE XLVII.
COMPOSITION OF FUELS.
Fuel.
Composition of the Sub-
stance (free of Water and
Ash).
Ther-
mal
Value.
O&l.
Coke.
Volar
tile
Mat-
c%
H%
0+N%
tere.
%
Wood
51
58
70
80—84
84—88
86—90
90-93
95
6
6
5
5.5
5
5-4.5
4.5-3.6
2
43
36
25
12—10
9-10
7—5.5
5.5—4.5
3
4700
5900
6500
8200
8600
8700
8600
8200
non-coking . . .
Peat
non-coking . . .
non-coking . . .
badly coking. .
coking
coking
badly coking .
non coking. . .
70
Lignite
50
Bitum. coal:
lean, long flam-
ing
35—40
fat, long flaming
fat, short flam-
ing
30-35
1ft— 23
lean, short flam-
ing
ft— 14
Anthracite
3
The ash content varies from about 5 per cent to 15 per cent.
The amount of hygroscopic water depends on the humidity of
FUELS 143
the atmosphere, and the nature and porosity of the fuel; it
generally increases in direct proportion with the volatile matter.
C!oke forms an exception as it sometimes contains considerable
water, which however is not hygroscopic but was introduced by
the manufacturing process (coohng of the hot coke with water).
The coking of fuels by heating is of great practical importance,
preventing small-size coal from falling through the grate bars.
Small-sized lean coal is troublesome to bum on a grate. On
the other hand coking too much may cause trouble, as thereby
a considerable amount pf coal is prevented from burning up and
the grate cannot be properly cleaned.
Some lean fuels have the property of disintegrating in heat
and falling through the grate before being burned up.
The natural solid fuels are of great importance for the indus-
tries on account of their low cost. They can be classified in
(a) Vegetable fuels : wood.
(/?) Fossile fuels: peat, lignite, coal and anthracite.
(6) Artificial Solid Fuels.
For certain purposes it is of advantage to use fuels richer in
carbon than the ones occurring in nature. This is done by
subjecting the natural solid fuels to dry distillation, whereby
the following products of decomposition are formed :
1. Gases.
2. Tar.
3. Tar-water.
4. Carbonaceous residuum.
The relative quantity of these substancas depends on the
nature of the substance from which it originated, and the tem-
perature of distillation. With increasing temperature the quan-
tity of gas is increased, but the content of heavy hydrocarbons
and therefore the illuminating power decreased.
The advantages of the coked fuel are :
1. A fuel of higher thermal value :
(a) The content of carbon of the coked fuel being higher than
that of the raw fuel.
(6) The gaseous products of distillation requiring a great
amount of heat for their gasification in using crude
fuel.
144 HEAT ENERGY AND FUELS
Thereby the cost of transportation per heat unit is decreased.
2. Coked fuel bums without smoke.
3. Coked fuel does not cake or form clinkers.
4. The sulphur content of the raw fuel is decreased by coking.
5. Valuable by-products are furnished by the coking process.
On the other hand we have to consider the following disadvan-
tages of coking.
1. The coking entails a certain expense due to heat, fuel,
wages and machinery.
2. Coked fuel never bums with a long flame, which is essential
in certsun cases.
3. Coking increases the ash content.
According to the raw material used the coked products are
called:
(a) Charcoal.
(6) Peat coal.
(c) Coke.
(d) Briquettes.
CHAPTER DC.
WOOD.
The industrial importance of wood as fuel is not very great.
It is, however, used to a large extent for building and con-
struction purposes which makes a detailed discussion desirable.
According to the trees from which the woods originate they
may be classified as:
(a) Leaved woods: maple, birch, beech, oak, alder, ash,
linden, poplar, elm, willow, etc.
(6) Coniferous woods: red pine, pine, larch, fir.
TABLE XLVIII.
CLASSinCATION OF WOODS ACCORDING TO SPECTHC GRAVITY.
Hard Woods.
Soft Woods.
Speci6c Gravity (air dry]
>0.55
Specific Gravity (air dry) < 0.55
Specific Gravity (green)
>0.90
Speciac Gravity (green)
< 0.90
Beech
= 0.77
Silver fir
= 0.48
Oak
= 0.71
Red pine
- 0.47
Ash
= 0.67
Fir
- 0.55
Maple
- 0.64
Larch
- 0.47
Elm
- 0.57
Linden
- 0.44
Birch
- 0.55
Willow
-0.48
Alder
= 0.54
Trembling poplar
Poplar
Black poplar
- 0.43
= 0.39
« 0.39
The specific gravity of wood is somewhat variable : it is greater
the slower the growth of the tree, i.e., the dryer the soil. Some-
times the following classification is used.
1. Hard woods (leaved woods only) : oak, beech, white beech,
ash, maple, birch, etc.
2. Soft woods (soft leaved woods) : chestnut, linden, trem-
bling poplar, willow, etc.
3. Coniferous woods : fir, silver fir, etc.
146
146
HEAT ENERGY AND FUELS
The specific gravities given above include the pores of the
wood. Excluding the pores these figures are considerably
higher (Rumford). See Table XLIX.
TABLE XLIX.
SPECIFIC GRAVITY OF WOOD SUBSTANCE.
Wood.
Oak .
Beech .
Elm . .
Poplar
Specific
Gravity.
1.5344
1.5284
1.5186
1.4854
Wood.
Birch.
Linden
Fir ... .
Maple .
Specific
Gravity.
1.4848
1.4846
1.4612
1.4599
The following figures relative to specific gravity of woods will
be of interest:
TABLE L.
SPECIFIC GRAVITY OF VARIOUS WOODS.
Bri»-
8on.
HartiR.
Wemek.
Winkler.
Kind of Tree.
Green.
Seasoned.
Well
Seasoned.
Well
Seasoned.
Muschen-
brock.
Scarlet oak
1.0754
0.9822
0.9476
0.9250
0.9121
0.9036
0.9036
0.9012
0.8993
0.8941
0.8699
0.8633
0.8614
0.8571
0.8170
0.7795
0.7654
0.7634
0.7155
0.7075
0.5907
0.5474
0.4735
0.5502
0.6592
0.6440
0.5550
0.4716
0.5910
0.5749
0.5001
0.4390
0.3656
0.4302
0.3931
0.4302
0.3931
0.5289
0.6441
0.5452
0.5788
0.663
0.560
0.518
0.441
0.485
0.618
0.619
0.598
0.552
0.493
0.434
0.549
929
Beech
0.85
0.67
852
Elm
0.600
Larch
Pine
0.4205
0.5779
0.6337
0.5699
Maple
0.75
0.84
755
Ash
734
Birch
Service
Fir
0.55
0.4303
0.3838
550
Red Dine
Mealy pear
874
Chestnut
Alder
0.80
0.60
0.443
0.431
0.346
0.418
800
Linden
0.3480
604
Black DODlar
383
Aspen
Italian poplar
0.4402
Sallow
0.501
Pomegranate
Ebony
1.35
1.33
1.32
0.94
0.92
0.91
0.89
0.80
Dutch box
Medlar
Olive
French box
Spanish mulberry.
Spanish yew ......
WOOD 147
Another classification of woods is baseil on the following
properties:
The youngest wood of a tree trunk is called sai)-w()()(l. It
contains more sap and is lighter in color than the older wood.
In some trees the older wood hardly changes (maple, bin^h,
white beech, etc.); in some the sap-wood is darker and dryer
(linden, red pine, fir tree, etc.) ; in some trees a darker, dryer
and stronger wood is formed in the course of time, which is callcHl
heart-wood (ebony, walnut, larch, fir, etc.).
The weight of wood piles is of more imi)()rtan(re than the
specific gravity. The net cubic contents of a wocmI pilcj in the
volume of wood substance including the pores. Its weight in
kilograms is 1000 times the specific gravity of the» wockI. I'he
gross cubic contents of a pile depends uiK)n the» (U^nnity of the
pile and the moisture of the wood. Furthennore, the dennlty
depends upon the shape and form of the piecres of W(mm1 (cord
wood, stove wood and brush wood). Tin» moisture deereiiH<^
with the length of time the wood is stored, down to from 12 to
13 per cent. The actual contents of the w(khI pile is the vohini«
of wood substance in a certain volume c>f woo<J pile.
TABLE LI.
ACTUAL CX)XTEXT IX PER CENT OF UtyVyJlKSt WfPOtfH
Kind or Wood, 1 ***"» 1**-*^ h^'*
Cord wood of leaved wood. loirw<Mj'J ^ti^i hilWi wt^^i i
of coniferous trees. fftrocMT. «fTi/x/tb »ryl ütfMJir^it. T4 I 77 ! 7^
Cord wood of leared aiyJ (i:^ßUifer*ß*iti i/f*MfU, wt'i^k, \ I
smooth and strmiicbt ^^ , -,, -^
Cord wood of eooi/erciu% w/^^lit. ietf//fi|r «#W vn-nk, r i* 1 9
knottT and eroolud
Stove wood of leavad w*ßu4. iixnm$:, tefft^MAlt kirnif^ti,
Cord wood of ie^r^ w^mA. kXr*ßh$i ^Hfi w*r»fe, kit^My ,
and crooked | ^.. ^.. ^*
Stove wood of lear^ lucad ^mii^f^P^u ^^mA. *Utm¥ J
and weak. wa0j0Äkx TtiA ktMAty. t-^nt^ttr^fi mA I
crooked . . )
Brushwood frw» truxik. *y^itif^*/^j^ w<^y| fA ^'4 W
Br ush wood from trvjük. k:»v«fd wv/^ C^ (^ ^^
Br ush wood frvai brkbeHU?» *>i/Uii*^'^'^ ¥i'yA . in^ (/% t^
Brushwood frwBb l/noW«^ Urus*A ^^yA i a., a^ am
Rootwood 'leav^ ^aA ^nxiWi*rjM h^a-, ' *^ * *^
148
HEAT ENERGY AND FUELS
TABLE LII.
WEIGHTS OF WOOD IN PILES.
(Woods cut In winter.)
Green.
Seasoned.
Cordwood.
Stove-
wood.
Brush.
Cord wood.
Stove-
wood.
Brush.
Kind of Tree.
Bark.
Heart-
wood.
Bark.
Heart-
wood.
Weight in Kilogramm of 1 Solid Cubic Meter.
Red pine
Pine
892
950
717
690
881
937
929
937
968
955
1019
926
869
457
554
445
503
334
551
624
469
703
696
762
511
516
L&rcli
Silver fir
Oak
741
790
923
878
903
930
1045
986
781
548
687
669
734
702
Red beech
673
HornbeftfP - ^
780
Birch
978
734
712
Linden
484
Maple
979
717
Norway maple
1051
933
741
797
Chemical Composition.
Wood is composed chemically of (1) fiber and (2) sap.
The wood fiber consists mainly of cellulose CeH^^O, (C, 44.44
per cent; H, 6.17 per cent; 0, 49.39 per cent). Besides ceUulose
we find other organic matter, both nitrogenous and non-nitroge-
nous, which are generally caUed ''incrustating materials. " They
increase towards the center and cause the dark color.
The analyses given in Table LIII show the variations in the
composition of diflferent woods dry and free of ash: (H. Che-
vandier).
TABLE LIII.
COMPOSITION OF DIFFERENT WOODS.
Kind of Tree.
Maple .
Oak .
Pine . . .
Willow
c
Per cent.
49.80
50.64
49.94
51.75
H
Per cent.
6.31
6.03
6.25
6.19
OandN
Per cent.
43.89
42.05 1.28
43.81
41.08 0.98
WOOD
149
The average composition therefore \s\
C 49.2
H 6.1
and N 44.7
The sap is a solution of various organic (protein, tannic acid,
vegetable acids, starch, sugar, essential oils, resins) and inorganic
substances in water.
Considering the use of wood as fuel, only the content of resin,
water and ash has to be considered.
With increasing content of resin, the thermal value increases.
In order to determine the resin content Hampel treated
Austrian woods with 90 per cent alcohol. Table LIV gives the
per cents dissolved.
TABLE LIV.
RESIN CONTENT OF WOODS.
Kind of Tree.
Taxus baccata L. (yew)
Abies excelsa D. C. (fir)
Larix europsea D. C. (larch)
Pinus silvestris L. (pine)
Acer pseudoplatanus L. (maple).
Fraxinus excelsior L. (ash)
Fagus silvaticus L. (red beech) . .
Betula alba L. (birch)
Per cent.
7.514
2.734
1.807
1.744
1.69
1.47
1.44
1.167
The ash content of various woods may be taken from Table
LV.
TABLE LV.
ASH CONTENT OF VARIOUS WOODS.
Fresh
Wood.
Old
Wood.
Trunk
Wood.
Branch
Wood.
Brush
Wood.
Pine
Oak
Pitch pine . .
Birch . . . .
0.12
0.15
0.15
0.25
0.15
0.11
0.15
0.30
Oak
Beech
Aspen
Willow....
1.94
0.73
1.49
2.94
1.49
1.54
2.38
3.66
1.32
0.72
The ash content depends largely on the ash content of the
soil. The moisture changes with the seasons, is the lowest in
winter and the highest in spring. It also changes with the
different trees.
150
HEAT ENERGY AND FUELS
Kind of Tree.
Carpinus betulus
Salix caprea
Acer pseudoplatanus
Sorbus aucuparia. . .
Fraxinus excelsior . .
Betula alba
Quercus robur
Pinus silvestris
Pinus larix
H,0
£nglbli
Per cent.
Name.
18.6
Hornbeam
26.0
Sallow
27.0
Maple
28.3
Service
28.7
Ash
30.8
Birch
34.7
Oak
39.7
Pine
48.6
Larch
TABLE LVI.
MOISTURE IN VARIOUS WOODS.
Kind of Tree.
Hornbeam (Carpinus betulus) . .
Sallow (Salix caprea)
Maple (Acer pseudoplatanus) . .
Service tree (Sorbus aucuparia)
Ash (Fraxinus excelsior)
Birch (Betula alba)
Oak (Quercus robur)
Pine (Pinus silvestris, L.)
Larch (Pinus larix)
Water
Content.
18.6
26.0
27.0
28.3
28.7
30.8
34.7
39.7
48.6
The researches of Vrolle (Table LVII) show how great are the
variations in the ash content, for instance, in the case of the
cherry tree.
TABLE LVn.
ASH CONTENT OF VARIOUS PARTS OF A CHERRY TREE.
Part of Tree.
C
Pter cent.
H
Per cent.
O + N
Per cent.
ABh
Percent.
Leaves
Upper point of branch, bark.
Upper point of branch, wood
Middle part of branch, bark.
Middle part of branch, wood.
Lower part of branch, bark . .
Lower part of branch, wood .
Trunk, bark
Trunk, wood
Upper part of root, bark. . . .
Upper part of root, wood . . .
Middle part of root, bark —
Middle part of root, wood . . .
Lower part of root
45.015
52.496
48.359
48. 855
49.902
46.871
48.003
46.267
48.925
49.085
49.324
50.367
47.399
45.063
6.971
7.312
6.605
6.342
6.607
5.570
6.472
5.930
6.460
6.024
6.286
6.069
6.259
5.036
40.910
36.637
44.730
41.121
43.356
44.656
45.170
44.755
44.319
48.761
44.108
41.920
46.126
43.503
7.118
3.454
0.301
3.682
0.134
2.903
0.354
2.657
0.296
1.129
0.231
1.643
0.223
5.007
WOOD
151
Henneberg's researches show how the ash content depends on
the soil. Table LVIII shows the composition of beech wood
aäh:
TABLE LVIII.
ASH ANALYSES.
Oomponents.
Carbonate of potash . .
Carbonate of soda
Sulphate of potash —
Chloride of sodium
Soluble salts
Carbonate of lime
Magnesia
Phosphates
Silicic acid
Insoluble components .
Kind of Soil.
Limestone.
Per cent.
6.7)
11.0 J
4.4
.0.7
22.8
27.4
17.7
15.6
16.9
77.6
Gypsum.
Par cent.
14.6
3.4
trace
18.0
30.9
12.2
9.7
28.7
81.5
Sandstone.
Per cent.
(4.7
\ 3.2
23.3
5.0
36.2
21.1
12.4
10.9
18.4
61.0
For metallurgical purposes the quantity of phosphorus in wood
is of interest. R. Akerman and Sarnstroni found that:
1. Leaved wood contains from 4 to 5 times as much phos-
phorus as coniferous trees.
2. The quantity of phosphorus in the same kind of wood
varies 100 per cent according to the country of ori^n.
3. Fir wood cut in winter contains more phosphorus than
when cut in spring or summer.
4. The trunk contains the least, branches, twigs and especially
the bark contain the most.
5. The phosphorus of sap-wood can to a large extent easily be
washed out.
The moisture of wood depends considerably on the season
(Schuebler) :
Kind of Tree.
Percentage of Water.
End of January.
Beginning of
April.
Aflh
Maple
Horse chestnut.
Fir tree
Fresh ash
Red pine (root)
28.8
33.6
40.2
52.7
28-29
52
38.6
40.3
47.1
61.6
38-39
61
162
HEAT ENERGY AND FUELS
The moisture varies in the different parts of the trees. It is
higher in the outer parts than in the inner parts, higher in the
branches than in the trunk. It also depends on the soil and
climatic conditions.
Air drying reduces the moisture after two summers to about
20 per cent, in very dry summers to from 15 to 16 per cent.
For drying wood more perfectly higher temperatures have to
be applied. Woods exposed for two years to 125° C. and 225° C.
lost water as shown in Table LIX. (Violette) :
TABLE LIX.
DATA ON THE SEASONING OF WOOD.
Temperature.
100 Parts of Wood give off Water.
Oak.
Ash.
Elm.
Walnut.
125*» C
150*» C
175*»C
200*» C
225*» C
15.26
17.93
32.13
35.80
44.31
14.78
16.19
21.22
27.51
33.38
15.32
17.02
36.94
33.38
40.56
15.55
17.43
21.00
41.77
36.56
At 200° C. dry distillation begins. Wood dried at higher
temperature readily absorbs water. Wood (shavings) dried at
136® C. absorbed in 24 hours in winter from 17 to 19 per cent, in
summer from 6 to 9 per cent water.
By drying, the volume is decreased; by moistening, increased.
TABLE LX.
THERMAL VALUE OF VARIOUS WOODS (per kg.).
KlQdofWood.
Pb reduced
by 1 Part of
Wood.
Calories.
Specific
Qravity.
Air-dried wood (20% water).
Dried wood (10% water) . . . .
White beech, air dried
Oak, air dried
Maple, air dried
Pine, air dried
Willow, air dried
Linden, air dried
Birch, air dried
Fir tree, air dried
12.5
14.05
14.16
13.27
13.10
14.48
14.08
13.86
3600
4100
3100
2400—3000
3600
3400— 4000
0.770
0.708
0.645
0.550
0.487
t).439
0.627
0.481
The heat of combustion of cellulose per kilogram is as follows,
(if the water formed appears in liquid form) for:
WOOD
158
Purified cotton 4200 cal.
From paper 4188.1 cal.
From ammoniacal solution of cupric oxide 4174.1 cal.
Purified with bromine water and ammonia . 4191.9 cal.
Average 4188.5 cal.
For water vapor 3591 cal.
Boise has found the evaporating power of different kinds of
wood to be as given in Table LXI.
TABLE LXI.
EVAPORATING POWER OF WOOD.
Kind of Tree.
Water.
Ash.
Kilograms of Water
transformed into
Steam by 1 Kilo-
gram of Wood.
Unseasoned. Seasoned.
Unseasoned. Seasoned.
'
Ptr cent.
Wood.
Old pine
16.1
19.3
14.7
12.3
1.92
1.73
0.95
1.00
1.13
1.43
1.39
2.17
2.29
2.15
Ml
1.14
1.39
1.84
1.62
2.48
'4.18
3.62
3.84
3.72
3.54
3.39
3.49
3.62
5.11
YoiinflT Dine . .
4.77
Alder
4.67
Birch
4.39
Oak
18.7
22.2
14.3
12.5
4.60
Old red beech
4.63
Young red beech
White beech
4.25
4.28
Winkler has found the comparative fuel value of woods,
considering the same volume, to be as given in Table LXII.
TABLE LXn.
COMPARATIVE FUEL VALUE OF VARIOUS WOODS (Winkler).
Kind of Wood (dry).
Red Pine
= 100.
Red Beech
= 100.
Oak
169
156
153
152
143
112
110
109
106
100
92
118
Elm , , , , -
109
Maple.
106
Birch.
105
Beech
100
Pir
78
Willow
77
Poplar
76
Pine
74
Red pine
70
Linden
64
154 HEAT ENERGY AND FUELS
Since wood, when used as fuel, is almost always measured
instead of weighed, this table is of considerable importance, also
on account of the volume being less afifccted by moisture than
the weight.
If we call best beech wood equal to 100 we get the following
scale for the value of woods.
I. Fuel quality = 100: beech, birch, pine rich in resin,
mountain pine, acacia.
II. Fuel quality = 95 to 90: maple, elm, ash, larch rich in
resin, chestnut, orchnary pine.
III. Fuel quality = 85 to 75: red pine, fir, Siberian stone
pine.
IV. FuelquaUty = 70: linden.
V. Fuel quaUty = ()5 to 00: alder, poplar, oak, aspen.
VI. Fuel quality = 55 to 50: willow.
These values naturally depend also on the use the wood is to
be put to. For quickly raising the temperature, for instance,
soft wood, especially coniferous wood is used. For domestic
use 1.5 cu. m. of soft wood take the place of 1 cu. m. of hard
wood.
The different parts of a tree have a different fuel quality.
Taking trunk wood as = 1, we have
Trunk wood 0.90 to 0.80
Branch wood 0.90 to 0.75
Twig wood 0.85 to 0.80
Root wood 0.65 to 0.50
Root wood, rotten 0.40
Wind-fallen wood 0.85 to 0.50
CHAPTER X.
FOSSIL SOLID FUELS. (IN GENERAL.)
All fuels contaming carbon are of vegetable origin and differ
From each other according to the kind of the plant from which
they come and the quality and quantity of the transformation
of the vegetable fiber. The course of carbonification is entirely
different if the vegetable masses are covered with water, and if
the plants are isolated from the atmosphere by layers of clay.
Geologically these fuels can be divided in :
1. Younger fossil coals:
(a) Peat.
(6) Brown coal (lignite).
2. Older fossil coals (bituminous coal and anthracite). These
coals are formed by a process called natural carbonification
(carbonaceous decomposition), which was studied by the Swiss
geologist, A. Balzer.
Balzer states that in this process two kinds of substances have
to be dealt with, namely : products of decomposition and resid-
uimi of decomposition.
We can obtain some idea of the nature of the products of
decomposition from the methane in the mines; the gases in the
fresh coal; the changes of frash coal in the atmosphere (which
changes are a continuation of the process of carbonification),
and from certain laboratory experiments on the behaviour of
wood in an atmosphere of oxygen.
The methane in the coal mines is a real product of decom-
position.
The gases held in absorption by coals are of the same nature.
Meyer found that 100 g. of coal yield from 17 to 59 cu. cm. of a
gas containing carbon dioxide, oxygen, nitrogen, methane, ethane
and probably butylene. It is undecided how much of the nitro-
gen has its source in the vegetable matter and how much in the
atmosphere.
165
156 HEAT ENERGY AND FUELS
Relating to the behavior of wood in an atmosphere of oxygen,
Saussure observed that wood shavings enclosed in an oxygen
atmosphere transformed the latter into the same volume of
carbon dioxide. The same observation was made by Liebig for
moist and old wood. Wiesner found that the first stage of
decomposition of wood consists in the appearance of gray color,
whereby the intercellular substance vanishes and practically
pure cellulose remains. Moist ligiiite absorbs oxygen from the
atmosphere and generates carbon dioxide.
Liebig made the conclusion from his experiments, that first of
all the hydrogen of the wood is oxidized, while the oxygen of the
hydrate water combines with the carbon of the wood to form
carbon dioxide. Considering the fact that methane is formed
during the transformation of wood into coal, he calculates that
cannel coal can be explained as wood fiber less 3 molecules
CH4, 3 mol. H2O and 9 mol. COj. Brown coal is oak wood less
2 H,0 and 3 CO,, etc.
Relating to the influence of the exclusion of air in the forma-
tion of coal, Bischof stated that atmospheric oxygen is not
essential and that the coal deposits must have been formed
mainly under exclusion of oxygen, water having served as the seal
in the sea, on the shores and in meadows. In some cases the
water was replaced by sand and clay deposits. The ash content of
coals proves this fact. The oxygen which is found dissolved in
sea water certainly did not have much effect, since according to
Hayes, metals kept at a certain depth in the sea are not oxidized.
As to the chemical expression of the carbonaceous decom-
position Balzer says: According to Bischof there are three ways
possible for the decomposition to take place according as carbon
dioxide and water, carbon diojdde and methane, or carbon diox-
ide, water and methane are formed. The one of these processes
which takes place is determined by the amount of the react-
ing air, temperature and pressure. When vegetable products
during the carbonaceous age were carried by rivers into basins
of salt or fresh water, where formation of coal took place, large
quantities of methane were formed. If by some geological
change the basin becomes dry, the process goes on principally as
oxidation. If now a considerable amount of sediment is deposited
the formation of coal has to continue, though slowly, without
oxygen.
FOSSIL SOLID FUELS
167
1^
a
13
b.
Ex
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o
•4
QQ
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00
p
O
p
s
GQ
O
oo
WW
<oao
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w
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oo
I i
w'^w"'
ÜÜ OÜ Ü
o
1
o
1
o
1
w
w
w*^
00
00
00
Q
Ü
O
s
^
s
oooo
CiJWWW
§^ I I
CO I
OOO
e
O
, cow
•f
a»
S-
w
ww*"k
Ä{§
s
^« 1
1
o
odd
c«
1 1 ^
CO
O
OO
o
^
<o
,«
C4
i|
w
WW
w
o» ,
"^
2i^
^
1
^
n
Ü
ÜÜ
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CO
1 «*»
«o
CO
1
CO
8 c
•s
158 HEAT ENERGY AND FUELS
According to Balzer the influence of temperature is as follows:
Low temperature decreases the velocity of coal formation. The
temperature in the deepest part of the Atlantic Ocean at from
49 to 57 degrees latitude is 2.1° C. In regions where the lowest
winter temperature of the air is 4° C, the deepest layers of water
have a constant temperature of from 5 to 6° C. The carbonifica-
tion, which is a "voluntary" decomposition of organic subtances,
is certsdnly an exceedingly slow reaction at this temperature, and
must have been much slower yet in the glacial age.
The influence of pressure is as follows : It is uncertain whether
an increase in pressure increases or decreases the velocity of
carbonification and the optimum of pressure is also unknown.
We cannot make any deductions from the fact that CaCO,
remains undecomposed at high pressure since in organic reactions
with closed glass-tubes the generation of gas and chemical
reaction ordinarily takes place at high pressure and high tem-
perature. Paraffin is decomposed by high pressure and high
temperature in hydrocarbons of the methane and ethylene
series. In such cases the reactions taking place change with
changes in temperature and pressure.
A certain semi-soft condition of the wet mass can be con-
sidered as advantageous for the reaction.
Valuable information relating to the changes of coals in the
atmosphere at ordinary and higher temperature are given by
Richter.
It is known that coal absorbs oxygen of the air. Charcoal
absorbs nine times its volume of oxygen. Coals absorb gases
as readily as a dry sponge absorbs water. If coal is sat-
urated with one gas, some other gas can be absorbed in
addition. With the assistance of moisture the oxygen is com-
pressed in the coal, ozonised and thereby becomes chemically
active, causing an increase of temperature. (Self-ignition of
powdered coal.)
Richter observed that the capacity of coal for absorbing
oxygen increases up to 200 degrees, at which temperature the
absorption stops. Hydrogen and oxygen are absorbed in the
proportion 2 : 16. On account of oxidation in the air deteriora-
tion of coal takes place, shape and color are changed, thermal
value and coking capacity decreased.
Since only a part of the hydrogen of the coal is oxidized the
FOSSIL SOLID FUELS 159
hydrogen must be present in different combinations, which is
important for the theory of the constitution of coals.
Considering the residuum of decomposition Balzer mentions
the constitution of the wood-substance. The coals are chemical
derivatives of cellulose, consequently of the wood-substance.
The constitution of these substances and their relations to each
other are not positively known. It seems, however, that
cellulose does not occur in a free state in wood. From fir wood
we can isolate by extraction with ordinary solvents a yellowish-
white substance having the formula C^ll4n02iy which is only
slightly soluble in ammoniacal cupric oxide, being thereby essen-
tially different from cellulose. By boiling with hydrochloric
acid, glucose and lignose (Cj^Hj^Oj,) was formed. The latter,
which is also insoluble in ammoniacal cupric oxide, is trans-
formed by boiling with nitric acid, into cellulose and certain
substances of the aromatic series. From these reactions we
can conclude that fir wood contains, besides the cellulose-group,
a sugar-forming and an aromatic group, so that its composition
is much more complicated than that of cellulose.
What is the relation of wood substance to coal? It is known
that in the carbonaceous decomposition the relative quantity
of carbon and ash increases and the quantity of hydrogen,
oxygen and nitrogen decreases. The different quaUties of coal
from peat to anthracite show different stages of this process, but
the formation of one kind of coal from the other cannot be
expressed by a chemical equation.
Balzer makes the following hypotheses relative to the con-
stitution of coals :
1. The coals are mixtures of complicated carbon compounds
(organic substances),
2. Which form a continuous (or possibly homogeneous) series.
3. The carbon ring of these compounds is complicated and
somewhat analogous to aromatic compounds.
Balzer states that bedsides the carbonaceous decomposition
proper a destructive distillation can take place, for instance, by
contact with hot bodies or fires. In Hessen, Germany, molten
basalt has in this way transformed lignite into anthracite coal,
the anthracite deposit changing gradually into the lignite deposit.
In some places eruptive porphyry has transformed hgnite at the
contact points into coke.
160
HEAT ENERGY AND FUELS
Supposing an increase of temperature towards the center of
the earth, we can assume 100® C. at a depth of 2600 m. Products
of distillation formed in these regions can condense in the upper
regions, the lower layers forming the retort, the upper the con-:
densing chamber. Balzer believes that this reaction takes place
with petroleum, which is "distilled" from coal deposits, bitu-
minous slates, etc.
Since petroleum occurs in silurian, devonian and tertiary
formations it is apparent that the place of "occurrence" is
different from the place of "formation, " which can be explained
by distillation, above referred to.
Supposing that the carbon in the coals is present as such, we
consider the coal deposits äs end products, while according to
the above mentioned statement they are in a process of contin-
uoas transformation, which however cannot be fully explained at
present.
The fact that the temperature in coal mines increases with the
<lepth faster than elsewhere is of practical importance and
theoretical interest. A case where it was believed that hot
springs were the cause of the high temperature of the mine waters
was investigated to find out whether the formation of coal is
accompanied by a sufficient generation of heat to explain the
high tem{)eratures.
The following results were obtained :
TABLE LXIV.
avera(;e composition of fuels.
(Muck.)
