S:S^; illif
.
’ Jf'-V * •*,!/?. " fi'iw ■• # C/f
'ERSITY OF ILLINOIS BULLETIN
Issued Weekly
HVA^M Av r i APRIL 1, 1918 No. 31
(Entered as second class matter Deo. 11, 1012, at tbe Post Office at Urbnna, 111., under the Aot of Auk. 24, 1012]
FUEL ECONOMY IN THE OPERATION
OF HAND FIRED POWER PLANTS
T HE Engineering Experiment Station was established by act of
the Board of Trustees, December 8, 1903. It is the purpose
of the Station to carry on investigations along various lines of
engineering and to study problems of importance to professional engi-
neers and to the manufacturing, railway, mining, constructional, and
industrial interests of the State.
The control of the Engineering Experiment Station is vested in
the heads of the several departments of the College of Engineering.
These constitute the Station Staff and, with the Director, determine
the character of the investigations to be undertaken. The work is
carried on under the supervision of the Staff, sometimes by research
fellows as graduate work, sometimes by members of the instructional
staff of the College of Engineering, but more frequently by investigators
belonging to the Station corps.
The results of these investigations are published in the form of
bulletins, which record mostly the experiments of the Station’s own
staff of investigators. There will also be issued from time to time, in
the form of circulars, compilations giving the results of the experi-
ments of engineers, industrial works, technical institutions, and gov-
ernmental testing departments.
The volume and number at the top of the front cover page
are merely arbitrary numbers and refer to the general publications
of the University of Illinois: either above the title or below the seal is
given the number of the Engineering Experiment Station bulletin or cir-
cular which should be used in referring to these publications.
For copies of bulletins, circulars, or other information address the
Engineering Experiment Station,
Urbana, Illinois.
UNIVERSITY OF ILLINOIS
ENGINEERING EXPERIMENT STATION
Circular No. 7
April, 1918
FUEL ECONOMY IN THE OPERATION
OF HAND FIRED POWER PLANTS
Prepared under the Direction of
A Committee consisting of A. C. Willard, Professor of Heating
and Ventilation (Chairman), H. H. Stoek, Professor of Mining
Engineering, 0. A. Leutwiler, Professor of Machine
Design, C. S. Sale, Assistant Professor of Civil
Engineering and Assistant to the Director of
the Engineering Experiment Station, and
A. P. Kratz, Research Associate in
Mechanical Engineering
ENGINEERING EXPERIMENT STATION
Published by the University of Illinois, Urbana
Digitized by the Internet Archive
in 2017 with funding from
University of Illinois Urbana-Champaign Alternates
https://archive.org/details/fueleconomyinope00will_0
CONTENTS
PAGE
6 xi. in
iHi
I. Introduction 7
1. Purpose 7
2. Authorship 8
II. Fuels Available for Power Plant Use in the
Middle West 9
3. Kinds of Fuel 9
4. Properties of the Central Bituminous Coals . . 11
5. Preparation, a Factor Affecting the Value of Coal . . 14
6. Storage of Coal 18
7. Storage Systems 22
III. The Combustion of Fuel and the Losses Attending
Improper Firing 24
8. Principles of Combustion 24
9. Significance of Draft 26
10. Significance of C0 2 in the Flue Gases 29
11. Losses of Heat Value 33
Excess Air and Air Leaks 34
Loss Due to the Presence of Combustible in the Ash . 38
Loss Due to the Presence of Carbon Monoxide in the
Flue Gases 39
Loss Due to Soot 39
Loss Due to Moisture in the Coal and Air ... 40
Loss Due to Heat in the Escaping Gases .... 40
Loss Due to Radiation ... 40
12. Significance of Smoke 40
13. Methods of Hand Firing ...... 41
14. Stoker Firing 42
3
(>1346
CONTENTS (Continued)
PAGE
IV. Features of Boiler Installation in Relation to
Fuel Economy , . . 44
15. Boiler Settings 44
Foundation 44
Side and End Walls 44
Settings for Horizontal Return Tubular Boilers . 45
Settings for Water Tube Boilers 48
Defects in Settings 50
V. Installation Features Affecting Draft Conditions 52
16. Stacks and Breechings 52
The Stack Damper and Its Use 52
“Draft” is in Reality a Pressure 54
Air Leaks Affect the Draft and Waste Coal ... 56
Breechings for a Battery] of Two or More Boilers . 57
Conditions Under Which a Stack will Operate Eco-
nomically 57
VI. Feed Water Heating and Purification as Factors in
Fuel Economy 60
17. Feed Water Purification 60
18. Treatment of Feed Waters 61
Chemical Treatment 61
Heat Treatment 61
Combined Chemical and Heat Treatment .... 62
19. Boiler Compounds 62
20. Feed Water Heaters 62
Exhaust Steam Heaters 63
Closed Heaters 63
Advantages and Disadvantages of Exhaust Steam
Heaters 64
21. Economizers 65
22. Live Steam Heaters 65
23. Feeding Boilers 65
CONTENTS (Concluded)
5
PAGE
VII. Steam Piping Requirements for Fuel Economy in
Small Plants 67
24. Possibility of Fuel Loss in the Transmission of Steam . 67
25. Value of High Pressure Drips as Hot Feed Water . . 67
26. Leakage Losses at Valves and Fittings 67
27. Size of Steam and Exhaust Mains 68
28. Heat Insulating Materials Required on Piping, Boilers
and Breechings 73
29. Requirements for a Good Covering 77
30. Bad Effects of Water of Condensation in Steam Lines . 78
31. Uncovered Pipes Waste Steam as Well as Coal . . .78
VIII. Record of Operation 81
32. Purpose of the Record 81
33. Character of the Record 81
34. Profit Sharing or Bonus Systems 84
IX. Summary of Conclusions 85
35. Conclusions 85
Coal 85
Principles to be Observed in Firing 85
Features of Boiler Installation 86
Stacks and Breechings 87
Feed Water and Fuel 87
Steam Piping Requirements 88
Record of Operation 88
LIST OF FIGURES
NO. . PAGE
1. Map Showing the Locations of the Coal Fields of Illinois, Indiana, and
Western Kentucky 15
2. Chart Showing the Theoretical Value of Coals of Different Heating Values
at Various Prices per Ton . 19
3. Manometer Tube for Showing the Difference in Pressure between the Out-
side and the Inside of Boiler Wall 27
4. Sketch Showing the Correct Method of Connecting Draft Gages ... 28
5. Apparatus for Determination of C0 2 in Flue Gas 30
6. Sketch Showing the Proper Location for Gas Sampling Tubes to Avoid
Damper Pockets for Both Front and Rear Take-off 32
7. Curve Showing Relation between Excess Air and C0 2 in Flue Gas . . 37
8. Hartford Setting for Return Tubular Boilers 45
