f?T ft
STATE OF ILLINOIS
DWIGHT H. GREEN, Governor
DEPARTMENT OF REGISTRATION AND EDUCATION
FRANK G. THOMPSON, Director
DIVISION OF THE
STATE GEOLOGICAL SURVEY
M. M. LEIGHTON, CkUf
URBANA
REPORT OF INVESTIGATIONS — NO. 78
CORRELATION OF DOMESTIC STOKER COMBUSTION
WITH LABORATORY TESTS AND TYPES OF FUELS
I. PRELIMINARY STUDIES
BY
L. C. McCABE, S. KONZO, AND O. W. REES
In Cooperation With the University of Illinois
Engineering Experiment Station
PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS
URBANA, ILLINOIS
1942
ORGANIZATION
STATE OF ILLINOIS
HON. DWIGHT H. GREEN, Governor
DEPARTMENT OF REGISTRATION AND EDUCATION
HON. FRANK G. THOMPSON, Director
BOARD OF NATURAL RESOURCES AND CONSERVATION
HON. FRANK G. THOMPSON, Chairman
EDSON S. BASTIN, Ph.D., D.Sc, Geology
ROGER ADAMS, Ph.D., D.Sc, Chemistry
LOUIS R. HOWSON, C.E., Engineering
WILLIAM TRELEASE, D.Sc, LL.D., Biology
EZRA JACOB KRAUS, Ph.D., D.Sc, Forestry
ARTHUR CUTTS WILLARD, D.Engr., LL.D.,
President of the University of Illinois
GEOLOGICAL SURVEY DIVISION
M. M. LEIGHTON, Chief
(22289)
14
SCIENTIFIC AND TECHNICAL STAFF OF THE
STATE GEOLOGICAL SURVEY DIVISION
100 Natural Resources Building, Urbana
M. M. LEIGHTON, Ph.D., Chief
Enid Town-ley, M.S., Assistant to the Chief
Jane Titcomb, M.A., Geological Assistant
GEOLOGICAL RESOURCES
GEOCHEMISTRY
Coal
G. H. Cady, Ph D., Senior Geologist and Head
L. C. McCabe. Ph.D., Geologist (on leave)
R. J. Helfinstine, M.S., Assoc. Mech. Eng.
James M. Schopf, Ph.D., Asst. Geologist
J. Norman Payne, Ph.D., Asst. Geologist
Charles C. Boley, M.S., Asst. Mining Eng.
Bryan Parks, M.S., Asst. Geologist
Industrial Minerals
J. E. Lamar, B.S., Geologist and Head
H. B. Willman, Ph.D., Assoc. Geologist
Douglas F. Stevens, M.E., Research Associate
Robert M. Grogan, Ph.D., Asst. Geologist
Robert R. Reynolds, B.S., Research Assistant
Oil and Gas
A. H. Bell, Ph.D., Geologist and Head
G. V. Cohee, Ph.D., Asst. Geologist
Frederick Squires, B.S., Assoc. Petr. Eng.
Charles W. Carter, Ph.D., Asst. Geologist
William H. Easton, Ph.D., Asst. Geologist
Paul G. Luckhardt, M.S., Research Assistant
Wayne F. Meents, Research Assistant
Areal and Engineering Geology
George E. Ekblavv, Ph.D., Geologist and Head
Richard F. Fisher, M.S., Asst. Geologist
Subsurface Geology
L. E. Workman, M.S., Geologist and Head
Tracy Gillette, Ph.D., Asst. Geologist
Arnold C. Mason, B.S., Asst. Geologist
Kenneth O. Emery, Ph.D., Asst. Geologist
Merlyn B. Buhle, M.S., Asst. Geologist
Frank E. Tippie, B.S., Asst. Geologist
Ruth E. Roth, B.S., Research Assistant
Stratigraphy and Paleontology
J. Marvin Weller, Ph.D., Geologist and Head
Chalmer L. Cooper, M.S., Assoc. Geologist
Petrography
Ralph E. Grim, Ph.D., Petrographer
Richards A. Rowland, Ph.D., Asst. Petrographer
Physics
R. J. Piersol, Ph.D., Physicist
B. J. Greenwood, B.S., Mech. Engineer
Donald O. Holland, M.S., Asst. Physicist (on leave)
