Relation between rate of combustion and draft pressure for a chain-grain stoker applied to a 350 H.P. Sterling boiler

RATE OF COMBUSTION

AND DRAFT PRESSURE FOR A STOKER

APPLIED TO 350 H. P. STERLING BOILER

BY

J. R, LEVALty
W. L. JUTTEMEYER

p, E. WlLtSON

ARMOUR INSTITUTE OF TECHNOLOGY
19 15

621. 183

I 51

lilinois Institute

of Technology

UNWERSyTY LIBRARIES

AT 379

Levally, J. R.
Relation between rate of
combustion and draft

For Use In Ubranf (Wy

ILLINOIS INSTITUTE OF TECHNOLOGY
PAUL V. GALVIN LIBRARY
35 WEST 33RO STREET
CHICAGO, IL 6061^

RELATION BETWEEN RATE OF COM-
BUSTION AND DRAFT PRESSURE FOR
A CHAIN-GRATE STOKER APPLIED
TO A 350 H. P. STERLING
BOILER

A THESIS

PRESENTED BY

JOHN R. LEVALLY

WALTER L. JUTTEMEYER

HUBERT E. WILLSON

PRESIDENT AND FACULTY

OF

ARMOUR INSTITUTE OF TECHNOLOGY

FOR THE DEGREE OF
BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING

HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN

MECHANICAL ENGINEERING

MAY 27, 1915

•^YA^^^^y^^^^^

^5T

TABLE Oi' COUTKNTS.

Page,

Bi"bliography 20.

DimensioriS and Proportions .........*• 7«

Discription o£ Boiler and Setting .... 2«

DiacusBion l8*

Introduction !•

Installation and Precautions 9*

Prcpceed Method o£ Procedure 14-.

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.61 iioiaawoell

.1 .» ,.!,,,,,.. noi J3.;/5o-i^nI

,§ .......... enot^iJBOfit'i bna notfsLL&fenJ

-1-

IFTROBUCTIOK
There has been Taut little or not attempt
made to discover Just what the relation "between
the rate o£ combustion and draft pressure in a
furnace really is, and no authentic data has
as yet been compiled.

It was with the above idea in mind that
this thesis was started No attaacpt A^as to
have been made tc acciunulate data whereirom
an accurate heat balance might have been con-
structed, but simply to find what infulenoe
the draft and thickness of fire really had
upon the rate of combustion.

However, after all apparatui? ha* been
installed, the coal was of such a mixed
variety of sizes and kinds, and there being
no call for steam, the attempt was abandoned.

The enclosed report is then only an
expression of what was really done in instal-
lation of apparatus and a proposed method of
procedure for some one to follow for the
actual detsimination*

5foiTau(TOflm

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.6«Iiqaoo need +e^ si-?

iaoiia-xtui'F ii^.Bf.' ©Isltjuivfooe ->j fet^iii rtescf ST^ri
-noo rraecT svf.ri Sd^lm sotisiscf iBsrf ot^xuDOff is£

. no X i ""^ 1^70' .1300 1 0 © ?s 1 ? r{ t noq tj

ns vli^o nsrft si .tio'^e-i issoloris sriT

-Xb^8-?x -li fffiob vXX,';ea ^pvj :tBf{"w lo i^oxsasaqys

lo bofitsni fceeo.io'iq ^ briB B-jf^t&qc^ xo .Toi^sX

erfj ro'i voXIoi oT SiTO nuoe -lox "nubsooiq

• n J X iis ax iia s J'eJb li' u Jof*

-2-

DESCRIPTION 01 BOILER AWD SETTIFO

The teste were to have "been made upon one
c£ a "battery o£ five located at the Axaioux
Institute of Technology, at Chicago, Illinois.
The boiler is of a Sterling type and consists
mainly of three upper, or steam drums, and a
large lo'ver mud drum. These sets of drums
are connected "by 3-1/4" inch, lap welded,
mild steel tu"be8. The tu"bes are bent at the
ends in such a way that they enter the drums
radially. The drvims are constructed of the
best quality of flange steel, and are 3 feet
6 inches in diameter by 12 feet in length.
Two hundred-fifty water'^ tubes, and twenty nine
tubes afford a heating surface of approximately
3500 square feet. "Raffle^ suitably placed, on
the tubes direct the flow of the heated gases
80 that they pass up the first pass, down the
second, and across the third pass.