9. Double Arch Bridge Wall Setting for Smokeless Combustion .... 46
10. Sketch Showing Effects of Baffling and Dampers in Causing Pockets and
Eddies in the Flue Gas Stream 50
11. An Approved Form of Hinged Damper 52
12. Isometric Sketch Illustrating the Principle that Light Fluids or Gases are
Pushed Upward when in Contact with Heavier Fluids or Gases . . 55
13. Sketch Showing Variations in Draft at Different Points and Indicating
Tendency Toward Air Leakage 56
14. Stack and Breeching Connections for a Battery of Three Boilers ... 58
15. Diagrammatic Section and Energy Transformation Chart for Small
Steam Power Plant 70
16. Chart Showing Amount of Heat Transmitted by Steam Pipes Insulated
with Commercial Coverings 75
17. Chart Showing Heat Lost by Bare Steam Pipe and Saving which may
be Secured by Using a Good Covering 76
18. Diagram Showing Comparative Saving in Water and Steam to be Effected
by Covering Live Steam Mains 79
LIST OF TABLES
NO. PAGE
1. Analyses of Coals of Illinois, Indiana, and Western Kentucky ... 12
2. Sizes of Central Bituminous Coals 17
3. Stack Sizes Based on Kent’s Formula 54
4. Impurities in Feed Waters, Their Effects and Remedies 60
5. Coal and Steam Loss Based on 100 Feet of Uncovered Steel Pipe ... 74
6
FUEL ECONOMY IN THE OPERATION OF HAND FIRED
POWER PLANTS
I. Introduction
1. Purpose .— The need for greater economy in the use of coal
is too apparent, under present conditions, to need emphasis. The
demand for coal is unprecedented, and production is proceeding at a
rate which is barely, or perhaps not quite, keeping pace with the
demand. The U. S. Geological Survey reports that, during 1917, ap-
proximately 545,000,000 tons of bituminous coal were produced and
used in the United States. The demand, moreover, is increasing at
the rate of about ten per cent per year, so that at present the rate of
consumption is about 600,000,000 tons per year. Illinois produces
about 12 y 2 per cent of this amount, or 78,000,000 tons.*
Approximately 45,000,000 tons of bituminous coal are used with-
in the state of Illinois, and of this amount about 6,000,000 tons are
consumed in hand fired power plants. It is believed to be within the
limits of practical attainment to effect a saving of from 12 to 15 per
cent of this fuel. Expressed in tons and dollars, such a saving amounts
to 750,000 tons, or $3,500,000. The possible saving in the case of many
individual plants is much greater than the percentage stated.
It is the purpose of this circular to present to owners, managers,
superintendents, engineers, and firemen of hand fired power plants
certain suggestions which, it is believed, will help them in effecting
greater fuel economy in the operation of their plants, and in deter-
mining the properties and characteristics of the coal purchased. Fea-
tures of installation essential to the proper combustion of fuel are dis-
cussed and their importance emphasized; the practice to be observed
in the operation of the plant is outlined ; and the employment of sim-
ple devices for indicating conditions of operation is prescribed.
Special attention is called to the fact that, to secure the greatest
degree of success, cooperation between owners and managers, and the
men who fire the coal is essential. Mechanical devices to increase
* It is estimated that Illinois will produce more than 85,000,000 tons of coal in 1918.
7
8
ILLINOIS ENGINEERING EXPERIMENT STATION
efficiency in the use of coal cannot produce satisfactory results un-
less the firemen who handle them are impressed with the importance
of their duties. While the suggestions presented apply particularly
to hand fired plants and no attempt is made to define practice for
stoker fired plants, many of the factors affecting fuel economy are
common to all power plants, and for this reason much of the informa-
tion contained herein will, no doubt, be helpful to those interested in
more economical operation of stoker fired power plants.
To the experienced engineer much that is presented here will seem
elementary apd inadequate. If, however, the plant owner who is
not familiar with the extreme refinements of practice may obtain here
the facts which will enable him to improve his results to the extent of
the modest saving suggested, the purpose of the publication will have
been fulfilled.
2. Authorship . — The information contained in this circular has
been compiled under the direction of a committee consisting of A. C.
Willard, Professor of Heating and Ventilation (Chairman), II. H.
Stoek, Professor of Mining Engineering, 0. A. Leutwiler, Profes-
sor of Machine Design, C. S. Sale, Assistant Professor of Civil Engi-
neering and Assistant to the Director of the Engineering Experiment
Station, and A. P. Kratz, Research Associate in Mechanical Engi-
neering.
This committee has had the assistance of an advisory committee
consisting of Joseph Harrington, Advisory Engineer on Power Plant
Design and Operation, Chicago, Arthur L. Rice, Editor, Power Plant
Engineering , Chicago, John C. White, Chairman, Educational Com-
mittee, National Association of Stationary Engineers, Madison, Wis.,
O. P. Hood, Chief Mechanical Engineer, Bureau of Mines, Washing-
ton, D. C., D. M. Myers, Advisory Engineer on Fuel Conservation,
United States Fuel Administration, Washington, D. C., and C. R.
Richards, Dean of the College of Engineering and Director of the
Engineering Experiment Station of the University of Illinois. Each
member of this Advisory Committee personally reviewed the original
manuscript and a meeting was held at Urbana on March 21, 1918, at
which the work was examined in detail. The authors gratefully ac-
knowledge the valuable assistance and cooperation of the members
of this committee and feel that the value of the publication has been
greatly enhanced as a result of their efforts.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
9
II. Fuels Available for Power Plant Use in the Middle West
3. Kinds of Fuel . — The varieties of fuel used by hand fired
power plants in Illinois are :
Central bituminous coals as represented by those from the coal
fields of Illinois, western Kentucky, and Indiana.
Eastern bituminous and semi-bituminous, or soft coals, from the
Pennsylvania, West Virginia, and eastern Kentucky fields.