Wood 50% C
Peat 59% C
Lipnite ; 69% C
Bituminous coal 82% C
.Vnthracitc , 95% C
%H,
%H,
5%H
%H
5%H
% o,
% o,
%o,
% o,
5% O,
1 %N,
2 %N,
0.8% N,
0.8% N,
Spur
Therm&l
Value,
kg^l.
-4800
--6000
-6800
-7900
-8300
TABLE LXV.
THERMAL VALUE OF THE ELEMENTARY CONSTITUENTS.
WocxI 0.50X8080+0.06 X34,000-6080 kg-cal.
IVat 0.59X8080+0.06 X 34.000= 6807 kg-cal.
Li^mito 0.69X8080+0.055X34,000-7445 kg-cal.
Bituminous coal 0.82x8080+0.05 X34.000-8326 kg-cal.
Anthracite 0.95x8080+0.025X34,000-8526 kg-cal.
FOSSIL SOLID FUELS 161
The diflference between the thermal value of the elementary
constituents and the thermal value of the fuels is the heat of
formation of the respective fuels (see Table LXVI).
TABLE LXVI.
FORMATION HEAT OF FUELS.
Wood
Peat
Lignite
Bituminous coal I 8326- 7900= 426 kg-cal.
Anthracite I 8526- 8300= 226 kg-cal.
6080-4800=1280 kg-cal.
6807-6000= 807 kg-cal.
7445-6800= 645 kg-cal.
The heat of formation decreases with the increasing thermal
value.
To get an idea about the (juantity of fossil fuel produced from
wood we have to consider the gases enclosed in the coal, as these
gases are also produced in the carbonizing process. They are
mainly methane, carbon dioxide and nitrogen. The latter
proves admission of air to the coal deposits. Relative to the
first two gases we find (carbon dioxide mainly in younger coals
(lignite) and methane in the older coals (bituminous). We
therefore have in the younger coals mainly a formation of COj
(heat of formation 8080 cal. per kg. carbon), in the older coals
mainly of CH^ (heat of formation 1833 cal. per kg. carbon).
Besides this the formation. of H2O (34,000 cal. per kg. Hj) and
of small quantities of heavy hydrocarbons (C2H4) can take
place.
Since in the progressive process of coal formation, the heat
of formation of the elements decreases, while the heat of forma-
tion of the generated products of decomposition has a con-
siderable positive value, the heat balance of the coal formation
is equal to the difference of the heats of formation referred to.
The balance therefore will be positive if the heat of formation of
the products of decomposition is greater than the decrease of
the heats of formation of the fuels. For getting this effect only
a very small amount of CO2, H^O or CH4 is required as is shown
in Table LXVII.
162
HEAT ESERGY AND FUELS
TABLE LXVII.
DATA ON THE FORMATION HEATS OF FÜET.R.
1.^
Difference between the Heat of Formation of Wood.
This Amount of Heat Oorreaponds
to the Heat of Formation of
\v^
CO,
H,0
CH,
1
and
kg-cal.
In Per cent Cor H, of theoriginal
Weight of Wood.
Y
Peat
473
635
854
1054
5.8% C
7.8% C
10.5% C
12.0% C
1.4% H,
1.9% H,
2.5% H,
3.1% H,
25.7% O
34.6% ^
46.5% ^
57.4%^^
m
Lignite
1
Bituminous coal
^
Anthracite
There is also corresponding to the
The Formation of
^
Difference between Heat of Formation of
C,0 H,0 CH,
_^
From Per Cent
Peat and lignite
Lignite and bituminous coal
Bituminous coal and anthracite
Percent
l.OC
2.7C
1.5C
Per cent
0.5H,
0.6H,
0.6H,
Percent
8.9C
11.9C
10. 9C
0^
If these figures are compared with the difference in the average
composition of the various fuels, we see that the formation of
coal takes place accompanied by the generation of heat.
For forming an approximate idea of the quantitative changes
during the transformation of wood into coal, we are going to
deduct the changes from the average composition of the diflFerent
fuels, following GriesehacKs (hypothetical) table.
We therefore have for the formation of bituminous wood:
^86^44022
= wood.
There is given off:
(a) with absorption of oxygen
of the air Hj
03) directly from the wood-sub-
stance 3 CO2
there remains 033114001« = bituminous
wood.
\ C3HA
«r3
^Z»
i
FOSSIL SOLID FUELS 163
For the other kinds of coal we can imagine the process of
carbonification as follows:
2 (C„H,,0 J = wood.
There is given oflF from wood
2 (3C0, + 2H,0) =2(C3HA)
there remains 2 (C3jH^Oi4) = peat.
From peat is given oflf:
(a) with oxygen of the air 4 HJ ^ prr /-.
09) direct 6 H,0 + 2 CO, ^ ^^''^'
there remains 2 (C^Hj^jO^) = earthy lignite
(brown coal).
From earthy lignite is given off:
(a) by reaction with oxygen
2(C,+H,) 2(C3HA)
0?) direct 8CO2
there remains 2 (Cj^Hj^O) = splint coal.
Therefrom given off direct 4 C^H, 2 (C^H^)
there remains 2 (C^B.^^) = cannel coal.
From this is given off:
(a) by reaction with oxygen
9H,
0?) direct H3O
there remains C^oHi«0 = sand coal.
From this is given off :
H,0
(a) by reaction with oxygen
7 H,
(ß) direct HP
H,.0
there remains C^^o = graphite.
This enables us to calculate the quantity of products of trans-
formation obtained from wood as given in Table LXVIII.
From Table LXVIII we can calculate the heat of formation
of the different fuels as given in Table LXIX.
164
HEAT ENERGY AND FUELS
TABLE LXVIII.
PRODUCTS OF TRANSFORiiATION OBTAINED FROM WOOD.
Solid
Substance
Gases Generated kg.
Fuel.
kg.
CO,
C,H,
H,0
Wood
1
0.797
0.674
0.398
0.333
0.309
0.290
0.838
Peat
0.159
0.053
0.425
0.043
Earthy liimite
0.109
Soliiit coal
0.043
Cannel coal
0.067
Sand coal
0.109
Graohite
0.086
Bituminous wood
0.159
0.022
I. Wood.
Heat of formation of wood 1280 kg-cal.
cal.1
cal.J
517 kg-cal.
II. Peat.
Heat of formation of 0.797 kg peat 643 kg-cal.
Heat of formation of 0.159 kg CO, = 347
Heat of formation of 0.043 kg Ufi = 170
Heat of formation of wood minus heat of form.
(peat + CO, + H3O) = 120 kg-cal.
The transformation takes place with a consumption of outside
energy.
III. Lignite.
Heat of formation of 0.674 kg lignite 435 kg-cal.
Heat of formation of 0.053 kg CO, =113 cal.1 c^. , ,
Heat of formation of 0.109 kg H,0 = 408 cal.J ^
Heat of formation of peat minus heat of form.
(lignite + CO, + H,0) =313 kg-cal.
The formation of lignite from peat takes place, accompanied
by the generation of energy (heat).
IV. Bituminous Coal.
Heat of formation of 0.346 kg coal 147 kg-cal.
Heat of formation of 0.425 kg CO, = 937 cal.
Heat of formation of 0.041 kg C,H, = 27 cal. [ . 1206 kg-cal.
Heat of formation of 0.079 kg H,0 = 296 cal.
Excess of heat generation over the difference of the
heat of formation of Ugnite and coal = 1206 -
288 =918 kg-KÄl.
FOSSIL SOLID FUELS 165
Not considering bituminous wood wherein we find similar
conditions as in peat, we have the following excess of heat in the
transformation of:
1 kg wood in 0.797 kg peat = - 120 kg-cal.
0.797 kg peat in 0.674 kg lignite + 313 kg-cal.
0.674 kg lignite in 0.346 kg bit. coal + 918 kg-cal.
0.797 kg peat in 0.346 kg bit. coal + 1231 kg-cal.
These figures are not absolutely correct, as we have supposed
only the formation of CO,, C^H^ and H^O, while according to
analysis, especially of bituminous coal,. CH^ plays an important
part. The heat of formation of C^H^, however, is - 642 cal., of
CH4 1833 cal. per one kilogram of carbon, so that we gain + 2475
cal. for every kilogram of carbon which is transformed into CH4
instead of C^H^, while we lose 6247 cal. for every kilogram of
carbon, which escapes as CH4 instead of CO^. Taking even this
most unfavorable possibility by supposing that in the process
of carbonification exclusively CH4 and H, and no CO, at all is
generated, we still get the following quantities of heat, which
are produced by the reaction
1 kg wood in 0.797 kg peat = - 138 kg-cal.
0.797 kg peat in 0.674 kg lignite = + 246 kg-cal.
0.674 kg lignite in 0.346 kg bit. coal = + 333 kg-cal.
0.797 kg peat in 0.346 kg bit. coal = + 579 kg-cal.
Similar results were obtained by F. Toldt and F. Fischer.
\
CHAPTER XL
PEAT.
Peat is the youngest member of the fossil fuels, and the result
of the first stage of carbonaceous transformation of vegetable
matter. It consists mainly of decayed moss and plants growing
in bogs and swamps. The peat deposits can be classified accord-
ing to Stentrupp in forest, meadow and high bogs. While the
first is composed of decayed trees and forest plants, the two
others can be described (Griesebach) as follows:
Moss-peat. . .
Heath-peat . .
Meadow-peat
Main Comiwnents.
Sphagnum varieties
Roots and trunks of Erica tetralix
and Calluna vulgaris.
Roots and trunks of Glumacc»... .
Occurrence.
In all bogs.
In high bogs.
In meadow-bogs.
F. Schwackhoefer proposes the following classification:
1. High bogs (heath and moss bogs) are found in higher alti-
tudes and are characterized by swamp-moss (sphagnum), heath-
plants (Calluna, Erica, Andromeda and Vaccinium), also by the
occurrence of mountain pine (Pinus pumilis). The ground is
generally clay and lays above the level of summer water. The
surface is always curved. In some localities the bog is 10 to 15 m.
thick.
2. Low bogs (meadow-bogs) are found in the territory of
rivers, creeks and lakes, and consist of plants entirely different
from the high bogs, since swamp and heath plants are entirely
absent. Besides some Hypnum varieties, mainly sour grasses
are found in this kind of peat. The ground is chalky and below
the level of summer water. The layers are not as thick as in .
high bogs.
There are many connecting links between these two main
groups. Without taking into consideration the origin and
166
PEAT
167
[leurreiicCp peat t'an be olassificÄi according to its ap{)earauoe
larsch) as follows:
A, Turf-peat (wliite or ydlow).
B, Young brown and black peat,
(a) Fibrous |x^at.
(b) Root-pt'at,
(c) Leaf-peat.
(d) Womi-peat.
C, Old peat.
(a) Earth-peat.
(6) Pitoh'peat.
A. Turf-peat. tJrayish yellow to yellowiü^h brown color is also
mUed white or yellow peat. Its constituents can be distinctly
recognized in the wlutc, .spongy, ela^tir, fibmus mass. Enclo-
sure's of roots are rare.
f B. Young broim and black peal. Wliilc t!ie f larker color shows
a further progr^s of carbonaceoiii^ decay, the organic constituents
can yet be distinguished.
(a) F-QjTOits peal seems to be fonned by further decompi:Jsi-
tion of turf-peat. The fibrous structure is preserved, but
the fiber is more brittle ami partly earthy; shows less
ela.sticity and is denst^ly pressed by its own weight.
(6) Other kinds contain short fibers only, and are some^
times earthy \jc\ a large extent.
(tt) Thick, light brown, tough, long fibers (fibrous peat).
iß) Containing roots ami stems (root-peat)-
(7) Containing dried and decayed! leaves (leaf-peat),
(S) Cf>ntaiinng pieces of coarse wood (wood-peat).
C. Old peal. The original organic structure can hardly be
distingaished. On account of the progress of decomposition the
fibrous texture has gone over into earthy structure, occasionally
of such density that the peat showa a sharp and brilliant fracture.
Organic resiilue such as roots and stems are rarely found. The
color is brown to pitch black. The strength varies considerably
from brittleness to extreme hardness. Accordingly okl peat is
classified into the follomng varieties:
i
168
HEAT ENERGY AND FUELS
(a) Earth-peat (to wliich also belong drag-peat and swamp-
peat) with earthy texture, rough fracture and practically^
without fibers.
(6) Pitch-peat, dense, heavy, strong and with smooth frac-
ture. The average composition of peat is ^ven in Tabl^
LXIX.
Ferstel has published the following complete analysis of a peat
from Upper Austria:
I. Components soluble in water,
(a) Organic substances with traces
1.G5 per cent
of
anmionia
1.50 per cent]
(6) Inorganic substances
CaSO,
0.04 per cent
NaCl
0.01 per cent
•
MgCl,
Fe,03
0.01 per cent
0.05 per cent
0.15 per cent
AiPa
0.01 per cent
LiO,
0.03 per cent
II. Components soluble in hydrochloric acid.
(a) Organic substances with traces
of ammonia 0.13 per cent
(6) Inorganic substances:
PPs 1.07 per cent
CaO 1.05 per cent [3.07 per cent
MgO 0.30 per cent
Fe^Oj 0.12 per cent [ 2.94 per cent
MnO 0.04 per cent
AljO, 0.31 percent
liOj 0.05 per cent
III. Components insoluble in water and hydrochloric acid :
(a) Organic
Ulmicacid 22.60%
Uhniccoal 34.70%
Resin 4.10% 79.02% [ 93.36 per cent
Wax 1.40%
Vegetable fiber... 16.22%
(6) Inorganic 0.29%
(c) Water .14.05%
Sum 98.08%
AVERAGE COMPOSITION OF PEAT.
Websky.
Schwack-
höefer.
Scheerer.
MareiUy.
Knapp.
Air Dry.
Air Dry.
Free of Water and Ash.
c
49.6-63.9
4.7- 6.8
28.^-44.1
0.0- 2.6
50-60
5- 6
30-35
1- 2
10-20
5-10
45.0
4.7
25.3
50-54
7- 6
1 43-40
59 10
H
5 83
O
; 35.16
N
H-O
25.0
Ash
The ash-content of peat varies from 1.50 per cent and has the
following average composition:
Sand and clay (mechanically admixed) 5.70%
Silicic acid (from plants containing silica) 1.30%
Lime (combined partly with CO,, partly with H3SO4) 10.50%
Oxide of iron up to 50%
Only traces of chlorine and alkalies are present. The content
of phosphoric acid sometimes exceeds 6 per cent, which has to be
considered. A considerable amount of sulphuric acid may also
be present.
Tlie specific gravity of peat varies according to structure and
quantity of ash. Karmarsch found:
Turf-peat 0.113 to 0.263
Young brown peat 0.240 to 0.676
Earth-peat 0.410 to 0.902
Ktch-peat 0.639 to 1.039
By dressing (mechanically purifying) the specific gravity can
be increased to 1.3 to 1.4.
Peat is easily ignited (easier, the looser the peat). Very
porous varieties show a point of ignition of 200^ C.
Peat bums with a long smoky flame.
170 HEAT ENERGY AND FUELS
The thermal value of peat is as follows (in calories) :
Peat with 30 per cent water and 10 per «cent ash. 2090 Scheerer
Peat with 25 per cent water and free of ash 3800 Scheerer
Peat with per cent water and 15 per cent ash . . 4440 Scheerer
Peat with per cent water and per cent ash . . . 5250 Scheerer
Dry peat free of ash 5250 Tunner
Dry peat with 4 per cent ash 5090 Tunner
Dry peat with 12 per cent ash 4686 Tunner
Dry peat with 30 per cent ash 3636 Tunner
Peat with 25 per cent water 3800 Tunner
Peat with 30 per cent water 3313 Tunner
Peat with 50 per cent water 2182 Tunner
On account of the low specific gravity, the large amount of
water and ash, which increases the cost of transportation, also
on account of the great variety in quality, peat is only of local
importance as a fuel.
Lately peat has been used as a disinfecting material and for
coarse textile products.
Production of peat.
1. Cut peat. Peat of sufficient consistency is cut out in the
shape of bricks. For the purpose of digging a specially shaped
spade is used, with a wing at one side, in order to cut out rect-
angular blocks.
(a) Peat cut by hand,
(a) Horizontal cut. The bricks are cut out horizontally.
(ß) Vertical cut. The bricks are cut out vertically.
(6) Peat cut by machine. (Cutting machine systems,
Brosowsky, Diesbach and Hodge.)
The cut peat is either dried in piles in the air or by arti-
ficial heat.
2. Molded peat (drag peat). Peat which is too earthy (dry)
or too swampy (wet) cannot be cut. If of suitable consistency
it is molded (formed) directly, otherwise after previous moisten-
ing (in moistening boxes) or desiccating (in tanks or on dry
earth). The molding is done as follows:
(a) The wet mass of peat is distributed on level ground
fenced in by boards. The peat is given proper consistency
PEAT
171
TABLE LXX.
ANALYSES OF PEATS.
CoEnpositi
n-
C
Per
Cfiiit
n
Pel
Cunt
lr«tfrad
5^05
ä.S>
n, IreUaU
AI. 04
6.87
WD, Ire-
M.«»
6.97
MIea. I»^
61.02
5.77
amt Ab-
57,(ß
5.63
kr Abbe-
30.0»
5.W
S7,79
62. rj
57 50
6JI
6,29
690
in.
Ib.
Lb.
or»
a».
47.90
50 J3
5 i
4.20
to
55.01
to
5.36
57 16
57.66
5.65
5.52
^a 85
4 64
57*4
5 es
h/Würt-
57.03
5J,59
5 56
5 60
cm.
mbarflc.
49,44
46 73
5 28
3 57
60.79
to
7 01
UvfllnJ*-
56 43
5.72
la^'tiltiie-
53.11
5 90
;, Jdoor .
57.20
5.52
4
49. 9S
50 Sä
62.54
5fl.47
59.70
6 5
5 60
6 Bl
6 52
5,70
üv.::::::
lor
9S.«J
5.72
>r Hatte.
54 61
5 4J
(r
54.01
46.70
4 B4
4.38
4
tot
».5r
0.17
!id
40 ID
4 53
51 .M
6 49
Per
Cent
O
Per
Cent
3*. 55
30.46
.45 I 32. 6S
oar
2.09
32.40
29.67
3J.77
30.37
1.66 I 27.20
I 73 j 31.01
42, ao
31. E4
to
33.24
33.3»
3^71'
30.23
0.93 3.7ft
1.67
2 71
t.46
67
34 13
30 32
26 21
2« a7
to to
6 33 ? 49 .0!
}9 }^
40.59
37,36
I 16
0.77
1 41
2 51
1.56
42 42
42 70
Z9 24
31 51
33.04
33 33
31.64
28 36
28 5«
33.32
2.srr2i.5(
1 6B I 35 43
Ktth
Per
Ccdt
2. 55
I U
1.99
7.90
5,5fl
4.61
3,33
2. 3D
2.04
3.50
e.20
to
2M7
3.eo
D.91
14.25
2.6
I 57
8,10
71.60
09
to
14 76
9.06
6 60
2.31
5 72
57
1 09
1*53
2.92
S.43
3.32
12.59
20.28
4 21
707
5.02
Mois-
ture
of Ait
Driixl
ES
SpÜ
403
0,619
to
0.072
16.7
16.0
17.0
I* 17
to
21 7
2D.0
18.0
M 77
Lü
ie.55
17.63
19.32
rs.B3
15.50
t03
17.1
15.72
15.50
^,17
Propcrtiflftn
Palflf nd-
brqwti.
IMrk brown,
dea».
Dark brown.
Sunt».
Ini?on]pJet«ly
dccompoHU.
Solid Aii<i
Somewhat
Ll^t, fdty
.07
Dark brttwtiL
deiip** hea\'y
Same
Dafk brown,
d«nie.
Saih« ,
Authority
Do.
Do.
..Do,
.,,.Do.
..Do,
WaU.
..Do,
.Do,
UuMfrr
Do.
. Dfl.
Heavy, den«,
brown.
Light, loose.
Red brown,
heavy
Preaied-iMat.
Do
Peat prepared
after CbaJJe-
ton.
SamA H +
Pt«»ed-'peat
Veiy den>e .
...Do.
.Do
SN ens I er
and
Pot«rBeji
Jawk«J.
. .Do.
...Do
WtUky
. . Do.,
...Dd.
...Do.
....Do.
Knut.
...Do,
,..Do.
..Do.
Wimtier.
Goppf'Ls-
Jieob*eö.
* Calculated f r«e of ash.
172 HEAT ENERGY AND FUELS
by evaporation, trickling of the water into the ground,
by pounding, treading and beating. The boards are then
removed and the mass cut with sharp knives into regular
bricks.
(6) The mass, compressed from the top is beaten into forms,
(a) Containing only one brick (beaten peat).
(ß) Containing space for several bricks (molded peat).
3. Machine peat.
(a) Without pressure (machine peat proper). The cut peat
is formed into bricks and dried. Occasionally it is pre-
viously carded so as to get a denser product.
(6) With pressure (pressed peat),
(a) Dry pressed : small-sized peat is sifted, dried by heat,
and briquetted in a heavy brick press. Such peat iß
expensive on account of the cost of drying and is dis-
integrated by heat.
(ß) Wet pressed, most of the water is removed by pressure.
There are many constructions of peat-brick presses in
successful use.
Peat molded in the form of balls or eggs is very convenient to
handle and makes firing easy. Analyses of some dry peats are
^ven on page 171.
CHAPTER XII.
BROWN-COAL (LIGNITE).
Brown-coal is the next stage of carbonaceous decay and was
formed mostly by transfonnation of plants rich in resin (conifer-
ous trees, palm tree and cypress; later, also leaved trees).
The specific gravity of this coal varies from 0.8 to 1.8 (in coals
very high in ash), but in most cases from 1.2 to 1.5. It has
various colors, and the touch is generally bro^^^l. In the air
brown-coal easily absorbs oxygen and evolves carbon dioxide,
whereby on account of the loss in carbon, the thermal value is
decreased; at the same time the temperature is increased and in
large piles causes spontaneous combustion.
Brown coal does not occur before the tertiary period. The
gases found in brown-coal deposits consist generally of carbon
dioxide (not of hydrocarbons as in soft-coal deposits). Zitowich
published the gas analyses of such coals (Table LXXI).
TABLE LXXL
ANALYSES OF GASES FOUND IN BROWN-COAL. (Zitowich).
CO,.
CO.
N..,
o...
In Bohemian Patent-Brown Coal.
89.66
1.80
8.03
0.51
82.40
3.00
14.15
0.45
In Earthy Coal
of Inferior Quality.
83.99
1.04
14.91
0.65
Sum.
100.00
100 00
100.59
Gases from :
Julli»-Mine In Bruex (Bo-
hemia).
(>»! from
Rossitz.
Goal from
Habichtswald.
CO,
37.62
35.13
31
91
CO....
9
CH.
33.34
29.04
36.06
28.81
30
20
N^..:
O
CH...
19
173
174 HEAT ENERGY AND FUELS
While previously the brown-coals were classified as lignite or
fibrous brown-coal, earthy brown-coal and conchoidal brown-
coal, Zinken has suggested the following classification :
1. Common brovmrCocU. Compact, more or less dense and
strong. The fracture may vary in character from dense to
earthy ; in structure it may be more or less conchoidal; in appear-
ance it may vary from dead to slightly brilliant; in color from
light brown to dark brown, and lightrbrilliant touch. This coal
is between earth coal and pitch-coal, and is produced in all sizes.
2. Earthy brown-coal. More or less brittle, light to dark
brown, showing dead, uneven fracture, without any organic
structure. The lighter varieties bum with a long, the dark ones
with a short, but intense flame.
3. Lignite or fibrous brown-coal. More or less fossil wood-
substance, yellow to dark brown, specific gravity 0.5 to 1.4,
fracture depending on the nature of the wood.
4. SkUe-cocU. Slaty, dense, dark-brown to black.
5. Paper-coal. Thin, elastic layers of gray to dark-brown color.
6. Leaf-coal. Formed of very thin leaves of plants.
7. Reed-coal. Reed-like strips formed into ribbon-like layers.
8. Moor-coal. Compact without wood-texture, of even,
uneven or conchoidal fracture, sometimes slaty, mostly loose,
spongy and brittle; dark brown to pitch black. Specific gravity
1.2 to 1.3. Occurs mostly in the lower part of lignite deposits.
9. Pitch-coal. Compact, brittle to tough, mostly weak, black-
brown to pitch black; has the lustre of pitch or wax. Brown
touch; fracture imperfect to conchoidal. Specific gravity 1.2 to
1.3. Occurs near volcanic rocks.
10. Lustre-coal. Compact, conchoidal, jet black, very brilliant.
The hardest and strongest variety. Specific gravity 1.2 to 1.5.
11. Gagat (from the river Gages in Licia). Dense, conchoidal,
pitch-black. So strong that it can be worked into ornaments.
12. Stalky brown-coal. Like common brown coal but stronger.
The average composition of brown coals is :
Carbon 50 to 65 per cent
Disposable Hydrogen 1 to 2 per cent
Water chemically combined 20 to 30 per cent
Water hygroscopic 10 to 25 per cent
Ash 5 to 10 per cent
BROWN-COAL 175
The quantity of nitrogen present is nearly alwajrs less than 1
per cent. The quantity of water varies as follows :
Fresh-mined coal 30 to 40 per cent
Sometimes up to 60 per cent
In air-dry coal 10 to 30 per cent
Coal which has been completely dried at 100 degrees absorbs
in the air from 10 to 15 per cent of moisture. The ash varies from
1 per cent to over 50 per cent ; it may contain from 1 to 2 per cent,
and sometimes more, sulphur combined with iron (detrimental
sulphur).
The organic components in brown-coal are mainly ulmic acid,
its derivatives and resinous substances. Otherwise the compo-
sition varies considerably even in coals from the same mine.
The following table shows the composition of some brown-
coals:
TABLE LXXII.
COMPOSITION OF BROWN-OOALS.
Pi«».
GftJ.
Cote.
GbmpofiJtEoia af OmI In 1^ cent.
ji
Yield.
Pfercent.
C
49 95
44.93
50.12
77,04
03.42
74.19
72.19
58-50
H
3'fl7
3,21
4 06
7.S5
4.gs
5.36
5,95
O
10.93
12.51
13 M
14.51
27.11
20.13
22.45
20.85
X
B,0
6.03
10.77
20.15
34.28
25,50
Anh.
4.02
4.34
8.43
4.43
6.53
Sulphur.
0.90
I. AufltriaHun-
(irsTyria:
Johtt^dorf. . .
Leoben
Tnfail
(2) Bohemia:
Teplitjs
Dax
II. Germany,
Elbogen
Cologne
II L France.
Dax
Middle Alysea
IV. Ireland:
Lough Neagh.
25.73
30.07
63.32
54,82
20
40 6
48.0
97
64
05
104
0.50
93
'4360
3925
4030
As can be seen from the above table the composition of brown-
coal of the same origin and mine varies considerably. It is,
176
HEAT ENERGY AND FUELS
therefore, very difficult to get an exact average sample for analy-
sis. For determining the non-uniformity in the composition,
the author broke several small pieces from a piece of coal (of
Johnsdorf) about the size of a fist. The results of the analysis
are given in Table LXXIII.
TABLE LXXIII.
COMPOSITION OF BROWN-COALS.
No. of Test.
Percentage of
Hygroscopic
Moisture.
Yield in Gas.
Percentage.
Percentage of
Coal Resid-
uum.
Ash.
1
2
3
4
5
6
7
8
8.49
8.02
7.77
7.63
6.87
9.13
8.17
7.24
28.57
29.07
27.95
28.41
31.67
29.76
28.81
31.90
53.85
53.57
54.79
54.15
52.31
53.27
53.21
51.54
9.09
9.34
9.49
9.81
9.15
9.94
9.81
9.32
Average. .
7.91
29.52
53.33
9.37
Another series of tests with the same piece are given in
Table LXXIV.
TABLE LXXIV.
COMPOSITION OF BROWN-COALS.
Weight of the Lead Regulus
in Grams.
Theoretically
No. of Test.
Grams Used.
Required for
Directly
Found.
Pter 1 g. Fuel.
Burning 1 kg.
of Fuel.
1
1.00
21.98
21.98
1.6990
2
1.00
22.31
22.31
1.7245
3
5.00
110.30
22.06
1 . 7052
4
5.00
109.38
21.88
1.6910
5
5.00
111.59
22.795
1.7252
6
5.00
111.36
22.68
1.7216
7
5.00
111.68
22.34
1.7269
8
5.00
115.42
23.08
1.7841
9
5.00
110.09
22.02
1.7021
10
5.00
112.52
22.50
1.7393
Average.
22.3645
1.72189
BROWN-COAL
Table LXXV gives several analyses of brown-coal ash.
TABLE LXXV.
CX3MP08ITION OF BROWN-COAL ASH.
177
Goal Ash from . . .
Analyst.
SiO,..
SO,...
W::::
A1.0..
Fe,03.
MnO..
MnA.
CaO .
MgO..
K,0. .
Na,0..
Chlorii
Total . . .
Krem-
ers.
3.12
9.17
29.50
32.18
20.56
2.16
0.99
1.72
99.40
IS
Var-
ren-
trapp.
17.27
33.83
11.57
5.57
23.67
2.58
1.90
96.39
O. Kot-
20.67
15.45
13.52
1.23
45.60
1.67
1.86
100.00
.1
Son-
nen-
schein.
36.01
12.35
23.7
5.05
1.13
15.62
3.64
2.38
0.38
1.55
101.81
H
S .2
20.5
30.3
14.7
18.1
10.0
3.4
1.9
98.9
I
I
jUptner
2.88
0.23
Trace
14.62
39.28
7.43
34.15
0.94
}o.47
100.00
13.47
0.13
17.47
5.32
15.96
19.86
15.67
0.38
1171
100.00
2.52
0.15
10.86
12.17
45.44
2.35
16.60
Trace
[9.91
100.00
CHAPTER XIII.
lilTUmNOUS AND ANTHRACITE COALS.
A. Bituminous Coal.
The older fossil coals, ordinarily called bituminous coals, are
mostly black in color and have a high lustre; no organic structure
can be discerned without a microscope. The fracture varies.
The coals are not hard but brittle.
In destructive distillation they yield more soUd residuum and
less water than the fuels previously treated and their tempera-
ture of ignition is higher.
The great commercial importance of bituminous coals early
caused their division into groups, many different schemes being
proposed.
Schondorf based his classification on the coking quality:
Coke rough, / loose I. Sand-coal.
fine, sandy < molten hard, loose in the center. . II. Molten sand-coal
and black. ' molten hard all over III. Sinter coal.
Coke gray and solid, opening like a bud III. Baked -sinter-coal.
Coke smooth, metallic, strong V. Baking coal.
Gruner based the following classification on the character of the
flame:
I. Long-flame sand-coals (sand-coal rich in gas) can be used
for reverbatory furnaces and as inferior gas coal. They bum
with long, smoky flame, crack in the heat, and disintegrate
without baking.