Frank H. Reed, Ph.D., Chief Chemist
H. W. Jackman, M.S.E., Chem. Eng.
Roberta M. Langenstein, B.S., Chemical Assistant
Melville A. Rogers, B.S., Research Assistant
Coal
G. R. Yohe, Ph.D., Assoc. Chemist
Myron H. Wilt, B.S., Research Assistant
Industrial Minerals
J. S. Machin. Ph.D., Chemist and Head
Delbert L. Hanna, A.M., Research Assistant
Fluorspar
G. C. Finger, Ph.D., Assoc. Chemist
Everett W. Maynert, B.S., Research Assistant
X-ray and Spectrography
W. F. Bradley, Ph.D., Assoc. Chemist
Analytical
O. W. Rees, Ph.D., Chemist and Head
L. D. McVicker, B.S., Asst. Chemist
P. W. Henline. M.S.. Asst. Chemical Engineer
William F. Wagner, M.S., Asst. Chemist
K. F. Bursack, B.A., Research Assistant
Marion Lund Dickman, B.S., Research Assistant
MINERAL ECONOMICS
W. H. Voskuil, Ph.D.,
Grace N. Oliver, A.B.
Mineral Economist
Assistant in Mineral Economics
EDUCATIONAL EXTENSION
Don L. Carroll, B.S., Assoc. Geologist
PUBLICATIONS AND RECORDS
George E. Ekblaw, Ph.D., Geologic Editor
Chalmer L. Cooper, M.S., Geologic Editor
Dorothy E. Rose, B.S., Technical Editor
Kathryn K. Dedman, M.A., Asst. Technical Editor
Alma R. Sweeny. A.B., Technical Files Clerk
Portia Allyn Smith, Research Assistant
Meredith M. Calkins, Geologic Draftsman
Leslie D. Vaughan, Asst. Photographer
Dolores Thomas Sims, B.A., Geologic Clerk
Special Staff to Aid in the War Effort
Oil and Gas Resources
Earle F. Taylor, M.S., Asst. Geologist
Arnold Brokaw, M.S., Spec. Asst. Geologist
M. W. Pullen, Jr., M.S., Spec. Asst. Geologist
Paul K. Sims, M.S., Spec. Asst. Geologist
John A. Harrison, B.S., Spec. Research Assistant
Underground Water Geology
Carl A. Bays, Ph.D., Spec. Geologist
C. Leland Horberg, Ph.D., Spec. Asst. Geologist
Stewart Folk, M.S., Spec. Asst. Geologist
Ernest P. DuBois, B.S., Spec. Asst. Geologist
Robert R. Storm, A.B., Spec. Asst. Geologist
Paul Herbert, Jr., B.S., Spec. Asst. Geologist
Charles G. Johnson, A.B., Spec. Asst. Geologist
Consultants: Ceramics, Cullen W. Parmelee, M.S., D.Sc, and Ralph K. Hursh, B.S., University of Illinois;
Pleistocene Invertebrate Paleontology, Frank Collins Baker, B.S., University of Illinois;
Mechanical Engineering, Seichi Konzo, M.S., University of Illinois.
Topographic Mapping in Cooperation with the United States Geological Survey.
April 1, 1942
CONTENTS
Page
Introduction 7
Description of the coals studied . . . ." 7
Description of stoker and furnace 11
Laboratory tests 12
British Standards Swelling Index Number 12
Agglutinating value 13
Agde Damm test 13
Photographic procedure 14
Results of tests 14
Discussion of results 15
Summary 19
TABLES
1 Analyses of coals used in tests
2 Comparison of laboratory test values with stoker operation
ILLUSTRATIONS
Figure
1 Block of banded coal from southern Illinois showing fusain, vitrain, and
clarain 10
2 Block of banded coal from southern Illinois showing clarain and durain 10
3 Diagram of conversion stoker installation 12
4 View of the furnace 14
5 British swelling index buttons for hand-picked banded ingredients 15
6 British swelling index buttons for certain stoker fuels studied 16
7 Photographs of stoker fires with various fuels 17
8 Photographs of stoker fires with various fuels 18
9 Clinkers from vitrain- and clarain-rich fuels 19
Digitized by the Internet Archive
in 2012 with funding from
University of Illinois Urbana-Champaign
http://archive.org/details/correlationofdom78mcca
CORRELATION OF DOMESTIC STOKER COMBUSTION WITH
LABORATORY TESTS AND TYPES OF FUELS
I. PRELIMINARY STUDIES
By
L. C. McCabe,* S. Konzo,t and 0. W. Rees %
INTRODUCTION
I n 1937 the Illinois Geological Sur-
* vey made exploratory stoker tests of
coals from Franklin Comity, Illinois.1
which demonstrated that in these coals
concentration of vitrain causes excessive
swelling and coke-tree formation where-
as clarain is more free-burning and has
considerably less tendency to form coke
trees. The behavior of these two types
of coal or mixtures of them could be
demonstrated in stokers but no exact
tests short of combustion were available
for determining their suitability. The
need for such test methods to evaluate
coals for stoker use is generally recog-
nized.