Water for the boiler is fed into the upper
rear dnaui which is the coolest part of the
boiler and flows to the bottom mud drum. The
steam is taken from the middle upper drum.

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erfT .Ti-cib bfMn ^Ioic^ocf ©■■f;r oJ p*oXi £)>>£ ittX.'orf

..n;jib i-rqqu sXb&lai eitf >-ao:c'i. nejUs^t pi ixaala

-5-

Two safety valves are also placed on the
dmm and are set to release at 150 pounds
gauge pressure. The valves are piped to
the atmosphere. The Id low o££ valve is
located at the hottom of the mud drumo A
manhole placed in the ends o£ the three
drums for the purpose of permitting inspection
and cleaning.

The whole comlDination is enclosed hy a
'brick setting. I^or the dimensions of setting
see "dimensions and proportions," The upper
drums rest upon wrought iron "beams. These
■beams are in turn supported "by wrought iron
colu/nns whose hases are set in cast iron
foundations. The weight of the lower dxvm is
carried hy the tubes connecting it to the steam
drums. This arrangement allows the entire
mass to move with the contraction and ex-
pansion of the metal due to the heat*

Two fire doors are cut through the
hrick work to permit inspection of the fire
in the furnace aid over the "bxidgs wall.

-^-

erii no tsofilq onl^ BZB eeyX^T 'c*€iE8 cv;T
efcrryoq OcX *£ eefieloa o;t Jfejs ©at' bns- injj'i^
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sri[;+ My^uoirii ti-^o tie frzoob sxil ovT

,IXb^ • tMud srl:} isvo err eofniui 9r:& nl

-4

A fire taick arch projects to vvithin one
foot of the front row of tubes. This arch "be-
comes incadescent from the heat that it has
absorbed, and ignites the green fuel, as the
fuel comes into this region.

The grate employed, is the one manu-
factured by the Green Chain Grate Company.
For dimensions of grate, see "dimensions and
proportions".

Coal is shoveled into the hopper irhich
extends across the full v^idth of the grate.
The depth of the fire on the grate is regulated
by means of an adjustable sheet iron gate.
Raising or lower this allows more or less
coal to pass into this ignition zone, and
also serves to keep a constant depth of coal
on the grate.

Draft is produced by means of a one
hundred- seventy five foot brick chimney.
The diimney is connected to the furnace
by a sheet metal breeching. / damper l
placed in this breeching serves to regulate
the drsift in the iUrnace. It may be opened

i--

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iBoo lo rf;fq©i; ^n^'iJenoo £ qe&ji ot asTiee ceXjf.

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jberfsqo ©rf vsxn -iM .feoanxi/i. en J' ni i'l^nb sc'.*

-5-

or closed I'xom the boiler room floor "by releas-
ing the wires that hold the damper in position.

The feed water £rom the returns o£ the
heating system is piped to a surge tank, From
this tank the water is pumped through a yen-
turi meter, constructed "by The Builders Iron -Se
Foundry Co., to the rear drum ol the boiler.
The height o£ the water in the "boiler is deter-
mined "by the use o£ the ordinary water column.

The chain grate stoker is operated by a
three horse power vertical steam engine belted
to ^ Jack shaft. This shaft is connected to a
rocker arm by means of an eccentric rod and a
slip connection. The rocks r arm is furnished with
a ratchet working on a ratchet wheel. The
ratchet ^eel is connected to the axis of
rotation of the grate through the ordinary
reduction gearing. The speed of the grate is
regulated by throttling the engine, or by
changing the effective length of the rocker aim.

Coal is \mloaded from the cars into bins,
and thenee gravitates to the boiler room floor.

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-lecefc !?i aeXiocf ?rfvt ni aei^ew erlJ xo Jn'sleji sxi?

£ Yd Jfce:^faeqo si lejioiB eiei-g nieiio »/•'-
fcet/.s'^ anlsfis n»Pe;te Ii3oi:^a©v :[ev oq eeiorf f.-eir:.:f
i5 Ov -^eiosnnoc pz *'ieris ein'T •;tleff8 iio^t ^ O'^

rf+lv berifi-nvl el itiax. i.s3{ooic sriT .noii-cennoo c.rXe
prfT .Xserfv .t'l-rfo^iJi /■ no gnijtio*' cf&rfoctfia «

• iia£ T*;3iooi eric^ io iiSt\ael efiJoexi© sirfi «rii^jj;.jio

-6-

It is shoveled into the hopper o£ the
stoker Toy hand.