Sand coal. — Composition of coal substance:
C = 75 to 80 per cent
\j =^ to i/U ou per ucub
H = 5.5 to 4.5 per cent
+ N = 19.5 to 15.5 per cent
The ratio of (0 + N) to H equals 3 or 4.
By destructive distillation these coals yield from 50 to 60 per
cent of sandy to slightly molten coke, evaporate from 6.7 to 7.5
178
BITUMINOUS AND ANTHRACITE COALS 179
times their weight of water and have a thermal value of 8000 to
8500 cal.
The soot-coal, which is of fibrous structure and contains only
3 per cent of hydrogen also belongs to this class.
II. Long-flame baking coals (long-flame caking coals, gas-coals,
sinter and baking coals rich in gas) are used mainly as flaming
coals and gas-coals, less suitable for coking (however, in special
ovens a coke of medium quality can be produced). They bum
with a long, smoky flame, get soft in the heat and fritted. (Coals
standing in quality between these coals and the long-flame sand-
coals are called sinter-coals).
Composition of coal substance:
C = 80 to 85 per cent
H = 5.8 to 5 per cent
+ N = 14.2 to 10 per cent
The ratio of (0 + N) to H equals 2 or 3.
Coke residuimi of destructive distillation 60 to 68 per cent (per-
fectly molten, not baked). These coals evaporate 7.6 to 8.3
times their weight of water and generate 8500 to 8800 cal.
III. Baking coals proper (medium-flame caking coal, forge
coal), especially adapted to coking, gas making and heating.
Bum with less smoke and more brilliant flame than the previous
kinds, melt in the heat and bake together to solid masses.
Composition of coal substances :
C = 84 to 89 per cent
H = 5 to 5.5 per cent
+ N = 11 to 5.5 per cent
O + N ^ „
-^ = lor2.
Coke residuimi by destmctive distillation from 68 to 74 per
cent; the coke is molten and more or less puffed. These coals
evaporate from 8.4 to 9.2 times their weight of water and generate
from 8800 to 9300 cal.
IV. Short-flame baking or caking coals (coking coal poor on
gas). Best coking and boiler coal. Difficult to ignite, bums
with an illuminating, short, slightly smoky flame. Cakes some-
what in the heat.
180 HEAT ENERGY AND FUELS
Composition of coal substance:
C = 88 to 91 per cent
H = 5.5 to 4.5 per cent
+ N = 6.5 to 4.5 per cent
— =j — = about 1.
il
Coke-residuum of destructive distillation from 74 to 82 per cent.
The coke is molten, and compact. These coals evaporate from
9.2 to 10 times their weight of water, and generate from 9300 to
9600 cal.
V. Anthracitic coals (poor in gas, older sand-coals). Esj)ecially
adapted to shaft furnaces, boilers and domestic uses. Cannot be
coked. Difficult to ignite; bum with short, weak and practically
non-smoking flame. Cakes slightly in the heat and frequently
disintegrates.
Composition of coal-substance :
C = 90 to 93 per cent
H = 4.5 to 4 per cent
+ N = 5.5 to 3 per cent
O + N
H
about 1.
Residuum of destructive distillation from 82 to 90 per cent,
slightly molten, mostly sandy. These coals evaporate from 9 to
9.5 times their weight of water and yield from 9200 to 9500 cal.
A similar classification was made by Hilt. If we determine
the ratio fin weight) of volatile matter to the coke dried
at 100 degrees a^d free of ash, we get the results shown in
Table LXXVI.
TABLE LXXVI.
CLASSIFICATION OF COAL. (Hilt.)
Kind of Coal.
I. Anthracite
II. Semi-caking sinter-coal (poor in gas)
III. Caking or baking coal
IV. Baking gas-coal
V. Sinter-coal rich in gas
VI. Sand-coal rich in gas
Ratio of Residuum.
Free of Ash and Vol-
atile Matter.
1 : 20 to 1 : 9
1:9 to 1 :5.5
1 : 5.5 to 1 : 2
1:2 to 1 : 1.5
1 : 1.5 to 1 : 1.25
1 : 1.25 to 1 : 1.11
BITUMINOUS AND ANTHRACITE COALS 181
Expressing the volatile matter as given in Table LXXVI in
per cents free of ash, we get the results ^ven in Table LXXVII.
TABLE LXXVII.
CLASSIFICATION OF COAL. (Hilt.)
Kind of Coal.
Volatile Matter.
Pfer cent.
I . Anthracite
5 to 10
II. Semi-caking coal
10 to 15.5
III. Caking coal.
15.5 to 33.3
IV. Bakins: iras-coal
33.3 to 40
V. Sinter-coal rich in gas
40 to 44.4
VI. Sand-coal rich in gas
44.4 to 48
Dr. E. Muck based a classification on simple laboratory experi-
ments.
If a small quantity (about a teaspoonful) of finely powdered
coal is quickly heated, preferably in a platinum crucible, until no
flame is visible at the cover, the quality of the cooled residuum
varies according to the coal used, as follows :
Powder, just like the coal-powder used . . I. Sand-coal.
Somewhat molten, partly powder II. Molten sand-coal.
Molten but not puffed III. Sinter-coal.
Molten, somewhat puffed IV. Caking sinter-coal.
Thoroughly molten and puffed up in a
form similar to a potato V. Caking coal.
The properties are the same in using the fuel on a large scale.
In heating under admission of air (grate-firing), I, II, and III do
not melt; but IV and V do melt to such an extent as to clog the
grate openings, so that only I, II and III can be used under boilers
and for household purposes.
If melting (caking) coals III and IV are slowly and gradually
heated, they do not melt properly and the coke-residuum is poor-
looking, soot-black and strongly puffed. This also takes place at
high temperature and too large an air supply, since the fusible
coal substance is destroyed by long heating (partial degasifica-
tion) and excess of air (oxidation). If caking coal is heated for
182
HEAT ENERGY AND FUELS
some time in the open air (to about 300 degrees), it no longer
cakes at all if afterwards heated to a high temperature.
Depending on the fact, whether the coal sample is heated to
high (normal test) or low temperature (pufling test) the coke
obtained shows different volume and color. After heating to a
high temperature the volume is smaller than after heating to a
low temperature. The color after the normal test is more or
less brilliant, silver-white, after the pufläng test black and not
brilliant. We find the same phenomena in coke ovens at low
and high temperature.
Considering besides the quality of the coke, the fusibility and
the flame of the coal, the classification given in Table LXXVUI
can be used (Muck).
TABLE LXXVIII.
CLASSIFICATION OF COALS.
Quality.
Elementary Compo-
»itioQOf tbeCoal,
Dry and Free of Ash,
in Per cent.
Yield
in
Coke.
Pfer
cent.
Quality of Coke.
8ped6c
Qrayity.
C
H
o
I. Dry bituminous
coal with long
flame.
II. Baking bitum.
coal with lone
flame, or gas coal.
III. Baking coal
proper, or forge
coal.
IV. Baking bitu-
minous coal with
short flame, or
coke-coal.
V. Semi-anthracitic
coal.
75
to
80
80
to
85
84
to
89
88
to
91
90
to
93
5.5
to
4.5
5.8
to
5.0
5.0
to
5.5
5.5
to
4.5
4.5
to
4.0
19.5
to
15.0
14.2
to
10.0
11.0
to
5.5
6.5
to
5.5
5.5
to
3.0
50
to
60
60
to
68
68
to
74
74
to
%2
82
to
90
Powdered or
fritted.
Molten and ri-
mous.
Molten and
compact.
Molten, very
compact,
slightly ri-
mous.
Fritted or pow-
dered.
1.25
1.28
to
1.3
1.3
1.3
to
1.36
1.36
to
1.4
From these figures we see the relation and connection between
the properties of the coals and their chemical compositions. But
there are also cases of isomerism where coals of about identical
composition show an entirely dififerent behavior in heat.
BITUMINOUS AND ANTHRACITE COALS
188
TABLE LXXIX.
CLASSIFICATION OF COALS.
Oocuneooe.
Composition of Coal,
Dry and Free of Ash,
in Per cent.
Yield
of
Coke,
Per
cent.
Quality of Coke.
C
H
O+N
Niederwuschnitz, Saxony . .
Zwickau. Saxony
82.34
82.59
87.47
87.79
4.73
4.76
5.03
4.78
12.93
12.65
7.50
7.24
66.43
77.29
75.80
77.60
Sandy.
Caked
Alma Mine, Flöz 4, West-
phalia.
President Mine, Dickebank,
Westphalia.
Slightly molten.
Caked and
strongly puffed.
Coal deposits are not at all homogeneous, and we can generally
distinguish the following components:
1. Malting coal, jet black, brittle, brilliant, easily split per-
pendiculariy to its layers.
2. Dull coal, brown to gray-black, hardly any brilliancy,
stronger and less brittle. Is not scissile and shows rough frac-
ture.
Malting coal is the only constituent of sand and sinter-coals,
semi-baking, and is the principal constituent of the baking and
coking coals, while gas-coal consists of alternate layers of malting
and dull-coal. A coal extremely rich in dull coal is called cannel-
coal. Since the malting coal occurs in every kind of coal, it is
self-evident that it has widely varying composition and fusibility.
The dull coal is usually richer in ash and always richer in hydro-
gen and gas than the malting coal.
3. Fibrous coal is widely distributed in all parts of the coal-
deposits, forms generally thin layers, is similar to charcoal (there-
fore called mineral charcoal) is infusible, low in volatile matter
and is therefore detrimental in coke and gas production.
4. Bituminous shale, i.e. slate impregnated with coal sub-
stance, is frequently similar to cannel-coal. The coal Huljntance
of bituminous slate is rich in hydrogen. The moisture of freshly
mined coals varies. In air-dry state they contain from 2 to 4 per
cent, sometimes up to 8 per cent of water. The ash varies from
2 to 20 per cent. For some special metallurf^cal uses, the com-
184
HEAT ENERGY AND FUELS
position of the ash has to be considered, as a coal rich in sulphur
or phosphor is detrimental for certain uses.
TABLE LXXX.
ANALYSES OF BITUMINOUS COALS.
Gas. Coke.
Composition of coal tn P^ cent.
£
Sulphur
l_
Per cent.
P
Locality.
Yield in
V^*r cent.
C
H
O
^'
H,0
ABh.
i .
^
i±
P
^
|£
Aüfltri«:
Kladufl
51». 48
3.55
8.89
M6
7.90
19 02
5497
Pilsen.
. ~ .
75.09
4 51
8.41
8.41
6.08
5.31
. . , .
709«
Karwin .
7(i!fi
es 80
3 99
8.23
1.36
5.65
a 97
90
6420
Maehr. Oatrau
77.21
4.00
8.32
1.39
2.41
6.07
....
0.58
7296
Germany:
ÜDDer äileäla.
73 20
4.93
19.11
2.76
Sliarbrüc ken , .
72. 3&
S9 32
85.62
4.46
3.80
4.65
15 05
2.71
5 93
1 71
...
S 11
4.17
2.09
Aachen ......
Essen
Bochum.
85.90
4.56
4 77
1,56
3.21
....
Weatphalia. ..
69^9
79.82
4.&e
4 79
1.25
3^00
5.36
o;82
■-■
St. Etjcnne. . .
10.75
79.0
84.54
4.77
4.59
0,S4
1 25
4 00
....
8392
England :
Tyldesley...
32. OB
57 75
74.46
5.10
8.25
1,52
6.07
4.08
0,49
7Ü69
Bickershaw,..
29.81
63.87
78.93
4.00
7.24
1 57
4.35
1 96
1.04
74S5
By dressing and washing, the ash-content can be considerably
decreased.
Of technical importance is the decomposition of coal in the
atmosphere by absorption of oxygen, which takes place in two
stages; at first the available hydrogen and some carbon are
oxidized to water and carbon dioxide; in the second stage oxygpn
is absorbed by the coal, but no carbon dioxide nor water escapes,
so that an increase in weight takes place, sometimes as much as
4 per cent. Thereby not only the thermal value, but also the
property of caking and the yield of coke is decreased.
By this absorption of oxygen and oxidation the coal is heated,
sometimes to such a high temperature that not only the included
gases escape (causing decrease in weight) but also spontaneous
combustion can take place. This spontaneous combustion
is facilitated by the oxidation of pyrite, which is present in the
BITUMINOUS AND ANTHRACITE COALS 185
coal. The gases included in bituminous coals vary in composi-
tion as follows :
Methane per cent to 90 per cent.
Carbon dioxide 0.2 per cent to 54 per cent.
Oxygen trace to 17 per cent.
Nitrogen 10 per cent to 90 per cent.
The quantity varies between 18 and 190 cu. cm. in 100 g.of coal.
TABLE LXXXI.
ANALYSES OF BITUMINOUS COALS. (G. Arth.)
BITUMINOUS COAL FROM THE FRANKENHOLZ MINE WITH 8.1 PERCENT
OXYGEN.
Ash.
Per
cent.
C Per
H Per
O Per
cent.
cent.
cent.
2.08
81.69
5.79
8.15
1.75
82.24
5.70
7.88
1.82
82.15
5.62
7.94
1.96
81.45
5.58
8.80
C Pter
cent.
H, Pter
cent.
of Organic
Compounds.
Fresh mined
After 12 months:
In running water
In stagnant water
Expoi^ to the weather .
83.42
83.70
83.67
83.08
5.91
5.80
5.72
5.49
BITUMINOUS COAL FROM DROCOURT (PAS DE CALAIS) WITH 3.7 PER
CENT OXYGEN.
Fresh mined
After 12 months:
In running water
In stagnant water
Exposed to the weather .
4.08
4.33
4.78
5.77
85.06
85.70
84.67
82.78
5.20
5.26
4.87
5.00
3.68
2.71
3.74
4.54
88.68
89.58
88.92
87.84
5.42
5.49
5.11
5.30
BITUMINOUS COAL FROM AISEAU-PRSlE (CHARLEROI) WITH 1.6 PER
CENT OXYGEN.
Fresh mined
After 12 months:
In running water
In stagnant water
Exposed to the weather .
2.86
89.83
3.88
1.59
92.41
2.64
3.31
3.19
89.30
89.01
88.77
3.79
3.84
3.99
2.61
2.05
2.38
91.70
92.05
91.69
3.99
3.89
3.97
4.05
186
HEAT ENERGY AND FUELS
B. Anthracite.
Anthracite is the last stage of carbonaceous decay. It is black,
very hard and strong, has generally conchoidal fracture (some-
times it is very slaty), and has a specific gravity of 1.40 to 1.80.
Anthracite bums without smoke, with a short, weak, reddish
flame. By distillation an extremely small quantity of volatile
matter is obtained. The composition of the organic component
is:
C 93 to 95 per cent
H 4 to 2 per cent
O + N 3 per cent
100 per cent.
TABLE LXXXII.
ANALYSES OF ANTHRAaTES.
Gu
Coke
C
Pter
oentn
C
H
O
N
H,0
Ash
4
1
OocumjQoe,
cent.
Per
coat.
Per
cent.
cent.
cent.
oent.
Pw
cent.
|g
Ob«rver
Denver, Ruby
Mfn«, U.S.A.
S7.5Ö
3.11
2 fl&
0.13
0.72
4,15
80
Denver, An-
thracite Mine.
Flsdief.
U.Ö.A
80,49
3.33
1.1&
O.Gfl
0.50
4.00
0.7«
. L K .
t^nnsylviLaiii,
Wilkeatwre. .
86 tfl
3,»0
3 SO
5 07
0.43
Schult«.
.,.,Dq
2.7Ä
87.00
86.456
1.1*95
1.440
Ü.75
3.45
5 00
■ . . ,
7484
R Mahler.
Tonkin^.
KebHO
4 5fl
85 19
65.740
3.733
a. 671
0.60
a.SÜ
a. 45
7838
.../Da.
TufBchrr-Alpo
öiyrift
S4.14
2,fiJS
4.16
4 31
4.82
7a30
R.Schö/TeJ.
Wen^lrrti-
Alpe, Styrift.
75.48
2.05
3.86
2.56
16.03
aedo
,..Do.
The distillation yields :
Powdered coke 90 to 92 per cent
Gas 10 to 8 per cent
100 per cent.
The anthracites are of the greatest importance in America,
where they occur in immense deposits. They are of no impor-
tance in Europe.
BITUMINOUS AND ANTHRACITE COALS 187
Suggestions for Lessons.
Examination of various solid fuels. Elementary and interme-
diate analysis, fuel tests, ash analysis.
Determination of the density and of the weight of 1 cu. m.
Examination of green and seasoned fuels.
Determination of the quantity and composition of the included
CHAPTER XIV.
ARTIFICIAL SOLID FUELS.
For certain purposes it is advantageous to use fuels richer in
carbon than the ones occurring in nature. Such fuels are pre-
pared by destructive distillation of the natural solid fuels,
whereby the following products of decomposition are formed:
(1) gases; (2) tar; (3) tar water, and (4) residuum rich in carbon.
The quality and quantity of the products of decomposition
depend on the nature of the raw material, temperature of decom-
position and other circumstances. With increasing temperature
the output of gas increases both as to weight and volume, but
simultaneously the quantity of heavy hydrocarbons in the gas
decreases, and therefore also the illuminating power of the gas.
The pressure under which the distillation is carried out is also
of importance relative to the products formed.
The advantages of producing carbonized (coked) fuels are:
1. A fuel of higher thermal value is obtained.
(a) As the carbon-content of the coked fuel is higher than
that of the natural fuel.
(6) As the volatile substances in spite of their combustibility,
require for their gasification a considerable amoimt of heat,
which is at our disposal when we use coked fuels.
Thereby the cost of transportation per heat unit is decreased.
2. Combustion of coked fuels is smokeless.
3. Coked fuel does not bake.
4. Coked fuel contains less sulphur than does raw fuel.
5. Under certain conditions valuable by-products can be
collected. On the other hand coking has the following disad-
vantages :
1. The carbonizing (coking) of the natural fuels requires a
certain amount of heat, fuel, wages and machinery.
1S8
ARTIFICIAL SOLID FUELS 189
2. C!oked fuel bums with a short flame, while for certain
operations a long flame is essential.
3. The ash-content is increased by coking.
Heat of formation of 1 kg. of a fuel is the number of calories
which were set free by the formation of such fuel from its ele-
ments, and which naturally have to be added again for the
decomposition into the elements. Heat of decomposition is
obtained by deducting the directly observed heat of combus-
tion of the fuel from the sum of the heats of combustion of the
elementary components.
Schwackhöfer found for Ostrau (Austria) nut coal:
C 73.55 per cent
H, 4.54 per cent
11.38 per cent
N 0.46 per cent
Hygr. H jO 2.44 per cent
Ash 5.63 i)er cent
Combustible sulphur 0.60 i)er cent
Thermal value 7433 cal.
The heat of combustion of the elementary components of this
coal are:
C 0.7355 X 8080 = 5942.84 cal.
Hj 0.04;54 X 29,600 - 1343.84 cal.
S 0.0060 X 2500= 15.00 cal.
Toüil 0301.68 cal.
Thermal value of coal deduct 7433.00
Heat of formation of 1 kg. coal - 1131.32 cal.
For coal from Leoben (Styria) Schwackhöfer found :
C 60.91 per cent
H, 4.22 per cent
17.99 per cent
N ; 0.71 per cent
Hygr. HjO 9.92 per cent
Ash 6.25 per cent
Combustible sulphur 0.52 per cent
Thermal value 6013 cal.
190
HEAT ENERGY AND FUELS
The heat of combustion for the elementary components is:
C 0.6091 X 8080 = 4921.53 cal.
H 0.0422 X 29,600 = 1249.12 cal.
S. 0.0052 X 2500 = 13.00 cal.
Total 6183.65 cal.
Thermal value of coal deduct 6013.00 cal.
Heat of formation of 1 kg. coal + 170.65 cal.
The heat necessary for gasifying coal depends on the nature of
the gasification, i.e. the nature of the products of decomposition.
If the gasification is effected by destructive distillation, the heat
necessary equals the difference of the heat of formation of the
coal and the heat of formation of the distillation products
(from the elements). The heat nece^ssary for gasifying can also
be calculated by deducting the thermal value of the distilla-
tion-products (calorimeter) from the thennal value of the coal.
Therefore the heat required for the destructive distillation of
1 kg. of this coal is 254.792 cal.
According to the nature of the raw material, the coked mate-
rials are named:
1. Charcoal.
2. Peat-coal.
3. Coke; to the class of artificial fuels belong also the
4. Briquettes.
TABLE LXXXIII.
CX)MPOSITION AND PRODUCTS OF DESTKUCTn'E DISTILLATION OF COAL.
(P. Mahler.)
SubMtance.
Percentage of Elementary Compo-
Hition.
Ther-
mal
Value
in Cal.
Yield
in Kg.
from
of CoaT.
Thermal
Value of
Products
in Cal.
C
Hj
O
N
A.Hh
H-O
Bitiira. ooal of Coin-
men try
75.182
5.176
8.202
94
7 05
3.45
7423.2
100
742326
Coke
Tar from hydraulic
main
85.773
90.186
89.910
87.222
85.183
55.086
0.414
4.848
4.945
5.499
5.599
21.460
2.043
4
0.62
4M
10 27
0.88
7019.4
8887.0
8942.8
8831.0
8538.4
IIIM.O
65.66
3.59
0.87
1.46
1.89
17.09
9.36
460893 8
319043
7780.2
10243 9
Tar from tar collector.
Tar from cooler
5.145
7.279
9.218
23 4S4
Tar from condenner. . .
16137 6
(las
189887.0
Ammonia water
17 g. per liter
Total
99.62
716846.8
Heat lost in destruc-
tive distillation
25479 2
Coke used as fuel
7019 4
21.09
148055.2
CHAPTER XV.
CHARCOAL.
The dry distillation of wood yields
(a) Hygroscopic water.
(b) Illuminating gas, consisting mainly of
Acetylene, CjH,.
Ethylene, C^H,.
Benzol, CfHe.
Naphthalene, C^^g.
Carbon Monoxide, CO.
Carbon Dioxide, CO,.
Methane, CH^.
Hydrogen, H,.
(c) Tar, consisting of
Benzol, CeH,.
Naphthalene, Cj^Hg.
Paraffin, C^U,^ to CJH^.
Retene, CigHjg.
Phenol, C.H.O.
Oxyphenic Acid, CeHeO,.
Kresylic Acid, C,HgO.
Phloiylic Acid, Cß,,fi.
rC,HA.
Creosote ] CgHj^Oj.
(c,H,A.
Resins
(d) Pyroligneous acid, consisting of
Acetic Acid, CjH^j.
Propionic, Acid, CjHeOj.
Acetone, C3H5O.
Wood Alcohol, CH,0.
(e) Charcoal.
191
192 HEAT ENERGY AND FUELS
Charcoal contains, besides carbon, H, and ash, and generally
also hygroscopic water. The average composition of air-dry
charcoal is
C (including H and 0) 85 per cent
Hygroscopic H^O 12 per cent
Ash 3 per cent
100 per cent.
Tamm takes the average composition of charcoal as follows:
Air-Dry Perfectly Dry
C 75.5 ) 83.0)
12.0 [-90.0 per cent 13.2 [^98.9 per cent
H 2.5 ) 2.7)
Ash 1.0 1.1
Hygr. H,0. 9.0
100.0 100.0
According to the researches of Violette on charring wood, the
wood remains unchanged up to a temperature of 200*^ C; at
232° C. it gets brown; between 270 and 350 ° C. red coal and at
400° C. black coal is formed.
The so-called red wood, which stands between red and black
coal, has the following composition (Fresenius) :
C 52.66 per cent
H 5.78 per cent
O 36.64 per cent
Ash 0.43 per cent
HjO 4 .49 per cent
100.00 per cent.
Violette 's researches comprise the following series:
1. Coals made at different charring temperatures (150° to over
1500° C.) from one kind of wood {Rhamnus frangula).
2. Coals from the same wood produced at different tem-
peratures in entirely closed vessels.
3. Coals from those kinds of wood which are mainly used in
France for gimpowder manufacture.
4. Coals made at 300° C. from 72 different varieties of wood.
CHARCOAL
198
o
o
o
>°
X b;
w ^
O
2
I
SB.
|Ä
I
liili
^ o
12
illllii&
J«1tJ1l|i MUK
if
I
£*
1 1
I
1 I
I i
?i
UttÜ9UmmilUUi^M%Ul
I-«*---«
-V> IFO F »1
t-, ^H!Ei£9aSUJUtU;9;H^'ii»lf^
—'*'*'*» ts::i3S^L5i*r,;ir,XAAitH
194
HEAT ENERGY AND FUELS
For these experiments the wood was cut into cylindrical
pieces of 1 cm. diameter and dried in a current of steam at 150® C^
The charring (except in the second series) was effected up to
350° C. with superheated steam, at higher temperatiu« in a^
crucible at the melting point of antimony, copper, silver, gold,.^
steel, iron, and platinum.
The results of the first series are given in the table on-^
page 193.
TABLE LXXXV.
YIELD OF COAL BY CHARRING. (Karaten.)
Kind of Wood.
Oak wood, young
Oak wood, old
Red beech, young
Red beech, old
White beech, young
White beech, old
Alder, young
Alder, old
Birchwood, young
Poplar
Birchwood, old
Birchwood, well preserved.
Red pine, young
Red pine, old
Fir wood, young
Fir wood, old
Pine, young
Pine, old
Linden
Ash
Willow
Rye straw
Fern
Rapid
Distillation,
Karsten.
16.54
15.91
14.87
14.15
13.11
13.65
14.45
15.30
13.05
12.20
12.15
14.25
14.05
16.22
15.35
15.52
13.75
13.30
13.40
17.00
Slow Distillation.
Karsten.
25.60
25.71
25.87
26.15
25.22
26.45
25.65
25.65
25.05
24.70
25.10
25.25
25.00
27.72
24.75
26.07
25.95
24.60
24.60
27.96
Stolze.
26.1
24.6
23.8
24.4
28.8
24.4
23.4
21.5
23.7
22.8
21.1
22.2
Winkler.
22.8
17.8
li
17.6
17.7
17.6
20.6
20.1
16.2
19.4
15.0
The tests show that quick coking yields only about half as
much charcoal as slow coking.
Violette obtained by charging wood into a preheated (432
degrees) charring vessel about 8.96 per cent coal, while he
obtained 18.87 per cent by heating the same kind of wood for
six hours gradually up to 432 degrees.
In the second series of Violette's experiments the wood pieces
(Rhamnus frangula) were weighed, dried at. 150° C. and were
kept in closed glass tubes at constant temperature with super-
heated steam. The results were :
CHARCOAL
196
>
X
X
X
S3
i
Red brown coal. The tube covered with reddish
tar drops.
Ck)al of ordinary structure. Heavy Ur deposit in
tube.
Black coal of ordinary appearance.
Same.
Black coal covered with drops of molten tar.
Black coal very hard. Appearance of a substance
in the first sUge of meltmg.
Black molten mass without a trace of structure of
wood.
Black, brilliant, entirely molten coal, somewhat
like baked soft coal.
Substance similar to molten, fat. bituminous coal.
s.
§
c
§•3
5
S
1
1
154
0.198
0.294
0.5885
1.7705
2.0315
3.2005
0.5835
4.0720
3.8375
+
45.5325
37.0940
33.4270
28.0150
25.9230
25.2580
26.7680
27.3270
25.5425
14.0415
t3
5.3045
6.1880
5.2470
4.9830
5.1675
5.0995
5.4245
4.5655
4.7600
4.7065
o
1 49.0175
1 56.5235
1 61.0420
1 66.4185
67.1340
J 67.6215
64.6010
J 67.5760
1 65.6185
1 77.0705
2
s
1
1
ee oo oo »^z^, •r»*> •'>«r» *>•'> «o«o ee oo
— — iriirC — —' — — — — — — — — — — ' imm' imc^
1
«e Oflo t^o r»« oir» mM mi^ •▼i>. i#m#> »«>
1
1
sis sisi S5S2; ii as s^s as ^^ ^^ ^^
ll
P= P= P= P: P= P-- P-. P: P: P:
88 88 88 88 88 88 88 88 88 88
1 1 1 ^ 1 1 1 1 § 1
p
i^
5
'^'^^'^^^^•o^S.
196
HEAT EX ERG Y AXD FUELS
The third series of experiments with coals made from different
kinds of wood showed the variable composition of the charcoal
obtained. Violette found in the interior part of the apparatus
coal ¥»ith 85 per cent carbon, on the walls with 70 per cent of
carbon.
In the fourth series of experiments 72 kinds of wood were
dried for two hours with steam of 150° C. and then charred for
three hours with steam of 300° C. The results were as follows :
TABLE LXXXVII.
YIELD OF COAL BY CHARRING.
No.
Kind of Wood dried at 150
Degrees, Charred at
300 Degrees.
Cork wood
Ebony
Satinwood
Willow (foul)
Wood from Herculaneum .
Wheat straw
Oak
Yew tree
Mahogany
Beech
Ironwood
Juniper
Pockwood
Moor pine
Poplar (leaves) .......
Poplar (root)
Fir ..
Fungus growing on willows
Box
Lote-tree
Bird cherry
Palm-tree
Thuja, Canadian
Hemp stalk
Virgin's bower
Rush
Cocoanut-tree
Carded cotton
Elder-tree
Varnish-tree
Rose-tree (wild)
Honeysuckle
Spindle- tree
Vine
Chestnut
Bean trefoil. . .
Yield
of Coal.
Pfer
cent.
62.80
54.30
52 00
52.17
49.69
46.99
46.09
46.06
44.89
44 25
43.75
43 07
41.86
41.48
40.95
40 90
40.75
40 64
40.44
40 35
40.31
39.49
39.44
39.22
38.83
38 46
37.93
37.41 ;
37.31 '
37 27i
37.21
36.96'
36.60,
36.53
36.06;
36 01
No.
Kind of Wood dried at 150
Degrees. Charred at
300 Degrees.
Currant bush
Medlar tree
Cherry bush
American aspen
Hooded milfoil
Ivy
Hawthorn
Plane-tree
Apple-tree
Elm-tree
Hornbeam
Alder-tree
Barberry
Furae . .*
Birch-tree
Plum-tree
Sycamore
Maple
Willow
Alder — buckthorn .
Virginian acacia. . .
Flowery dogwood . .
Broom
Ash-tree
Quince-tree
Hazel-tree
Bird cherrv
Holly-tree*.
Alaternus
Guelder-rose
Pear-tree
Linden
Lilac
Begonia
Poplar
Horse-chestnut. . . .
Yield I
of Goal ,
Pfer I
cent. I
35.66
35.57
35.53
34 87
34.85
34.75
34. 7(
34.69
34.69
34.59
34.44
34.40
34.28
34.24
34.17
34.06
33. 7t
33.75
33.74
33.61
33.42
33.36
33.33
33.28
33.28
32.79
32.70
32.21
32.05
32.03
31.88
31.85
31.84
31.33
31.12
30.861
CHARCOAL 197
The conclusions that can be drawn from Violette's experi-
ments are :
1. Wood yields less coal the higher the temperature. For
the same kind of fuel the yield for instance is :
At 250'' C 50 per cent weight,
At 300° C 33 per cent weight,
At 400° C : . . 20 per cent weight,
At 1500° C 15 per cent weight.