It was with this need in mind that
the exploratory stoker tests were con-
tinued and were supported by a variety
of laboratory procedures in 1939 and
1940 by the Illinois Geological Survey
in cooperation with the Department of
Mechanical Engineering of the Univer-
sity of Illinois. These tests and the sup-
porting laboratory data are described
in this report.
The coals were collected and prepared
under Dr. McCabe 's supervision. Dr.
Rees directed the routine analyses and
the special laboratory tests. The com-
bustion tests were made in a domestic
underfeed stoker in the Warm Air Re-
search Residence at the University of
Illinois under Professor Konzo's super-
vision.
The writers gratefully acknowledge
the helpful suggestions of Dr. G. H.
Cady, Head of the Coal Division of the
Survey, and of Professor A. P. Kratz
of the Engineering Experiment Station
of the University of Illinois.
DESCRIPTION* OF THE
COALS STUDIED
The investigation was primarily con-
cerned with Illinois coals and the differ-
ences inherent in them. However in
order to inquire more adequately into
the problems met in burning bituminous
coals in stokers and better to test the
laboratory procedures, a few coals that
originated outside the State were in-
cluded. The origin and the proximate
and ultimate analyses of the coals used
in the tests are given in table 1.
The banded character of coals, in
southern Illinois particularly, has an
important bearing on their preparation
and utilization. The three most common
components, fusain. vitrain, and clarain,
are illustrated in figure 1. The fourth.
durain or splint ('fig. 2), occurs infre-
quently in Xo. 6 coal in Franklin County
and more abundantly in the splint coals
of the Appalachian fields.
Fusain, the most friable of the four
components, breaks down during the
mining and preparation until the greater
part of it will pass a 100-mesh screen.2, 3
Little of it is found, therefore, in well
prepared stoker coals.
Vitrain does not break as easily as
fusain but it is much more friable than
clarain. Clarain is closelv knit and
* Geologist, Illinois Geological Survey.
t Special Research Associate Professor of Mechanical
Engineering, University of Illinois.
% Chemist, Illinois Geological Survey.
1 McCabe, L. C, Illinois coals; Constitution important
with reference to their utilization: Mech. Engr.. p. 217,
March 1933 ; Illinois Geol. Survey Cir. 26, 1938.
2 Parks, B. C, and McCabe. L. C Fusain content of
fine sizes of Illinois coal : Trans. Illinois Acad. Sci.
vol. 33, no. 2, Dec. 1940 ; Illinois Geol. Survev Cir. 68,
1940.
3 Thiessen, Gilbert, Fusain content of coal dust from
an Illinois dedusting plant : Am. Inst. Mining and Met
Engr. Tech. Pub. 664, 1936.
[7]
Location
DOMESTIC STOKER COMBUSTION
TABLE 1. — Analyses of
Fixed
carbon
Illinois
Franklin Co
Franklin Co
Franklin Co
St. Clair Co.
St. Clair Co,
Gallatin Co.
West Virginia
Raleigh Co.
Raleigh Co.
Labor-
Vola-
Coal
atory
Condi-
Mois-
tile
bed
Sample
number
tion*
ture
matter
6
A
C-2204
1
2
5.7
42.8
45.4
6
E
C-2212
1
2
7.9
35.0
38.0
6
B
C-1988
1
2
6.5
34.4
36.8
6
C
C-2133
1
2
9.2
41.8
46.1
6
D
C-2134
1
2
10.2
36.9
41.1
5
G
C-2132
1
2
3.6
36.6
38.0
Eagle
F
C-2252
1
2
1.5
29.9
30.3
Poca-
H
C-2135
1
0.8
18.3
hontas 3
2
18.4
46.6
49.4
48.1
52.2
52.2
55.9
43.2
47.5
42.2
47.0
48.0
49.8
63.4
64.4
75.2
75.9
TABLE 2. — Comparison of Laboratory
Coking tendency
British Standard
Agglutinating
Softening Temp.
observed in the fuel bed
Swelling Index No.
Value (15:1)
Agde Damm
Sample1
Indication
Sample1 Value
Sample Value
Sample1 Value
A
None
A 3
A 2.5
G 324 °C
B
None
B 3
F 2.02
C 330
C
None
C 4
E 4.1
D 331
D
Slight
D \y2
H 6.3
E 348
E
Slight
E 4H
C 6.6
F 353
F
Positive
F 5
G 8.0
A 361
G
Very positive
g iy2
D 8.1
B 366
H
Very positive
H 9
H 412
( 1. As received ; 2. Moisture-free.
