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Bulletin No. 9



ENGINEERING EXPERIMENT STATION
IOWA STATE COLLEGE

AMES, IOWA.

Mechanical Engineering Section



NOTES ON STEAM GENERATION



WITH IOWA COAL



BY



G. W. BISSELL, M. E.



September, 1904.



f HfOH PRINTING A HFG. CO., DES MO/NES



ENGINEERING EXPERIMENT STATION

IOWA STATE COLLEGE

AMES, IOWA



STATION STAFF

PRESIDENT A. B. STORMS . Ex-Officio

DIRECTOR A. MARSTON Civil Engineering

PROFESSOR G. W. BISSELL Mechanical Engineering

PROFESSOR L. B. SPINNEY Electrical Engineering

PROFESSOR S. W. BEYER Mining Engineering

ASSOCIATE PROFESSOR W. H. MEEKER Mechanical Engineering

Bulletin No. 9



MECHANICAL ENGINEERING SECTION

NOTES ON STEAM GENERATION OF
IOWA COAL



G. W. BISSELL, M. E.
September 1904.



INTRODUCTION.

During 1 the past few years a number of investigations
bearing upon the problem of the combustion of Iowa coals
have been conducted under the direction of the writer and
his colleague, Dr. S. W. Beyer.

The object of this bulletin is to present in a single pub-
lication the results of these investigations and such conclu-
sions as can reasonably be deduced therefrom together with
other conclusions based upon the observation and the
experience of the writer.

It is expected that the work will continue in the future
and additional bulletins issued as results of value are ob-
tained. Valuable assistance in the preparation of this
bulletin has been rendered by Mr. H. F. Bishop, who has
compiled the tables and charts and written much of the text,
and by Professor W. H. Meeker in the revision of the text.

G. W. BISSELL, M. E.
Iowa State College,

September, 1904.



539614



4 NOTES ON STEAM GENERATION

CHEMICAL AND PHYSICAL PROPERTIES OF
IOWA COALS.

In 1902, Mr. F. M. Weakly, under the direction of Dr.
S. "W. Beyer, determined the proximate chemical composi-
tion of a number of Iowa coals and Messrs. J. C. Austin and
E. E. Peshak, under the direction of the writer, determined
with a calorimeter the heat value of the same and some addi-
tional coals and other fuels.

Table I exhibits the combined results of both investiga-
tions. All computations are based upon oven dried samples.

TABLE I.



COAL COMPANY AND LOCALITY


COMBUS1IBLE


Ash


Sul-
phur


*B. T.

U.

13,050

!3>i4i
12,560


Vol-
atile


Fixed


Total


Whitebreast Fuel Co.,
Pekay Wapello Co


46.06
42.72
45-18
40.02
45.62
39-06
40.61

37-79
37-09
48.69
41.46
37.98
39.07
36.94
40.54
42.24


46.89
47.78
45-34
44-8.6
50.29
53-46
48.21
54.85
50-83
45.02

50-33
47.98

54-9 1
54.20
51.04
50.27


9 2 .95
90. 5<-
90.52
84.88

95 -9 1
92.52
88.82
92.64
87.92

93-71
91.79
85.96
93.98
91.14
91-58
92-51


7-05
9-50
9-48
15.12
4.09
7-48
11.18
7.36

12. 08
6.29
8.21
14.04
6.02

8.86
8.42
7-49


2.81
. 4.96
3.98
7.41
2.74
2.38
3-26

3-29
2.27
3-58
4.16
5-9t>
3-15
2.86
3-68
3-o8


Eldon Coal Co.,
Laddsdale Wapello Co


Mine No. 2,
Hocking Monroe Co .


Mine No. 3,
Hocking Monroe Co


Des Moines Coal Co.,
Marquisville Polk Co .'


12,041
13,204
12,396
12,681
12,030


Lunsden Coal Co.,
Bloomfield Davis Co


Whitebreast Fuel Co.
Hilton Monroe Co


Block Coal Co.,
Centerville, Appanocse Co
Consolidation Coal Co., No. 10,


Consolidation Coal Co., No. n,
Buxton Monroe Co


Crowe Coal Co.,
Boone Boone Co . . .