The ashes drop into a pit under the
grate and are removed "by hand.

sriS 7£baw *i:cf £• c-*rii qcib eerfer. sxlT

DIMMSIOilS AST) PROPORTIOHS .

BOILER.

-7-

Type o£ boiler ,
Dlamstar o£ shell,
Length or shell >
Thlclcnass o£ shell ,
Thioicnsss o£ head ,
Bumhar o£ tubes ,

Water tube .
42.00 inches .
12.00 £eet«
9/16 Sc 7/16 inches
5/8 & 5/4 inches.
279

Diameter o£ tubes ,( inside) 5.25 inches .

Diaaetar o£ tubes, (outside) 5 •79 inches.

Length o£ tubes ,(over beading) 18 feet ^ inches .

Steam taken dirsctly from central drum .

Kind of grata , Green C!hain Grate Stoker .

Size of grate ^ Width 9 ft, Length 9 ft. 2 in.

Araa of grate surface , 82-1/2 Sq. ft.

Heating surface of boiler, 5500 sq. feet ,

Ratio heating surface to

grate surface 1 to 42.5

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.:;! S .>ri ^ rfrf-nnsJ , .tl ? rf.^friW ,^ e^i<i5 xo SoiP

,:M .p'3 G\i-S£ , eofil-iys e:tf=as Io sf'-rK

. ;feex .ps . 0C< ^as-Moc*' Io ea^'lxjje ^ni^eeH

BRICK BOILER SSTTIKG .

Height , 18.5 feet,

Width , 1^ feet

Length, 22 .75 feet

-8-

Sizt,

BOILISR PUMP .

7-1/2x4-1/2x10.

VEI^TURI METER ,
Make , Builders Iron Pdy. Co.

Size , Indicating & recording.

Diameter , (Inlet) ^' inches.

Diameter , (Throat ) 1 inch .

-c-

. ♦eel 'vi , rUbiW

. rbni: I ( tBoxn'T), aeieiaeiCr

-9-

INSTALLATIOB OF APPAB/TUS AKD PRECAUTIOFS .

A rigid inspection o£ the boiler setting
was made, and all of the air leaks stopped up
as tax as possilDle, The cracks in the "brick
settings, and small openings along the sides
o£ the grate entrance and around all connect-
ions to the interior of the furnace, cemented
over with fire clay» The doors to the bridge
wall and grate were removed, and the opening
covered with a sheet of 1/2 inch asbestos.
Before putting the asbestos sheet in place,
the surface axposed to the heat was covered
with a thick layer of fire-proofing. This
combination was then held in place over the
door opening by s^iiall machine screws set
into the metal frame work of the door* The
adgas around the asbestos sheet were then
sealed with fire-proofing. The above pre-
cautions were taken to prevent air leakage
as far as possible.

The asbestos covering for the door over
the fire was fitted with two openings. One

qu b^qqcie exesi axB «ri;? io J.J.J? bas" ^itSAH ee*-
xclir' sr * al 8/iOfio en'T .eXtfieroq 8b xs'i e5»

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«Si>iacf 9ni oi sioofc &r:T .-^io sil'i ritxv. aevo

fcsaevoo Cf,\R ^i^srf «■!? ocf bieoqxs eos'X'i.sjs f-rit
ein'T •gnllooiq-^i ii -o -xf-vfil XoirTct .^ (rjir.

?se evvsaoa snirio^iii XIfc;;.e.Xtf ^nlneqo looi:

eriT .acofc erft ic xic^ eioeii i£fem er-H o;tni

nsrfi eisv. ;teeri» eoi^ecee- eris bcujoip sjrjJb©

levo -3 00? P.:M lo'l ^niaevoo Rcd-gecfes er"?