A — Franklin County, 111. Durain-rich No. 6
B — Franklin Countv, 111. Clarain-rich No. C
C— St. Clair Countv, 111. Top coal No. 6
D— St. Clair County, 111. Bottom coal No. 6
E — Franklin County, 111. Vitrain-rich No. 6
F — Raleigh County, West Virginia. Eagle seam
G — Gallatin County, 111. No. 5
H — Raleigh County, West Virginia. Pocahontas No.
1 Silicon carbide to coal ratio, 20 to 1
Coals Used in Tests
COALS STUDIED
Ash
Sulphur
Hydrogen
Carbon
Nitrogen
Oxygen
B. t. u.
Description
4.9
1.37
5.99
73.66
1.58
12.50
13,260
Durain-rich
5.2
1.46
5.69
78.13
1.68
7.84
14,064
9.0
1.75
5.43
67.29
1.49
15.00
11.941
Vitrain-rich
9.8
1.90
4.94
73.08
1.62
8.64
12,971
6.9
1.09
12,532
Clarain-rich
7.3
1.16
13.405
5.8
3.03
5.94
67.05
1.68
16.48
12.212
Top coal
6.4
3.34
5.43
73.84
1.85
9.14
13.449
10.7
3.71
5.53
61.77
1.19
17.06
11.131
Bottom coal
11.9
4.13
4.89
68.79
1.32
8.91
12.395
11.8
3.85
5.19
70.02
1.42
7.76
12,719
2x1 in. screen
12.2
3.99
4.97
72.60
1.48
4.76
13,189
5.2
0.59
5.14
81.57
1.54
5.96
14,468
Lump
5.3
0.60
5.06
82.81
1.57
4.68
14,688
5.7
0.77
4.59
84.24
1.59
3.13
14,576
Lump
5.7
0.78
4.54
84.92
1.60
2.43
14,693
Test Values With Stoker Operation
Decomposition
Setting Temp.
Initial Contraction
Plastic Interval
Temp. Agde Damm
Agde
Damm
Interval. Agde Damm
Agde Damm
Sample1 Value
Sample1
Value
Sample1 Value
Sample1 Value
G 384°C
D
414°C
H 38°C
H 58°C
C 392
C
416
B 49
B 67
D 401
B
433
A 58
A 73
F 415
F
434
C 62
F 81
B 415
E
436
F 62
D 83
E 417
A
438
G 64
C 86
A 419
G
>444
E 69
E 88
H 450
H
470
D 70
G >120
10
DOMESTIC STOKER COMBUSTIOX
Fig. 1. — Block of banded coal from southern
Illinois showing fusain (F), vitrain (V),
and clarain (C).
withstands breaking when mechanically
handled. Durain is the toughest and
most resistant component. The follow-
ing excerpt from a recent U. S. Bureau
of Mines publication4 describes the
energy consumed in pulverizing the
four coal constituents :
" Contrary to general belief the ash-
bearing constituents are not always most
resistant to crushing, as was shown in
tests of coal constituents, that is vitrain,
clarain, durain, and fusain — from the
Southern Illinois field. The net power
consumed in crushing the constituents
from minus 20-mesh to minus 150-mesh,
with their ash content is given in the
following table :
Coal
Constituent
Fusain
Vitrain
Clarain
Durain
Net horse
power —
hours per
ton of
minus
150-mesh
product. .
1.8
3.8
5.1
13.6
Ash, per-
cent
15.6
22
8.3
5.2
Fig. 2. — Block of banded coal from southern
Illinois showing clarain (C), and
durain (D).
It is shown that the durain, the hardest
constituent, contains less ash than the
clarain, although comparison of the
values for fusain with any of the others
is even more startling. It has been
recognized that fusain is the most easily
crushed constituent, in spite of its rela-
tively large percentage of ash."
Study of production has shown that
the breakage characteristics of the con-
stituents in commercial coal are reflected
by the energy necessary to pulverize
them. Both vitrain and clarain can be
found in lump sizes, and the parting
surfaces may have a thin layer of fusain
on them. Most of the fusain will have
been broken off, however, and can be
found in the screenings ; or if the coals
are dedusted, it will be in the deduster
dust. In wet-washing most of the fusain
is carried to the settling pond. For this
reason, it is not considered in the stoker
tests.
The 3- by 2-inch egg contains some of
the smaller vitrain bands, but for the
most part is clarain. The No. 2 nut (2- by
l^-inch) is still richer in clarain. The
4 Fieldner, A. C, and Rice, W. E., Annual report of
research and technologic work on coal, fiscal year 1940:
U. S. Bur. Mines I. C. 7143, pd. 23-24. 1940.
STOKER AND FURNACE
11
No. 3 nut (1U- by %-inch) of well-
banded coals has eight to ten percent
more vitrain than the coal bed from
which it is mined. This concentration
prevails down to the 100- or 200-mesh
size, but fusain is the predominant com-
ponent in smaller sizes.