12,729

12, 43 1
12,780


Corey Coal Co..
Lehigh Webster Co


D. Lodwick,
Mystic Appanoose Co


L. L. Lodwick,
Willard Wapello Co


Platt Coal Co.,
Van Meter Dallas Co


[1,941
I2 ,i34


Jasper Co. Coal Co.,
Colfax jasper Co




Average of above Coals


41.49


49.62


91.11


8.89


3-72


12,547





*B. T. U. = British Thermal
temperature of i ft of water i deg



Unit = the amount of heat required to raise the
F. from 39 deg. F.



OF IOWA COALS 5

Table II is introduced for comparison, tHe B. T. U. not
being given.

TABLE II.





COMBUSTIBLE


Ash


Sul-
phur


Moist-
ure


Vol-
atile


Fixed


Total


*Average of Table I


41-49
38.14
39-24
35-89
32-77
31.60
18 10


49.62

45.60
45-42
49.90
56 74
46.72
74-52


91.11

83.74
84.66

85-79
89-51
78.32
92.62


8.89
8.18
6-77
8.31
7-75
11.49
6.65


3-72
3-42

*

1.58

3-09
0.60


Oven
Dry

8.08
8-57
5-90
2.74

JO.OO

0.73


*Avera*ge of same coals


**Average of 64 Iowa coals.


*Hocking Valley, Ohio Lump


*Youghigheny Penn Lump . .


^Illinois Coals, average of 22
*Pocahontas, W. Va Lump





*The Iowa Engineer, June, 1902.

**The Iowa Geological Survey, Vol. II, page 192.



Ill summarizing his work Mr. Weakly says :

"The moisture in Iowa coals varies (for the coals tested)
from 4.03 to 17.47, the average being 8.08. The moisture
is high as compared with that in coal of other states.

"Eliminating moisture from our comparisons, in volatile
matter the Iowa coals are rich, varying from 36.94 to 48.69
with an average of 41.49.

"The fixed carbon ranges from 44.86 to 54.91 with an
average of 49.62, slightly lower than that of many coals
from other states.

" Total combustibles are high, running from 84.88 to 95.
91, with an average of 91.11.

"Ash is high being from 4.09 to 15.12, with an average
of 8.89.

Sulphur is high, from 2.27 to 7.41, with an average of
3.72. The coals high in sulphur are also high in ash."

The results above given are for selected samples.



NOTES ON STEAM GENERATION



Table III exhibits the chemical and physical properties
of a few Iowa and other coals from samples taken from the
coal piles of power stations and other consumers.

The low total combustible, high ash and low B. T. U.
of the samples of Table III furnish conclusive evidence that
much additional information, derived from the actual coal
pile, is needed before it is possible to intelligently estimate
the steam producing power of Iowa coals.

TABLE III.



NAME OF COAL OR
LOCALITY OF MINE.


USED AT


COMBUSTIBLE


jd

(r.

<


Sulphur.


Moisture.


EP

h

CQ


Volatile.


tJ

i>

X

2


0!



Bloomfield Coal Co.
Steam coal


Iowa State
Capitol.. .

Mason City


33-9


38.9


72.8

68.1


19.2
27.1

2? O


4-4
6.38


8.00
4.80




Mahaska Co., la


9,696


Mahaska Co. la


Oskaloosa






Flint Valley Coal Co.. .
?


Des Moim s
Edison Co

Iowa Sol-
diers Home








23-03
22.6





5-


9.292






72.4









In the spring of 1900, Messrs. W. S. Marston and E.
Hayter made a series of tests to determine the cost of
generating steam with different kinds of fuel. A 100 horse-
power, marine type boiler was used at its regular duty of
furnishing steam to the various engines of the College
power station. All tests were conducted in accordance with
the directions laid down in the alternate method of the
American Society of Mechanical Engineers. The results
appear in table IY, showing quite conclusively that the
cheapest coal to buy is the cheapest to use. Table V is
confirmatory evidence from a test at City Electric Light
Plant, Ames, Iowa.



OF IOWA COALS

TABLE IV.











i




i


1,.


|i


w












V


M


'ii "^







O *








V


3


<ii


< tJ' C


0^


^


M S











l..


. .


V V*


0,3


CU


1-t ^*




en
D







^


gf 3


> tn Q.


rt O

> a


a


a|j


^J


**- en


KIND OF COAL.