A classification of solid fuels available for this purpose will, of
course, include anthracite and coke but none of these is used to any
considerable extent for power purposes in Illinois. The liquid fuel,
petroleum, is produced in large quantities in Illinois but is not used
directly for fuel purposes to any great extent.
All these coals are composed of the following materials in varying
proportions :
(1) Solid or fixed carbon which burns with a glow and without
flame.
(2) Gases or volatile materials which escape from the coal when
it is heated and which burn with a flame.
(3) Gases or volatile matter and water which escape from the
coal when it is heated and which do not burn.
(4) Ash or mineral matter which does not burn and which
remains as ashes after the coal is burned.
The relative proportions of these materials in different coals
determine their value for particular purposes.* Fuels having a large
amount of fixed carbon and a relatively small amount of volatile
matter burn with a short flame and the whole process of combustion
takes place at or near the surface of the fuel bed. Such fuels can
be burned without developing visible smoke. On the other hand coals
containing a relatively large amount of volatile matter and a lower
proportion of fixed carbon burn with a longer flame and tend to pro-
duce more visible smoke than the high carbon coals because the volume
of combustible gases distilled from them is greater.
The bituminous coals of the central field (Illinois type) contain
* The “fuel ratio,” which is the quotient obtained by dividing the fixed carbon by the
volatile matter, is often used as a means of classifying coals, and for bituminous coals it
answers fairly well.
10
ILLINOIS ENGINEERING EXPERIMENT STATION
from 40 to 55 per cent of fixed carbon, 10 to 25 per cent of com-
bustible gas, 5 to 15 per cent of non-combustible gas, 8 to 15 per cent
of moisture, and 8 to 15 per cent of ash. When improperly fired or
burned in furnaces not adapted to their use, central bituminous coals
give off so large an amount of sooty material that flues are often
quickly clogged. These unconsumed volatile products also represent
a direct loss of heat value. Coals of the Illinois type ignite easily
and burn freely.
Because the amount of solid carbon in most Illinois coal is lower
and the percentage of ash and moisture higher its heating value is
usually less than that of most eastern bituminous coals, but the cost
is usually so much less that it is more economical to use local coals.
At this time (March, 1918) the transportation of fuel over long dis-
tances is not only undesirable, but it is practically impossible, and
bituminous coals of the central field constitute the only fuel available
in quantities for use in Illinois.
The moisture and non-combustible gases present in all coals are
detected only by chemical analysis. They not only do not produce
heat, but represent a definite loss because they absorb and carry off
heat which would otherwise be available for useful purposes. The
term moisture in coal does not mean the water adhering to the sur-
face of the lumps, but that contained^ within the pores of the coal. A
coal containing a high percentage of moisture by analysis may appear
perfectly dry.
The ash content of different coals varies greatly. Ash is non-
combustible mineral matter which not only has no heating value and,
therefore, represents a portion of the coal from which no return is
received, but it may hinder the free burning of the combustible com-
ponents of the coal. If the ash contains certain mineral substances,
it may by clinkering greatly interfere with the process of firing and
with the cleaning of grates. The ash normally is removed through
the ashpit into which often passes also a certain amount of unburned
coal. For this reason the amount of ashes removed from the pit usu-
ally represents a larger percentage of the fuel fired than the analysis
of the ash content indicates. It should be clearly understood that
ash will not burn and that no treatment with chemicals, or “secret
processes, ” will cause it to burn. Likewise, it is not possible to increase
the heat value of coal by treating it chemically or by adding a nostrum
to it.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
11
The ash in coal may be divided into two classes ; first, that which
is a definite part of the composition of the coal and which cannot be
separated from the coal by hand or by mechanical process, and, sec-
ondly, that which is due to rock, slate, and shale which become mixed
with the coal in mining and which can in a large measure be separated
from the coal either in the mine or in the tipple.
Bituminous coal may be either of the coking or the non-coking
variety. Coals vary widely with reference to their coking properties.
A true coking coal when fired swells, becomes pasty and fuses into a
mass of more or less porous coke. Such coke will burn without flame
and will hold fire for a considerable period. This fusing or coking
takes place without respect to the size of the piece of coal. A non-
coking coal does not swell and become pasty but burns away gradu-
ally to ash, the pieces becoming gradually smaller and smaller. There
is a gradual gradation from true coking to true non-coking coals and
many coals cannot be distinctly placed in either class. Coal which
will not coke on a furnace grate may, however, give good coke in by-
product coke ovens, particularly when mixed with other more easily
coking coals. This is the case with many Illinois coals.
The eastern bituminous coals contain from 5 to 10 per cent of
ash, from 25 to 35 per cent of combustible gases, from 2 to 5 per cent
of moisture and non-combustible gases, and from 55 to 65 per cent of
solid carbon. They are more generally of the coking variety than are
the Middle West coals. In general, they are higher in heating value
and lower in ash. They are more friable and are not so well suited
for transportation and repeated handling as are many of the central
bituminous coals.
4. Properties of the Central Bituminous Coals . — Coals used in
Illinois power plants come mainly from the Illinois, Indiana and
western Kentucky fields. The properties of these coals as disclosed
by analyses of samples from different localities are given in Table 1.
The average analyses of the important Illinois coals have been
determined with great care. The averages for Kentucky were obtained
by average analyses of composite samples from several mines. Aver-
age analyses are not available for Indiana coals and instead analyses
are given of samples from three important Indiana coal counties,
namely, Clay, Green and Sullivan counties.
12
ILLINOIS ENGINEERING EXPERIMENT STATION
Table 1
Analyses of Coals of Illinois, Indiana, and Western Kentucky
(Figures are for face samples and for coal “as received”)!
District
Coal
Bed
Moisture
Volatile
Matter
Fixed
Carbon
Ash
B. t. u.
(Heating
Value)
Illinois (Average Analyses)
La Salle
2
16.18
38.83
37.89
7.08
10,981
Murphysboro
2
9.28
33.98
51.02
5.72
12,488
Rock Island and Mercer Counties . .
1
13.46
38.16
39.75
8.63
11,036
Springfield-Peoria . :
5
15.10
36.79
37.59
10.53
10,514
Saline County
5
6.75
35.49
48.72
9.04
12,276
Franklin and Williamson Counties . .