In general, 800 to 1000 pounds of coal
were prepared for the stoker tests, and
about 50 pounds were riffled from this
sample for the proximate and ultimate
analyses and special tests. The high-
vitrain sample (70 percent vitrain, 30
percent clarain) from Franklin County,
Illinois, was taken directly from the
7/16-inch by 10-mesh stoker coal-load-
ing chute at the mine. The high-clarain
sample (84 percent clarain, 16 percent
vitrain) from the same mine was pre-
pared by crushing 3- by 2-inch egg-coal
to stoker size. The durain sample was
prepared by crushing to stoker size 6- by
3-inch egg-coal from which the other
constituents had been removed.
In the Belleville district near Darm-
stadt in St. Clair County the upper two
feet of Xo. 6 coal is a bright micro-banded
clarain with silky luster, low ash and
high volatile content, and a relatively
high B.t.u. value. The lower four feet
of the bed consists of alternating bands
of clarain, vitrain. and fusain. The ash
of the bottom coal is higher and the
volatile matter and B.t.u. values are con-
siderably lower than in the top coal
(table 1). When coals of this type are
poorly prepared, lack of uniformity due
to segregation and other factors may
cause difficulties in stoker operation.
Because the rocks of Gallatin County
have been folded and faulted, the Xo. 5
coal bed of that region is of higher rank
than the same bed in Saline County. Al-
though clarain predominates in this bed,
the coal has been so increased in rank
that it is all strongly swelling.
The Eagle Seam and Pocahontas coals
of Raleigh County, West Virginia, are
high-rank coals not represented in Illi-
nois but were tested in order to have a
wider range of coals in the stoker and
laboratory tests. Run-of-mine was
crushed in both instances to make the
stoker coals used in the tests.
DESCRIPTION OF ST< >KER
AND FURNACE
A complete description of the Warm
Air Research Residence and the forced
warm-air heating system, together with
the automatic control system used to
operate the stoker and the circulating
fan, has been reported in two papers.5, 6
The heating plant consisted of a warm-
air furnace used in connection with the
forced-air heating system. The furnace
was of the cast-iron circulator-radiator
type having a 27-inch firepot and 23-inch
grate. As shown in figure 3. the stoker
was of the underfeed type, and the coal
was delivered from the hopper to the re-
tort by means of a rotating screw. The re-
tort was located in the center of the
hearth. Both the rate of fuel input and
the rate at which air was supplied to
the tuyeres could be independently regu-
lated. Xo cut-off damper was provided
in the air tube to prevent air being
drawn through the blower and into the
fuel bed during the off periods of the
stoker. The overfire damper in the fir-
ing door was left open prior to the
photographing of the fuel bed. The
pyrex plate glass door which was placed
in position just prior to the photo-
graphic study was fitted loosely on the
furnace front to give a total overfire air
opening approximately equivalent to
that provided by the regular firing door
and the overfire damper opening. A
balanced check damper was installed in
the clean-out of the chimney and was
regulated to maintain a constant draft
of approximately 0.05 inches of water
in the smoke pipe.
After a new batch of coal had been
added to the hopper the plant was al-
lowed to operate intermittently under
thermostatic control for two or three
days, at the end of which time the fuel
bed had assumed the characteristics of
the coal under test. During this pre-
liminary period of adjustment approxi-
mately 300 to 600 pounds of coal were
5 Kratz, A. P., Konzo, S., and Engdahl, R. B., Per-
formance of stoker-fired and hand-fired warm-air fur-
naces in the research residence: A.S.H.V.E. Journal
section. Heating, Piping, and Air Conditioning, pp.
732-742, Nov. 1933.
12
DOMESTIC STOKER COMBUSTION
PLAN VIEW
22'
18" 6f
BALANCED DRAFT
DAMPER IN CLEANOUT
ELEVATION
VIEW
77
POT
BRICK
OVERFIRE
DAMPER 300- LB. j HP.
-""' HOPPER MOTOR
29^
Fig. 3. — Diagram of conversion stoker installation in furnace in research residence.
burned. The feed rate maintained dur-
ing the tests was about 26 pounds per
hour. The setting for air-rate to the
stoker was maintained the same in all
eases. The resulting burning rate6
varied somewhat depending upon the
coal used, but averaged about 13 pounds
per hour. It is possible that the rate at
which air is supplied to the fuel bed
may affect the coking characteristics of
the fuel. Hence the results obtained in
this preliminary survey may not be en-
tirely representative of the coking action
of the coal over a wide range of air rates
and feed rates. It would be advisable
in any later studies to investigate this
phase of the problem.