2. From woods treated at the same temperature the yield of
coal is proportional to the time of distillation. With slow dis-
tillation the yield is twice as great as with quick distillation.
3. The carbon content of the coal is proj)ortional to the tem-
perature of distillation; the coal contains for instance:
At 250° C 65 per cent,
At 300° C 73 per cent,
At 400° C 80 per cent.
At 1500° C 96 per cent.
4. By distillation in perfectly closed vessels very little carbon
is gasified, as most of the carbon is retained in the coal in solid
form on account of the increased pressure. This explains the
higher yield in retorts as compared to pile-charring.
5. The charring of wood in perfectly closed vessels 5delds at
280° C. 80 per cent of red coal, while by means of superheated
steam only 40 per cent can be obtained. This is due to the
increased pressure, which changes the equilibrium towards a
smaller volume.
6. In perfectly closed vessels wood melts at from 300 to 400° C.
under formation of a black, brilliant mass, without any organic
structure, similar to melted pitch-coal.
7. Coals produced in cylinders or iron pots are of variable
composition (70 to 84 per cent C), while with superheated steam
— according to temperature — coal of any constant comj)osition
can be made.
The red coal used in gunpowder manufacture is nothing but
half-charred wood of red-brown or brown-black color. It bums
with a long illuminant flame and therefore contains less carbon
and more hydrogen than charcoal proper (black coal).
198
HEAT ENERGY AND FUELS
Good charcoal is black in color with a steel-blue lustre. It
has a distinct wood structure, conchoidal fracture, low specific
gravity (0.17 to 0.24), is fairly strong, easily ignited, and bums
with a very short, blue, smokeless flame.
By lying in the atmosphere charcoal absorbs about 10 per
cent of water; if moistened directly with water, 50 per cent is
absorbed.
WEIGHT OF CHARCOALS (Ptetraschfik).
Charcoal.
100 Liters
Weigh. Kg.
From soft wood, average
From hard wood, average
Hard and soft wood mixed . . .
17
24
21
The loss of volume of charcoal during transportation, etc., by
breakage and friction is, according to Wessely:
Decrease In Volume.
Per cent.
Carting.
Sleighing.
Hours according to quality of
road.
I
2
3
4
Limits. Average.
3-8
1-3
1-2
5i
2
Limits. Average.
3-6
11-3
l-2i
1-U
5
2i
U
One volume of charcoal from boxwood absorbs the following
quantities of gas (Saussure) :
NH, 90 vol.
Ha 85 vol.
SO, 65 vol.
H^ 55 vol.
NO, 40 vol.
CÄ 35 vol.
CO, 35 vol.
CO. 9.42 vol.
9.26 vol.
N 7.50 vol.
CH, 6.00 vol.
H, 1.76 vol-
0.59 g. of different kinds of coal absorb the quantities of dif-
ferent gases (in cu. cm.) given in Table LXXXVIII.
CHARCOAL
199
TABLE LXXXVIII.
ABSORBING CAPACITY OF COALS.
Gases.
Charcoal.
Peat.
Bone
Black.
NH,
HCi
O..
SO,.
98.5
45.0
30.0
14.0
0.8
32.5
96.0
60.0
28.5
10.0
0.6
27.5
43.5
9.0
5.0
0.5
17.5
The temperature of ignition depends on the temperature of
distillation as shown in Table LXXXIX.
TABLE LXXXIX.
TEMPERATURE OF IGNITION OF CHARCOAL (Violette).
Temperature of Charring.
Temperature of Ignition.
300*» C.
260-280° C.
290-350*» C.
432*» C.
1000-1500*» C.
Melting point of plati-
num.
360-380*» C.
340-360*» C.
36O-370*» C.
400*» C.
600-800*» C.
1250*» C.
We can classify as follows the different methods of producing
charcoal.
A. Charring in the
woods or carbon-
izing under mov-
able cover (with
changeable volume
of the charring ap-
paratus).
B. Charring in ap-
paratus with con-
stant volume of
the charring space.
(a) Without
covery of
products.
by-
(a)
inpitH.j^j.
m piles J )2)
vertical,
horizontal.
(6) With recov-
ery of by-prod-
ucts.
(a) Pile-charring
(the heat re-
quired is gen-
erated in the
interior of the
coking Mpiice).
ih) Thc5 hottt for
charrintf is fur-
n i M h c (J tfuMi
outnidif.
(a) in pits.
iß) in piles.
^0 The heat necessary for char-
ring is furniNhod by partly
burning the wood to be charred
(piles with admission of air to
the interior).
' li) The heiit necessary for char-
ring is fiirnished by combustion
l»y gostis tr^^^"» '»' oxygen (piles
with a^lmission of combustion
tciiMiiH trm of oxygen to the
rriturior). , , ,
(>) 1*he heat !• furnished by
superheated steam.
200
HEAT ENERGY AND FUELS
A. Charring in the woods.
(a) Charring without recovery of by-products,
(a) Charring in pits.
The pits are about 1 m. deep, 2 m. wide at the top,
somewhat narrower at the bottom. The fire is started
with brushwood, then the wood is piled up and cov-
ered with earth. The coal is light and unequally
burned,
(^i) Charring in round piles.
These piles have generally the form of a paraboloid,
and their cubic content is calculated according to the
formula
dPn h _ <Phiz
or, as on the finished pile, the circumference can be figured more
easily than the diameter:
M*
t: h
4*2
8;:
u^ h
25.31 '
As, however, the shape of the piles is not exactly like a para-
boloid, from 4 to 6 per cent is deducted from the volume calcu-
lated according to above formula.
The following varieties of wood are mainly used for charring
in piles: — of coniferous trees: pine, fir, red pine, and larch; of
leaved wood: oak, red beech, white beech, ash, elm, alder, and
birch. The most favorable age of trees for charring is given in
Table XC.
TABLE XC.
PROPER AGE OF TREES FOR CHARRING. (Sdieerer.)
Wood.
Age of most Per-
fect Development.
Aice at which TYee
can be cut.
Pine
140
150
80 to 100
80 to 90
200 to 250
\ 120 to 140
80
40
80 to 100
70 to 80
60
50
50 to 60
120
20 to 30
18 to 20
20
Red pine
Fir
Larch
Oak
Red beech
White beech
Elm
Alder
Birch
CHARCOAL 201
In winter time the wood contains less moisture than in sum-
mer; winter is therefore the most favorable time for cutting the
wood. For the erection of piles, locations are selected that are
protected from wind, and a ground not too dry and not too wet.
A dry ground will break and crack, allowing too much air to enter
into the pile. A wet ground generates steam, which, with the
glowing coal, is decomposed into hydrogen and carbon dioxide.
In both cases a loss of coal results. The foundation ground of
the pile, which is a little inclined towards the center, is first of all
covered with a layer of eulm coal. In the center a strong,
straight post (center pole) is driven into the ground (Slavic piles,
Figs. 32 and 33), or three posts of even length are driven in,
forming an equilateral triangle, the length of the sides being
about 20 cm. These three posts form the center shaft (Italian
piles. Fig. 34). Logs are now laid around, the center of the
charcoal kiln (pile), either vertical as in Fig. 34, or horizontal, or
both ways combined, as shown in Fig. 33. Depending on the
size of the pile, one, two, or more layers of logs are put together,
the upper layer always being less steep than the lower. Small
logs are used to fill the spaces between the large logs. The
upper layer is covered with small logs and small pieces of wood,
for rounding the shape of the pile (peak of the pile). In piles
with center shafts the logs are always vertical, except the dome,
which consists of horizontal logs. In these piles the center shaft
is used for starting the fire, while in piles with a center post a
channel is left open for this purpose on one side of the bottom
part, extending to the center. The pile is then covered on the
outside with branch wood, then with leaves and grans (smoke
cover), and at last with earth, sand, and coal cuhn (earth cover).
This cover does not reach to the ground (Fig. 32, C, D), but is
supported by timber. For starting the fire some kindling wood
is put in on the bottom at the center.
The fire is started by inserting glowing coal in the kindling
wood through the center shaft or through the alK)ve-nientionc(l
channel. Then the shaft is filled with Hrnall piecc^s of wood and
covered. The fire now ext^^nds upwards and to iha Hides; the
hygroscopic water is evaf^orated and coruhnmes again on the sur-
face of the pile (the pile Hweats). Then acid ganen and laUT com-
bustible ga-ses escajK», and whenever they «el. mixed with air an
explosion takes place, throwing olT parln of the cover or parts of
CHARCOAL 203
the pile. Such damage to the pile has to be repaired instantly.
This first period of charring lasts from 18 to 24 hours.
Meanwhile the center shaft is burned out and pieces of wood
have to be filled in again and again until the period of sweating
is over. The bottom of the pile is now also covered, and by mak-
ing openings into the cover (driving the pile) the fire is drawn
gradually to the lowest parts. The upper openings are closed
as soon as blue smoke starts to escape, the lower as soon as the
flame shoots through.
The "drawing" of the coal is performed by removing the cover
on one side and cooling the hot coal with cold water.
The coal is marketed in the following sizes :
(1) Lump coal; (2) blacksmith coal; (3) small size; (4) culm;
(5) half-charred wood.
According to the size of the pile (120 to 300 cu. m.) the process
of charring requires from 15 to 20 days.
Probably the largest pile kilns are operated at Neuberg
(Styria, Austria). They are built up to 400 to 430 cu. m.
capacity, the 500 cu. m. size having been abandoned on account
of difficulty of regulation. Red pine and red beech are charred
at Neuberg in separate piles. The following data, gathered from
these plants might be of interest:
•1 cu. m. hard wood half dry weighs 550 kg.
1 cu. m. soft wood half dry weighs 400 kg.
1 cu. m. (cord wood) hard wood green weighs 900 kg.
1 cu. m. (cord wood) hard wood half dry weighs 700 kg.
1 cu. m. (cord wood) hard wood dry weighs 580 kg.
1 cu. m. (cord wood) soft wood green weighs 800 kg.
1 cu. m. (cord wood) soft wood half dry weighs 600 kg.
1 cu. m. (cord wood) soft wood dry weighs 400 kg.
100 liters hard coal weighs 23 kg.
100 liters soft coal weigLs 14 kg.
The piles have a diameter of 14 m., a height of 4.7 m., and a
cubic content of 400 cu. m. of wood. They are built with five
layers of log wood of 1 m. height. The yield of such a pile is
Kece coal (large pieces) . . . 2000 hectoliters ) GO per cent volume
Piece coal (small pieces) . . 400 hectoliters ) of the wood,
Culm 1 per cent,
Half-charred wood 1 per cent.
204
HEAT ENERGY AND FUELS
TABLE XCI.
COMPOSITION OF KILN GASES. (Ebelmen.)
No.
I
Hours after
Starting.
48
72
96
66
71
95
Appearance of das.
white opaque
white opaque
white opaque. .
white transparent
fairly transparent
bluish and transparent.
Composition in Per Cent.
(Volume.)
CO,
25.67
26.68
27.23
2aL51
23.28
23.08
CO
8.68
9.25
7.67
5.00
5.88
6.04
H,
9.13
10.97
11.64
4.
13.53
14.11
N,
56.62
53.40
53.46
66.60
57.31
55.77
The time required is :
Erection of pile 4 da3rs,
Starting fire \ hour,
Charring process 18-28 days^
Remo\ang charcoal 4 days.
In working shifts :
Erection 4 days per 10 men 40 shifts,
Covering with branch wood 1 day per 2 men 2 shifts,
Coveringwith leaves 2 shifts,
Covering with earth 1 day per 12 men 12 shifts.
Charring, average 8 shifts,
Remo\ing charcoal 4 days per 8 men 32 shifts.
Preparing ground 2 shifts.
Night-watch (average) 2 shifts.
100 shifts.
The temperature of the escaping gas right below the cover
was from 230 to 200° C. One liter of same showed the following
content of condensable products (tar, water, etc.):
1. White and opaque 0.987 g.
2. Similar to ^4 1.068 g.
3. Bluish and transparent 0.531 g.
(^j) Charring in rectangular piles.
CIIAHCOAL
306
Tlie horizontal piles are not circular but oblongs generally
hftving a length of from 9,5 m. to 12.5 in. and a width of from 2
to 3 m, (Fig, 35), They arc surrounded by posts wMch are
connected by timbcri?. The log>s arc put in ixTt>endicular to the
Flu 35. — tt^^^tmiKuJtir Pile»
longitudinal a>ü.s of the pile. The liollow spates are filleil nut
\vith branch wood. The height in front i« about 0,(> and
increases towanls the Imck part at an angle of from 15 to 20
degrees. The fire is startal in the front and goe^ slowly through
the entire leugtli of the pile,
(i) Charring in the woods with recovery of by-product^s.
(a) When charring in pits a ve^^sel covered with a grate is
put on tlie b<^>ttoni for collecting the tar,
(ß) In pileH^harring (for recovering by-prod uct-^) iron ])it)es
are put into the cover, lea^ting to a condensing chamber.
This is done 24—CJ(i hours after starting the fii^^ as in the
first periof.! almost nothing but ,steara escapes.
36 shows a French pile with a channel leading to a tar-
ag vei>sel, AUnit 20 |K?r cent of tar is obtained.
ß, Charrinfj in apfxiratuK with condant mlmne of the
cftarring apace*
(a) Pile-charring,
(a) The heat necessar>' for charring is furnished by partly
burning the wood to be charred (piles with a^lmission of
air to the interior).
206
HEAT ENERGY AND FUELS
As an example we will describe the round pile oven (kiln),
Fig. 37, which has a grate on the bottom for the admission of air,
the quantity of the latter being regulated by means of the ash-
Fio. 36.— French Pile.
door. The wood is charged first through the main door, then
through the upper charging-chute. After starting the fire the
main door is closed with bricks and mortar and as soon as steam
Cbarging
Hole -^
yjf9e>y/yAyyjy/XY/yyy/>yyyy/>yxy^^
Fio. 37. — Round Pile Oven.
and tar be^n to escape, the upper char^ng-chute is also closed,
so that the escaping gases have to go through the pipe shown at
one side of the cover (dome) to the condensing vessels. When
the oven is sufficiently heated, the ash-door is closed. When
CHARCOAL.
207
the charring is finished, the oven is allowed to cool and the coal
removed through the main door.
(ß) Charring in pile-oven with admission of combustion
gases free of oxygen to the interior.
Such an oven was built by Grill for the iron works in Dalfors
(Sweden), Figs. 38 and 39. It is rectangular and provided with
Stack
Fio8. 38 and 39. — Grill's Pile Oven.
charging openings on both short sides. The gases of combustion
rise from a fireplace below the oven, pass vertically through the
center of the oven and escape in four directions through side-
flues. The volatile products of distillation escape through two
208
HEAT ENERGY AND FUELS
channels arranged in opposite comers, and pass throu^ iron-
pipes to a tar-collecting vessel, the stack being arranged above
this vessel. After getting the fire up, the oven is closed tight.
A charge consists of 172.26 cu. m. of wood; 37.58 cu. m. of wood
are used for heating; the yield is 147.31 cu. m. charcoal. The
wages per cu. m. of charcoal at this plant are 6.25 cents.
The Schwartz oven is of similar construction. Figs. 40 and 41.
It is provided with two fireplaces in the middle of its length, and
Fireplace
Vu.H. 40 and 41. — Scliwartz Oven.
with two flues in the middle of the short sides, whereby a more
unifomi heat i« obtained.
(;-) Heating by means of superheated steam (Fig. 42).
Tliis process, which was introduced by Violette for the manu-
facture of red coal (gunpowder coal), yields about 36^^ per cent
of red coal and no black coal, and is therefore very much superior
to the old process by which 14.18 per cent red coal and 17.81 per
cent black coal (total 31.99 per cent) is obtained. Fig. 42 shows
a longitudinal section. Steam from a boiler is led through a coil
located in the oven. By the direct fire the steam in the coil is
CHARCOAL
209
superheated. The fire gases play around the retort and escape
through the flue. The superheated steam from the coil enters
the sheet-iron cylinder (retort), which is closed in front with a
wrought>-iron cover, and then passes into the inner cylinder,
which is charged with the wood to be charred. Steam and
Fig. 42. — Charring with Superheated Steam.
5
FUfipUcfl
Fio. 43. — Section through French Oven heated from the Outsitlr.
products of distillation escape through a pipe into the atmos-
phere or into a suitable condensing apparatus. Opposite the
entrance of steam a baffle-plate is provided for distributing the
steam.
(6) Charring by heat supplied from the outside.
210
HEAT ENERGY AXD FUEL
Figs. 41-47. — Pile Retort Oven.
Figs. 48-52. — Ovens with Horizontal Retorts.
CHARCOAL
211
Charring is performed in retorts or large cylindrical vessels.
In Russia, vertical sheet-iron cylinders are used, having a cubic
content of about 8 cu. m. : a special fireplace is provided for heat-
Fio. 53. — Longitudinal Section of a Modem Charring Plant with Vertical Retorts.
ing the vertical shell. For quickly preheating the wood to 100
degrees, steam is admitted at the bottom of the cylinder. The
tar flows through a pipe arranged at the bottom, to a collecting
Fio. 54. — Cross-section of a Modem Charring Plant with Vertical IletorUi.
vessel, while the vapors leave through a pipe on the tof), and go
to a condensing apparatun, from which ihr condenHod tar passes
to the above-mentioned collecting vohhcI. The products of dis-
212
HEAT ENERGY AND FUEL
tillation pass through a cooled pipe, while the combustible gasses
are lead back into the fire.
t^^^^^^^'^^^^^.^.:::7?^^^^±^^E^^
Fio. 55. — Plan of a Modem Charring Plant with Vertical Retorts.
Fio. 56. — Modem Charring Plant
with Vertical Retorts.
Fig. 43 show's a vertical section through a French oven of simi-
lar type. Vertical, horizontal and inclined retorts are used with
equal success for charring wood.
At present pile ovens are used
only for certain purposes, as, for
instance, for charring pine wood,
where the recovery of the valuable
Swedish tar and pine oil more than
pays for the loss of wood-alcohol
and acetate of lime.
Modern pile ovens are built of
sheet iron for avoiding the loss
through brickwork.
Such a modern pile-retort oven
is shown in Figs. 44 to 47. In the
fireplace the grate e (Fig. 46) and
the arch dd (Fig. 44) can be seen.
Through the arch the fire gases go
into the pipes /, while another part
of the fire gases goes upwards near
the arch and enters the pipes, e.
Fi«.
57. — Oven with Stationary*
Permanent Retort».
All these vertical pipes go
CHARCOAL 213
through the interior of the pile-retort. The doors bb are used
for discharging.
Similar ovens with horizontal retorts are shown in Figs. 48
to 52. Figs. 53 to 56 show a modem charring plant with verti-
cal retorts. The retorts a can be lifted out of the furnace by a
crane gf, and can be brought to a suitable place for charging or
discharging. Fig. 57 shows an oven where the retorts remain in
permanently; they are discharged into small cars that can be
moved right under the retorts.
To the rotary retort, however, belongs the future of the char-
coal industry.
The increase of the charcoal industry is shown by the following
figures, which relate to this industry in Austria-Hungary:
About 30 years ago the output of charcoal was about 10,000
cu. m., ten years later 120,000 cu. m., and today it is 350-400,000
cu. m. per year.
For the prosperity of forestry this industry is of the greatest
importance, as only hereby are we enabled thoroughly to utilize
widely distributed forests (by the utilization of refuse wood).
CHAPTER XVI.
17.625 gas
PEAT-COAL, COKE AND BRIQUETTES.
The destructive distillation of peat, lignite or coal yields:
(1) gases, (2) tar, (3) tar water, and (4) a solid residue very
high in carbon, which, depending on the raw material used, is
called peat coal or coke.
For conveying an idea of the process of destructive distillation,
we give below tables for the two extreme cases (peat and bitu-
minous coal).
Destructive Distillation of Peat. (H. Vohl.)
100 parts of peat of a Swiss bog yielded by destructive dis-
tillation :
'Heavy Hydrocarbons, CnH^n
Methan, CH,
Hydrogen, H^
Carbon Monoxide, CO
fTar 0.820 sp. g.
5.375 tar ^ Heavy Oil 0.855 sp. g.
I Paraffin
Ammonia
Methylamin
Picolin
Lutidin
Anilin
Caespidin
'CO,
H^
CyH
Acetic Acid
Propionic Acid
Butyric Acid
Valerianic Acid
Phenol
25.00 tar water
bases
acids -«
water
25.00 peat coal
214
PEAT-COAL, COKE AND BRIQUETTES 216
Destructive Distillation of Bituminous Coal.
(R. Wagner.)
100 parts gas coal of the following composition :
C 78 . per cent
Disposable Hj 4.0 per cent
N 1.5 per cent
S 0.8 per cent
KjO chemic combined 5.7 per cent
KjO hygroscopic 5.0 per cent
Ash 5.0 per cent
'0
J
100.0 per cent.
Products of dry distillation :
1 70-75 Darts of coke \ ^^^^^ containing H, and 0, 90-95%
1. 70-75 parts ot coke | ^^^ ^^^ ^^^^^ xmMij^T^, 10- 5%
2. Tar water (ammonia water) containing
(a) Main components (water, carbonate of ammonia and
sulphide of ammonia).
09) Additional components (chloride, cyanide and sulfo-
cyanide of ammonia).
Tar, containing:
(a) Liquid hydrocarbons (Benzol, Tolnol, Pseudocumol,
Cyanol, Propyl, Butyl, etc.).
09) Solid hydrocarbons (Naphthalin, Acetylnaphthalin, An-
thracen, Reten, Chrysen, Pyren).
ijf) Substances containing oxygen (Phenol, Kresol, Phlorol,
Rosolic Acid, Oxyphenolic Acid, Creosote, Pyridin, Anilin,
Picolin, Lutidin, Collidin, Leukolin, Iridolin, Akridin).
{S) Asphaltic substances (Anthracen, Resins, Cüoal).
piuminating Gas:
"Gases: Acetylen, Ethylen, Propylen, Bu-
(a) Illuminante \yl^^ g^nzol, Styrol, NaphthaUn,
Acetylnaphthalin, Propyl, ButyL
216 HEAT ENERGY AND FUELS
(ß) Diluting parts (Hydrogen, Methane, Carbon Monoxide).
(y) Impurities (Carbon dioxide. Ammonia, Cyanogen, Rho-
dan, Sulfuretted Hydrogen, Sulfuretted Hydrocarbons,
Bisulphide of Carbon, Nitrogen).
The manner in which the distillation proceeds and the
(juantity and composition of the various products are distinctly
aflfected by other factors than the character of the raw mate-
rials. The most important of these factors is the gasifying
temperature.
L. T. Wright has distilled at diflferent temperatures a coal of
the following composition:
C 75.71 per cent,
H2 6 . 27 per cent,
S 1 . 72 per cent,
N 1 .72 per cent,
O 11 . 59 per cent,
Ash 2.99 per cent,
100.00 per cent.
The yield of 100 kg. of coal at a gasifying temperature of 800° C.
is given in Table XCII.
TABLE XCII.
ANALYSIS OF DESTRUCTIVE DISTILLATION PRODUCTS.
100 Kg. Coal
Yielded.
Coke
C
",
s
N
Ash.
Total.
Liters.
57.38
6.11
0.08
7.56
0.22
1.24
0.46
1.06
2.85
0.02
Kk.
1.05
0.05
0.12
trace
0.39
1.06
0.06
0.22
0.36
0.56
1.28
0.60
8.30
1.46
0.56
2.96
64.97
7.28
9.78
12.23
1.20
Tar
Gas water
Gas
6.43
9.78
21140.0
In purifying mass
Total
71.35
5.63
1.61
1.71
12.20
2.96
95.46
PEAT-COAL, COKE ASD BRIQUETTES
217
The yield obtained at a temperature of 1100° C. is given in
Table XCIU.
TABLE XCIII.
ANALYSIS OF DESTRUCTIVE DISTILLATION PRODUCTS.
100 Kg. OmJ
Yielded.
Ash.
Kg.
Toul.
Liters.
Coke
Tar
Gas water
Gas
In purifying mass
Total....
57.95
0.70
0.77
0.47
1.24
4.78
0.38
0.06
0.05
1.18
0.08
1.06
0.13
0.21
8.30
8.53
3.42
trace
0.86
2.30
0.38
0.04
0.74
0.02
0.93
71.73
5.61
1.70
1.61
13.95
2.97
64.10
6.47
9.78
15.11
2.11
5.37
9.66
31200.0
2.97
97.57
At 800° C.
At 1100**C.
There was further
Soot in tar
Specific gravity of gas water
Illuminating po^er of gas at an
hourly use of 150 liters
15 per cent
1.0
18 candles
25-30 per cent
1.2
15.3 candles
A further comparison shows:
Coke
Tar
Gas water
Gas
At 800° C.
64.75 kg.
6.43 1.
9.78 1.
21.14 cu. m.
At 1100**C.
64.16 kg.
5.37 1.
9.96 1.
31.20 cu. m.
With increasing temperature the gas quantity (volume), the
specific gravity of the tar, and its content of soot, increase, while
the crude naphtha and, especially on light tar oil, content of tar
considerably decrease.
With increasing temperature the creosote and anthracen oil
content decreases, while the pitch content increases. The
sulphur content of the gas other than that in the form of H^ is
three times as great at the high as at the low temperature. The
ammonia content is small at low temperature, is a maximum at
medium and decreases with temperature rise at high temperature.
218
HEAT ENERGY AND FUELS
3
4 5 6
27
20 G
0.30
0.10 0.4
The course of distillation is different at the be^nning and at
the end. In the Paris gas plant at a temperature of 1000^ C.
there is obtained :
Time of distillation, hrs.O 1 2
Volume of gas 17 30
lUum. power per 105 1. . .0 1.15 0.90
C. G. Miller divides the time of distillation into two periods:
In the first — the period of distillation proper — at the com-
paratively low temperature of 500^-600° C. strongly iUuminant
gases, steam and tar are generated while the coal is coked. In
the second period (bright red glow) the coke, decreasing in
volume, yields gases (about one-third of the total gas volume)
which are free of tar and of low illuminating power. The coke
remaining at the end of the first period is probably a mixture of
very stable carbon-compounds having the average composition
Ci|Hp. This substance is further decomposed in the second
period at high temperature. But even at the highest practical
heat it is impossible to remove the traces of oxygen, hydrogen
and nitrogen.
If large quantities of coal are put into highly heated retorts,
both processes take place simultaneously. The two, however
(coal decomposition and coke decomposition), could be separated
by using two furnaces, one for heating the material to 600 degrees
and removing the tar, the other to decompose the coke. Such
a separation might be practicable under certain conditions.
The experiments made by Mueller on a small scale confirm the
well-known fact that only one-fifth of the nitrogen of the coal
is present in the form of ammonia compounds; further, that liie
ammonia is formed in the first part of the decomposition of
coke. The ammonia yield was
Test.
In the First Period.
In the Second Po-Jod.
No. 1
2
3
4
5
6
Average
0.065
059
0.108
0.120
0.063
0.056
0.267
0.144
0.145
0.178
0.183
0.242
0.0785
0.1931
PEAT-COAL, COKE AXD BRIQUETTES
219
How the composition of the products changes by using dif-
ferent qualities of gas-coal is shown in Table XCIV.
TABLE XCIV.
CHANGE IN COMPOSITION OF PRODUCTS WITH QUALITY OF COAL.
Bituminous Coal from
a
o
*5
'S
a
B
6
HjO, hygroscopic.
Ash...'
Gas.
Tar.
2
•3q ^ Ammonia water.
Kl
Coke.
Coal dust .
Pas de Calais.
2.17
9.04
5.56
$.06
88.38
1
13.70
3.90
4.59
71.48
6.33
2.70
7.06
6.66
5.36
86.97
1
15.08
4.65
5.57
57.63
7.07
Eng-
land.
Comen-
try.
3.31
7.21
7.71
5.40
85.89
I
15.81
5.08
6.80
64.90
7.41
4.34
8.8
10.10
5.53
83.37
16.95
5.48
8.61
60.88
8.08
Blanzy.
6.17
10.73
11.70
5.64
81.66
17
5.59
9.86
58
9.36
o
>
O
Volume, cu.m
Illuminating power, Carcell
30.13
131c
31.01
112c
30.64
104c
29.73
102.1c
27.44
101.8c
CO,.
CO.
C,H,..
1.47
6.68
54.21
34.37
0.79
2.48
1.58
7.17
52.79
34.43
0.99
3.02
1.72
8.21
50.10
35.03
0.96
3.98
2.79
9.86
45.45
36.42
1.04
4.44
3.13
11.93
42.26
37.14
0.88
4.76
The influence of the mineral substances on the course of dis-
tillation is remarkable, as is seen from Knoblauch's researches.
He mixed with his coal 2.5, 5, and 10 per cent of lime, and 5 per
cent silica respectively. The table on following page shows the
differences of yield with these mixtures (from 1000 kg. of coal).
We see that the quantity of products of distillation is not
chan^ng in proportion to the quantity of the addition. The
gas yield, however, seems to be an exception, as it increases in
proportion to the addition. The yield in ammonia increases
very slowly as the lime is added, so that with a certain quantity
of lime a maximum is reached, above which even a large addition
of lime has no effect. There is no relation between silica and
ammonia and H^S, since no reaction takes place. The small
differences shown in the above table are caused by variations in
220
HEAT ENERGY AND FUELS
the decomposition of the coal, since the quantity of coke
increases with additions more rapidly than the quantity of tar
decreases, and since at the same time gas quantity increases the
carbon content and therefore the illuminating power of the gas
Is necessarily decreased, which decrease is not sufficiently
counterbalanced by the increased yield of gas.
TABLE XCV.
EFFECT OF ADMIXTURE OF LIME AND SILICA IN DISTILLATION PRODUCTS.
1000 Kg. Coal.
Gas, cu. m. increase
Coke, kg. increase
Tar, kg. decrease
Ammonia, kg. increase
Sulphate, kg. increase
H^ö, kg. decrease
H^S, cu. m., decrease
Ammonia ) in per cent ( increase
H^S J of yield | decrease
Addition of Lime.
2.5
Pkt cent.
14.7
16.8
5.2
0.483
2.02
1.42
0.93
21.3
59.7
5
Prt cent.
20.1
18.2
7.9
0.608
2.53
1.58
1.03
26.7
66.2
10
Per cent.
35.3
17.5
9.0
0.929
3.88
1.81
1.19
40.9
76.2
Addition
of
Silica.
5
Percent.
21.5
27.4
11.8
0.15
0.67
0.21
0.138
0.7
8.8
For coals of approximately the same composition as the test-
coal we can estimate the effect of adding 2.5 per cent of lime as
follows:
1. The yield of gas is increased 5 per cent, the illuminating
power decreased 5 per cent.
2. The yield of coke is 4 per cent higher, of which 2.5 per cent
is lime, so that the actual increase of coke-output is 1.5 per cent.
This increase is not accompanied by an increase in thermal
value, on account of the higher ash content.
3. The quantity of tar is decreased 10 per cent and its quality
deteriorated.