IM




I


a3X


4-* QJ U


4) ^


"a;


^- en


J5


11




C




0)

o> o.


lo ai S


I<N


!gl


f |


^s


~E




m


s.




*E w C/5


^ ^-4 *""




Q C


o






t -*-*


UM


v*^ flj




^ d C/5




+- S





3




CC





><


S r* J ^






la





Q




Q


H


Q rt


w rt


W *


* w


u


I


IO


Marquisville Lump




-6




2.82


7.18


$2.89


1 24


2


IO


Boone Lump


. 21


3 " 60




2.84


/**-'

777


2 . Q2


^ **f


7,


IO


Marquisville Slack


. 21


420


I 7 ,. 12


1.84


o/
6.04


1.47,




O

4


10


Summit Lump


. 21


T 1 W

45'


A j * *
18.75


3-4


7.16


* ' HO

2.60


234


5


9


Marquisville Steam


.21


448


18.14


2-83


6.99


2.33


.212


6


IO


Foundry Coke


. 2O


o


9IQ


i 8s


7 28


8.00


.6O4


7


IO


Blossburg Forge . ...


.20





. i y

8.33


i v J
2.O8


/ ^ u

9.QI


7.4C


. vyvy^f.


/

8


IO


Anthracite Nut


. 21


383


8.s


2.O4


y *

12. 2


/ HO
8.95


.528




IO


Marquisville Nut


.20


429


O

M. 7


* * ^^T 1

2 . 4Q


7.6l


2 .54


o
2IS












O




/ **




O



* Includes cost of hauling 50 cents per ton. ** From and at 212.

TABLE V*.









|


Si .


"o











,


o 3


c




M




DURATION




1U'


O M '.




|*'




OF TEST.


KIND OF COAL.


fc J


io -g


^


^1


i

i. ,






sg.


ill


J.S


f|


e








^S rt


.> 3


n


.


d


Hrs.


Min.




b^"


3 o


5 ~.


j


^








Q


W


5


u~
















CENTS


j


J7


20


^ijarquisville Slack


jC I


7-7


$1.10


10.


2


*o
6




Marquisville Mine Run


20.


6.8


2.00


17-3






3


12


48


Marquisville Mine Run


15.9


7-4


2.OO


16.6




4


6




Marquisville Steam .


20.


6.2


1-50


14-3




5


6




Marauisville Pea .


15-3


9.2


i-75


12.4



* From test of Ames Electric Light Plant by E. E. Savre and E. Peshak.
**From and at 212.



8 NOTES ON STFAM GENERATION

Figures 1 and 2 show these results very strikingly



COST Or COAL PER 2000 LBS.



o
a v





^ S
o

Co

?

^ Co


O


r>

Co

1 &

o

^

3


ro <; <3\ oo Jo

8 18 i "l $


V
























\


























V
























\


^
























\


























\
























\


\
























\


























^\




*






















\


Sy


















1 (
1 1






X


s^
















,s
























5
























||
























^1
























,**
















































^3

















OF IOWA COALS



COST OF COAL PER 2000 LBS.











CD

^>

C/i

a

> *:



o





Oo



X)



f\>



18







: OD



t



00

l



6



10 NOTES ON STEAM GENERATION

The test tabulated in table VI is of interest because of
the fact that it was made under ordinary running condi-
tions, and because of its long duration, 744 hours.

TABLE VI.

Duration of test 744 hours

Steam coal burned 204,834 pounds

Moisture in coal 5 per cent

Ash 22.6 per cent

Total combustible 147,720 pounds

Total water evaporated 952,881 pounds

Average temperature of feed water 213^ degrees

Average temperature of flue gases 384 j degrees

Actual evaporation per pound coal 4.67 pounds

Actual evaporation per pound combustible 6.44 pounds

Average horse power developed 42.6

Coal burned per hour per horse power 6.36 pounds

Coal burned per square foot of grate per hour I3-3 1 pounds

Average steam pressure 75. pounds

Equivalent evaporation from and at 212 per pound combustible 6.64 pounds

Cost of coal per ton $ i .30

Fuel cost of 1,000 pounds of steam from and at 212 13.5 cents

Test of plant at Soldiers' Home, Marshalltown, Iowa.

C. A. DUNHAM, C. E., Chief Engineer.



OF IOWA COALS

TABLE VII.