LABORATORY TESTS
Proximate and ultimate analyses were
made on all samples tested according to
standard procedures of the American
Society for Testing Materials.7
British Standards Swelling
Index Number
Swelling index numbers were deter-
mined according to the British Standard
method8 with the following modifica-
tions :
1. Instead of the B.S. 72-mesh test
sieve specified by the British Standard
method for preparation of the test
sample a No. 60 U. S. Standard sieve
was used.
8 Kratz, A. P., and Konzo, S., Performance of a stoker-
fired warm-air furnace as affected by burning rate and
feed rate: A.S.H.V.E. Journal section, Heating, Piping,
and Air Conditioning, pp. 55-60, January 1940.
7 Standard methods of laboratory sampling and analy-
sis of coal and coke: A.S.T.M. designation, D271-37.
8 British standard method for the crucible swelling
test for coal: British Standards Institution pub. no.
804, 1938.
LABORATORY TESTS
13
2. In place of the "Teclu" burner a
Fisher high temperature usual style
burner with grid top was used. By plac-
ing- a thermocouple inside the crucible
and experimentally adjusting the gas
flow to the burner, it was possible to es-
tablish conditions of proper temperature
and proper rate of heat rise. Natural
gas of approximately 1000 B.t.u. calo-
rific value was used.
3. Transite pipe class F was used for
the draught shield. This pipe was 4%
inches outside diameter and 4 inches in-
side diameter. It was cut according to
the specifications given in the standard
method.
4. The crucibles which were used
were glazed vitreosil of the following
specifications :
External height 26 to 26.6 mm
External diameter at top. .40 to 41.5 mm
Internal diameter at base. .13 to 14 mm
Capacity 17 to 17.5 ml
Weight 11 to 12 gms.
5. Silica triangles which are supplied
as standard items by most chemical ap-
paratus supply houses were used. Those
used in this work were about 63.5 mm in
length of side with a diameter of in-
scribed circle of about 31.75 mm.
Briefly the test consists of heating
one-gram portions of coal in the stand-
ard crucibles at a specified rate of tem-
perature rise until all the volatile mat-
ter has been expelled. The buttons are
then removed from the crucibles and
compared to standard outlines to which
have been assigned numbers from 1 to 9.
The average of four such tests is the
value reported.
Agglutinating Value
Agglutinating value determinations
were made according to the "Proposed
Method of Test for Agglutinating Value
of Coal" as published by the American
Society for Testing Materials.0 A ratio of
15 silicon carbide to 1 coal was used for
all samples with the exception of sample
F where a ratio of 20 to 1 was used.
The apparatus used for crushing test
buttons was designed and built in this
laboratory.
This method is a laboratory test for
obtaining information on the coking and
caking properties of coal. It is an ap-
proximate measure of the material in
coal which becomes plastic under the
influence of heat. Briefly the procedure
consists of mixing coal with an inert ma-
terial such as silicon carbide, coking the
mixture as in a volatile matter deter-
mination and determining the compres-
sion strength of the buttons so formed.
Agde Damm Test
The apparatus used in this test was
similar to that described in U. S. Bureau
of Mines Bulletin 344.10 This apparatus
was further described by Thiessen.11 It
consists essentially of a cylindrical cop-
per block three inches in diameter and
seven inches long which is fitted into a
specially built electric furnace. Two
V2-inch holes are provided in this copper
block for the small sample tubes. The
apparatus is so arranged that a one-
pound rod rests on one sample while a
micrometer distance gauge is mounted
on the top of the rod in such a way as to
register contraction or expansion of the
sample. The other sample is allowed to
expand and contract freely. Thermo-
couples are provided for temperature
readings. In the tests the samples of
coal which have been compressed in the
sample tubes under a weight of 5.8 kilo-
grams are heated at a specified rate, and
distance gauge and temperature read-
ings are recorded. When plotted, these
data show the initial softening tempera-
ture, the decomposition temperature, the
solidification temperature, and the plas-
tic interval.
9 Proposed method of test for agglutinating value of
coal (proposed draft) : A.S.T.M. Standards on Coal and
Coke, p. 96, 1938.
10 Fleldner, A. C, Davis, J. D., Thiessen, R., Kester,
E. B., and Selvig, W. A., Methods and apparatus used
in determining the gas-, coke-, and by-product-making
properties of American coals : U. S. Bur. Mines Bull.
344, p. 16, 1931.
11 Thiessen, G., Coke from Illinois coals: Illinois
Geol Survey Bull. 64, Appendix B, page 22"), 1937.
14
DOMESTIC STOKER COMBUSTION
Fig. 4. — View of the furnace showing pyrex door, lamps, and camera in position for
photographing fuel bed.
PHOTOGRAPHIC PROCEDURE
A pyrex glass door replaced the firing-
door while the fuel beds were being
photographed (fig. 4) so that the normal
operation of the stoker was not affected.