6
9.21
34.00
48.08
8.71
11,825
Southwestern Illinois
6
12.56
38.05
39.06
10.33
10,847
Danville: Grape Creek coal
6
14.45
35.88
40.33
9.34
10,919
Danville : Danville coal
7
12.99
38.29
38.75
9.98
11,143
Indiana (Typical Analyses)
Clay County
( Brazil 1
15.
.38
32
.66
46.
.08
5.88 ‘
11,680
| block )
Greene County
IV
13.
53
33
.54
45
.38
7.55
11,738
Greene County :
V
10.
30
36
.31
41,
.64
11.75
11,218
Sullivan County
IV
12.
15
33
.48
46.
23
8.14
11,722
Sullivan County
V
12.
,14
35
.17
43.
73
8.96
11,516
Sullivan County
VI
14.
86
31
.65
46.
14
7.35
11,324
Kentucky (Average of Composite Samples)
9
8.17
36.82
45.17
9.83
11,867
11
7.33
38.28
45.28
9.11
12,056
12
9.67
34.86
46.46
9.01
11,695
1“ As received” samples represent the coal as taken from the mine. It is probable that the values
given are fairly representative of the coals as purchased from local dealers.
A study of the values presented in Table 1 reveals the following
facts :
(1) The amount of ash in the various coals as they exist in the
mine varies within a range of about 6 per cent. With in-
adequate preparation of the coal for the market, however, the
range of difference may be as much as 12 or 15 per cent.
(2) There is a variation in the percentage values over a range
of about 5 per cent in the volatile matter in the different coals,
an amount which is negligible in view of the proportionately
greater variations in heating value and in ash.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
13
(3) The variation in the amount of moisture present in the dif-
ferent coals is considerable, but this variation is reflected to
some extent in the B. t. u.* values. If two coals have about
the same amount of fixed carbon, volatile matter and ash, the
coal having the higher moisture content has the lower B. t. u.
value. Accordingly, if the B. t. u. value of a coal is known,
the moisture content is not important. This statement is also
true as regards ash, except that the ash represents a residue
to be handled.
With regard to the B. t. u. values, the table shows that there are
important and distinguishable differences in the heating quality of
the different coals found in the three states, yet the extent of dif-
ference is not sufficient to justify extravagant statements in praise of
certain coals or in disparagement of others. On the basis of heating
value alone, the difference between the value of the poorest and that
of the best coals, as they are found in the mine, amounts to about one-
fifth of the value of the poorest coal.f As stated previously, however,
the care with which coal is prepared affects its value as fuel (see sec-
tion 5 ‘‘Preparation, a Factor Affecting the Value of Coal,” p. 14).
The values given cover the most wide-spread and most important
coal beds of Illinois, Indiana, and western Kentucky. It should be
observed that the variations are as great between coals which come
from the same bed in widely separated localities as between coals
which come from different beds, for instance, the No. 6 coal of Frank-
lin and Williamson counties differs nearly as much from the No. 6
coal of the Belleville region of southwestern Illinois as it does from
the No. 5 coal of Saline County. For large areas, however, the char-
acteristics of each bed are remarkably constant and variations in the
character of the coal are regional rather than local. It is possible
therefore, to subdivide the large coal fields of the three States into
districts as shown on the accompanying map (Fig. 1).
The subdivisions of the Illinois field as shown on this map were
based mainly upon geological conditions and upon the general sim-
* For a definition of B. t. u. see foot-note on page 17.
t Comprehensive tables giving analytical values for Illinois coals are contained in Bui.
29 of the State Geological Survey, Urbana, 111., entitled “Purchase and Sale of Illinois Coal
under Specifications,” by S. W. Parr, and in Bui. 3 of the Illinois Coal Mining Investiga-
tions, Urbana, HI., entitled “Chemical Study of Illinois Coals,” by S. W. Parr. Professional
Paper 100A, U. S. Geological Survey, Washington, D. C., contains analyses of coals from
all parts of the United States.
14
ILLINOIS ENGINEERING EXPERIMENT STATION
ilarity in the methods of mining in each district rather than upon a
difference in the quality of the coal. This fact should be understood
in considering the analyses of coals from the different districts. For
instance, the coals from the eastern part of Perry County are very
similar to those from Franklin and Williamson counties, although
classed by the map as being in a different district. The dividing line
accepted by the Illinois Coal Mining Investigations between District
6 and the southern part of District 7 is the Duquoin anticline, a dis-
tinct geologic structural feature which has, however, not effected any
distinct change in the character of the coal, that just west of and near
the anticline being practically of the same quality as that east of the
anticline in the same locality.
The several Illinois coals do not differ materially in appearance
and it is often difficult to distinguish one from another without more
careful tests than the ordinary purchaser can make. The apparent
difference is frequently due to preparation rather than to actual differ-
rences in chemical composition and in heating quality.
5. Preparation, a Factor Affecting the Value of Coal . — Coal oc-
curs in the earth in beds or seams, and usually in a solid mass as a rock.
In mining it is blasted with powder, shoveled into cars, and conveyed
to the surface. In the process of mining and handling it becomes
broken up into pieces of all sizes. It may have some rock or dirt from
the floor and roof of the mine mixed with it or there may be bands
or layers of earthy matter in the coal seam itself. Coal as it comes
from the mine is therefore not usually in condition for immediate
delivery to the consumer, but ordinarily must first be “ prepared ’ 1 in
order to remove these impurities and to separate it into the proper
sizes for various purposes or markets. The impurities in the large sizes
of coal are removed by picking them out by hand, and in the smaller
sizes by treating the coal in cleaning machinery. Separation into dif-
ferent sizes is accomplished by sending the coal over screens having
holes of the proper size.
Table 2 gives the customary sizes and the corresponding names of
central bituminous coals as they are available in the market.