11



1

<u
H

3

6
S3


Height of Stack


Draft, Inches of
Water


Temperature of
Flue Gas


51

*

^H t| !-

bc<c rf

Sft'J




Efficiency of
Combustion


Dry Fuel persq.
ft. Grate Area
per hour.


Equivalent Eva-
poration from
and at 212 per
sq.ft. Heating
Surface per
hour.


Equivalent Eva-
poration from
and at 212 per
pound C o m-
bustible


Efficiency of
Boiler based on
Combustible.


I


6o x


.20


478






1^.76


1. 96


6 7


41 2


a


6o 7


31


CQ7


26 4


61.3


IQ.22


3- 17


7 ^


47. Q


3.


6c/


. 30


5 6s


iq.q


59.2


23. OS


3.8


7.2Q


48.2


4. .


68 X


. 3 )


Sio


27.


56.


16.8


2.64


7.77


46. S


5-


68 7


. T.A


568


22.6-


59.2


22.1


3.6


7. 77


47.4


6

7


68 X
76 X


33

1C


6o 5

400


16.
26.


69.7

44.7


25-37
17 . 22


4.19
3.2


7.42

8 5


49-4
1:4.


8


7*'

76 X


.38

30


500
CCQ


28.

22 3


53-9
61.


21.27
23. 33


3.38

70


7.02

7 02


4 6.
42 8


10
ii


84 X
84 7


35

. 3Q


510
4.8O


I 9 .
IQ.


68.6
60.4


21.98
24.. 2S


4.14
4. 76


8.15

7.Q


54-6

52. 2


12


84 X


.44


S8o


17. 2


60.4


34.. 27


4.7S


6.58


4O.Q























Test of 100 H. P. Marine Type Boiler at I. S. C. Power Station by Moorhouse &
Battey.

The tests shown in table VII were made for the study
of rates of combustion, and the effect of varying the
height of stack. A uniform grade of coal was used.



NOTES ON STEAM GENERATION



DRY TUEL PER Sa.FT. GRA TE PER HOUR.



30 VO 50 60 7Q 7 8, 9

PER CENT EFFICIENCY OF COMBUSTION. EVAPORATION PER POUND COMBUSTI


\ f\j Co <:
o o o C^>






























\
























\


\ *
























\
























\
























- \


\






















*


\
























\





















































/























/]






1














o

y


/

o o








5

a












/


/











03

x:










/


/












o
o
























o

















































g

D3
























5









DO

r-



OF IOWA COALS 13



Fig. 3, which is based upon the same data as table
seems to show that a high rate of fuel consumption gives
high efficiency of combustion as measured by analysis of
the flue gas. Considering however the performance of the
boiler as shown by the amount of evaporation from and at
212 per pound of combustible supplied, it would seem that
a low rate is the more economical. This is a very reason-
able i esult, though seemingly contradictory. The high rate
of fuel combustion, resulting as it does in a very hot fire,
insures the union of a larger per cent, of the combustible
with the oxygen of the air supply, than would be the case
at a lower rate of combustion. On the other hand, the
higher temperature of the fire thus resulting means, because
of deficiency in water heating surface, a much larger loss in
the stack from increased temperature of gases.

DIFFICULTIES OF BURNING IOWA COALS.

The principal reasons for poor results in using Iowa coals
are: (1) High percentages of moisture, ash and sulphur.
(2) The large proportion of volatile matter or hydro carbon.
Theoretically this may not be a detriment, for it is often the
case that the hydro carbon possesses a higher calorific power
than pure carbon. The great loss encountered in using a
fuel rich in volatile matter is due to the sweeping away of
this substance into the flue before its mixture with oxygen
has been eifected and its temperature raised to the ignition
point.

The elements in soft coal which unite with the oxygen
of the air to produce heat are : carbon, hydrogen, and
sulphur, the latter however being of small value as far
as its heat producing power is concerned. Carbon unites with
oxygen in two proportions, forming C O and C O 3 , know
as carbon monoxide, and carbon dioxide respectively. If
the air supply be scanty, C O is formed and the combustion



14 NOTES ON STEAM GENERATION

produces 4,400 B. T. U. per pound of carbon so burned.
With sufficient air present, however, C O 3 is formed and
there are produced for each pound of carbon 14,500 B. T. U.
Hence the necessity of sufficient draft and thorough mix-
ture. Hydrogen combines with oxygen in the proportions
to form water, and for each pound of hydrogen, 62,000 B.
T. U. are given off. The carbon found in soft coal is present
in two forms: (1) as fixed or free carbon, which is a solid,
(2) combined with the hydrogen present, forming a com-
pound variously called hydro-carbon, volatile matter, or
volatile combustible.