4. The ammonia output is increased 20 per cent.
5. The H^S output is decreased at the rate of 1.4 per 1000 kg.
coal.
6. The CO2 of the crude gas is increased 10 per cent.
7. The formation of cyan is somewhat decreased, but the
quantity of ferrocyan is not changed.
PEAT-COAL, COKE AND BRIQUETTES
221
This point, however, and also the question as to what extent
the higher sulphur content of the coke (m the above case about
0.2 per cent) appears as combustible sulphur, have to be further
considered.
W. Jicinski made experiments with Moravian (Austria) coal
from Ostrau of 5 mines; the composition is given in Table XCV,
and the yield from destructive distillation is given in Table XCVI.
TABLE XCV.
COMPOSITION OF MORAVIAN COALS. (Jicinski.)
Air>dried
Coal from
C
H
O
N
Ash.
Johann ....
81.74
5.53
6.18
1.31
5.24
Adolf
81.80
5.23
8.31
1.76
2.89
Günther . . .
80.54
5.09
7.66
1.43
5.27
Franziska..
83.35
4.66
5.06
1.52
5.37
Juliana —
86.76
4.06
3.51
1.30
4.73
Coking
Quality.
Quality.
Good
Very good
Very good
Excellent
Fair
Gas coal
Gas coal
Coking coal
Coking coal
Anthracite coal
S Content : . 50 to 1 . 05 per cent. P Content : . 004 to . 108 per cent.
TABLE XCVI.
YIELD FROM DESTRUCTIVE DISTILLATION OF COALS GIVEN IN TABLE
XCV.
Mine.
Ptr 1 Kg. of Coal
Cu. M. of Gas.
Coke Residuum.
Percent.
Johann. . . .
30.86
30.02
29.96
28.60
27.12
• 67.00
76.00
75.00
81.38
86 62
Adolf
Günther
Franziska
Juliana
The ammonia output is not in proportion to the nitrogen
content of the coal. Ammonia seems to separate from some
coab easier than from others. As an average about 0.75 of the
total nitrogen of the coal remains in the coke; this is the so-called
222
HEAT ENERGY AXD FUELS
coal-riitrogen, wJiich is only gasified by the complete combustion
of the coal. About 0.25 of the total nitrogen — the anamonia
nitrogen — takes part in the formation of ammonia. But even
from this, one part escapes as cyan or as free nitrogen, so that
the quantity of nitrogen actually available for the ammonia
formation is only 0.188 to 0.089 of the total nitrogen. The table
below shows the available quantity of ammonia nitrogen in some
coals.
The tar from coke ovens contains generally
Benzene 0.9 -1.06 per cent,
Naphthalene 4.26-5.27 per cent,
Anthracen 0.57-0.64 per cent.
Pitch 50 per cent,
Other residuum 40 per cent.
TABLE XCVII.
AVAILABLE QUANTITY OF AMMONIA IN COALS.
Available
for NH,.
^i
11
^|!
Mint*.
55
In Per
Cent of
Coal.
«6
P
Kaiserstuhl
1.39
0.144
0.200
0.244
0.94
Pluto Westphalia
1.45
0.146
0.212
0.258
1.00
3.4
Wilhelmine
1.77
0.142
0.252
0.306
1.18
Johann i
1.31
0.140
0.184
0.244
0.94
1.7
Adolf
1.76
0.126
0.222
0.270
1.04
1.7
Günther
Austria
1.43
0.120
0.172
0.210
0.81
1.3
Franziska
1.52
0.089
0.135
0.165
0.64
2.6
Juliana
1.30
0.134
0.175
0.213
0.82
1.8
Upper Silesia, averac'e
2.49
0.188
0.296
0.360
1.40
3.6
FriedenshoflFnung
Un-
Un-
0.168
0.204
0.79
3.0
Karl, Georg
Lower Silesia
und Viktor
known
known
0.148
0.180
1.69
2.5
England, average
1.40
0.167
0.235
0.286
1.11
3.12
The average tax output on a large scale is from 2 to 3 per cent
of the coal. The diflference between coke oven gas and gas
hoase gas is given in Table XCVIII.
peat-coal, coke axd briquettes
223
TABLE XCVIII.
ANALYSIS OF COKE OVEN AND ILLUMINATING GAS.
Components.
Benzole vapor .
Ethylene
HJS
C(^
CO
Sum
Coke Oven
Gas.
Per Cent.
0.61
1.63
0.43
1.41
6.49
53.32
36.11
100.00
From Gas
House
Per Cent.
1.54
1.19
0.87
5.40
55.00
36.00
100.00
The experiments relative to the yield of carbonizing (coking)
peat made by Sir Robert Kane and Professor Sullivan have given
the following results :
TABLE XCIX.
ANALYSIS OF COKE OVEN GAS.
Products Obtained
by Coking.
Methane
Carbon monoxide . . . .
Carbon dioxide
Olefine gas
H^S
NÜ,*: :!!!!! !!!;"!"""
N
H,0
Tar
Coke
Volatile components .
Combustible gases . . .
From an Oven at
Serai ng (Ebeimen).
7h
14
Hours after Starting.
1.44
4.17
10.13
6.28
77.98
1.66
3.91
9.60
3.67
81.16
0.40
2.19
13.06
1.10
83.25
Aver-
age.
1.17
3.42
10.93
3.68
80.80
From
Ga»-
forth
Coal
(Bun-
sen).
7.0
1.1
1.1
0.7
0.5
12.23
68.92
From Alfre-
ton Coal,
Distilled
(Bunsen).
For-
ward.
6.6
1.6
1.1
0.5
0.2
0.4
0.2
12.4
9.7
67.2
30.8 to 32.
19.2 to 22
Back-
ward.
6.2
6.3
2.3
1.6
0.2
1.4
0.3
[16.6
'65.1
7%
3%
100 pounds of peat of dififerent quality was coked in retorts
similar to illuminating gas retorts. The volatile matters were
224
HEAT ENERGY AND FUELS
condensed in a number of Woulf-bottles and in a cooled coil.
The gases were also collected (Table C).
TABLE C.
PRODUCTS OF PEAT DISTILLATION.
Origin.
Light peat .
Dense peat
Even mixture of
light and heavy
peat of Mount Lu-
cas Bog near Phil-
« lipstown.
Light peat from Wood of Allen . . . .
Heavy peat from Wood of Allen . . .
Upper layer of Ticknevin
Upper layer of Ticknevin, distilled
at red glow
Upper layer of Shannon
Dense peat
Average .
Water.
23.600
32.273
38.102
38.628
32.098
38.127
21.1^9
31.378
Tar.
2.000
3.577
2.767
2.916
2.344
4.417
1.462
2.787
Coal.
37.600
39.132
32.642
31.110
23.437
21.873
18.973
29.222
Gas.
36.900
25.018
26.489
32.346
42.121
35.693
57.746
36.606
TABLE CI.
PRODUCTS FROM DISTILLATION OF PEAT.
Tar Water.
Tar.
Ammonia.
Acetic Acid
_.
Origin.
<
1
5
1
h
2
2;
i
O
<
fEven mix-
tures of
Ught
light and
peat
Dense
heavy peat
0.302
1.171
0.076
0.111
0.092
0.024
0.684
0.469
of Mount
peat
Lucas Bog,
near Phil-
lipstown
Light peat from
Wood of Allen . . .
0.187
0.725
0.206
0.302
0.171
0.179
0.721
0.760
Heavy peat from
Wood of Allen ...
0.393
1.524
0.286
0.419
0.197
0.075
0.571
0.565
Upper layer of Tick-
nevm
0.210
0.814
0.196
0.287
0.147
0.170
0.262
0.617
Upper layer of Tick-
nevin, distilled at
red glow
0.195
0.756
0.208
0.305
0.161
0.196
0.816
0.493
Upper layer of Shan-
non.
0.404
0.181
1.576
0.702
0.205
0.161
0.299
0.236
0.132
0.119
0.181
0.112
0.829
0.647
0.680
0.266
Dense i
)eat
erage
Av
0.268
1.037
0.191
0.280
0.146
0.134
0.790
0.550
PEAT-COAL, COKE AND BRIQUETTES
225
The analysis of the tar water and tar showed for the qualities
given in Table CI.
Table CII gives the results of another series of experiments in
which a part of the peat was burned by means of a blower.
TABLE CII.
PEAT DISTILLATION.
Origin.
Water.
Tar.
Ash.
Gases.
Light peat from Wood of Allen
Heavy peat from Wood of Allen . . .
Upper layer of Shannon
30.678
30.663
29.818
2.510
2.395
2.270
2.493
7.226 .
2.871
63.319
59.716
65.041
For further comparison the figures given in Table CIII, taken
from both series of experiments, will be interesting:
TABLE CIII.
PEAT DISTILLATION.
Origin.
Tar Water.
Tar.
NH3.
Acetic
Acid.
Alcohol
CH^O
Paraf-
fin.
Oil.
Liflrht Deat from Wood of Allen
0.322
0.344
0.194
0.179
0.268
0.174
0.158
0.156
0.106
0.169
0.086
0.119
1.220
0.946
1.012
Heavy peat from Wood of Allen
Upper layer of Shannon
Averaere
0.287
0.207
0.140
0.125
1.059
These tables also give an idea of the valuable products obtained
by distilling peat. Tabic CIV from Muspratt's Chemistry gives
the yields from Irish peat.
TABLE CIV.
DESTRUCTn-E DISTILLATION OF PEAT.
Products of Destructive
Distillation.
In Closed
Vessels.
With Admission
of Air.
Ammonia
0.268
1.037
0.192
0.280
0.146
1.340
0.134
0.287
1.110
0.207
0.305
0.140
1.059
0.125
or sulphate of ammonia
Acetic acid
or acetate of lime
Wood alcohol
Oils
Paraffin
226
HEAT ENERGY AND FUELS
TABLE CV.
DESTRUCTIVE DISTILLATION OF FEAT.
Yield in Per Cent.
Sulphate of ammonia .
Acetic acid
or acetate of lime . . .
Wood alcohol
Tar
Paraffin ...
Oils
&nd
Sullivan,
Pfer Cent.
HodgBB.
Pfer Cent.
Prospectus
of Irish
Peat Company.
PterCeni.
1.110
0.207
1.000
0.328
1.000
0.305
700
0.140
2.390
0.232
4.440
0.185
0.125
104
1.059
0.701
The average composition of perfectly dry peat-coal is
C 75 to 85 per cent
Hj 2 to 4 per cent
10 to 15 per cent
Ash 5 to 10 per cent.
The per cent of ash can be as high or higher than 60 per cent.
Air-dry peat-coal contains at least 10 per cent of hygroscopic
water. The sulphur and phosphorus content of the ash is some-
times considerable.
TABLE CVI.
DESTRUCTIVE DISTILLATION OF PEAT.
Products of Distillation.
Water in peat .
Ash in peat .
Coke
Ammonia water
Ammonia in same
light oil
heavy oil.
paraffin matter
asphalt
Tar paraffin
creosote
carbonaceous residuum
loss
Gases
Vapors
Total .
Peat from Neumarkt
(Wagenmann.)
A.
B.
Peat from
Oldenburg.
(Vohl).
Pfer Cent.
33.58
6.76
27.70
50.01
32
0.435
1.103
1.943
1.105
0.304
17.400
100.32
36.26
5.49
25.77
58.03
0.25
0.380
1.124
2.389
0.663
0.634
11.11
S
100.10
air dry
35.3120
40.0000
1.7633*1
1.7715
r5582
0.3005
3.6695
15.6250
100.0000
• This tar-output is, according to Stohmann, entirely too high, probably on
account of some water being present.
PEAT-COAL, COKE AXD BRIQUETTES 227
Peat-coal is very porous and light, has a specific gravity of
0.23 to 0.38, absorbs dyes and odoriferous substances, and is
therefore used for removing fusel oil from brandy, as disinfectant,
and as fertilizer.
It is easily ignited and continues to bum even with very weak
draught. The calorific value varies from 6500 to 7000 cal.
Brown coal (lignite) coke. Earthy brown coal disintegrates in
the heat and therefore cannot be coked. Of this class of fuels
lignite and pitch coal are almost the only ones that can be used
for this purpose, and lignite furnishes a coke similar to charcoal.
The destructive distillation of lignite yields
40 to 50 per cent Coke
12 to 20 per cent Tar water
14 to 35 per cent Tar
12 to 25 per cent Gases.
Coke from bituminous coal is generally dark gray, sometimes
silver gray, light gray or black. The light coke is melted, the
dark generally baked.
Coke-oven coke is generally less dense than gas-retort coke,
which explains the advantage of the former in metallurgical
operations and firing. According to Muck the specific gravity
varies from 1.2 to 1.9.
In practice the strength and composition of the coke is of
importance, the former for blast furnaces on account of the great
weight of the charge, the latter on account of deleterious effects
of certain substances.
Director Jugnet has found the following data relating to
strength of coke :
Carve's oven 70 cm 0().4 kg. per sq. cm.
Carve's oven 6(3 cm 79.72 kg. per sq. cm.
Carve's oven 50 cm 92.32 kg. per sq. cm.
Beehive oven 50 cm 43.92 kg. per sq. cm.
Smet oven 50 cm 42.12 kg. per sq. cm.
Copp6e oven 50 cm 80.50 kg. per sq. cm.
Relative to the composition, tlio cjuantity of sulphur and
phosphor is of technical importance.
Coke is hard to ignite, burns with a short, blue flame, and
228 HEAT ENERGY AND FUELS
requires a strong air draught. The calorific value is from 7000
to 7800 cal.
A hair-like formation, called coke-hair, is sometimes formed
on the surface of the coke. This coke-hair is free of ash and is
the coked residuum of tarry products of distillatioa. The
composition (dried at 110° C), according to V. Platz, is
C 95.729 per cent
H, 0.384 per cent
3.887 per cent
Ash
100.000 per cent
We will now discuss in a few words pressed coal, or briquettes.
In order to utilize the culm coal it has been attempted (with or
without suitable binding materials) to combine the small pieces
into larger pieces called briquettes, and we have:
Peat briquettes or pressed peat, which is made and used in the
vicinity of peat deposits.
Soft coal briquettes, in which tar, pitch, asphalt, starch,
molasses, clay, gypsum, alum, lime or soluble glass, etc., is used
as binder. The coal dust is mixed with the binder and pressed
into bricks. They have frequently the disadvantage of develop-
ing smoke of disagreeable odor or containing too much ash.
Charcoal or coke briquettes are made in the same way.
Lignite briqueäes. Here the resinous and other organic
matters of the coal serve as a binder. The coals are dried until
they contain about 15 per cent of water and are then pressed hot
(at lOOft-1500 atm. presvsure). The content of water is necessary
for preventing the decomposition of the organic substances.
The manufacture of such lignite is steadily increasing in Germany
and Austria. In 1901 120,000 carloads of briquettes were sold
for domestic use in Berlin, and only 5(XX) carloads of soft coal.
The combastion of these briquettes is peculiar, as for a good
utilization of the fuel a very weak draught has to be used, where-
by the lignite is burned very slowly, giving most of its heat off
to the stove. With a strong draught the briquettes are burned
quickly, and the largest part of the heat is lost through the
chimney.
The analysis given in Table CVII is taken from the Zeitschrift
des Vereines deutscher Ingenieure (1887, page 91).
PEAT-COAL, COKE AND BRIQUETTES
229
TABLE CVII.
COMPOSITION OF LIGNITE BRIQUETTES.
1
2
3
4
Ash
5.83
19.81
48^83 r^^^
3203 Cal.
5.59
18.67
50.79^^^2
3215 Cal.
5.93
21.10
5.95
Water
22.46
Volatile matter. ... .
Fixed carbon
Calorific value
28.52). 2 85
44.83 r
3159 Cal.
^^^*i71 48
54.74r***
2784 Cal.
I and II are good, III and IV inferior briquettes. Briquettes
from Schallthal (Styria) contain :
C 48.21 per cent,
Hj 3.99 per cent,
0., 19.92 per cent,
S 1.35 per cent,
H,0 (hygroscopic) 15.63 per cent,
Ash 10.91 per cent
Thermal value 4280 cal.
The analysis of the so-called Clara briquettes shows:
Elementary analysis :
C 48.72 per cent,
Hj 5.80 per cent,
O and N 22.93 per cent.
Ash 12.62 per cent,
H,0 (hygroscopic) 10.93 per cent.
Intermediate analysis:
HjO (hygroscopic) 10.93 per cent,
Volatile matters 44.21 per cent.
Fixed carbon 32.24 per cent,
Ash 12.62 per cent.
Calorific value (determined in calori-
meter) 4650 cal.
Effective thermal value (H/) formed
calculated as steam) 4349 cal.
Calorific value of the coal f roci of ash and
H,0 5688 cal.
CHAPITER XVIL
COKING APPARATUS.
Thk apparatus for manufarturing coke (and peat-Cüal) fmiu
raw fue!>^ can be classified as follows:
A, Coking in pile.s.
(a) The pile^t arc built \vith ooal lumps exclusively outl
covered with earth. The pile ha^ a shaft opening in the
center and draught holes (Fig, 58).
(ß) The pile has a brick shaft in the center (Fig. 59),
{y) A channel on the bottom of the pile and a movable pis-
ton in the shaft serves for 8a\1ng the pnxtucts of distilla-
tion: Dudley'« coke pile.
I
B, In heajjs.
(a) Analogous to the heaps used for charring wood*
iß) Heaps temporarily surrounded with l>^arde (like Fou-
pault*s charring system). The heaps are made either rec-
tangular or circular.
COKING APPARATUS
281
C. In closed piles (kilns) with brick walls on the sides. Gen-
erally rectangular and provided with charging doors in the center
of both short sides. Vertical and horizontal air channels, which
Charging Door
D a
D ^ Q
D a
a a
o D
□ g n p
Fios. 60 and 61. — Closed Piles (for coking).
Figs. 62 and 63. — Riesa Oven.
. J
r'-.:.T
..•■-
-4-
FlGS. 64 and 65. — Bee Hive Oven.
can be partly or entirely closed with bricks, etc., transverse
the walls and serve for regulating the air admitted. The pile
is covered with coke culm (Figs. 60 and 61). The Schaum-
burger coke ovens belong to this class.
282
HEAT ENERGY AND FUELS
D. Coking in closed ovens.
(a) Ovens with admission of air to the interior, the heat for
coking being furnished by partly burning the coal to be
coked. To this class belong the older construction of
Riesa (Figs. 62 and 63), and the beehive ovens (Figs. 64
and 65). The latter are largely used in America and
England. '
Fig. 66. — Section of Francois-Rexroth Coke Oven.
rfw - . . -^ b»
Fia 67. — Section of Francois-Rexroth Coke Oven.
The composition of the gases from these ovens was given in the
last chapter (Table XCIX). Since these gases contain a large
amount of combustible matter at a high temperature, their util-
ization for heating purposes was suggested. This purpose is
frequently accomplished (in connection with the beehive type)
by heating boilers with the gases; in this case the boilers are
COKING APPARATUS
233
built on top of the oven. Some of the other methods of utilizing-
this heat are :
(6) Coke ovens without admission of air to the interior,
which are heated by the gases generated during the
coking process. The coking is performed in chambers
of prismatic form, which are classified as
(a) Horizontal ovens:
1. Without condensing plant for the gas.
2. With condensing plant for the gas.
(ß) Vertical ovens :
1. Without condensing plant for the gas.
2. With condensing plant for the gas.
(y) With inclined axis (system Powel and Dubo-
chet) has not come into practical use.
Fia. 68. — Coke Oven, System Smet (elevation).
The horizontal ovens are constructed in different styles accord-
ing to the path of the gas through the furnace. The most im-
portant types are :
Frangois-Rexroth coke oven (Fig. 66 cross-section, Fig. 67
longitudinal section through chamber).
234
HEAT EXERGY AXD FUELS
Fin. 69. — Coke Oven, System Smet (plan).
Fins. 70 and 71. — Coke Oven. System Smet (details of doors).
Fir.. 72. — Coke Oven, Francois (cross-section).
COKIXG APPARATUS
235
The gases leave the chambei's at the .sides, pass through two
horizontal channels (in the side walls) then through two horizon-
tal channels in the bottom into the flue.
Smet coke oven (Fig. 68, front view and section; Fig. 69,
section through chambers and channels in the bottom; Figs. 70,
71, details of doors).
The gases go as in the previous type through horizontal chan-
SCO
Hi ' ;
iiiiiiiliiiiiNiiiiiiiniiiiiiiii
tr, M m m
Fig. 73. — Coke Oven, Francois (longitudinal section).
nels near one of the side-walls and under the floor of the chamber.
The gases leave the chamber at the highest point.
Frangois coke oven (Fig. 72, cross-section; Fig. 73, longitudinal
section). The gases of distillation leave at the side, the same as
in the Frangois-Rexroth system; the gases are carried parallel to
the wall of the chamber in vertical channels downward, under the
floor of the chamber (however, in horizontal channels) into the
flue.
Similar are the systems of Coppfee (Figs. 74, 75, 76, 77, and 78),
and Dr. Otto. The main difference between these and the
former types is the greater height, and length and smaller width
of the chambers, whereby an increase in the heating surface is
effected.
Vertical coke ovens without condensation belong to the oldest
types (Appolt system, 1854). They have an exceedingly large
heating surface and were at one time held in high esteem.
They are, however, very much more expensive to build and
COKISG APPARATUS 237
operate than the horizontal ovens, so that tliey are only of
historical interest.
In the destructive distillation of coal, besides coke, a number
of by-products, as tar, gas water, etc., are obtained, the recovery
of which in many cases is desirable on account of their content of
valuable substances (ammonia, benzol, etc.), notwithstanding the
loss of heat by cooling and the decrease in calorific value by
removal of the products of condensation.
As the by-product recovery in the coke industry is coming
more and more into use, we want to show the changes in oven
construction caused by the introduction of this process, taking
as an example the bottom-fire oven of Dr. Otto (Figs. 79, 80, 81).
The gases pass up through two pipes provided with valves and
connected to the highest point of every chamber into the receivers
a, which extend across the entire battery of ovens, analogous to
the hydraulic main in a gas plant. In the receiver a part of the
tar is condensed, ^nd the gas goes through condensing and puri-
fying apparatus, from here returning to the ovens. It passes
through gas pipes 6 (one for every two ovens) to the burners of
the combustion chambers. The air of combustion enters around
every burner. The combustion gases go through the center of
the combustion chamber down wan! , through slots into a side flue
(below every coking chamber), which conducts to the main flue.
In the more modem ovens the combustion air is preheated in
regenerators before entering the ovens.
The coke obtained in such an oven is removed rod hot and
cooled with water, for preventing combustion in the atin()H|)h<Te.
For making peat-coal (coke) we have, besides the alxive
apparatus,
E. Ovens heated exclusively from outside:
(a) With a special fireplace (Ix^ttmann's oven; Crony
retort oven).
(6) With superheated steam (VignohNs' ()V(»n).
(c) With combustion gases Crane's ov(^n, using solid or
gaseous fuel.
Finally we want to say a few words alniut coking of ligniUj
(brown coal), which is carried on mainly in Saxony and Thuringia,
where coaLs rich in paraffin an» mined. Kolh^'s plat/C oven is
almost exclusively ased for this pur[)OH<». Such an oven can coke
240 HEAT ENERGY AND FUELS
2500 kg. of lignite in 24 hours, with a coal consumption of 25 to
30 per cent and at a temperature of 800 to 900° C. The yield is
Tar 10 per cent,
Water 50 per cent,
Coke 32 per cent.
The specific gravity of the tar at 35° C. is 0.82-0.95.
Siiggestions for Lessons.
Examination of different artificial solid fuels; elementary
analysis, calorific value, determination of the ash, sulphur and
phosphorus content, ash analysis; determination of specific
gravity, strength and porosity.
Yield by destructive distillation of carbonized fuel, gas, tar
and tar water, also ammonia, acetic acid, etc. Herein the influ-
ence of the temperature of distillation, slow or quick heating, of
admixtures, etc., has to be studied.
CHAPTER XVIII.
LIQXnD FUELS.
To this class belong oil (petroleum), tar from destructive dis-
tillation of coal and wood, schist-oil, and to a small extent certain
vegetable oils, alcohol, turpentine, benzine, etc.
The liquid fuels have the advantage of burning up without
residuum. Such a residuum as remains of solid fuels might
obstruct the grate, cause uneven air supply and incomplete com-
bustion.
The utilization however, of liquid fuels presents some serious
difficulties and makes the construction of well designed and
carefully tested burners imperative. The main difficulty is the
atomization, otherwise carbon is deposited, which m\[ cause
stoppages and block the flow of the liquid.
A general use of liquid fuel is prevented by high cost. How-
ever, under certain local conditions it can be used economically.
The experiments for introducing alcohol as fuel on a large scale
have so far not been successful.
Table CVIII contains some data relating to the use of liquid
fuels.
TABLE CVIII.
COMPOSITION OF LIQUID FUELS.
Kind of Fuel.
American crude oil
Caucasian crude oil
Refined American oil
Coal tar
Heavy oil from American petroleum
Heavy oil from Caucasian petroleum
Schist oil
Tar oil
Rape oil.
Composition in Per cent.
77.2
14. ()
11.5
14.2
5.0
13.0
13.0
11.7
3.0
3.5
0.3
5.0
11.1
Ash.
o.a
Calorific
Value la
241
242
HEAT ENERGY AXD FUELS
The source of oxygen in petroleum is dissolved water; in coal
tar the oxygen is partly chemically combined, partly from water.
TABLE CIX.
COMPOSITION OF LIQUID FUELS.
Liquid Fuel.
Burnt to
(Calorific Valut* in
Kg-cal. |>er
1
i
1 Kk.
1 Mol.
Benzole
Hexane
Hexane
HeDtane
CO, and Hfi liquid
" " " vapor
" 'j 1^ licjuid
.< a i( n
it 11 (( .<
9997
11525
10636
11375
7054
4316
9231
9500
779800
991200
914800
1137500
324500
397100
Alcohol
Givcerine
Butter
Animal fat averaj?e
The residuum of the first distillation of crude oil is sold in
Russia under the name of Masut. When heated to 150 degrees
it generates combustible gases, can be ignited at 215 degrees,
ignites itself at 300 degrees, and its specific gravity is 0.91.
The calorific value is 11,000 cal. In practice 62 kg. Masut
replace 100 kg. good bituminous coal. 1000 liters of air are
necessary to bum 1 kg. Masut completely.
Table CX shows comparative data (Wright) which, however,
change according to the construction of the fire-place.
TABLE CX.
THERMAL EFFICIENCY OF FUELS.
Nottingham cannel cual .
Gas coal
Cannel coal.
Gas-house coke
Tar
Creosote
Calculated
Evai)oration.
Lb. English.
12.27
14.24
12.23
13.83
15.06
16.78
Actual
Evaporation,
Lb. English.
8.78
10.01
9.91
11.15
12.71
13.35
Thermal
Efficiency,
Per Cent.
71.56
70.30
81.03
80.62
84.40
79.56
CHAPTER XIX.
GASEOUS FUELS.
The gaseous fuels have, like the liquid fuels, the advantages
of burning up without residue, of easy transportation . to the
place of combustion, and of convenient regulation of tempera-
ture. Furthermore, the length of the flame can be varied within
certain limits, and for complete combustion a considerably
smaller excess of air is required than with solid and liquid fuels.
The gaseous fuels, therefore, have a higher temperature of com-
bustion, and generate a smaller quantity of gaseous products of
combustion than other fuels of the same composition, whereby
a better utilization of the generated heat can be secured.
Another advantage is that in this cavse not only the air for com-
bustion but also the gas can be preheated.
Such gaseous fuel occurs in nature and is then called natural
gas. The average composition of Pennsylvania natural gas is
Methane 67 per cent.
Hydrogen 22 per cent.
Nitrogen 3 per cent.
Ethane 5 per cent.
Ethylene 1 per cent.
Carbon dioxide 0.6 per cent,
Carbon monoxide 0.() per cent.
As the occurrence of natural gas is limited, similar gases are
artificially produced for industrial use by the following methods:
1. Dry distillation of substances containing carbon, as coal,
lignite, peat, wood, fat, etc., whereby gases of distillation (illu-
minating gas) are obtained. According to the raw material used
the manufactured gas is called coal gas, peat gas, wood gas, fat
gas, oil gas, etc.
2. Incomplete combustion of. coal with iasufficient amount
of air, whereby generator gas, also called producer gas or air gas,
is obtained.
243
244 HEAT ENERGY AND FUELS
3. Decomposition of water (steam) by glowing coal or com-
bustion of coal by means of steam, whereby water gas is obtained.
In special cases other methods are used for producing fuel
gases, as for instance :
4. Incomplete combustion of coal by simultaneous action of
air and oxides, the latter thereby being reduced. This reaction
takes place in iron blast furnaces and furnishes a gas of high
fuel value, low in nitrogen and high in carbon monoxide, which
is called blast-furnace gas. If water is used as oxide, semi-water
gas or Dowson gas is obtained.
5. F(5r getting high temperatures or high luminant power,
acetylene C2H2 is sometimes used, which is obtained by reaction
of calcium carbide and water:
CaC, + 2 H,0 = Ca (OH)^ + C^^.
We therefore have the following summary of methods for the
Production of Fuel Gases.
1. By dry distillation :
From coal, coal gas,
From peat, peat gas.
From wood, wood gas.
From fat, fat gas,
From oil residue, oil gas.
2. By incomplete combustion of coal :
(a) With air alone, producer gas (air gas).
(6) With air and oxides of metals Fe^O,, etc., blast-furnace
gas.
(c) Air and steam, Dowson gas.
{d) Air and carbon dioxide, regenerated combustion gases.
3. By decomposing carbides with water:
Mainly calcium carbide, acetylene.
Leaving aside the acetylene and the blast-furnace gas, which
are only of local importance, the following industrial gases have
to \)c mainly considered:
(1) Gases of distillation, obtained by dry distillation of car-
bonaceous substances.
(a) Illuminating gas made in retorts. It is used for illum-
inating, heating and for internal combustion en^es.
GASEOUS FUELS 245
As an example, the composition of French illuminating gas
is given below, which is identical all over France :
Weight of cubic meter = 0.523 kg.
Thermal value of 1 cubic meter = 5600 cal.
Weight of 22.42 liters = 2 grams.
Thermal value of 2 grams = 125 cal.
Analysis in per cent by weight:
Carbon, 43.2 per cent.
Hydrogen, 21.3 per cent.
Oxygen and nitrogen, 25.5 per cent.
Analysis in per cent by volume:
51.0 per cent H,
33.0 per cent CH,
8.8 per cent CO
1.8 per cent CO,
1.0 per cent 0, + N2
1.1 per cent CeH,
3.3 per cent absorbable CnHjn
100.0
(6) Gases of distillation, produced as by-product in the
coking or charring of fuels, mainly coke-oven gas.
(2) Generator gas, air gas, or producer gas is properly the
name of such gas only, which is made from carbon (charcoal or
coke) ; i.e., from a coal free from hydrogen and oxygen, and using
dry air for the incomplete combustion. In practice, however,
we comprise under the classification "generator gas" any gas
generated in certain apparatus (gas producers) by leading air
without steam through a glowing layer of fuel of sufficient height.