9Cf
99 *
88*
bukkn
tlvjnoliT
N Kf'
W'jmMicfe
vltknxedUo
STTL
jwqw
| y
r\S^KF^Kvii
^iin^nn . J/
•jAU)
Coal Fields op Illinois, Indiana, A ^ 1 ; f 'V* JK« ^ v^ifs ‘ K -‘t 1 :'
and Western Kentucky *-t» '4—^4*— * — ■ — Sfe i ~S«,4li»'ty L i (
Districts for Classification of \8L'>iV>X t 7 ^ r - 1 f’ VN ' 1,111
Coals in Illinois \ I*£jU„ | } ftakf " \ij_ ) ^ ^
jl. Longwall district: No. 2 coal . 1 VpTwr
! (“Third Vein”) JM/f&tfLr wM‘< N
12. Jackson County district: No. 2 T'I ; kT-'^x V f n. — VVaiJiW-^T’- 1 ''
i coal (“Murphysboro” coal: M&j,' ,. \S V, SrWf j i, yo .-V 1 ” “ T "V
■ 3 - *$£, n “f .“i Mercer oooa - :% Sa ' < > - V
4. Peoria-Springfield district: No. 5 coal (“Central Illinois” coal) ?V'' VdiFtfsnAX| | \
5. Saline and Gallatin counties: No. 5 coal (“Harrisburg” coal) ’ / &'¥VA j TOU|, l r 'i *\£.
6. Franklin, Williamson, and Jefferson counties: No. 6 coal (“Franklin- Williamson” coal) %
7. Southwestern Illinois: No. 6 coal
8. Danville district: No. 6 and No. 7 coal (“Grape Creek” and “Danville” coals) v
(Note: The districts as indicated in this list were arranged for convenience of classification IT,:- .<
of the coals by the Illinois Coal Mining Investigations; they do not correspond to theSfeta
j Mine Inspectors’ districts nor to the trade subdivisions.)
tf^OKU
■vet §m^ A^'
_i7j '
V
1
Fig. 1. Map Showing the Locations of the Coal Fields of Illinois,
Indiana, and Western Kentucky
THE LIBRARY
OF THE
UKivsasiiv e» : ill::::';
FUEL ECONOMY IN HAND FIRED POWER PLANTS
17
Table 2
Sizes of Central Bituminous Coals
Name
Size op Pieces
Run of Mine
Mixture of all sizes
Lump
Large lumps separated from the finer sizes
Egg or Furnace
Lumps 3-6 inches
No. 1 Nut or Small Egg
2-3 inches
No. 2 Nut or Stove
1M _ 2 inches
No. 3 Nut or Chestnut
inches
No. 4 Nut or Pea or Buckwheat
inch
No. 5 Nut
Under M inch
Screenings
A mixture of all sizes under 2 inches
For large power plants the custom of purchasing coal on the
B. t. u.* basis is increasing and if the specifications for such purchase
are properly drawn and understood it is the logical way to buy coal, be-
cause it is equivalent to buying so many heat units instead of so many
tons of coal. Upon this basis a purchaser should be able to determine
whether a low priced coal which gives less efficient boiler service and
involves greater expense for handling ashes is really cheaper than a
higher priced coal.
With reference to the selection of different Illinois coals, the
B. t. u. value and the percentage of ash furnish a general guide to their
relative values. If two coals are otherwise alike in composition, the
ash content increases as the B. t. u. value decreases; hence their rel-
ative values may be expressed with fair accuracy by either the B. t. u.
or the ash value alone, although the evaporative value of any coal
drops off more rapidly than its B. t. u. value when the ash content
exceeds 10 or 15 per cent. A close approximation of the percentage of
actual heat producing material in Illinois coal may be obtained by
dividing the B. t. u. value of the coal by 155. Thus, a 12,000 B. t. u.
coal contains 12,000 -f- 155, or 77 per cent of heat-producing mate-
rial. In order to enable the small consumer to judge the relative values
of coals offered at different prices, the chart, Fig. 2, has been prepared
* B. t. u. is a term made use of by engineers to express a certain amount of heat. It
is an abbreviation of “British thermal unit.” One B. t. u. is the amount of heat required
to raise the temperature of one pound of water one degree Fahrenheit. If a coal has a
heating value of 14,000 B. t. u., there is sufficient heat in one pound of it to raise 14,000
pounds of water one degree Fahrenheit.
18
ILLINOIS ENGINEERING EXPERIMENT STATION
to show the theoretical value of coals of different heating or B. t. u.
values at various prices per ton.
It should be understood that the purchase of coal on the B. t. u.
basis does not insure a maximum evaporative value from the fuel, be-
cause a high-grade coal carelessly fired may give poorer results than
a low-grade coal carefully fired. In other words, the B. t. u. value
of a coal is simply an indication of what should be obtained with care-
ful firing and the person who furnishes coal of a high B. t. u. value
cannot be held responsible for poor results obtained from that coal
through improper use. It should also be remembered that while the
B. t. u. value shows the chemical composition, it indicates nothing with
regard to the physical properties of the coal, and these properties may
be equally as important as the chemical properties in their effects upon
firing, storing, and transportation.
6. Storage of Coal . — The storage of a certain amount of coal by
every power plant is both desirable and essential in order to insure
continuous operation. Although there is some misapprehension with
regard to the practicability of storing bituminous coal, a study of the
subject based upon the reported experience of more than a hundred
firms and individuals indicates that the difficulties attending storage
are not serious.* These investigations have shown that:
(1) It is practicable and advantageous to store coal, not only
during war times, but also under normal conditions, near
the point of consumption. The practice of storing coal has
the advantage of (a) insuring the consumer a supply of coal
at all times, (b) permitting the railroads to utilize their cars
and equipment to the best advantage, and (c) permitting
the mines to operate at a more nearly uniform rate of produc-
tion throughout the year. The expense of storage may be
regarded as the expense of insurance against shut-downs.
(2) Certain requirements affecting the kinds and sizes of coal
must be observed as follows :
(a) Most varieties of bituminous coal can be stored successfully
if of proper size and if free of fine coal and dust. The coal
must be so handled that dust and fine coal are not produced
* For a more nearly complete discussion of the problem of coal storage, see Bulletin 97
of the Engineering Experiment Station, University of Illinois, entitled “Effects of Storago
Upon the Properties of Coal,” by S. W. Parr, and Circular 6 of the Engineering Experiment
Station, University of Illinois, entitled “The Storage of Bituminous Coal,” by H. H. Stock.
Fig. 2. Chart Showing the Theoretical Value of Coals of Different Heating Values at Various Prices Per Ton
To make a comparison between coals of different B. t. u. values, locate the point on the line representing the B. t. u. value of the coal in question
directly opposite the price involved. Through this point draw a vertical line, and from the intersection of this with the diagonal lines representing
any other B. t. u. value read the comparable price from the price scale at the left. For Example: If a 12,000 B. t. u. coal is offered at $7.10 per
ton, a coal having a heating value of 11,000 B. t. u. will be worth $6.45.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
Price per ton of coa/.