The combustion chamber was illuminat-
ed by two No. 2 Photoflood lamps in re-
flectors; this lighting was necessary to
properly distinguish between coke and
clinker masses.
A Weston meter was used to deter-
mine the proper exposure of the film.
Exposures were made at 16 frames per
second with a 15 mm, F 2.7 lens. Four
hundred feet of 16 mm, Type A, Koda-
chrome film was used in making the
moving pictures of the fuel beds of the
eight coals. This was supplemented by
300 feet of film showing the coals, special
laboratory equipment, and titles. Photo-
graphs of the fuel beds were taken at
intervals as follows :
Fuel bed prior to stoker operation
Start of stoker operation
Fuel bed after five minutes of stoker
operation
Beginning of off-period
Photograph of clinkers.
RESULTS OF TESTS
Analyses of the coals used in this
study are given in table 1. Results of
the special tests are given in table 2, and
British Standards Swelling Index but-
tons are shown in figures 5 and 6. Photo-
graphs of stoker fires for the fuels
studied are shown in figures 7 and 8, and
clinkers from vitrain- and clarain-rich
fuels are shown in figure 9.
RESULTS
15
Fig. 5. — British swelling index buttons for hand-picked banded ingredients.
a. durain; b. clarain; c. vitrain.
DISCUSSION OF RESULTS
The correlations attempted in this
study were (1) correlation of laboratory
tests with combustion behavior in the
underfeed stoker, and (2) correlation of
types of coal with combustion behavior.
There appeared to be no correlation be-
tween agglutinating and AgcleDamm val-
ues and the formation of coke in the fire
bed, which was the principal combustion
behavior characteristic observed. How-
ever the authors believe that results of
these tests may be correlated with com-
bustion characteristics other than coke
formation. A study of such correlations
and of correlations with other chemical
tests is now in progress. Correlations of
British Standards Swelling Index values
and types of coal with combustion be-
havior were possible and the discussion
deals mainly with these correlations.
Figure 5 illustrates the swelling but-
tons obtained from hand-picked samples
of durain, clarain, and vitrain from a
mine in Franklin County, Illinois. The
durain sample (figure 5a) showed no
tendency to swell and is therefore as-
signed a swelling index of one. Clarain
(figure 5b) and vitrain (figure 5c) had
swelling indices of 3 and 5 respectively.
Large samples having the purity of
small hand-picked samples could not be
readily prepared. While the 800- to
1000-pound samples were not composed
entirely of a single ingredient the con-
centration obtained by the preparation
methods described earlier in this report
is sufficient to illustrate the characteris-
tics of the predominant ingredient in the
sample.
The egg-coal crushed to make the
durain-rich stoker fuel contained some
vitrain and clarain. The standard coke
button for this fuel is given the number
3 in table 2. The predominant durain
influence on the swelling is brought out
by comparing these buttons (figure 6a)
with the hand-picked durain and clarain
buttons (figures 5a and 5b). British
Standards Swelling Index buttons for
coals A, F, G and H are shown in figures
6a, b, c, d. Figures 7a and 7b are en-
largements from moving picture film of
16
DOMESTIC STOKER COMBUSTION
a
Fig. 6. — British swelling index buttons for certain stoker fuels studied.
a. Durain-rich stoker fuel; b. Eagle Seam, West Virginia, stoker fuel
c. Gallatin County No. 5 stoker fuel; d. Pocahontas stoker fuel.
two stages in burning of the durain-
rich coal. The stoker is just coming on
in figure 7a and the fuel bed is readily
seen. Figure 7b, after five minutes of
stoker operation, illustrates the freedom
from coking and the uniformity of the
fuel bed. There is somewhat more
smoke at the beginning of the off-period
with durain than with the clarain or
vi train.
The clarain-rich fuel ("B", table 2)
had a swelling index of 3 as did the
hand-picked sample (figure 5b). Figure
7c illustrates the beginning of stoker
operation and 7d shows the open nature
of the fuel bed after five minutes in the
on-period.
The vitrain-rich sample ("E", table
2) has a swelling index of 4% as com-
pared with an index of 5 for the care-
full}^ hand-picked sample, which indi-
cates the presence of a small amount of
durain or clarain. However, figure 7e
illustrates the tendency of the vitrain to
form coke in the off-period. Figure 7f
illustrates the behavior of this friable
coke tree after five minutes of stoker
operation. Only in mild weather when
the stoker operates infrequently might
any difficulty be encountered with a
vitrain-rich coal of this type.