The air never being dry, we get in practice always a mixture of
generator gas and water gas, and also gases of distillation if
crude, uncoked fuel is used.
(3) Water gas is used for illuminating and fuel purposes.
(4) Semi-water gas or Dowson gas is used for fuel and power
purposes, and is prepared by leading a mixture of air and steam
through a coal layer in a producer.
CHAPTER XX.
PRODUCER GAS.
If air is led at moderate speed through a layer of pure carbon
(in practice charcoal or coke), incomplete combustion takes place;
i,e, by the reaction of oxygen on the glowing coal, formation of
carbon monoxide occurs:
C + i O3 = CO.
Supposing the air to contain 4 moLs nitrogen to 1 mol oxygen,
which is probably correct, we can write the reaction:
C + i 0, + 2 N, = CO + 2 N„
and we get a gas which theoretically contains 2 mols Nj to 1 mol
CO, and should have the composition :
CO 33 . 3 per cent by volume.
N 66.7 per cent by volume.
This gas ought to yield per 22.42 liters if burned at constant vol-
ume 0.333 X 67.9 = 22.61 cal. If burned at constant pressure
22.61 + 0.5 X 0.54 = 22.88 cal. The thermal value of the same
at constant pressure would be per cubic meter 1020.5 cal.
The thermal value of 1 gram of gas is calculated as follows:
According to the equation the gas has for every gram atom of
carbon
12 grams carbon J ^o , . ,
^n (28 grams carbon monoxide.
16 grams oxygen ) ^
56 grams nitrogen.
Sum 84 grams.
As 84 grams of gas contain 3 mols (CO + 2 N,), 22.42 liters of
the same at 0° C. and 760 mm. are equal to 28 grams, and there-
fore 1 gram of gas generates 817 cal.
This reaction, however, only takes place at very high tempera-
246
PRODUCER GAS 247
tures. At lower temperatures a second reaction occurs simul-
taneously, and the extent to which it occurs increases with
decreasing temperature. This reaction is
+ 0,== CO3,
or, if the air is used instead of oxygen,
C + 0, + 4 N, = CO, + 4 N„
Between these two reactions there exists a certain equilibrium
for every temperature and pressure. If we subtract the equation
0+0,= CO,
from 2 C + 0, = 2 CO,
we get 2 CO = CO, + C,
which reaction actually takes place at fairly high temperatures,
and determines the proportion of the two first reactions. It is
reversible :
2 CO <=^ CO, + C.
That is, while pure CO within certain temperatures is decom-
posed into COj and C, we find that under similar conditions CO is
produced by reduction of CO, by means of C. Therefore, there
exists necessarily an equilibrium between CO, CO, and C, which
depends on the temperature and concentration (gas pressure).
Since out of two volumes CO only one volume CO, is formed,
and since the reaction, according to our equation (from left to
right), takes place without decrease of volume, it is clear that an
increase of pressure facilitates the formation of CO,, while a
decrease of pressure favors the formation of CO. Therefore, the
primary air (wind) in a gas producer should be of low pressure if
a gas high in CO is desired.
The influence of temperature on the equilibrium is shown by
the balance of the reaction heats :
C + 0, = CO, + 97,600 cal.
2 (C -h O) = 2 CO + 57,800 cal .
2 CO = CO, + C + 39,800 cal.
248
HEAT EX ERG Y AXD FUELS
i.e., the decomposition of 2 CO into CO, and C takes place under
generation of heat. Therefore an increase of temperature facili-
tates the formation, a decrease of temperature the decomposition
of CO. Thence it is clear that the gas will be the richer in CO
with higher temperature.
All these observations are of importance for the state of equi-
librium. Whether this is reached in practice or not depends on
Vol.%
too
1
k
/
A
f
1
V
f
1
1
Ht
♦
m
\i
\
i
1
(
I
^ii
r
^
^
u
N
^
—
4al
^
--
Jl« —
C^>
_ —
^
^
CO J
/j
f
It
s
^
\
^
T
GU> UXt MO iOD uoo luoo liUO lajo uuo
V\Q. 82. — Ideal CompoHition of Gener-
ator Gas from Pure Oxygen.
000 TOO 800 000 1000 UMiaooi»
Fia. 83. — Ideal Composition of Gener-
ator Gas from Dry Air.
the height of the coal, porosity of same, velocity of wind, etc. It
is, however, of the greatest importance for the theory of the gas
producers as well as for the practice, to know the equilibrium for
all the different conditions, since the only way to judge the
PRODUCER GAS
249
quality of a gas producer process is to compare the results
obtained in practice with those corresponding to the theoretical
equilibrium.
We therefore give in Tables CXI, CXII, and C^^III the ideal
composition of generator gas at different temperatures and
pressures.
Table CXI gives the ideal composition of producer gas, pro-
duced with pure oxygen. Fig. 82 shows the content of this table
graphically.
TABLE CXI.
roEAL OOBffPOSmON OF PRODUCER GAS (GENERATOR GAS) PRODUCED
WITH PURE OXYGEN.
Air Pressure.
Volumetric Composition
1 Atmosphere.
2 Atmospheres.
at a Temperature of
CO
CO,
CO
CO,
22r C. 500*» aba.
0.004
99.996
0.0028
99.9972
327*» 600°
0.123
99.877
0.087
99.913
A2r 700°
1.427
98.573
i.Oll
98.989
527° 800°
8.794
91.206
6.303
93.697
627° 900°
32.542
67.458
24.809
79.191
727° 1000°
70.35
29.65
58.105
42.259
827° 1100°
92.75
7.25
87.198
12.802
927° 1200°
98.445
1.555
97.00
3.00
1027° 1300°
99.50
0.50
99.00
1.00
Air Pressure.
Volumetric Composition
3 Atmo
spheres.
4 Atme
»pheres.
at a Temperature of
CO
COj
CO
COj
227° C. 500° abs.
0.0023
99.9977
0.002
99.998
327° 600°
0.0711
99.9289
0.061
99.939
427° 700°
0.826
99.174
0.716
99.284
527° 800°
5.177
94.823
4.499
95.591
627° 900°
20.408
79.592
17.945
82.055
727° 1000°
51.788
48.212
47.017
52.983
827° 1100°
82.72
17.28
78.987
21.013
927° 1200°
95.65
4.35
94.315
5.685
1027° 1300°
98.97
1.03
98.67
1.33
Table CXII ^ves the ideal composition of producer gas, pro-
duced with dry atmospheric air. The data of this table are
graphically shown in Fig. 83.
25a
HEAT ESEHGY AND FUELS
TABLE CXII.
IDEAL COMPOSITION OF PRODUCER GAS (GENERATOR GAS) PRODUCED
WITH DRY ATMOSPHERIC AIR.
Air Pressure = 1 Atmosphere.
Partial
Gasifying Temperature.
Pressure of
Composition in Per Gent by Volume.
co+co,.
°C.
T*»abs.
In Atm.
CO.,.
CO.
NV
227*»
327°
427*»
500*»
600*»
700°
0.21
0.21
0.2145
21.00
21.00
20.31
79.00
79.00
78.55
1.14
527*»
800*»
0.24
16.40
7.60
76.00
627*»
900*»
0.29
8.75
20.25
71.00
727*»
1000*»
0.334
2.14
31.26
66.60
827*»
1100*»
0.344
0.47
33.93
65.60
927*»
1200*»
0.346
0.14
34.46
65.40
1027*»
1300*»
0.3465
0.01
34.65
65.35
Air Pressure
= 2 Atmospheres.
227*»
327*»
500*»
600*»
0.42
0.42
21.00
21.00
79.00
79.00
427*»
700*»
0.4228
20.39
1.01
78.60
527*»
800*»
0.466
18.14
5.82
76.70
627*»
900*»
0.555
11.94
17.09
72.25
727*»
1000*»
0.6535
4.31
29.56
67.32
827*»
1100*»
0.6865
0.83
33.74
65.67
927*»
1200*»
0.692
0.21
34.44
65.40
1027*»
1300*»
0.693
0.10
34.56
65.35
Air Pressure
= 3 Atmospheres.
227*»
327*»
427*»
500*»
600*»
700*»
0.63
0.63
0.6395
21.00
21.00
20.51
79.00
79.00
78.68
0.81
527*»
800*»
0.686
18.14
4.76
77.00
627*»
900*»
0.8075
11.94
14.98
73.08
nr
1000*»
0.957
4.31
27.59
68.10
827*»
1100*»
1.625
0.83
33.37
65.80
927*»
1200*»
1.0365
0.21
34.34
65.45
1027*»
1300*»
1.04
0.10
34.56
65.34
PRODUCER GAS
251
TABLE CXIL— Continued
Air Pressure = 4 Atmospheres.
Gasifying Temperature.
Partial
Pressure of
co+co,.
Composition in Per Cent by Volume.
*»C.
T*»abs.
In Atra.
CO,.
CO.
N,.
227*»
327*»
427*»
527*»
627*»
727*»
827*»
927*»
1027*»
500*»
600°
700*»
800*»
900*
1000*»
1100*»
1200°
1300°
0.84
0.84
0.851
0.905
1.056
1.258
1.359
1.381
1.385
21.00
21.00
20.59
18.52
12.73
5.00
1.13
0.28
0.13
79.00
79.00
78.70
77.37
73.60
68.55
66.02
65.47
65.37
0.71
4.11
13.67
26.46
32.85
34.25
34.50
TABLE CXIII.
IDEAL COMPOSITION OF PRODUCER GAS (GENERATOR GAS) PRODUCED
WITH 50 PER CENT OXYGEN.
Air Pressure = 1 Atmosphere.
Partial
QasifyiDg Temperature.
Pressure of
co+co,.
Composition in P^ Cent by Volume.
*»C.
T*»ab8.
In Atm.
CO,.
CO.
N,.
227*»
500°
600°
700°
0.50
0.50
0.502
50.00
50.00
49.40
50.00
50.00
49.80
327*»
427*»
0.80
527*»
800°
0.522
43.40
8.80
47.80
627*»
900°
0.568
29.60
27.20
43.20
727*»
1000°
0.633
10.10
53.20
36.70
827*»
1100°
0.66
2.00
64.00
34.00
927*»
1200°
0.663
1.10
65.20
33.70
1027*»
1300°
0.6655
0.35
66.20
33.45
Air Pressure = 2 Atmospheres.
227°
327°
427°
527°
627°
727°
827°
927°
1027°
500°
600°
700°
800°
900°
1000°
1100°
1200°
1300°
1.
1.
1.0035
1.0295
1 . 1065
1.23
1.308
1.326
1.3305
49.56
45.65
34.03
15.50
34.03
15.50
3.80
1.10
0.43
0.61
5.83
21.30
46.00
61.60
65.20
66.10
50.00
50.00
49.83
48.52
44.67
38.50
34.60
33.70
33.47
252
HEAT ESEHGY AND FUELS
T.\BLE CXlll. --Continued
Air Pressure = 3 Atmospheres.
Gasifying Temperature
Partial
Pressure of
CO+COj.
OompositioD in Per Gent by Volume.
°C.
T*»abs.
In Atm.
COj.
CO.
N,.
227*»
327°
427*»
527*»
627*»
727*»
827*»
927*»
1027*»
500°
600°
700°
800°
900°
1000°
1100°
1200°
1300°
1.5
1.5
1.5045
1.538
1.6345
1.814
1.9455
1.986
1.9955
50.00
50.00
49.55
46.20
36.55
18.60
5.45
1.40
0.45
50.00
50.00
49.85
48.73
45.52 1
39.53
35.15
33.80
33.48
1
0.60
5.07
17.93
41.87
59.40
64.80
66.07
Air Pressure = 4 Atmospheres.
227*»
327*»
427*»
527*»
627*»
727*»
827*»
927*»
1027*»
500°
600°
700°
800°
900°
1000°
1100°
1200°
1300°
2.
2.
2.0053
2.0443
2.1615
2.384
2.588
2.6435
2.6605
50.00
50.00
49.60
46.68
37.89
21.20
5.90
1.74
0.46
50 00
50.00
0.54
4.43
16.15
38.40
58.80
64.35
66.05
49.86
48.89
45.96
40.40
35.30
33.91
33.49
Since it is not improbable that in future a mixture of 50 per
cent oxygen and 50 per cent nitrogen may be used in gas pro-
ducers, the data for this case are given in Table CXIII. Fig. 84
gives the results graphically.
The following important general conclusions may be drawn
from these tables and diagrams :
1. In all cases the CO, content of the ideal generator gas at
low temperature is a maximum, which is practically constant
up to 400° C.
2. With increasing temperature the COj content is decreasing;
between 800° and 1000° C. no CO, is present.
3. No CO is found up to about 400° C.
4. With increasing temperature the CO content is increasing
and is reaching a maximum at 800° to 1000° C.
5. At constant temperature the CO, content is increasing with
PRODUCER GAS
253
the pressure, and therefore also with the oxygen content of the
primary air.
6. CO shows the opposite property.
7. At low temperatures the ateolute CO, content is increasing
with the oxygen content of the primary air.
8. At high temperatures the absolute content of the gas in CO
is increasing with the oxygen content of the primary air.
Vol.%
TP
A
CO
f
—
«
§
r
1
i
^
I
30
\1
^
,s^
■SB 1
1
1
—
/'
f
^
^0.
-i
^
r^k-
__r
Fig. 84.
OOO 1D0 WW 900 UWO DM 1300 VOO
■ Ideal Composition of Generator Gas from 50 per cent Oxygen.
Therefore the following facts have to be considered for getting
a generator gas of the highest possible thermal value and also rich
in CO.
1. The oxygen content of the primary air being the same, the
gasif5dng temperature has to be high. In practice a temperature
of 700° to 900® C. is sufficient, as at this temperature the maxi-
mum CO content is practically reached.
2. At high gasifying temperatures the quality of generator gas,
i.e., the content of CO, is increasing with the oxygen content of
the primary air.
3. High air (wind) pressures are unfavorable, as thereby, under
otherwise constant conditions, the CO2 content is increased. If,
254 HEAT ENERGY AND FUELS
however, it is desired to generate the largest possible quantity of
COj in the producer, which is sometimes the case in the hot blow-
ing period of the water-gas process for the purpose of rapidly
increasing the temperature, a very low temperature has to be
kept during the process if the equilibrium is to be reached. This
is easily understood, as vAih. increasing temperature the quantity
of the CO formed is rapidly increasing, and the quantity of COj
is decreasing. If in the producer the equilibrium is reached, the
temperature of the producer must not get high if it is the inten-
tion to get a high yield of CO2. These conditions are not changed
by increasing the oxygen content of the primary air.
From the above facts we can calculate the volume proportions
of CO, to CO, of CO, to CO + CO, and of CO to CO + CO,, also
the quantity of carbon gasified by a certain volume of air, the
quantity of air necessary for gasifying a certain quantity of car-
bon, and also the quantity of carbon and air required for
generating a certain volume of ideal generator gas.
We have so far treated the ideal generator gas, i.e., a gas which
is produced by the action of dry primary air on glowing coal,
under the supposition that in the process of combustion the state
of equilibrium is reached.
We now have to consider the case in which equilibrium is
not reached, this case occurring very frequently in practice.
Every single layer of coke consists of pieces of coke and air
spaces between. The larger the pieces of coke the larger the air
spaces. With coke of fist size, the air spaces amount to one-
quarter to one-fifth of the total volume, and these spaces allow the
air to pass through the producer.
Every piece of coal, therefore, is surrounded by a layer of air
varying in thickness from a few millimeters to a few centimeters.
The reaction between the oxygen of the air and the coal takes
place only on their contact points, and the question arises which
reaction will occur first. The law of the gradual reactions states
that wherever several reactions might take place, the first reac-
tion is that one which corresponds to the least stable state, then
the next stable, and at last the most stable.
In our case we have but two possible reactions : The formation
of CO, and CO, and we have to find out which one of the two is
more stable. We, therefore, have to consider the free energies
of formation of the two compounds.
PRODUCER GAS 255
Under the supposition that the concentration of the free oxygen
is one atmosphere, we find that the curves of the two energies of
formation go through the same point at a little below 1000° abs.
(about 700° C), and that at lower temperatures the free energy
of formation of the COj is the larger one, at higher temperatures,
that of CO. We find the same relation in the stability of the two
compounds, and, therefore, at the beginning of the reaction at
low temperatures first of all CO, at higher temperatures first of
all COj, will be formed. In rising upwards the gases will further
react with the upper layers of coal and with the air contained in
the interior part of the gas current.
The reaction of the outer part of the gas current with coal con-
sists either in combustion of coal by means of COj or in formation
of carbon from carbon monoxide (2 CO = CO2 + C). Since at
low temperatures first of all CO, is formed, the most plausible
reaction under such condition is the decomposition of the CO and
formation of C. The reaction, however, between the inner and
outer parts of the gas current counteracts this decomposition,
since the of the inner part would bum any C which was depos-
ited from the CO. The velocity of diffusion and mixture between
the inner and outer parts of the gas current being sufficiently
large, no C will be deposited ; on the contrary, the CO formed will
be burned to CO,, and the oxygen going to the outer part will
oxidize some more carbon. Therefore the average composition
of the gas will approach more and more the equilibrium.
At higher temperatures at first COj is formed, and this will, by
contact with the higher layers of coal, oxidize some C to CO. On
the other hand, the oxygen of the inner part will tend to oxidize
the CO present to CO,.
In both cases we have two effects counteracting each other.
At low temperatures the reaction between coal and the outer layer
of gas tends to prevent the reaching of equilibrium, while the
reaction between outer and inner layers favors the approach to
the equilibrium. At high temperatures, however, we find that
the reaction between gas and coal favors the equilibrium, and
the reaction in the gas current works against it.
The conditions become still more complicated if we consider
that the actual velocity of the gas current at different points of
the generator varies according to the unequal dimensions of the
air spaces, and that also the temperature throughout the genera-
256
HEAT ENERGY AND FUELS
tor is not at all uniform. If the generator is working with the
fire on top (maximum temperature in the upper parts of the
charge), the state of equilibrium of the rising gas current is getting
more and more favorable to the formation of CO.
The reverse is true with the maximum temperature in the
lower parts of the producer. The location of the maximum tem-
perature of the producer, however, changes during the operation.
In starting the fire the upper layers of the generator will be cold,
and will allow the formation of COj. They are gradually heated
up by radiation of heat from the combustion gases to the coal,
and the hot zone will therefore extend from the bottom further
upwards. After continued blowing we can imagine a coke col-
umn which has the combustion temperature of the hot carbon in
cold air.
As will be seen from the above considerations the research of
the generator process is extremely difficult, and we have but a few
scientific investigations on this subject. One of the best is by
0. Boudouard, even this being not free from objectionable points.
He passed air at different speeds through a tube filled with char-
coal and analyzed the gases obtained. He found at 800° C. the
results given in Table CXI V :
TABLE CXIV.
ANALYSIS OF PRODUCER GAS. (IVr Cent by Volume.)
Gas.
Flow in Liters per Minute.
0.10
0.27
1.30
1 . 4656
1
3.20
CO.
18.2
5.2
18.43
3.8
0.47
77.30
18.92
1.88
0.94
78.26
19.9
1.83
19.4
0.93
0.93
78.74
CO"
O.
N2 (difference)
76.6
78.27
The analysis corresponding to the equilibrium at this tempera-
ture is
CO3 . 92 per cent by volume,
CO 34.32 per cent by volume,
N 74 . 76 per cent by volume.
PRODUCER GAS
257
It will be noticed that the gases from Boudouard's experiments
are very high in (X), and very low in CO. In three cases they also
contain free oxygen. This is in accordance with the fact that at
800° C, CO, is less stable than CO, so that, therefore, CO, must
be formed first and the gas composition is approaching the equi-
librimn but gradually.
To better understand these conditions we are going to decom-
pose the gases into the elementary components. We have in
22.42 liters of gas the amounts given in Table CXV.
TABLE CXV.
ELEMENTARY COMPONENTS OF PRODUCER GAS.
Flow In
Liters per
Minute.
Gram-atORLS C. in
COj.
Mol. Oxygen
in
Total.
Nilro-
Prim-
ary
Air.
CO^
CO.
Total.
CO.
Free.
0.
0.0
0.27
1.30
1.465
3.20
0.92
18.2
18.43
18.92
19.9
19.4
34.32
5.2
3.8
1.88
1.83
0.93
35.24
23.4
22.23
20.80
21.73
20.33
0.92
18.2
18.43
18.92
18.9
19.4
17.62
2.6
1.9
0.94
0.92
0.47
0^47
0.94
0*93
18.54
20.8
20.8
20.8
20.18
21.20
64.76
76.6
77.30
78.26
78.27
78.74
83.30
97.4
98.1
99.06
98.45
99.94
According to the law of gradual reaction in the l)eginmng, a
thin layer of COj is formed, which then oxidizer the coal layer
through which it passes. It will, therefore, 1x5 pretty nearly
correct to suppose that the outer layer (surface) of the gas cur-
rent will have, shortly after its entrance into the tulx% the com-
position which corresponds to the e(iuilibriuni. In this case the
ratio of CO, to COj 4- CO must be etjual to ().()2()1 , and there must
have been formed the amounts given in Table CX VI :
TABLE CXVI.
Flow in
Oxygen In
Same.
Corrmponding
Liters per
Vol. COj.
Vol. CO.
Amount
Minute.
of Air.
0.10
0.61
22.79
12.01
57.19
0.27
58
21 65
11.41
54.33
1.30
54
20.26
10.67
50.81
1.465
0.54
20.19
10.64
50.67
3.20
53
19.80
10.43
49.67
258
HEAT ENERGY AXD FUELS
If we deduct the air volume actually used for the original com-
bustion from the volume of primary air, we get the surplus quan-
tity of air from which we can figure by a simple way the surplus
air given in Table CXVII and Fig. 85.
O 1 » BVi4^*^
Fig. 86. — Curve of Surplus Air.
TABLE CXVII.
SURPLUS AIR FOR COMBUSTION.
Flow in Liters
Iier Minute.
In 100 Volumen Generator
Gas Volumes of
Of 100 Volumes
Primary Air.
N Times
Surplus
Air.
Primary
Air.
Air for
Original
Combus-
tion.
Surplus
Quantity
of Air.
For
Original
Combus-
tion.
Surplus
Air.
0.10
0.27
1.30
1.465
3.20
97.40
98.10
99.06
98.45
99.94
57.19
54.33
50.81
50.67
49.67
40.21
43.77
48.25
47.78
50.27
58.72
55.38
51.29
51.46
49.70
41.28
44.62
48.71
48.54
50.30
0.737
0.805
0.949
0.943
1.012
The following consideration will be still more useful for the
practical regulation of this process:
PRODUCER GAS
259
We suppose again that in the first moment the least stable
gas is formed, but that in a short time on the surface area the
equilibrium corresponding to the actual gasif)dng temperature
will be reached. In the further course of the process this equi-
librium will, however, be disturbed by the gradual mixture of
the outer gas layer with the inner air volume, by the fall in tem-
perature resulting therefrom, and by the combustion of a part of
the ori^nal CO to CO,, due to the surplus oxygen.
Referring again to Boudouard's experiments at 800° C, wc
can calculate from the free oxygen content of the gases the
corresponding amount of air, deduct the latter from the com-
position of the gas, calculate the temperature of equilibrium
corresponding to the gas mixtm^ obtained, and compare the
temperature of equilibrium with the actual gasif)dng temper-
ature (800° C. = 1073° abs.). We obtain thereby the results
given in Table CXVIII.
TABLE CXVIII.
IDEAL GASIFYING TEMPERATURE, ETC.
Free oxygen i per cent by vol.
Corresponding amount of aii
per cent by volume .
Composition of the gas [CO,
free from'air, per centjCO
by volume IN,
Gasifying temperature (absol.)^
corresponding to the com-
position
Difference between the latter
and the actual gasifying tem-
perature, which is higher by
Flow in Liters per Minute.
0.92
34.32
64.76
1073*»
0^
0.10 0.27 1.30 1.466 3.»"
18.2
5.2
76.6
763*^
307^
0.47
2 24
18.85
3.89
77.26
749°
324<*
0.94
4 48
19.81
1.98
78.21
732*
341°
19.9
1.83
78.27
729°
344°
0.93
4.43
20.20
0.97
78.74
700°
373°
As may be seen from Table CXVIII and from Fig. 86, the
''ideal" (or apparent) gasifying temperature corresponding to
the actual composition of the gas is clearly below the actual, and
the curve of this difference of temperatures consists of two prac-
tically straight branches, which are connected with each other
260
HEAT ENERGY AND FUELS
by a short, sharply bent curve. In the one branch, which
is practically vertical, the velocity of reaction is the main factor,
while in the inclined branch the velocity of the wind is of main
importance.
Naturally, the position and shape of this curve depends, not
only on the gasif)dng temperature, but also on the size of coal
used, and on the height of the fuel layer. Under conditions,
however, which can be compared with each other, these additional
factors will have the same
character and the position of the
bending point of the curve seems
a very suitable characteristic
point for the conditions.
With increasing gasif)dng tem-
perature, the velocity of reaction
increases, and the bending point
of the curve will move to the
right. Increase of the fuel
height and decrease of the coal
size will have a similar effect.
In the latter cases, however,
some other influences have to
be considered, such as friction
between gas current and coal
pieces, heating of the upper layers by the rising gas, location
of the maximum temperature in the generator, etc.
The following figures are given as practical results of genera-
tors that were charged with carbonized fuel.
Ebelman gasified at Audincourt small-sized charcoal in a
pressure producer, which had the shape of a small blast furnace,
and he obtained a gas of the following composition (per cent by
weight) :
Fio. 86. — Difference of Temperature
between Actual and Apparent Gasi-
fying Temperature.
CO ;M . 1 per cent
CO2 0.8 per cent
N 04 .9 per cent
Hj 0.2 per cent
100.0 per cent.
PRODUCER GAS 261
In a gas producer at Pous TEvequc, wliich was charged with
coke, he obtained a gas of the following composition:
CO 33.8 per cent
CO, 1.3 per cent
N 64.8 per cent
H, 0.1 per cent
100.0 per cent.
Mixed Distillation and Combustion Gases.
If we subject natural uncarboiiized fuel in proper apparatus
(gas generators, also called gas producers) to incomplete com-
bustion, mixed distillation and combustion gases are formed.
In the upper layers of the producer the hygroscopic water Ls
removed. In further going downwards the fuel (material to be
gasified) is subjected to dry distillation, coke being the result of
this process. The coke is burned incompletely in the lowest
part of the producer, whereby, besides the heat necessary for
evaporation and dry distillation, CO is also generated. The
water which is introduced as moisture with the atmospheric air
is also decomposed. A clear idea of these processes is given in
the table below, without, however, taking into account the
formation of tar, which is inconsiderable.
Composition of the coal used (bituminous coal of Ostrau,
Moravia) mixed with lignite of Leoben (Styria).
c
N
Chemically combined water
Hygroscopic water
Ash
= 64.92
= 2.50
= 0.50
14.22
12.42
5.44
Combustible sulphur
Calorific value
100.00
0.52
6374 calories.
(a) Process in the upper part of the generator (drying of coal) :
100 kg. coal yield 12.42 water (steam), and 87.58 kg. dry coal.
(6) Process in the middle part of the generator (dry distilla-
tion of coal).
262
HEAT EXEHGY ASD FUELS
TABLE CXIX.
ELEMENTARY ANALYSIS OF COAL AND PRODUCTS OF DISTILLATION.
Yield.
87 . 58 Kg. Dry Coal
Contain.
Coke.
Gases of Distillation Kg.
1
Kif.
R.O.
CO.
CH,.
H,.
NH;^
H,S.
Ash
4.92
64.92
0.50
0.52
4.08
12.64
4.92
58.73
c
5.67
0.52
N
0.50
40
025
S
0.12
Ho
0.635
5.08
7^56
0.17
3.14
0.11
o!....
Sum
87.58
63.77
5.715
13.23
0.69
3.14
0.61
0.425
TABLE CXX.
ELEMENTARY ANALYSIS OF COAL AND PRODUCTS OF COBfBUSTION.
Components in
Kg.
Coke.
Air.
Sum.
Yields.
Losses
thr'h
Grate
Open-
ings.
Gases.
CO,.
CO.
H,0.
N.
Ash
4.92
58.73
211^63
0^25
64.49
4.92
58.73
211.63
0.12
0.25
64.49
4.92
15.67
c
6.57
36.49
N
211.63
S..
0.12
0.12
0.25
^^ |o'.:.... ...
0.25
17.51
48.65
Sum
63.77
276.37
340.14
20.96
24.08
85.14
0.25
211.63
We suppose that the coke contains nothing but carbon,
besides the ash, and that the gases of dry distillation contain no
oxygen except as CO and H^O (the latter supposition is not
quite, but suflSciently correct, since the gases contain QO^ and
other oxygen compounds). The formation of tar is not taken
into consideration.
Since only a small amount of N is present, we calculate the
entire amount as NH,; actually, however, but one-fifth of the
nitrogen of coal is transformed into NH,.
FKryDOrtK GAS
Aki
(c) Process on and ji^t abox-e ^he $r»li^ v^^'*^^^*^ v'v**^^
bustion of the coke formed^.
The coal analyss shows 5.44 per cent ash. whiW ih^ l^bJk^ shv^WH
only 4.92 per cent, which is ex|.Jaim\l bv kvxkUÜwik uv^i^^y
formation of sulphates from Fe^, Tht^ i^MUiHvaluu^ \vj shm
shown in the last table results fi\>ni tht^ awn^^'^ wu^HViituM^ \v(
generator gas and the composition of the pt^vi \\i K\\M\\\^\\\\\\y
which is given in Table CXIX.
The distribution of heat in the generator is hIujwu \\\ \\\\^ \\\\^\
balance, Table CXXI.
TABLE CXXI.
HEAT DISTRIBUTION IN (UCNKUATOH.
Production of Heat and Non-Produced
Heat.
HliitfU«.
Cul
179000 4
3337 (*
I. Production of heat :
1. Heat produced in generator by
chemical processen
2. Heat introduced by coal tiiul
air (by their temperature). .
II. Non-produced heat:
1. Unburned coal falling through
the grate.. 1 120013
2. Heat capacity of generaUifguMi»« I y^m*lH
III. Heat losses:
1. By fuel and ash falling through
grate
2. By heat carried away by tlu'
gas produced . . .
3. Loss Dy moistur«; of |(a«> .
4. By deeompositkni of waUr
5. (a) RadUtion
(b) Heat tuati^sitbwry ior gaMfy
ingeoflJ
r^)0 t
«•»•III
:i0 07
4V
U 7V
(*IMIilfllM>l|
Cul.
U3<i04 3
I i^Mi «
I'M* iWof
g 341
Wlh% ii 4 m
\rwi 3 J i»3'
*0iO 1 :^'
1^4<rM^ r J4 MV
'4^W^ (r 4^
IV. Non-produeed UsuX
By tmbumed «xraJ
through grate .