-10-

opening vraa made small enough to "be fitted
with a one-half inch pipe plug. Through
this opening it was proposed to insert the
connection to the CO2 apparatus, to ot>ta.in
the sample of gas over the fire for analysis.
The second opening was ahout three inches,
high , by four inches long, and was coysred "by
a swinging screen of sheet mica* The sOieet
of mica was sufficient in area to completely
cover the opening and permit no great air
leakage around the edges. Through this
apparatus it was proposed to t«Uce the temper-
ature of the fire, A Jery pyrometer was set
up, the mica screen swung to one side for an
instant, and the pyrometer focused on the
fire. The temperature resulting showed on
the galvanometer. The reading of the temper-
ature of the fire should take place after
all other vaurious readings have "been recorded^
in order to prevent air leakage.

erf.t Jaeprrx o^ i)€>soqoTq e^v, tt gnlneqo ©Irf*

jBerfoni: e^ean'l Quod's sjbw grtinsqo inooes sr"^

User's srrr tfiz>lis ieeiis to n&fMioe "anisnliRs «

aiB iB^n-^ on fijtnsq i)nB- snineqo erfJ aftvco

Bir'^ jfr'Aro-ja'T .ee^fce erf* fcnuoiB ©se^i^el

-aeqmet e/f? exsJ- c* fceeoqoiq p«^- *i 80jrXBqqje

lis 10X siis e-nc o i' T>^ir^a nfiioe pois erf.t ,qu

erf? no fceetfool aewSisoxYq e/11 fcru ,JnP5-Fni

no fcevorfs j?ni tl i/Bsa tiL'^feieq^aeS edT .eill

-isqine'^ erf^J- io T?nJ'f-i?»T eriT ,af j6iC0rxeYi«:?( en'cJ-

is.tiis S'osiq e3ipi fcluorie stI i ©~':t Io savtfi

• e^ji^el xif :fiTS^eiq o^ lefcic nx

-n-

A Hayes C02 apparatus containing fresh
solution was set up and connected to a firs
foot length of quarter inch pipe "by the
usual rubber tubing. The gas sample from
over the fire was taken with this arrangement.
A long piece of quarter inch pipe was instal-
led permanently in theuptake» This length of
pips was fitted for proper connection to the
gas analysis apparatus, and through it a sample
of the gas in the uptsdce was obtained.

Two draft gauges were installed on the
wall at a convenient height, and the proper
connections to the interior of the furnace
over the fire .and in the uptake, were made.
The connections -.rere mads ndth quaitex inch
ca.Ft iron pipe. All connections were burred
out, and the pipes carefully cleaned before
installation. This removed all obstacles
for a true reading of the draft pressure,
except that which arises froni the friction
in the pipes. This latter error may be
neglected.

moil eltircK* sfi^s er!T •saitfwJ ^ee c'yi: I; jjsi.-
-IptBtl fi:» sql-T iforrl if>fiBU£ io eoexq ^ncl ^

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a&Xos^eifo IXjs bsroxnsi elrlT .rsotitsXlB^sai

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so' ■^e.ii xoii= X's.ttel eii>:T .Sflqlq ©rf-t ciL

. b« toe I ■g^ 'I

The quality o£ the eteaff. was ohtained
from the throttling calorimeter installed on
main steam line leading irom the central
steam drxaii. A one-half inch pipe connection
was already in place just abovethe dr\im, so
the calorimeter was connected at this point*
/ half inch glohe valve and a steam gauge with
the customary "curl* for the gauge, were
placed in the line leading to the calorimeter.
The laigth of pipe between the calorimeter and
the point of connection to the main steam line
was made as short as possible. The thermometer
cup was filled with a heavy cylinder oil, and a
thertiometer reading from zero to three hundred
degrees put in place. The pressure of the
steam as indicated by the gauge at the calori-
meter was taken as the tar ue boiler pressure.

Scales and baskets for the weight of
coal fired were provided.

The water fed to the boiler per hour is
measured by the venturi meter. A chart over
the recorder k^eps a record of the water
evaporated.

fcsnijsj-tfo sew 2i&BiB erit ic ifllBtip erfT
no .bdllisj-sni is^sixilxorso ^:ilLi&oicli ©rft .aioi'l

,J-nioq HJ■-•(^+ i£ ft3:^o8anoo 8i?w is JsflilioiBO sxl^

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io :+rf5il9\v srlt lol ?&s'As?xf bcis aelfio?