The top coal of the Belleville District
of St. Clair County has a swelling
index of 4; the bottom coal has a swell-
ing index of 4% (table 2, samples C and
D). There is practically no coke forma-
tion apparent when the top coal is burn-
ed, and only a slight tendency to form
coke in the bottom coal (figures 8a and
8b). The difference in swelling tendency
is attributed to the presence of a greater
amount of vitrain in the bottom coal. At
RESULTS
17
Fig. 7. — Photographs of stoker fires with fuels as follows:
a. Stoker fire, durain-rich fuel, stoker just turned on
b. Stoker fire, durain-rich fuel, after 5 minutes of operation
c. Stoker fire, clarain-rich fuel, stoker just turned on
d. Stoker fire, clarain-rich fuel, after 5 minutes of operation
e. Stoker fire, vitrain-rich fuel, stoker just turned on
f. Stoker fire, vitrain-rich fuel, after 5 minutes of operation
18
DOMESTIC STOKER COMBUSTION
Fig. 8. — Photographs of stoker fires with fuels as follows:
a. Stoker fire, top bench St. Clair County No. 6 coal, after 5 minutes of operation
b. Stoker fire, lower bench St. Clair County No. 6 coal, after 5 minutes of
operation
c. Stoker fire, Eagle Seam, West Virginia coal, after 5 minutes of operation
d. Stoker fire, Gallatin County No. 5 coal, after 5 minutes of operation
e. Stoker fire, Pocahontas coal, stoker just turned on
f. Stoker fire, Pocahontas coal, after 5 minutes of operation
SI' M MARY
19
Fig. 9. — Clinkers from vitrain- and clarain-rich fuels.
the beginning of the off-period the top
coal has a considerably greater tendency
to smoke than the bottom coal. This is
explained, in part at least, by the higher
volatile content of the top coal (46.1
and 41.1 per cent respectively on the
dry basis).
The Eagle Seam coal (Raleigh Coun-
ty, West Virginia) is assigned a swell-
ing number of 5. A peculiarity of this
coal is that after heat is removed from
the crucible the apexes of the buttons
collapse. This may have some bearing
on the behavior of this coal during com-
bustion. In assigning a swelling num-
ber this apex is restored, however. Fig-
ure 8c shows the condition of the fuel
bed after the stoker had operated for
five minutes. Part of the coke ring
formed on the hearth appears in the
foreground of the figure and a coke tree
appears in the center. The coke formed
in the stoker was dense but in spite of
this the response to combustion was not
unsatisfactory.
The Gallatin County (Xo. 5) coal,
with a swelling index of T1/^, had a tend-
ency to form flat masses of coke in the
furnace rather than coke trees (fig. 8d).
Such coke masses ignited less readily
than the original coal when the stoker
came on after being off for some time.
The Pocahontas fuel bed is shown in
figure 8e and f. Figure e shows the
appearance with the stoker just coming
on and f shows the appearance after
operation for five minutes. Reference
to this figure and table 2 shows that
there is considerable coke formation
with this fuel (swelling index number
9) under the conditions used for this
study.
Figure 9 shows a vitrain clinker as
compared to a clarain clinker. The vit-
rain clinker appears to be denser and
harder than the clarain clinker.
SUMMARY
This paper is a preliminary attempt
to correlate behavior of various types of
coal in an underfeed stoker with labora-
tory tests for the few samples studied
under one specific set of conditions.
The tests substantiate earlier findings
in regard to the importance of physical
composition of coal, that is, types of
fuel, as related to combustion behavior.
No correlations between agglutinating
value and Agde Damm plasticity tests
and coke formation were apparent.
20
DOMESTIC STOKER COMBUSTION
Correlation between British Stand-
ards Swelling Index values and coke
formation in the stoker fire was appar-
ent. This is in accord with the findings
of Sherman.12 On the basis of these
studies it appears that coals with B. S. I.
numbers below 4% or 5 do not form ap-
preciable masses of coke in the fuel bed
whereas coals with B. S. I. numbers of
5 or above may form large amounts of
coke.
Although coals of high-vitrain content
tend to form more coke than those of
high-clarain and high-durain content,
this difference is not as striking in the
present tests as might be predicted from
the swelling index numbers of the hand-
picked constituents of the Franklin
County coal.
Laboratory tests described in this re-
port measure more or less specific char-
acteristics of coal. On the other hand,
behavior of coal in an underfeed stoker
is influenced simultaneously by many
physical and chemical properties. The
influence of certain properties may
mask that of others. Studies are now in
progress to clarify some of these rela-
tionships.
12 Sherman, Ralph A., The evaluation of coal for use
in domestic stokers : Univ. Illinois Eng. Experiment
Sta. Cir. ser. 39, pp. 39-57, 1939.
Illinois State Geological Subvet
Report of Investigations No. 78
1942
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