Heat gaixfted
fuliilA^
27 i<>
72 JM
)>;^<M>4 3 :^' *♦'
13*//)/.
«
1/ r^
^0^nl
V
4f/ '#'.
¥ß¥t4r
<;
M </•'
*^/'>*/4^
V
iM<. (^.-
264
HEAT ENERGY AND FUELS
It is understood that the composition of generator gas depend^;,
besides the quality of fuel, on the size of same, height of fuel
layer, construction of generator, and also temperature and air
pressure during the operation. Table CXXI was prepared by
Richard Akerman.
TABLE CXXII.
GENERATOR GAS FROM WOOD OF FIR TREES.
Kind of Fuel.
Trunks
and
'Roots.
Brush-
wood.
LofTvood.
Sawmill
Refuse.
ize. <
Size
( Thickness. . .
Length . .
m.m.
m.m.
20-35
500-750
maximum
200
Contents:
Hygroscopic water, per cent . .
Ash, per cent
Wooa substance, per cent
Composition of woo<l substance :
C, per cent
H,, per cent
O, per cent
N, per cent
Grate area, square meter, of gen
Cubic content, cubic meters, of
generator
Consumption of fuel per day :
Per sq. meter grate area < » ' '
Per generator | ^^•"^•
Number of charges per 24 hours
Length of time of presence of fuel
in generator (hours)
Temperature of gas leaving gen
erator, degrees C
Kg. tar in 24 hours
Composition of tar:
C, per cent
H.2 per cent
O. per cent
N.per cent
Volume composition of gases free
of moisture and air:
CO,
CO
CA
CH,
H3
N,
12.
0.9
87.1
53.0
7.1
39.8
0.1
0.0
26.7
65.2
14866
2.8
8.6
180*»
3.8
29.8
0.6
4.2
6.4
55.2
16
83.
?
?
?
?
0.
81
1.9
8.1
1654
6.6
1340
5.6
4.3
505*
?
6.2
26.0
5.i
4.3
58.4
35-150 20-200
maximum maximum
890 340
27.
0.5
72.5
51.0
6.1
j 29.4 {
1.72
24.2
23.8
8891
41.0
15293
4.1
5.9
nr
444
75.5
7.4
16.6
0.5
6.0
29.8
0.3
6.9
6.5
50.5
60.
0.3
39.7
?
?
37
7.4
14.4
7909
19.7
10835
6.6
3.6
125**
9
11
19
4
7
56
PRODUCER GAS
265
TABLE CXXIII.
GENERATOR GAS FROM PEAT.
Origin.
Quantity of Feat.
-Is
Hygroscopic water, per cent
Gases, noncombustible
Gases, combustible
Fixed carbon, per cent
Ash, per cent
{C, per cent .
O*' percent
N, percent.
Grate area, square meters { c
Cubic content, cubic meters. . . j °^ generator
Per sq. meter grate area { ^^'"^ ™^^^'
J I I Per generator { ^'^ "^^^^^
Number of charges per 24 hours
Length of time for which fuel remains in gener
ator in hours
Temperature of gas leaving producer, deg. C. . .
Kg. tar in 24 hours
C
H.
O
N
COo, vol. per cent
Composition of tar
Composition of gas free of
air and water
CO.
CA.
CH,.
H,...
X...
MiinkfoTs
Good Fibrous
Peat.
25.0
8.3
39.0
24.9
2.8
57.8
6.8
34.0
1.4
0.0
22.8
20.6
6262
1.3
18.5
86-100°
152
79.6
9.3
I ■■ ' 1
6.6
29.6
0.7
4.0
5.3
53.8
Lotorp
Good Fibrous
Pteat.
36.0
17.6
16.9
24.0
5.
61.
6.
30.
2.
1.6
21.9
12.8
5279
40.2
8446
1.1
21.8
75-105°
173
79.8
9.2
9.6
1.4
6.8 - 7.
27.6 -26.
0.4 - 0.
3.75- 3.70
12.3 -13.5
49.15-48.8
TABLE CXXIV.
GENERATOR GAS FROM BITUMINOUS COAL.
Intermediate analysis
Composition of coal substance
Hygroscopic water, per cent 7.6
Gases, non-combustiole, per cent 9.1
Gases, combustible, per cent 13.6
Coked coal, per cent 64.6
Ash 5.1
/C, percent 79.0
2, per cent 5.9
, per cent 13.7
, per cent l-^
266
HEAT ENERGY AND FUELS
TABLE CXXIW. —Continued.
Limestone addition, per cent
r Weight in per cent of coal .
Residue in ash-pit
Composition-
C, per cent .
cent.
H-, per c(
Ash
per cent .
Grate area, square meters, of generator
Cubic content, cubic meters, of generator
, , ^ i Cu. m...
Sq. m. grate area< j^
Daily consumption of coal per
(Cu.m..
iKg...
Generator. ,
Niunber of charges per 24 hours .
• ' • sfo
Length of time for which fuel remains in generator
vol. per cent
Temperature of gas leaving generator, deg. C .
fCO„
Composition of gases free of air and
water
CO
a
cl
i:.
3.4
12.1
40.2
1.0
1.2
57.6
2.0
4.0
1.7
1251
3.4
2502
1.2
20
500**
1.8
27.3
0.4
4.2
6.2
60.1
TABLE CXXV.
GENERATOR GAS FROM LIGNITE.
Below are given results with a lignite generator:
Number of generators 3
Grate area per generator 2.5 square meters
Duration of test 12 hours 45 minutes
Coal charged 3600 kg. Leoben (Styria) coal
/C 61 . 72 per cent
Volatile H, 1 . 85 per cent
N . 22 per cent
HjO chemically combined 20.09
HjO hygroscopic 9. 34
Ash 6.78
^Combustible S 0.37
Calorific value 5446 kg. cal.
Composition of coal
Losses through grate
Composition of losses \ ^'i^
Composition of dry
generator gas. .
CO,,
vol. per cent
936.7 kg.
73.94 per cent.
26.06 per cent.
5.3
0.3
25.19
0.29
10.29
58.63
5.4
0.8
25.05
0.15
10.65
57.95
3
4.2
0.6
25.39
0.51
11.29
58.01
4.4
0.8
26.50
0.40
11.60
56.30
Aver-
age.
4.64
0.65
25.59
0.38
11.11
67.63
PRODUCKH OAS Urt7
TABLE t XXVI.
QUANTITY GASIFIED PER HOUK ANO Sgi'AUK MKTtCH UHA I »n
AKR\.
Logwood and sawdust mixed 4A AU Km
Sawmill waste m\ liiO '"
Logwood ,i7U "
Loose peat (bad quality) 7A IUI»
Good fibrous peat yOO SIA(I '
Lignite 40 Ml "
Bituminous coal IH) IIAO ' '
SUQGE8TION8 VOH l^mHiiNH,
Air (generator) gas has to \)c rna<l(* in it HMiitll i<K|M<fiffM<ffl#l
producer using different gra^lc^H of f\u*\, viiryihK liHghl/ of fM^^I
layer and air of different pre««tin»M, (Urn iumI fM4*l J« Ut titi
analyzed, the quantity of the fuifl rormurrM*^! nw\ nf iht m/m
generated to be found and i\w \m\Mm' of i\u* itrnrt^tui Ut h^ |/Mi
up. The results are to be c/ftnimrtul wiili Um* Jd^ttl fffof^fM
On a small scale <ln f^wm and if^fm*\hiti iuU'^; t^^if^nHt^'hl^
can be made for deroffttxirHiiun tint \ui\iU*MtM til i\^i Uiffji^U *4
the tube (fuel height; atA vt^pf^iy *A iU- Wit A
CHAPTER XXI.
WATER GAS.
Instead of producing fuel gases by the action of the oxygen
in the air on glowing coal, we can use for this purpose the oxygen
of water in place of the oxygen in the air.
If steam is led over glowing coal, two different reactions will
take place depending on the temperature. At very high tem-
peratures the reaction takes place according to the equation
C + H,0 = CO + H„
while with decreasing temperature a second reaction becomes
more and more prevalent according to equation
C + 2 H,0 = CO, + 2 H,.
The first equation is furnishing a mixture of equal volumes
of CO and H,, CO 50 per cent by volume and H, 50 per cent by
volume, while the second reaction, if taking place exclusively,
furnishes a gas containing two volumes Hj for every one volume
of COj, hence CO, 33.33 per cent by volume and H, 66.67 per
cent by volume. The thermal value of the first gas per 22.42
liters is 68 cal., of the second gas, 45.4 cal.
A comparison of the generator (air) gas process with the two
water gas processes shows:
TABLE CXXVII.
PRODUCER AND WATER GAS PROCESSES.
Volume Per Cent.
H,.
CO.
CO,.
N,.
Thermal
Value of
1 Volume.
C^l.
Of Mix-
ture at
Constant
Pressure.
Cal.
I C-fi(0,)-2N,= C()-f2N
2C-f2H,0-COsX2H,
3 C+H,0=CO+H,
66J
50
33^
60
33i
m
22.6
45.4
68.0
22.9
46.5
68.5
268
WATER OAS
269
The figures of thermal value refer to the same gas volume in
each case, and are well adapted for comparing the qualities of
the gases. In case, however, we want to consider the utilization
of fuel, we have to refer the thermal values to equal quantities
of carbon (equal volumes of CO and CO,), and we obtain:
12 Grams C.
Yield Liters
of Gas.
Value of the Gas at
Constant
Volume.
Pressure.
1
2
3
67.26
67.26
44.84
67.8 cal.
113.3 cal.
125.8 cal.
68.7 cal.
116.1 cal.
126.8 cal.
We see that water gas even under the most unfavorable cir-
cumstances yields more heat (thermal value) than the ideal air
(generator) gas, besides the fact that it contains less non-com-
bustible gases.
For making a perfect comparison we have to calculate at least
— if not the pyrometric heating eflfect — the quantity of air
theoretically required for combustion. We have for each 22.42
liters of gas :
TABLE CXXVIII.
COMPOSITION OF PRODUCER AND WATER GASES.
Oomposition of Ga8
in Per Cent by Volume.
Theoretical
Amount
of Air.
Combus-
tible In-
different
Gases.
Products of
Combustion.
H,.
CO.
CO,.
N,.
O,.
Na
HoO.
CO3.
Nr
1
2
3
66§
50
33i
50
33J
66}
16i
33i
50
64}
133}
200
33i 131i
66} 166}
100 200
66}
50
33i
33i
50
66}
133}
200
As the decomposition of water requires more heat than is
furnished by the formation of CO, and even COj, both water gas
processes are taking place only with the assistance of external
heat. We have
C + i (0,) = CO + 28,900 cal.
+ 2 H,0 = CO, + 2 H, + 97,600 - 116,120 = CO, + 2 H,
~ 18.5 cal.
C + H,0 = CO -f H, + 28,900 - 58,060 = CO + H, - 29.2
cal.
270 HEAT ENERGY AND FUELS
Considering the external heat we have:
Thermal
Value of
Gas per 12
Grams C.
External
Heat to be
Supplied.
Gain in
Heat.
C4-4rO,)4-2N,=C04-N,
68.7 cal.
116.1 cal.
126.8 cal.
-28.9 cal.
4-18.5 cal.
4-29.2 cal.
97.6
97.6
97 6
C4-2H,0=CO,4-2H,
C4-H,0=C0+H,
The advantage of water gas, therefore, does not consist in a
gain in heat, but exclusively in the higher thermal value of this
gas, which allows a better utilization in the combustion.
As can be seen from the above statements, the reaction,
C + HjO = CO + Hy will take place if steam is led through a
layer of sufficiently hot coal. As heat is absorbed by this reac-
tion, the coal will cool oflF, and besides the above reaction, the
process C + 2 HjO = CO, -I- 2 H, will take place. As the cool-
ing continues the second process will begin to outweigh the first,
and finally, since the second reaction also absorbs heat, the coal
will be so cold that the reaction will stop, and thus the steam will
go through the fuel undecomposed.
This necessitates reheating the coal in the generator. This is
done by shutting off the steam and blowing air through the
generator until the coal is sufficiently hot. During this period
air (generator) gas is produced which can be utilized independent
of the water gas. This period is called "hot-blowing." As soon
as the coal is hot again, the air blast is stopped and the steam
valve opened, and water gas is made until the cooling off of the
fire again prevents the rational production of water gas.
We have here, therefore, an intermittent process, which not
only requires careful supervision but also the erection of double
the number of generators in places where a continuous stream
of water gas is required, and where a large gas holder is objec-
tionable.
As we have seen, the two water gas reactions are taking place
in parallel. Since, however, the one furnishes a superior gas with
better utilization of coal than the other, it is of importance to
know the conditions which determine to which extent each of the
two reactions will take place. For this purpose we have to study
the state of equilibrium between the two reactions.
WATKK GAS J7I
To find the equilibrium of the gas pliHse, wt^ Imvt» tu t»uli»i«lnr
the reactions that are taking platte. If wo iKhIuoI
C + H,0 - a> f U,
from
C + 2H,0 - IH), I 2 11,.
we get
CO, + H,?=iCt) ♦ ll,().
This is a reversible reaction in which two vohliiu^N (('O I \ijh
are formed from two volumes (('O, I II,). It 1^, iUmtfnnh
independent of pressure at all U'tu\H*rn\MtVh lilwivn Um» ittM)hy
point of water. One might now conc|ii<|i^ thai tin» fniniinnU^tth
of water gas at a given t<!m|Kfratur<* in UnU*\H*iuU*h\, mMIm» li^vtm^f$:,
this, however, is not correct. From Um* Uu^l c'|MaUon w<' j^.t tnf
the isothermic e<|uiUbriurn
We therefore see tJiat at a j<:ivw^ O'/z^f/^'miOM Um^^< ^' ton^
sponding to everv' /^ a 'Uff*'r*'hi ,, / 'lo ^i«>h tUhh^l^
resuhi« we havf- Vj W/k for a i^a^Uvn whi^ h 'i*U muh* , ih* * u^^i
fibriuni betmeeu tJj<- »a^ jA*jia«< 'i^i '/«i* 'm./ rj,nt<i,fiiuf^ *fl ' >/^ />/
H^aod H5O' aijd lii«- »/>ii^i j^**Jiin« '^ '7 t*'*^'^ m. ^»/^ h wi 4^44 y/f^t*^ V/
use the eciuati'ju !:j*^jJt/ivJ**:'J a'h*'J*vJy i'* ♦-i*^ y^*iAii*^//i y/^ \uh*^^
And JKnr tli^ «.t/iiUiU^/Jtf 4*4* />»v4,*' fo< > »^U •ilti.iu.^ Üu u/i^a^ nn '
wtfier .ca^ a*e< '^rj>'ii*>. /• ''** i^i<,..4i<
{,i» '.*• '// / . ' • •,'/
, t " ' • ■ • . -i//.-
iu u fc» fwr»! r «r.i
I '.]/<• - ••/'
..I/,.'
iSMsfviiii^ vn.'ii^«^ #<'
. «.V'"-
4
ÜIÄJ of tl^ %v^*>-' >v*
>..'/' • •/"
'!/''■'
«fquilHmiui tt^^"^^-^ *
.V '.yl,'/..
272 HEAT ENERGY AXD FUELS
TABLE CXXIX.
EFFECT OF STEAM PRESSURE AND TEMPERATURE ON COMPOSITION OF GAS.
Steam Pressure, P. in Atmospheres.
Vol. Per
Cent. 0.1 0.25 0.5 0.75 1.0 1.5 2.0 2.5 3.0 4.0 5.0 10.0
1-400» C.
CO 0.24 0.12 0.06 0.04 0.03 0.02 0.02 0.01 0.01 0.01 0.01 0.00
OOi 10.88 7.86 5.97 5.04 4 46 3.73 3.27 2.97 2 73 2.40 2.15 1.55
Ha 21.99 15.84 11.99 10.12 8.94 7.48 6.56 5.94 5.47 4.82 4.31 3.11
H2O 66.88 76.18 81.98 84.80 86.57 88.77 90.15 91.08 91.79 92.77 93.53 95.34
t-600oC.
00 26.66 18.87 14.65 11.56 10.03 8.14 6.99 6.20 5.61 4.78 4.22 2.87
COx 12.84 16.06 17.15 17.79 17.86 17.67 17.41 17.12 16.84 16.32 15.88 14.32
Hj 52.34 50.89 48.95 47.14 45.75 43.48 41.81 40.44 39.29 37.42 35.99 31.51
HiO 8.16 14.18 19.25 23.51 26.36 30.71 33.79 36.24 38.26 41.48 43.91 51.30
t-800°C.
CO 49 04 47.81 46.04 44.46 43.06 40.56 38.53 36.83 35.41 32.81 30.69 24.38
COs 0.50 1.13 2.02 2.80 3.48 4.66 5.59 6.34 6.95 8.02 8.88 11.05
Hi 50.03 50.07 50.08 50.06 50.02 49.88 49.71 49.51 49.21 48.85 48.45 46.48
HiO 0.43 0.99 1.86 2.68 3.44 4.90 6.17 7.32 8.43 10.32 11.08 18.09
t-IOOO^C.
CO 50.00 50.00 50.00 50.00 50.00 49.42 49.42 49.00 48.57 48.35 47.98 46.24
COi 0.25 0.25 0.45 0.61 0.71 0.87 1.59
Hs 50.00 50.00 50.00 50.00 50.00 49.92 49.92 49.90 49.79 49.77 49.72 49.42
HtO 0.41 0.41 0.65 1.03 1.17 1.43 2.75
t-l200°C.
CO 50.00 50.00 50 00 50.00 50 00 50.00 50.00 50.00 50.00 49.32 49.31 49.31
COs 0.25 0.25 0.25
Ha 50 00 50.00 50.00 50.00 50 00 50.00 50 00 50.00 50.00 49.82 49.80 49.80
HsO 0.61 0.64 0.64
t-=I400«'C.
CO 50 00 50 00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00
CO»
Hi 50 00 50 00 50 00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00 50.00
HzO
Figs. 87 and 88 show the ideal composition of water gas at a
steam pressure of one and four atmospheres. We see from the
diagrams that with increasing pressure the curves are moving
towanls higher temj^eratures. We also see that the quantity of
undecomposed steam present is rapidly decreasing from a certain
temperature on, while the quantity of CO and H, is rapidly
increasing in the same manner. The curves of CO and H, are
in their middle part practically parallel, but the upward move-
ment of the H-curve is beginning 200° C. below the bend of the
CO curve.
The CO3 curve starts to rise together with the H-curve (but
more slowly), until it crosses the st<3am curve and falls with the
latter. The result of this discussion for practice is that the
most favorable gasifying temperature is between temperature
limits of about 200°, and increases with the steam pressure.
fe?
TTAr^fÄ OAS
27J
1
Ü
il
eS
I
I
V
J
fM 9»
a of Water Gas at
itmospheres.
p
^S^^^
/
\,
^'^'^i
fe
,<^
V
^^^^^
^
^,
AK?At?I^
»vo^
'^
^«ij
^^^
^
fe^\
5 -^
,— ^
,.^--
J^ti^
"^^
■^1
^
■^
•i
si
s
K 1
S f
5 S
I s
\ t
» s
? s
) $
J
o 2
274
HEAT ENERGY AND FUELS
Vol.%
IUI
A
fi
i
V
1Q
w
f
1
111
t
/
i
1 1
k
It
m
10
'/#/
1
i
1
/
*»
11
' ™
1
1
^vn wn ißo Wi 900 iQQ 900 «oiooouooiaoo
Temoeratare In de«. e«ot.
Fig. 89. — Coiubuätible Gases Present in Water Ga».
WATER GAS
275
This becomes clearer when we calculate the quantity of com-
bustible gases (CO and H,) present in water gas (Fig. 89).
TABLE CXXX.
QUANTITY OF COMBUSTIBLE GASES PRESENT IN IDEAL WATER GAS.
Steam Ftessure
in Atm.
Gasifying Temperature in Degrees Cent.
400
600
800
1000
1200
1400
0.1
22.23
79.00
69.76
63.60
58.70
55.78
51.62
48.80
46.64
44.90
42.20
40.21
34.38
99.07
97.88
96.12
94.52
93.08
90.44
88.24
86.34
84.62
81.66
79.14
70.86
100.00
100.00
100.00
100.00
100.00
99.34
99.34
98.90
98.36
98.12
97.70
95.66
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
99.14
99.11
99.11
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
0.25
0.5
15.96
12.05
10.16
8.97
7.50
0.75
1.0
15
2.0
6.58
5.95
5.48
4.83
4.32
3.11
2.5
3.0
4.0
5 0...
10.0
As the combustion of one mol CO yields 68,600 cal., the com-
bustion of one mol H, to liquid water 68,400 cal., which is prac-
tically the same amount of heat, we can use the above table for
comparing the thennal value of the diflferent gases. As one mol
of every gas at 0° and 760 min. pressure occupies a space of 22.42
liters, we can calculate the thennal value of 1 cubic meter of the
above gases in large calories by multiplying their content of com-
bustible gases with
1000X68.5 ^^^
100 X 22.42 " '^^•^•
TABLE CXXXI.
THERMAL VALUE OF 1 CUBIC METER OF IDEAL WATER GAS IX KG. CAL.
Steam Pressure
in Atm.
Gasifying Temperature in Degrees Cent.
400
600
800
1000
1200
1400
0.1
680
2417
2135
1946
1715
1707
1580
1493
1427
1374
1353
1230
1052
3032
2995
2941
2892
2848
2767
2700
2642
2589
2499
2422
2168
3060
3060
3060
3060
3060
3040
3040
3026
3010
2002
2990
2927
3060
3060
3060
3060
3060
3060
3060
3060
3060
3034
3033
3030
3060
3060
3060
3060
3060
3060
3060
3060
3060
3060
3060
3060
0.25
0.5
590
369
0.75
1.0
311
274
230
201
182
168
148
1.5
2.0
2.5
3.0
4.0
5.0
132
95
10.0
276
HEAT ENERGY AXD FUELS
This table shows more clearly that the thermal value of the
ideal water gas increases with increasing temperature and
decreases with increasing pressure.
VoL%
Fio. 90.
too 600 VOO 800 00
Temperatore In deg. ccnt.
■ Undccomposed Steam in Water Qas,
UOO ttW
At a steam pressure of 1 to 2 atmospheres the most favorable
gasifying temperature is between 800° and 1000° C, and at 10
atmospheres pressure between 1000° and 1300° C. It is, there-
fore, not advisable to use steam of too high pressure.
WATER GAS
277
The quality of the water gas is deteriorated by its content of
undecomposed steam and of COj. We, therefore, will consider
the influence of pressure and temperature on the quantity of HjO
and COj present in the gas.
The quantity of undecomposed steam in the ideal water gas
decreases rapidly (Fig. 90) with increasing gasifying tempera-
ture and slowly increases with the pressure. As thereby the
800 100 800 900 U» UOO UOO
Tampetatareindflg. oenU
Fia. 91. — CO2 in Water Gas.
inflammability of the gas is decreased, the gasifying temperature
should not be below 700° to 800° C, with a steam pressure of 1 to
10 atmospheres, since otherwise the quantity of undecomposed
steam wiU be considerably above 10 per cent by volume.
The content of CO2 (Fig. 91) is injurious, as it causes an unfa-
vorable utilization of the carbon. Moreover, it deteriorates the
gas, increasing the quantity of non-combustibles and lowering
the temperature of combustion. As the COj amounts only to a
few per cent at 600° to 700° C, it does not have to be considered
in the production of generator gas.
278
HEAT ENERGY AXD FUELS
In practice, however, it is of importance to know the quantities
of carbon and steam which are required for the formation of
1 cubic meter of water gas. This information is given in the
following tables:
TABLE CXXXII.
QUANTITY OF STEAM IN CU. M. REQUIRED FOR THE FORMATION OF
1 CU. M. OF IDEAL WATER GAS.
Steam Pressure
in Atm.
Gasifying Temperature in Def?rees Ce.it.
400
600
800
1000
1200
140O
0.1
0.25
0.5
0.8887
0.9202
0.9397
0.9492
0.9551
0.9625
0.9671
0.9702
0.9726
0.9759
0.9784
0.9845
0.6050
0.6057
0.6820
0.7065
0.7211
0.7419
0.7560
0.7668
0.7755
0.7890
0.7990
0.8280
0.5046
0.5106
0.5194
0.5274
0.5346
0.5478
0.5588
0.5683
0.5764
0.5917
0.6043
0.6457
0.5000
0.5000
0.5000
0.5000
0.5000
0.5033
0.5033
0.5505
0.5092
0.5094
0.5115
0.5217
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5043
0.5044
0.5044
5000
5000
0.5000
0.5000
5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.5000
0.75
1.0
1.5
2.0
2.5
3.0
4.0
5.0
10.0
TABLE CXXXIII.
THEREFORE ONE CUBIC METER OF STEAM FURNISHES THE FOLLOWING
NUMBERS OF CUBIC METERS OF IDEAL GAS.
Steam Pressure
in Atm.
Gasifying Temperature in Degrees Cent.
400
600
800
1000
1200
1400
0.1
0.25
0.5
0.75
1.0
1.125
1.087
1.068
1.053
1.047
1.039
1.034
1.031
1.028
1.024
1.022
1.015
1.653
1.537
1.466
1.415
1.386
1.348
1.323
1.304
1.289
1.269
1.251
1.208
1.981
1.958
1.925
1.896
1.871
1.825
1.789
1.759
1.735
1.690
1.655
1.548
2.000
2.000
2.000
2.000
2.000
1.986
1.986
1.978
1.963
1.963
1.955
1.916
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
1.983
1.982
1.982
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
1.5
2.0
2.5
3.0
4.0
5
10.0
WATER GAS
279
The last table is specially valuable for this practice, since it
permits an easy control of the operation of the generator and
allows the determination of the ideal gasifying temperature,
which corresponds to the process. The content of one component
of the gas, for instance CO, (which can be easily determined with
an Ados or Strache apparatus) being known, the complete analy-
sis of the gas can be found.
TABLE CXXXIV.
ONE CUBIC METER OF WATER GAS CONTAINS GRAMS OF C.
Steam Preasu.ie
in Atra.
Gasifying Temperature in Degrees Cent.
400
600
800
1000
1200
1400
0.1
59.51
42.71
32.27
27.19
24.03
20.07
17.61
17.05
14.66
12.90
11.56
8.30
211.40
186.95
170.19
157.08
149.27
138.14
130.59
124.81
120.15
112.93
107.58
91.96
265.14
261.23
257.22
252.94
249.08
242.07
236.13
231.05
226.71
218.52
211.78
189.62
267.60
267.60
267.60
267.60
267.60
265.83
268.83
264.66
263.21
262.57
261.45
255.99
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
265.30
265.25
265.25
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
267.60
0.25
0.5. ...
0.75
1.0
1.5
2.0
2.5
3.0
4.0 .. .
5.0
10.0
TABLE CXXXV.
ONE CUBIC METER OF STEAM GASIFIES GRAMS OF C. (Fig. 92).
Steam PtcsBure
Gasifying Temperature in Degrees Cent.
in Atm.
400
600
800
1000
1200
1400
0.1
66.96
46.41
34.81
28.64
25.16
20.85
18.21
17.57
15.07
13.22
11.81
8.43
349.44
287.30
249.54
222.34
207.00
186.19
172.74
162.77
154.93
143.13
134.64
115.06
525.44
511.61
495.23
479.59
465.92
441.89
420.77
406.54
393.32
369.31
350.45
293.67
535.20
535.20
535.20
535.20
535.20
528.17
528.17
523.56
516.91
511.52
511.14
490.68
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
526.17
525.87
525.87
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
535.20
0.26
0.5
0.75
1.0
1.5
2.0
2.5
3.0
4.0
5.0
10.0
280
HEAT ENERGY AND FUELS
If the steam of the gas condenses — which frequently happens
in practice — the composition and thermal value of the gas
changes accordingly. The calculation of the gas composition
from the CO, content is very simple. The COj of the dry gas
being c per cent by volume, the content of
C0= 50
- c per cent by volume,
id
H, = 50 + - c per cent by volume.
«J»
—-^
Oi4
A
y
h
r
?^^^^
%^
/
m
///
/
U
- _.J
k
§
V
• 1
/■
w
f\
llkt
'
u
'0
r
500 QU TM »M 900 1000 ÜOÖ 1^00 laoi
Temperature of gas Jzuleg. cent
Fig. 92. — Gasification of Carbon by Steam.
For example, we take a gas made at 800° C. and 2.5 atmospheres
steam pressure. The COj content having been found as 6.84
per cent by volume, the content of
CO = 50 - 1.5 X 6.84 = 39.74 per cent by volume,
Hj = 50 -h 0.5 X 6.84 = 53.42 per cent by volume.
The following two tables contain the most important data on
dry water gas. Compared with the wet gases, in which at con-
stant pressure the CO, content at first increases with the tem-
perature up to a maximum and then decreases, the dry gases
have far more regular properties. The CO, content at constant
pressure decreases with increasing temperature, while CO and H,
increase simultaneously. On the other hand CO, increases at
constant temperature with the pressure, while H, and CO
decrease simultaneously.
WATER OAS
281
TABLE CXXXVI.
QUANTITY OF DRY GAS PRODUCED FROM ONE CUBIC METER OF STEAM.
Steam Pressure
in Atm.
One Cubic Meter of Steam is Yielding, at the Temperatures
Stated Below, Cubic Meters Dry Water Gas.
400° C.
600° C.
800° C.
1000° C.
1200° C.
1400° C.
0.1
0.25
0.5
0.373
0.259
0.192
0.160
0.141
0.117
0.102
0.092
0.084
0.074
0.066
0.047
1.518
1.304
1.184
1.082
1.021
0.934
0.876
0.831
0.796
0.743
0.702
0.588
1.972
1.939
1.889
1.845
1.807
1.736
1.679
1.630
1.589
1.516
1.457
1.268
2.000
2.000
2.000
2.000
2.000
1.978
1.978
1.965
1.943
1.940
1.927
1.863
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
1.971
1.969
1.969
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
2.000
0.75
1.0
1.5
2.0
2.5
3.0
4.0
5.0
10.0
The most favorable conditioiLs for producing the dry water
gas are therefore the same as for the wet gas. We have so far
discussed the case in which the state of equilibrium is actually
reached in the producer. We are now going to consider the case
which is very common in practice, that the equilibrium is not
reached.
If steam is blown through a layer of glowing coal the reaction
will undoubtedly take place completely on the contact points of
steam and coal, i.e., the state of equilibrium will soon be reached
here. On its further way the gas current will undergo a change
in two respects. Partly by diffusion, partly by mechanical
mixture, a reaction will take place betw^een the outer part of the
current and the inner part, which is richer in steam; on the other
hand, the equilibrium of the outer layer will be disturbed by the
contact of same with other parts of the coal.
If the gas passes from the cold to the hot coal layers (*' Ge-
genstrom"), a gas rich in CO^ will be formed at first in the outer
layer; then, by coming in contact with hot coal, it is enabled to
oxidize new quantities of coal, getting thereby richer in (X). If,
however, the steam passes from the hot to the cold coal layers
("Parallelstrom"), a gas rich in CO will be formed at first in the
outer layer, and by passing further it will get richer in CO, and
poorer in 00.