♦ Jbsfcivo'iq 919W fcft'ii'i I.'aoo
8l 'xuo/i xsq ieX.:ocr 9 ft ot fcsl xstjsw ai-:?

xeti^ erf? Io £y?:ocex r« aqoejl t^tiooi^z 9rf.t

• be ts-i oqsro

-13-

Several small numbered "baking powder cane
were provided for samples o£ "Oae coal and
refuse. It was intended to take several
saoples of "both at intervals during the run,
and keep them in the cane for analysis at a
convenient time.

All apparatus was carefully calibrated
"before its installation.

.3 t& ^is^lerts -xol srteo srft ni ^aarfJ- qf59:i fins

-14-

PROPOSED METHOD Oi PE0CM)UE3? ,

OBJECT :-

The deteimination of the relation
betiveen rate o£ combustion and dralt pressure
for a chain-grate stoker,
APP/KATUS:-

The test will involve the installation and
use of the following inetruKents'.
Draft gauges over the fire and in the uptake .
Throttling calorimeter and eteaan gauge .
C02 Apparatus .
Smoke recorder •
Pery pyrometer •
Speed cotinter for grate.

Scales and "baskets for weight of coal fired.
Venturi meter for measuring water evaporated.

METHOD OP PROCEDURE:

The boiler should be in operation as long
as possible Toefore the test is started, 17o
riins should be attempted before the boiler and

. 8:ij4-:^qij er{-:t .Tci bns s'lcl erf:*- x5vo as^i^s c^xa'x'J

.disi'g lo'i xejrmoo foeaqr?

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. &9J.«'xoq^YS xstB¥: snii;/?»?5.i: 'xol iq&b,xi ixu&''.e''T

; SviOfKOOH? iO COHTEi
snoX 3i5 Aox^' xeqo 'tl scf f)I;;orf3 isXlod" ©n'T

o^^f *b9txt>iB si +8s:t srfct sxolesf sX.-.ia^'oq 36

-15-

and setting have had an opportunity to

reach a xmii'orm temperature •

When the above conditions have been

satisfied, the hopper o£ the stoker should

be rilled full and then leveled off and the

run started. Take the follovring readings

every five minutes:

Average Draft, inches of water,
Over the fire .
In the uptake .

Average Gas Analysis ,
Over the fire-
In the uptake .

Temperatures, degrees Fahrenheit,

Ertemal air) Average for test.
Boiler room )
Tire .
Steam .

Pressures ,

Parometer.
True Boiler •

Weights, pounds per hour,

Water fed to boiler .(venturi meter)

Coal fired .

Sample of coal fired for later analysis .

Sample of ash for later analysis.

(Kote in log sheet kind and size of coal)

Uote Carefully ;

Thickness of fire . (Constant for run)
Speed of grate, feed per minute.
Droppage of fuel through grate, if any.
Condition of fire ( IlIPORTAFT ) .
Smoke observations (Smoke recorder)*

ns«cf avjsrf anoi J"i:x)floo ©vorfe srft rfs.'fy
eri^ bas 'ilo bsIeTOi rrsiii' f/trc XXyi fcsCCil s-f

/xotsw "io asiioai , tisaCT e cif.it'»T.\

. 9iLe.tqif sriJ nl
( ^aoo'i x-ji.

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(Xboo lo s.xie fcnj'. bni^i ts&de ^oi ni ©J'o;'

; vlXj/i^-xeD eto'^I
( ruji i/'i j"'.i:ii's.io:)) , 9111 lo es^cfAzi .'^
.ei '-•■■. .: T'', (--ej. ,aJ-«jTs '10 £'- ■ '
, v;;.T£! li ,s: ' Xsi/i lo easq-:;.' ;.

«{ 31x1 lo noivi--, •,

-16-

Precaution must "be taJfen to provide for
an ample exceee o£ air in the "boiler room.
The firing of the coal should be in such a
manner that the conditions at the start of the
run and at the finish are the same. That is,
the water should he at the same level in the
"boiler, and the coal at the same level on the
hopper at the finish as at the start.

The speed of the grate should be maintained
as near uniform as possible, but every change
in speed should be noted in the log sheet.

The observations sb regards to the condit-
ion of fire should be watched very carefully.
The swinging cover in the asbestos sheet
provides a place where the fire may be care-
fully watched with blue glasses without open-
ing cover. Kotes as to whether the fire is
short, even, contains holes, etc. should be
made frequently.