I I I I I I I II I I I I %•>
Cl c ?/ // 0l6Q<L°)SPC2l
20
ILLINOIS ENGINEERING EXPERIMENT STATION
in excessive amounts, and allowed to remain during storage.
Although some coals can be stored with greater safety than
others, the danger from spontaneous combustion is due more
to improper piling of the coal than to the kind of coal stored.
The danger of spontaneous combustion can be very greatly
reduced if not entirely eliminated by storing only lump coal
from which the dust and fine coal have been removed.
(b) Fine coal or slack has sometimes been stored successfully in
cases in which air has been excluded from the interior of the
pile. Exclusion of air from the interior of a pile may be
acomplished (a) by a closely sealed wall built around the
pile, or (b) by very close packing of the fine coal. A pile of
slack must be carefully watched to detect evidences of heat-
ing and means should be provided for moving the coal
promptly if heat develops. The only absolutely safe way
to store slack or fine coal is under water.
(c) Many varieties of mine run bituminous coal cannot be stored
safely because of the presence of fine coal and dust.
(d) Coal exposed to the air for some time may become “sea-
soned” and thus may be less liable to spontaneous combus-
tion because of the oxidation of the surfaces of the lumps.
Experience covering this point, however, is by no means con-
clusive.
(e) It is believed by many that damp coal or coal stored on a
damp base is peculiarly liable to spontaneous combustion, but
the evidence on this point also is not conclusive. It is safest
not to dampen coal when or after it is placed in storage.
(3) The sulphur contained in coal in the form of pyrites is not the
chief source of spontaneous combustion, as was formerly
supposed, but the oxidation of the sulphur in the coal may
assist in breaking up the lumps and thus may increase the
amount of fine coal, which is particularly liable to rapid
oxidation. The opinion is wide-spread that, if possible, it is
well for storage purposes to choose a coal with a low sulphur
content.
(4) In piling coal for storage the following conditions should be
observed :
(a) To prevent spontaneous combustion, coal should be so piled
FUEL ECONOMY IN HAND FIRED POWER PLANTS
21
that air may circulate through it freely and thus may carry
off the heat due to oxidation of the carbon, or it should be
so closely packed that air cannot enter the pile and stimulate
the oxidation of the fine coal.
(b) Stratification, or segregation of fine and lump coal, should
be avoided, since an open stratum of coarse lumps of coal
may provide a passage or flue for air to enter and come in
contact with the fine coal, and thus to oxidize it and start
combustion.
(c) Coal can be stored with greater safety in piles not more than
six feet high than in piles of greater height since the coal
is more fully exposed to the air in low piles, the superficial
area of the pile in relation to its volume being greater. The
coal pile should preferably be divided by alleyways so as to
facilitate the rapid removal of the coal in case of necessity
and so that an entire pile may not be endangered by a local
fire.
(d) The practice of ventilating coal piles by means of pipes in-
serted at intervals has not proved generally effective as a
means of preventing spontaneous combustion in storage piles
in the United States and it is not advised. Such practice is,
however, reported to have been successful in certain parts
of Canada.
(e) Coals of different varieties should not be mixed in stor-
age, because a single variety of coal which has a tendency
toward spontaneous combustion may jeopardize the safety
of the entire pile.
(f) Storage appliances and arrangements should be designed
so as to make it possible to load out the coal quickly if neces-
sary. Coal should positively not be stored in large piles un-
less provision is made for loading it out quickly.
(g) Pieces of wood, greasy waste, or other easily combustible
material mixed in a coal pile may form the starting point of
a fire, and every precaution should be taken to keep such
material from the coal as it is being placed in storage.
(h) It is very important that coal in storage should not be
affected by external sources of heat such as steam pipes. The
susceptibility of coal to spontaneous combustion increases
rapidly as the temperature rises.
22
ILLINOIS ENGINEERING EXPERIMENT STATION
(5) The effects of storage on the value and properties of coal may be
summarized as follows :
(a) The heating value of coal as expressed in B. t. u. is decreased
very little by storage, but the opinion prevails that storage
coal burns less freely than fresh coal. Experiments indicate
that much of this apparent deficiency may be overcome by
keeping a thin bed on the grate and by carefully regulating
the draft to suit the fuel.
(b) The deterioration of coal when stored under water is neg-
ligible, and such coal absorbs very little extra moisture. If
only part of a coal pile is submerged, the part exposed to the
air is still liable to spontaneous combustion.
(6) In order to guard against loss in the event of fire in a pile of
stored coal the following facts should be understood:
(a) The best means of preventing loss in stored coal is to inspect
the pile regularly and if the temperature in any part of the
pile rises to 150 degrees F. to prepare to remove the coal from
the spot affected. If the temperature continues to rise and
reaches 175 degrees F., the coal should be removed as
promptly as possible. Temperature readings may be taken
by lowering a thermometer into the interior of a pile through
a pipe driven into it. The common methods of testing for
fires in coal piles are :
(1) By watching for evidences of steaming.
(2) By noting the odor given off.
(3) By inserting an iron rod into the pile and when drawn
out noting the temperature by applying the hand.
(4) By inserting maximum temperature thermometers into
pipes driven into the pile.
(5) By noting spots of melted snow on the pile.
(b) Water is an effective agent in quenching fires in a coal pile
only if it can be applied in sufficient quantities to extinguish
the fire and to cool the mass, but unless there is an ample
supply for this purpose it is dangerous to add any water to
a coal pile.
7. Storage Systems . — Since coal is a comparatively cheap and
bulky product, it must be handled as economically as possible, and also,
FUEL ECONOMY IN HAND FIRED POWER PLANTS
23
unless it is to be used in the form of screenings, in a way to produce a
minimum of breakage.
The ordinary power plant is frequently limited in the choice of a
storage system by a lack of available space and by the fact that ex-
pense must be kept at a minimum, but it should be recognized that
provision for storage may be counted as an insurance against inter-
rupted operation. The storage may be temporary or permanent, that
is, the coal may be stored for use within a comparatively short time
or it may be stored with the expectation that it will remain in storage
for a considerable period to serve as a reserve in case of an emergency,
the current daily supply being used as received.