When a shovel full of fresh coal is thrown into a furnace
the temperature of the coal increases and the volatile matter
is driven off. The fixed carbon being a solid, necessarily
remains on the grate until it combines with oxygen, since
not till then can it escape. This is the reason for the ex-
cellent results obtained with anthracite. There are soft coals
which surpass it in calorific power, but few in steam genera-
tion. This is because all the combustible is a solid, and must
remain in the furnace until its union with oxygen. Given a
fair draft, hard coal will render a good account of itself even
with other conditions adverse. The final condition of the
disengaged hydro-carbon gases as they rise from the bed of
burning soft coal may be variable. If they impinge upon a
relatively cold boiler shell, causing their temperature to fall
below the combustion point, they will probably be swept
into the flue in a half burned condition, producing smoke
and causing loss of heat. If on the other hand the temper-
ature of the gases be kept up until thorough mixture with
oxygen has been effected, the result is smokeless combus-
tion and a maximum of heat developed.

The best conditions for securing smokeless combustion
with maximum steam generating power are obtained with a



OF IOWA COALS 15

proper design of coking arch, or better yet, by the use of a
separate furnace known as the "Dutch Oven." In both
devices the grate is covered by a fire brick roof which is kept
at a high temperature by the heat of the fire. The mixed
gases on impinging against this roof are not chilled but on
the contrary are very highly heated and complete combus-
tion results.

The evil of insufficient air supply resulting in carbon
burning and C O instead of C O 2 has already been alluded
to. Too much air, though far preferable to too little, causes
loss by its cooling action. Theoretically, about 12 pounds
of air or 150 cubic feet at 60 degrees is required for each
pound of combustible. This supposes the mixture to be
perfect, but owing to the impossibility of securing thorough
mixture in the furnace, an excess of air must be supplied, so
that, in good practice, the air supply amounts to 250 or 300
cubic feet per pound of combustible. The amount of air
supplied depends: (1) upon the draft, (2) grates, (3) grade
of fuel and (4) thickness of the fire.

The draft if natural depends upon: (1) the height of
chimney, (2) temperature of chimney gases and (3) the total
resistance offered to the flow of air and products of com-
bustion by the fire, heating surfaces, flues, breeching and
chimney. It should be possible to secure proper draft with
a flue temperature of 350 to 450 degrees.

Grates should be adapted to the fuel. Rocking or shak-
grates are preferable. For fine coals the air spaces should
be narrow to prevent waste in unburned fuel. This is some-
times very large, ranging from 5 to 25 per cent of the fuel
fired.

The grade or average size of fuel and thickness of fire
are inter-dependent and should be adjusted so as to distri-
bute the air supply evenly over the fire. Fires from 3 or 4



16 NOTES ON STEAM GENERATION OF IOWA COALS

inches thick for slack with natural draft, to 16 inches for
lump with forced draft are found in practice. Special care
should be given to keeping a uniform thickness in order to
prevent the formation of "holes" in the fire.

The question of mechanical stokers comes in as a labor
saving proposition and for plants of above 500 horse power,
their use may lead to increased economy. However, the
adaption of this device to Iowa coals has not been as yet
sufficiently proven.

The proportions of the boiler are of some moment in
securing the best results. The .heating surface should be 45
to 50 times the grate surface and the length of the path tra-
versed by the gases to the chimney long enough to lower
their temperature to 400 degrees. This means that for hor-
izontal return tubular boiler 4 inch tubes should be 18 to 20
feet long ; where small boilers seem to demand smaller flues,
3J inch flues should be 16 and 3 inch flues 12 feet long.
The smaller sizes are objectionable with natural draft on
account of depositing soot thus lowering the rapid transfer
of heat.

Table VII confirms the belief, based upon other
experimental data, that the most economical rate of
evaporation is about 3 pounds of steam per square foot of
water heating surface per hour.



7/9 /



539614



UNIVERSITY OF CALIFORNIA LIBRARY





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