The analyses of the gases should be
carried on chiefly for the C02 content. If
no C02 recorder is available, the analyses
should be made at intervals not exceeding

■'DX"

,:zo(yi T?Xioo' &rii nl itf-- lo aaaoxe 3l\/.^ hb

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erii as. L^-7^1 e;nE.8 &iU iR ©"f bluoris xsj-sw sr?t
srfi no I«vel ease edi fs Ifloo e.ff^ br££ ,i3liocf
,.txiij-? srfi ^B sr dsinii srf^ :f£ laqqoxf
fc©nlfitnx£.3i ecf bluods etE-xg e-fc^ lo bssqe srf?

ssrsBilo ■\jiS7fl Jtjo' ,3lcfi3eoq bb sczollnsj lasnt as

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^tosn'e aoj39cfc» erf^ at xevoo ^rtisnl'ws ©r^T

-??xi?o ©o' -^^i:! sii'l erf* SiS.'-f^ soslq s es'^lroaq

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ecf bXuoriSJ .o?© ,^«Xoii •r>riXBtfxoo ,n©v-E ,i:i:o^!s

.-'jX tnsupeza. ©bs*:t£

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II .ine^noo SOD ^K* xol 'jXleliio no b^laxf-o

©©©■'iXfioe ©"^t ,«Xo'.9XiB-7£ si isbiooex SOO on

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-17-

firs minutes. The C02 should not get below
ten percent at any time.

Several xvmb should be made with dif-
£erent kinds o£ coal, varying the depth of
fire, draft, and speed of grate for each
kind of coal«

Have grate exactly level, and furnish
photograph showing that the gate and arch
are in satisfactory condition.

Too much stress cannot be put upon
the importance of keeping accurate readings
and conditions of fire. All air passages
except those leading through the grate must
be sealed off.

.eaUj vrte c^£ -fsiaoisq .TSt
-JLi fc fliiw ebea scf MiJOiie en:jx i«isvs3

ioBs -xoi e.t£a3 lo hesqe fca^a , + iBib ,eiH

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esnifcB**^ eteijjoos saicieejl io sortfiiTtoqiai e.fj-
aesBaaeq -xxb £X^ ,6ail lo e^-Toi-tlbnoo bnp

-18-

Discussion

The ccoibustiorx rate curves printed in
the various catalogues and magazines show
the combustion rate decreasing about in pro-
portion to the decrease in draft. This is
probably true for a draft of more than two-
tenths of an inch of water in the furnace,
but it is doubtful if the combustion rate
decreases as rapidly at the lower pressures.
/ set of tests of the aforementioned would
give an accurate determination of this.

The great trouble with the diain-grate
stoker is its small range of efficient
operation. By varying the depth of coal on
the grate, and the speed of the grate and then
by means of the damper , regulating the draft
pressure for each change in speed and depth
ojf Jul re, the limit of efficient operation
might be determined.

The lowest point of operation might be
taken as that point at ^ich the grate just
begins to turn red, as it comes over the
water back. The upper limit is held within
the capacity of the grate.

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vfo'ie esaisB^ei's bos b9Sj^oS.b&so ayolx^v s.it

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^o^t n^riS sioia lo Vlfiib .3 ^sol tun^ iLd&doiq

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ftoit^ie^o Jn©£orli« lo tiaiil ecit ,s'ii:x lo

,i)ST[I.Tns:)'sJb erf J^isinj

ill'Ulw .blftrf si +ijsil xeqqw srfT .Jio/^cf iscffi^

-19-

The perioimance o£ the "boiler and
t\x3na.ce may "be expressed in terms o£ weight
of water evaporated per hour per square foot
of heating surface. The results should he
plotted against the pounds of coal humed per
square foot of grate surface.

Combining the tests would give the re-
lation "between rate of comhustion and draft
pressure for a chain-grate stoker.

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-20-

BIILIOPBAPHY.

"Steam Power Plant Engineering", Ge"Hharclt«
"Experimental Engineering," Carpenter.
•Iron Age, Voiuir;e 40.

"Hand Booit lor Mechanical Engineers", Kent.
"Stirling Boiler Catalogue", Stirling "^oiler Co

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