At hand fired power plants coal is usually stored by dumping
or shoveling from a car or cart upon a pile or into a bin or bunker, or
merely by dumping upon the ground. From such storage piles coal
is shoveled directly into the furnace or, if the pile is at some distance
from the furnace, carried by wheelbarrow or conveyor to the furnace.
Trestle storage involves the dumping of the coal directly upon
the ground or into a bin from cars on an elevated trestle. Although
simple in construction and low in first cost, trestle storage produces
excessive breakage and unless drop-bottom or dump cars are available
the cost of unloading is high.
The cost of storing and reclaiming coal from storage by manual
labor varies from 15 to 64 cents.*
WARNING: — Special emphasis is laid upon the fact that safety
in the storage of coal depends upon a very careful and thorough con-
sideration of and attention to the details referred to in the foregoing.
Lack of attention to these details and lack of care in handling will in
many cases result in losses due to dangerous fires. Do not undertake
to store coal until you are sure you know how to do it properly and
safely.
* Stoek, H. H„ “The Storage of Bituminous Coal.” CJniv of 111
6. 1918.
Eng. Exp. Sta., Cxrc
24
ILLINOIS ENGINEERING EXPERIMENT STATION
III. The Combustion of Fuel and The Losses
Attending Improper Firing
8. Principles of Combustion —The combustion of coal in a fur-
nace is essentially a chemical process. The combustible in coal con-
sists of carbon,* hydrogen and sulphur. During the progress of com-
bustion these elements unite with oxygen to form carbon dioxide,
steam, and sulphur dioxide respectively. The air, which furnishes the
oxygen for this process, consists of a mixture of 21 per cent by volume
of oxygen and 79 per cent of nitrogen. Oxygen is the active element
as affecting combustion, the nitrogen being inert and taking no part
in the process.
When combustion takes place, heat is given off. For every pound
of carbon burned to carbon dioxide, 14,600 B. t. u.f are released. In
the same way, for every pound of hydrogen burned to water vapor
62,100 B. t. u. are liberated. One pound of sulphur in burning to
sulphur dioxide gives up 4,000 B. t. u. The heat liberated serves to
raise the temperature of the fuel bed, of the surrounding surfaces,
and of the products of combustion. Part of the heat delivered to the
water in the boiler is transmitted by direct radiation from the hot
surfaces, and the rest is absorbed by conduction from the gases, thus
lowering their temperature. The heat carried away by the gases after
they have left the heating surfaces of the boiler represents the loss
entailed in the process. The extent of this loss is, of course, indicated
by the temperature of the gases leaving the heating surfaces. The
nitrogen, as stated, takes no part in combustion, but on the contrary
it absorbs a certain amount of heat in having its temperature raised
from that of the air to that of the gases leaving the fire. Consequently,
the temperature of the other gases does not reach so high a point as
would be possible if oxygen alone could be introduced into the fuel
bed. When the nitrogen leaves the heating surfaces with the rest of
the gases, it carries away part of the heat released by the fuel, and,
* The chemical symbols used for these elements and compounds are as follows: Carbon
(O), hydrogen (H), sulphur (S), oxygen (O), carbon dioxide (C0 2 ), steam (H 2 0), sul-
phur dioxide (S0 2 ), nitrogen (N), and carbon monoxide (CO). Carbon dioxide is variously
known as carbonic acid gas and as black damp, while carbon monoxide is known as carbonic
oxide and as white damp.
t For definition of B. t. u. see foot-note on page 17.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
25
therefore, represents loss. This loss amounts to about 0.24 B. t. u.
per pound of nitrogen per degree F.
In the process of combustion, one pound of carbon unites with
2.67 pounds of oxygen to form 3.67 pounds of carbon dioxide. Since
the composition of the air is 77 per cent nitrogen and 23 per cent
oxygen by weight, 2.67 pounds of oxygen requires 11.6 pounds of air.
One pound of hydrogen in burning unites with eight pounds of
oxygen to form nine pounds of water vapor. In this case the amount
of air required is 34.8 pounds.
One pound of sulphur in burning unites with one pound of oxygen
to form two pounds of sulphur dioxide. The air required is 4.35
pounds.
It is evident that if the weights of carbon, hydrogen, and sulphur
in one pound of coal are known, the air necessary to burn completely
one pound of coal amounts to 11.60 times the weight of carbon, plus
34.80 times the weight of hydrogen, plus 4.35 times the weight of sul-
phur. This is about 12 pounds of air per pound of coal.*
Every cubic foot of oxygen used in the combustion of carbon is
replaced by one cubic foot of carbon dioxide. For this reason, the
percentage by volume of C0 2 in the flue gas is an indication of the
amount of excess air present in the furnace. A given amount of C0 2
will be formed for every pound of carbon burned. If just enough air
is used for the complete combustion of the carbon, the oxygen will be
replaced by the C0 2 formed and the latter will be the same percent-
age, by volume, of the mixture as the original oxygen. If twice as
much air as necessary is used, the same volume of C0 2 will be formed
as before, but this will replace only one half of the oxygen used, and
hence its percentage of the mixture will be only one half as great as
in the former case. These relations are somewhat affected by the fact
that hydrogen and sulphur are present, but their amounts are too
small to have an important bearing on the result.
If less than enough air is furnished for complete combustion, part
of the carbon in the coal, instead of being burned to carbon dioxide,
will form carbon monoxide. Under these circumstances the amount
of heat liberated per pound of carbon, instead of being 14,600 B. t. u.
will be only 4,500 B. t. u. The difference, 10,100 B. t. u., will represent
the heat lost for every pound of carbon burned to carbon monoxide.
* Any air above the chemical requirement for complete combustion is known as excess
air.
26
ILLINOIS ENGINEERING EXPERIMENT STATION
Since combustion is the result of the union of oxygen with the
various elements in the coal, and with the combustible products formed
in the fuel bed, it necessarily follows that in order to have complete
combustion, each particle of these elements must come into contact
with a sufficient amount of oxygen. To insure this contact between
the particles of the combustible and oxygen, it is necessary to supply
an amount of oxygen, and hence of air, somewhat in excess of the
amount theoretically required; otherwise carbon monoxide will be
found in the escaping gases. This excess acts as a further diluent,
and represents loss, just as the nitrogen in the air represents loss. A
compromise must, therefore, be made. The correct amount of air to
be used is obtained when the loss due to heating the excess just bal-
ances the loss due to the carbon monoxide appearing if the excess is
reduced. For best operating conditions it is found necessary to use
between 30 and 40 per cent of excess air.