282
HEAT ENERGY AXD FUELS
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WATER GAS 283
We will now consider again the reaction between the outer
gas layer and the inner steam current. In working according
to the "Gegenstrom principle/' the steam of the inner surface
can react with the outer gas layer, so that CO is oxidized to COj
and Hj is liberated. Supposing the temperature remains constant
or decreases, the thermal value of the gas remains unchanged.
If, however, the average temperature of the gas current rises —
which is probable, since the gas comes into the hotter parts of the
producer — this reaction decreases and the actually occurring
improvement in the quality of the gas cannot be explained but
by oxidation of glowing coal by means of the CO, and the steam
of the outer layer and also by the outward diffusion of the steam.
If we work according to the "Parallelstrom principle" the hot
outer layer formed in the start will react vigorously on the steam
(on account of the higher temperature both the diffusion and
velocity of reaction will be greater) and the gas without practical
change in thermal value will get richer in H, and poorer in CO.
Hereby the quality of the gas is improved, just the same as
above, by the reaction of the outwardly diffusing steam with the
glowing coal. On the other hand, the gas quality is deteriorated
as the steam gradually comes in contact with cooler coal, whereby
the quantity of COj is increased.
Undoubtedly the first mentioned way of gasifying is more
advantageous, the more so as in this case the gas and steam
current is also preheated gradually.
If we consider the average composition of water gas, in case
the state of equilibrium is not reached, we always find this
relation between COj, CO, and H,, that the volume of Hj is equal
to the sum of the CO volume and double the CO, volume. Besides
this some steam is also present. The composition of the wet
water gas as well as of the dry gas will, therefore, under all con-
ditions correspond to one equilibrium, which, however, at the
same steam pressure corresponds to another (the ideal) gasify-
ing temperature, the latter being lower than the actual gasifying
temperature.
Dr. Hugo Strache and R. Jahoda have studied the influence
of height of fuel and air and steam velocity on this process, both
during hot-blowing and gas making, and have found :
In the beginning of the hot-blowing period (when the tem-
perature of the fuel is rather low) CO, is formed almost exclusively
284
HEAT ENERGY AXD FUELS
without any CO, wliile with increasing temperature the forma-
tion of CO increases. We have here again the equilibrium which
was mentioned before : 2 CO <=i CO, -f- C.
As less C is absorbed by a certain volume of air for the forma-
tion of CO, than for the formation of CO, the fuel consumption
is considerably less in the first stages of hot-blowing than in the
later stage, while the quantity of heat developed per minute is
very much greater at the start than in the later stages.
The loss of heat by the hot gas leaving the producer increases
with the temperature. The heat accumulated in the producer
is evidently equal to the difference of generated and lost heat.
The ratio of accumulated heat and carbon used is called by
Strache "the efficiency in hot-blowing." This ratio is high in
the beginning (at low temperature) and decreases with increas-
ing temperature and fuel consumption.
Content of COj and efficiency in hot-blowing are as follows at
625° c.
672° C.
929° C
1300° C.
Efficiency.
Per cent.
80
70
40
30
CO,.
Per cent.
18
16
7.6
4.6
The total efficiency for a certain blowing period decreases
rapidly between 650 and 900 degrees; it is therefore advan-
tageous not to raise the temperature of the producer above
900 degrees.
The losses of heat during the hot-blowing period can be
utilized to a large extent for preheating the steam (m the manu-
facture of pure water gas).
The losses during gas making depend on the velocity of steam
and the temperature of the producer. Too low velocity yields
a rather small quantity of gas and causes comparatively great
loss of heat by radiation; too great velocity is disadvantageous
on account of the steam going through undecomposed; in this
case large quantities of heat leave the producer without being
utilized on account of the high specific heat of steam.
WATER OAS
285
The results of these researches are:
1. The quantity of undecomposed steam and the CO^ content
of the gas increase at constant temperature with the increasing
velocity of the steam in about the same proportion.
2. The content of steam and CO, of the crude gas at constant
velocity of steam decreases with increasing temperature.
3. Even at low temperature the content of CO, and steam
can be reduced to a minimum by decreasing the velocity of steam.
IUI dbv iMi iM« 1100 laoo lag» tiuü uno looo ko)
Fig. 93. — Efficiency of Water Ga« Makin« Referred to Velocity of Steani.
The efficiency in gas making is calculated from the carbon
consumption during gas making, loss of heat in the producer,
and the thermal value of the water gas produced. The total heat
loss is made up of the heat of fonnation, heat of the gas pro-
duced and of the undecomposed steam, and the radiation of heat
from the producer. For every temperature there is a certain
velocity of steam, with which a maximum efficiency is reached
(87 to 93 per cent).
286 HEAT ENERGY AND FUELS
The total efficiency for any given velocity of steam can be
calculated from the carbon consumption during blowing and
gas making and from the loss of heat during blowing and gas
making.
Fig. 93 shows a diagram of these conditions.
The total efficiencies also show a maximum at a certain velocity
of steam.
At 780° C 72.5 per cent,
At 860° C 77 per cent.
Suggestions for Lessons.
Experiments analogous to those under generator (air) gas can
be made.
CHAPTER XXII.
DOWSON GAS, BLAST-FURNACE GAS, AND REGENERATED
COMBUSTION GASES.
The production of pure water gas has the advantage of fur-
nishing a gas of high absolute and pyrometric efficiency, which
is of importance for certain purposes.
Besides the fact that this gas cannot be generated except by
employing external energy (for decomposing steam) and by
using an expensive boiler plant, the producer gas which is herein
obtained as by-product with a high percentage of carbon dioxide
can be used mostly for auxiliary purposes only. Furthermore
this process has two disadvantages :
1. It is an intermittent process (two stage), comparatively
difficult, complicated, and expensive.
2. It requires a plant of double the size of that of a continuous
process.
The idea presented itself of having the two processes of hot-
blowing and gas making take place in parallel and simultaneously
in one proiiucer, whereby Dowson gas or semi- water gas (some-
times also called producer gas) is obtained.
The purpose of this process being the generation of gas of the
highest possible heating value, the amount of carbon dioxide
has to be kept as low as possible. Since with decreasing carbon
dioxide the nitrogen content considerably increases, the thermal
value of the gas decreasing at the same time, this point deserves
serious consideration.
We will now consider the ideal conditions. The reaction
C + HjO = CO -f- Hj takes place with the consumption of
42,900 cal. for every 12 g. of carbon gasified, while in the reaction
C + i (O2) = CO 21,100 cal. are liberated for every 12 g. of
carbon.
Therefore in order to keep the temperature of the producer
constant we have to get as much heat from the second process
as is consumed by the first process (not considering the losses of
287
288 HEAT ENERGY AND FUELS
heat). We therefore have to gasify two atoms of carbon with
air for every atom of carbon gasified with steam. The ideal
equation for this process is
3 C + H,0 + O2 + 4 N, = 3 CO + H^ + 4 N„
which is equivalent to a Dowson gas of the following composition :
CO ^ 37.5
H^ 12.5
N 50.0
100.00
In the reaction
C + 2 H3O = bo, + 2 H„
on the other hand, for every 12 g. of carbon 40,400 cal. have to
be furnished by gasifying with air. This is also one atom of
carbon gasified with steam to two atoms of carbon gasified with
air. The ideal equation is
3C + 2H,0 + O3 + 4N, = CO, + 2H, + 4N3 + 2C0,
the analysis of the gas:
CO, 11.1
CO 22.2
H, 22.2
N3 45.5
101.0
In working with coal instead of with carbon, volatile matters
enter this reaction, whereby the nitrogen content is further
decreased.
In practice — on account of unavoidable losses — more than
two atoms of carbon have to be gasified with air for every atom
gasified with steam.
The equilibrium
CO + H,O^CO, + H,
causes the formation of steam, which can considerably deteriorate
the quality of the gas.
The principle of this process is the oxidation of carbon partly
GASES 289
by oxygen of the ^r and partly by oxygen of an oxide (water).
A similar reaction takes place in the blast furnace, where, besides
the oxygen of the air, the oxygen of the iron oxide is used for
oxidizing the carbon mainly according to
3 C + Fefi, = 2 Fe + 3 CO,
and to a small extent according to
3 C + FCjO, = 4 Fe + 3 CO,.
The ordinary composition of blast-furnace gas is
Average
CO3 5-16 12
CO 20-32 24
H. 0.1^.5 2
CH, Ü. 2-2.5 2
N, 56-03 6()
Blast-furnace gas has a fairly high thermal value. The source
of the hydrogen in this gas is the air moisture, which acts on the
carbon; the methane content is very probably caused by direct
synthesis. Since a considerable part of the oxygen of the blast-
furnace gas is derived from the ore instead of the atmosphere,
the quantity of nitrogen in furnace gas is lower than in producer
gas generated by an exclusive oxidation by means of air. The
content of carbon dioxide is partly explained by conditions of
equilibrium (in the cooler part of the furnace some of the carbon
monoxide is decomposed according to 2 CO = CO, + C) and
partly by the reduction process (3 CO + Fe^O, = 3 CO, -h 2 Fe).
Instead of using the oxygen of water or oxides of metals for
partly oxidizing carbon, the oxygen of carbon dioxide can be
used: C 4- CO, = 2 CO.
This can be done by passing gases rich in carbon dioxide
through a glowing layer of coal, which process is called regenera-
tion. Such "regenerable^' gases are for instance combustion
gases and gases from lime kilns or blast furnaces. The last
named gas seems to be especially adapted on account of the small
amount of nitrogen present.
If we should succeed in converting by this process the total
carbon dioxide of a blast-furnace gas of the above average
290 HEAT ENERGY AND FUELS
analysis into carbon monoxide, a gas of the following composition
would be obtained :
60
N = -— = 53 . 58 per cent,
24 + 2 X 12
CXj = — — = 42.80 per cent,
X . Xi^
2
CH^= — — = 1 .78 per cent,
X . x^
2
H = — - = 1 . 78 per cent,
X . x^
the thermal value of which would be considerably higher than
that of the original gas.
The heat consumption for this process is as follows :
The reaction CO^ -h C = 2C0 absorbs 97,600-2 X 26,100
= - 45,400 cal. If we want to reclaim this amount of heat (as
with Dowson gas) by the reaction C + = CO -f 21,100 cal.,
we have to transfonn for every mol of carbon dioxide contained
45.4
in the gas rr^ or about 2 atoms of carbon into air-producer gas.
<^X. X
We get about the same conditioas as with water gas, and in prac-
tice we will have to bum, instead of 2 mols carbon, from 3 to 5
mols to carbon monoxide. Supposing we should get 2 mols of
carbon monoxide by direct combustion, for every mol of carbon
dioxide, we would have the following theoretical composition for
the regenerated blast-furnace gas :
^ 60 + 45.14 _ _^.
N = — -— = 58.0() percent,
1 .81
CO = ^^ \ \^ ^ ' = 39.74 per cent,
1.81
2
CH^ = — — = 1 . 10 per cent,
1 .81
2
H2= T—7- = 1 . 10 i^er cent.
1 . ol
As above stated a larger part of the carbon will have to be
burned in practice on account of unavoidable losses in heat.
OASES 291
Supposing we take 3 gram-atoms of carbon for every mol of
dioxide to be reduced, we g?t a gas of the following theoretical
composition:
N= ^t?I^^ ° 59.21 per cent,
Ol -I- *^ -I- 24
CO = ^^-^^^rrr-^^ = 38.93 per cent,
2. Id
2
CH,= r-— = 0.93 per cent,
Z. lo
2
H, = r— := 0.93 per cent.
^ . xo
In practice this result could be obtained only by applying a
sufficiently high gasifying temperature, as otherwise the reaction
would be incomplete. So far this method is not in practical use-
Suggestions for Lessons.
Production of Dowson gas, same as in the two former lessons.
Elflfect of air and carbon dioxide upon a layer of glowing coal.
CHAPTER XXIII.
APPARATUS FOR THE PRODUCTION OF FUEL GASES.
(Generator or Producer Gas Plants.)
The apparatus which are used in practice for manufacturing
fuel gases are called gas-generators or gas-producers. These
are, generally speaking, chambers lined with firebrick. These
chambers are charged with coal, wood or peat respectively, and
the air of combustion or steam or a mixture of steam and air is
passed through, generally upward.
If air (generator) gas is produced the gas in the producer is
moved either by draft (chimney) alone or by pressure (blower).
Accordingly we have a classification in draft and pressure-
producers. The latter have to be closed tight at the bottom.
Fkj. !>4. — Boetius Gas Generator.
We shall consider first the air-gas generators, which were built
ori^nally right near the furnace, which was to be heated
(Siemens gas or half-gas). Their development is shown by the
following types:
292
FUEL GASES
293
Fig. 94. Boetius producer. The producer compartment, G,
is separated from the combustion chamber of the furnace by a
vertical wall and from the outside atmosphere by an inclined
wall upon which the charged coal slides down. The opening, a,
for the charge can be closed by means of the slide, ss. The
inclined wall is supported by the iron bar, b, which contains an
Figs. 95 and 96. — Boetius Double Generator.
opening for poking and air-admission. At the bottom the
producer compartment, G, is separated from the ashpit. A, by
the inclined grate, r. The channels, c, in the back wall allow a
preheating of the air of combustion.
Figs. 95 and 96. Boetius double producer, developed from
the former type by combining two producers (right and left)
Flos. 97 and 98. — Bicheroux Generators.
and leaving out the back walls. Thereby less brickwork is
required and loss by radiation from the back wall avoided (at
the same time doing away with the preheating of air). We find
here the air-channels in the side walls. The inclined grate is
supplanted by a plane-grate. R is the grate, c the air-channels.
Larger than these are the Bicheroux producers (Figs. 97 and
98) which are provided either with step-grate, T, and inclined
294
HEAT ENERGY AXD FUELS
grate, Ä, or with a plane-grate, r. / is the charging opening.
These producers are also built right near the fireplace.
Largely used are the shaft producers of William and Friedrich
Siemens. They are built independent of the furnace to Ix;
I-^OB. 99 and 100. — Siemens Generator.
heated. In order to avoid as far as possible losses of heat and
to save brickwork they are frequently built below the floor level
in rows or in squares. Figs. 99 and 100 show a plant of the latter
kind in elevation and ground plan. Fig. 99 shows two producers
with one common wall. These producers are provided with
step-grates, T, and inclined grate, Ä. The ground plan shows
four producers I, II, III and IV, arranged in the form of a square.
FUEL OASES
2U5
There are two charging chutes for each producer; tlie holes, .'f,
are for poking the fire. The gas leaves all four proilucers througli
one gas main. The back wall of these producers is inclineil, for
preventing the ^r from passing along the vertical wall (^^^t
resistance).
A charging hopper is shown in Fig. 101. Same is proxidcii
with a valve operated by a counterweight and a cover which
CoTer
Fio. 101 . — Charjcing Hopper.
closes gas-tight by means of a sand or tar seal. For charging
coal the cover is removed, coal filled in, the cover {)ut on and
then the valve opened. Thereby losses of gas an* pn^venteil.
In order to increase the fuel height, C, which is to be measureil
in the direction of the arrows, in some cases the charging hopper
Fig. 102. — Siemens Generator of Neuberg.
has been moved more toward the center (Fig. 102). For dis-
connecting one producer of a producer system, valves, V, are
provided. Below the ash-pit there is an excavation filled with
water, the latter being evaporated by the ash and fuel falling
through the grate, whereby the quality of the gas is improved
(Dowson gas).
If we omit one of the two separating walls in a square of
296
HEAT ENERGY AND FUELS
Fig. 103. — Siemens Double Generator.
Fio. 106. — Generator of Fio. 107. — Bituminous Coal Generator
Kolsva. of Odelstjema.
FUEL GASES
297
four Siemens producers, we arrive at double producers (Fig.
103) which can be built singly or in rows.
Shaft producers (old Donawitz type) for lignite and brown
coal are shown in Figs. 104 and 105. The inclined step, a, in the
brick lining is necessary for preventing the rising of the air
alongside the walls. Other types of shaft producers are :
The producer of Kolsva in Sweden (Fig. 106) in which Parry \s
hopper, p, is used for charging.
The different types of producers of Odelstjema are :
(a) For bituminous coal (Fig. 107). This producer is wider
at the. bottom to facilitate the downwanl movement of the coal.
For preventing the rising of the air alongside the wall an offset
is arranged at the bottom of the shaft.
(6) For peat, wood and shavings (Fig. 108). For these fuels
the shaft has to be considerably wider and the fuel-height
Fig. 108. — Odebtjema's Generator
for Peat, Wood and Shavings.
Fig. 109. — Generator of Tholander.
greater than for coal. A plane or step-grate is used in these pro-
ducers, which are generally arranged for blast and provided with
air-tight doors, T, The soft coal producer of Tholander (Fig.
109), which is of peculiar shape, is arranged for air blast at the
bottom. In this construction the active height of fuel (i.e. the
way along which the primary air comes in contact with glowing
coal, ab) is kept constant at all periods. The fuel rests on a solid
base, cd, F \s the charging hopper, xmv is the blast-channel, G the
298
HEAT ENERGY AND FUELS
producer-shaft, ss are the poke-holes and TT the ash-doors. As
seen from the above descriptions the cross-sections of producers
are made both square and circular. In single (isolated) pro-
Fia. no. — Fimnel-Shaped Grate.
Fio. 111. — Conical Grate.
ducers the circular cross-section is of advantage on accoimt of
more uniform operation and smaller loss of heat by radiation.
They are provided either with a plane-grate (as in the Odelstjema
Fio. 112. — Conical Grate.
Fio. 113. — Bottom of Generator
with Step and Plane Grate.
type for peat, wood, etc.), or with a funnel-shaped or conical
grate (Figs. 110, 111 and 112).
Less advantageous is the combined use of two step-grates and
one plane-grate (Fig. 113).
FUEL GASES
299
Plane-grates can be used only for large-size fuels as fuel of
small grain would fall through the grate-bars. Step-grates have
to be used for the latter fuel. In many cases the lichtenfers
construction of plane and step-grates is convenient, which com-
bines the good points of plane and step-grates (Fig. 114). The
Fio. 114. — Lichtcnfel'ä Plane Step Grate.
trouble of cleaning the grate is reduced to a minimum if the grate-
bars 1, 3 and 5 are arranged unmovable while 2 and 4 are kept in
motion at a right angle to the elevation of the producer, as
thereby most of the ash falls through automatically.
Figs. 115 and 116. — Turnable Eccen-
tric Cone-Grate.
Fig. 117. — A. Sailler's Pressure Pro-
ducer with Slag Openings.
The same effect is reached by revolving conical-grates, espe-
cially if the axis of rotation and axis of the cone are not the
same (Figs. 115, 116). Such an eccentric cone-grate can be
mounted upon a circular base-plate, which moves in a channel.
300
HEAT ENERGY AND FUELS
If the plate is provided with teeth around the edge it can be
driven by a simple worm gear.
On the other hand some rather complicated stirring-arrangp-
ments have been put on circular producers.
In pressure producers a grate is not an absolute necessity, as
we have seen on Tholander's producer. It is of advanta^ to
work without grate, if badly clinking and coking fuel is used, in
which case it is frequently advantageous to add a flux to the fuel
for forming an easily fusible slag, which is let off from time to
time. Saillers' producer (Fig. 117) shows such a construction.
Flo. 118. — Steam Jet-Blower for Dowson Gas Generator.
/ is the charging arrangement, ss are the poke-holes, WW the
blast channel, aa slag openings.
A convenient device for preventing the escape of gas during
poking was designed by Hofmann and Stäche. A steam coil
of pipe perforated on the side toward the center of the coil is
arranged around the poke-hole. If one of the holes is opened a
steam valve is opened automatically and steam blown through
the perforations, which prevents the escape of gas.
The disadvantages caused by putting green fuel into the pro-
ducer from time to time, namely non-uniform temperature of
the producer and uniform composition of the gas, was the rea-
son for experiments to separate the process of distillation from
the process of gasification. Such suggestions were made by
Minary, Brook and Wilson, Kleeman, C. Neese, Groebe-Lühr-
mann, Wilhelm Schmidhammer, Fr. Toldt, etc. All these pro-
ducers are rather complicated and better result can be obtained
more conveniently by combining a numlx»r of producers.
The manufacture of Dowson gas in draft-producers is effected
FUEL OASES 301
t>y arrangiüg a water-basin below the grate. By the radiating
Vieat of the grate-bars and the hot ash failing through, water is
evaporated and with the air carried through the producer.
In pressure producers air and steam are either led under the
grate separately (which allows independent regulation of air
and gas) or a steam jet-blower is used, which draws in the air
<Fig. 118).
The condensation of the products of distillation in the producer
gas by cooling and washing is, under ordinary conditions, unec-
onomical, as both by cooling and condensation considerable
quantities of heat are lost.
The apparatus for producing pure water-gas will be considered
later.
Suggestions for Lessons.
A producer gas plant is to be designed for a certain amount of
heat required per hour and a fuel of known composition and gas-
yield. Herein secondary circumstances can also be considered
(plan of the floor space at disposal, convenient transportation of
coal to the producers, reserve-producers, coal storage, etc.).
An existing draft-producer plant is to be changed into pressure-
producers or into a Dowson-gaa plant.
An existing producer plant is to be enlarged, so as to yield
double the amount of gas.
INDEX
Absorbing capacity of coals, 199.
Air, surplus, for combustion, 258.
Alloys —
melting points of, 54.
Princep's, 63.
Ammonia available in coals, 222.
Analysis of —
anthracites, 186.
ash, 151.
bituminous coal, 184, 185.
brown coal, 173.
brown coal ash, 177.
peat, 168, 171.
producer gas, 256.
products of destructive distilla-
tion, 216, 217.
Anthracites, analysis of, 186.
Arth's formula, 115.
Artificial fuels —
gaseous, 243.
solid, 143, 188.
Ash —
analyses, 151.
content of peat, 169.
of wood, 149, 150.
Berthier's method, 111.
Bessemer converter, temperature in,
72.
Bituminous coal —
analysis, 184, 185.
classification, 178.
destructive distillation, 215.
generating gas from, 265.
Blast furnace —
gas, 287.
temperature in, 72.
Boiling and melting points, 51.
Briquettes, 228.
composition of lignite, 229.
Brown coal —
analysis, 173.
ash, 177.
classification, 174.
Calculation of thermal values, 110.
Calibrating pyrometers, 83.
Calorimeter —
Fischer, 64, 93.
Mahler, 94.
Parr, 100, 104.
Weinhold, 61.
Carbon dioxide, dissociation of, 120.
Carbonaceous decomposition, 156.
Charcoal, 191.
absorbing capacity, 199.
classification, 199.
composition, 192.
temperature of ignition, 199.
weight, 198.
Charring, 193.
with steam, 208.
yield of, 194-196.
Classification —
charcoal, 199.
coal, 174, 178, 180.
fuel, 141.
peat, 166.
wood, 145.
Coal —
ammonia available, 222.
yield from destructive distillation
of, 221.
Coke oven —
Coppöe, 235.
Fran9oi8, 235.
Fran9oi8-Rexroth, 233.
Dr. Otto, 235.
gas, 223.
Smet, 233.
tar, 222.
303
304
INDEX
Coking apparatus, 231.
Combustion —
data, 130.
gases, regenerated, 287.
heat, 91, 105, 108.
incomplete, 117.
of producer gas, 139.
products of; 262.
surplus air for, 258.
temperature of coal, 136.
of producer gas, 138.
Composition —
of coals, 221.
of fuels, 142, 157, 160.
of Kiln gas^, 204.
of peat, 169.
of products of destructive distilla-
tion, 190.
of wood, 148.
Cones —
composition of, 57, 58.
melting points of, 56.
Seger, 55.
Content of wood, actual, 147.
Coppöe oven, 235.
Crony oven, 237.
Data on charring, 193.
Decomposition, carbonaceous, 150.
Depression of glass, 38.
Destructive distillation —
analysis, 216, 217.
effect of admixtures, 220.
of coal, composition of products of,
190.
of coal, yield from, 221.
of bituminous coal, 215.
of peat, 214, 224, 225, 226.
Determination of thermal value, 92.
Dissociation of carbon dioxide, 120.
Distillation, products of, 262.
Distribution of heat, 263.
Dowson gas, 287.
Economy of operation, 8.
Elementary composition of coal and
products of combustion, 202.
distillation, 262.
Elementary composition of producer
gas, 257.
Emissive power of substances, 73.
Energy —
changes of, 12.
chemical, change of, 26.
distance, 14.
electric, 27.
forms of, 13.
of reaction, 24.
radiant, 30.
radiation of, 78.
surface, 16.
volume, 25.
Errors in the measurement of temper-
atures, 38.
Evaporating power of wood, 153.
Explosives, 124.
External work, 132.
Fury's thermoelectric telescope, 79.
Fischer calorimeter, 64, 93.
Formula —
Arth, 115.
Gmelin, 112.
Goutal, 116.
Fran9ois oven, 235.
Fran9ois-Rexorth oven, 233.
Fuels —
artificial solid, 143.
classification of, 141.
composition of, 142, 157, 160.
formation heat of, 161.
liquid, 241.
composition of, 241, 242.
natural solid, 142.
thermal efficiency of, 242.
Fuel gases —
production of, 244.
value of wood, 153.
F'umace, ideal, 128.
Gas, producer, 240.
analysis, 256.
elementary components, 257.
influence of temperature in the
manufacture of, 247.
ideal composition of, 249, 250, 251.
IXDEX
305
Gases —
combustion temperature, 135.
mixed distillation and combustion,
261.
specific heat, 129.
Gasifying temperature, 259.
Generator —
gas from bituminous coal, 265.
lignite, 266.
peat, 265.
wood, 264.
gas plants, 292.
heat distribution in, 263.
Glass, standard thermometer, 39.
Glow colors —
temperatures corresponding to, 69.
of silver, 71.
Gmelin's method, 112.
Goutal's formula, 116.
Grates —
for producers, 297, 298.
Lichtenfels', 298.
Hartmann and Braun 's pyrometer, 81.
Heat —
capacities, 66.
combustion, 91.
distribution, 263.
of combustion products, 138.
Ideal furnace, 128.
Illuminating flames, 123.
Illuminating gas, 223.
Incomplete combustion, 117.
Increase of value of a substance, 7.
Kiln gases, composition of, 204.
Klinghammer's thalpotasimetcr, 32.
Law —
Joule's, 30.
Ohm's, 29.
Lichtenfels' grate, 298.
Light, intensities of, 74.
Lignite briquettes, composition of,
229.
Liquid fuels, 241.
composition of, 241, 242.
Lottmann oven, 237.
Mahler's calorimeter, 94.
Measurements —
pyrometrical, 80, 81.
with thermoelements, 82.
Melting point —
of alloys, 54.
of metals, 60.
Mixed distillation and combustion
gases, 261.
Moisture in wood, 150, 151.
Natural gas, composition, 243.
Natural solid fuels, 142.
Odelstjema producer, 297.
Optical methods of measuring tem-
peratures, 68.
Otto oven, 235.
Oven, pile retort, 212.
Parr, calorimeter, 100, 104.
Peat —
analysis, 168, 171.
ash content, 169.
classification, 166.
coke ovens, 237.
composition, 169.
destructive distillation, 214, 224,
225, 226.
generator gas, 265.
thermal value, 170.
Pile oven, 206.
Piles, 202.
Poking producers, 300.
Potential, chemical, 22.
Princep's alloys, 53.
Producers —
grates, 297, 298.
Odelstjema, 297.
poking, 300.
Siemens, 294.
Tholander, 297.
Producer gas, 246.
analysis, 256, 269.
elementary components, 257.
ideal composition of, 249, 250, 251.
influence of temperature in the
manufacture of, 247.
plants, 292.
306
INDEX
Production of fuel gases, 244.
Pyrometer —
calibrating, 83.
of Comu Le Chatelier, 73.
of Hart mann and Braun, 81.
of Mesurd and Nouel. 68.
of Wanner, 75.
of Weinhold, 61.
polariscopic, 71.
water (Siemens), 67.
Pyrometrical measurements, 80, 81.
Pyroscopes, composition, 57, 58.
Resin content of wood, 149.
Seasoning of wood, 152.
Seger cones, 55.
composition of, 57, 58.
melting points of, 56.
Siemens' producer, 294.
water pyrometer, 67.
Smelting furnace, 123.
Smet oven, 233.
Solid substances, combustion tem-
perature of, 135.
Specific gravity of woods, 145, 146.
Specific heat of gases, 129.
Superheated steam for charring, 208.
Tar from coke ovens, 222.
Temperatures —
corresponding to glow colors, 69.
determination, 75, 77, 86.
gasifying, 259.
measurement of high, 37.
of ignition of charcoal, 199.
optical methods of measuring, 68.
Thalpotasimeter, 52.
Thermal value —
Berthier's method for determining,
111.
calculation, 110.
direct determination, 92.
Gmelin's method, 112.
of peat, 170.
of wood, 152.
Thermodynamic laws, 19.
Thermoelectrife telescope, 7:).
Thermoelements, 85.
measurements with, 82.
Thermometers, 37.
correction factors, 40.
gaa or air, 43.
reading of, 39.
Thermophone, 87.
Tholander's producer, 297.
Vignoles* oven, 237.
Wanner pyrometer, 75.
Water gas, 268.
carbon content, 279.
combustible gases in, 275.
composition of, 269.
effect of steam pressure and tem-
perature, 272, 282.
equilibrium, 271.
quantity of steam required for
formation of, 278, 281.
theory of, 283.
thermal value of, 275.
Weight of wood, 148.
Weinhold 's pyrometer, 61.
Wiboigh's thermophone, 87.
Wood, 145.
actual content of, 147.
ash content of, 149, 150.
classification of, 145.
composition of, 148.
distillation of, 191.
evaporating power of, 153.
generator gas from, 264.
moisture in, 150, 151.
resin content of, 149.
seasoning, 152.
specific gravity of, 145, 146.
thermal value, 152, 153.
weight of, 148.
Work, external, 132.
Yield from destructive distillation of
coals, 221.
The Mechanical Appliances
OP THE
Chemical and Metallurgical
Industries
By OSKAR NAGEL, Ph.D.
A Detailed Description of all Machines, Appli-
ances and Apparatus Used in the Chemical
and Metallurgical Industries.
THE ONLY AMERICAN BOOK ON THIS SUBJECT
CONTENTS
I. General. II. Steam and Water Power. III. Gas
Power. IV. Electric Power. V. Transportation of
Solids. VI. Transportation of Liquids. VII. Trans-
portation of Gases. VIII. Grinding Machinery.
IX. Mixing Machines. X. Firing and Furnaces.
XL Separating Machines. XII. Purification of
Gases. XIII. Evaporating, DistilUng fiuid Condens-
ing. XIV. Drying.
300 Pages 8vo. 292 Illustrations
Price, $2.00
Sent Anywhere on Receipt of Price
OSKAR NAGEL
P. O. Box 885 NEW YORK
HT ,.
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