Before the union of oxygen and the elements in the coal can take
place with sufficient rapidity to be of any practical use, it is necessary
that -the whole mass be brought to a temperature known as the igni-
tion temperature. If, because of any condition, such as contact with
the cold surfaces of the tubes or the inrush of an excessive amount of
cold air, the temperature of the gases is lowered below the ignition
point before combustion is complete, combustion will cease and part
of the fuel will escape from the furnace unburned. This, of course,
represents a loss.
The three fundamental conditions necessary for complete and
smokeless combustion may now be stated as follows :
(1) A sufficient amount of air must be supplied.
(2) The air and fuel must be intimately mixed.
(3) The mixture must be brought to the ignition temperature
and maintained at this temperature until combustion is
complete.
9. Significance of Draft . — The technical meaning of the term
“draft” does not refer to the motion of the air or gases, but merely
defines the difference in pressure existing between the air outside and
the gases inside the furnace (See Figs. 3 and 13). If there is an
opening into the furnace and the draft is maintained, air will be forced
in from the outside. The amount of air which passes will depend
upon the size of the opening and the resistance offered to the flow;
FUEL ECONOMY IN HAND FIRED POWER PLANTS
27
Fig. 3. Manometer Tube for Showing the Difference in Pressure between
the Outside and the Inside of a Boiler Wall
hence the weight of air passing through the fuel bed from the ash-
pit for any given draft over the fire will depend upon the thickness
of the bed, the size of the pieces of coal, and the condition of the bed.
In any case, the combustion of a given amount of coal always requires
a definite amount of air. Since for large pieces of coal the voids in
the fuel bed are correspondingly large, a fuel bed of given thickness
will present less resistance to the passage of air than a bed of finer
coal of the same thickness. Hence it requires less draft with large
coal than with fine coal to pass a given amount of air through the fuel
bed. It is, however, advisable to use a thicker bed with large coal in
order to close up the holes. This in turn will make it necessary to in-
crease the draft to a point about equal to that used for fine coal, al-
though the exact relation existing between thickness of bed, draft, and
load on boilers must be determined by experiment in each case.
In view of facts developed in a recent investigation,* special atten-
tion should be given to the regulation of the overdraft in hand fired
furnaces, since, contrary to the generally accepted belief, it is shown
* “Combustion in the Fuel Bed of Hand Fired Furnaces,” by Henry Kreisinger, F.
K. Ovitz, and C. E. Augustine, Tech. Paper No. 137 U. S. Bur. of Mines, Washington, D. C.
The investigation reported in this publication discloses the following facts: “The current
of air in passing through a uniform fuel bed without holes will have all its oxygen used
within the first four inches from the grate. The rate of combustion therefore varies
directly with the rate at which air is forced through a uniform fuel bed. The completeness
of combustion is determined by mixing volatile gases with air in the space above the fuel
bed. The reactions here are between two gases rather than between a solid and a gas, and
the space required for this process is much greater. If only the theoretical amount of air is
here available, the mixing may not be sufficiently perfected before the gases have passed
out of the combustion space. Hence it is necessary to supply an excess amount of air over
the fuel bed. This air must be introduced through openings above the fuel bed or come
in through holes in the fire.”
28
ILLINOIS ENGINEERING EXPERIMENT STATION
that most of the excess air is admitted into the combustion chamber
above the fuel bed instead of through the fuel bed.
Every boiler should be equipped with two draft gages, one con-
nected directly into the space over the fire (Fig. 4), and one connected
Fig. 4. Sketch Showing the Correct Method of Connecting Draft Gages
both into the space over the fire and into the gas passage below the
damper, giving the drop in pressure through the tubes and baffling.
The operation of the boilers should be controlled by means of the draft
over the fire. The draft necessary to carry any given load and the
corresponding proper thickness of fuel bed with the grade of coal used
should be determined. With everything in good shape and no leaks
in the setting and a given draft over the fire, there should be a definite
loss of draft through the setting, or differential draft as it will herein-
after be called. When the damper is opened to increase capacity, both
the furnace draft and the differential draft will increase. Assuming
that the correct thickness of fuel bed is being used, an increase in the
differential draft reading over the normal reading with the given
FUEL ECONOMY IN HAND FIRED POWER PLANTS
29
furnace draft indicates that there are holes in the fuel bed or that the
tubes have become clogged with soot and ash. A decrease in the dif-
ferential draft indicates that the fuel bed is dirty and that the resist-
ance is greatly increased by ash or clinker, or that some of the baffling
is down, causing a short circuit of the gases.
10. Significance of C0 2 in the Flue Gases . — A study of the
amount of carbon dioxide (C0 2 ) in the flue gases affords the only
practical means of obtaining a knowledge of conditions existing with-
in the furnace on the basis of which correction or regulation to obtain
the best results may be made. The importance of making C0 2 determi-
nations, therefore, warrants a discussion of the methods by which
these determinations may be made. Every plant should be equipped
with some form of C0 2 analyzing apparatus and the fireman or other
employe taught to use it. Since it is comparatively inexpensive, the
outlay will be returned many times by the gain in efficiency and the
consequent saving of fuel. For this purpose an Orsat apparatus or
some of its modified forms should be used. The complete Orsat ap-
paratus provides a means of analyzing for carbon dioxide, oxygen, and
carbon monoxide, but since the C0 2 values give a sufficiently accurate
indication of the amount of excess air passing through the fire, the
analysis for the other two gases may be omitted and the apparatus
used in its simplest form, as shown in Fig. 5. This consists merely of
of a pipette, h, to hold the solution (potassium hydroxide), a measur
ing burette, e, of 100 cubic centimeters capacity, a leveling bottle, /,
containing water, and an aspirating bulb, m. The solution may be
made by mixing equal weights of potassium hydroxide (KOH) and
water. In the absence of this chemical, concentrated lye may be
used.
In using the C0 2 apparatus, the liquid in the pipette, h, is first
brought to the mark, o, just below the cock, d. This can be done
by lowering the leveling bottle, f, after which the cock, d, should be
closed. The 3-way cock, c, is then opened to the burette, e, and to
h, and by raising the leveling bottle, /, the water in the burette is
brought to the mark, g, and the cock, c, closed to the burette, and
opened through a and h. The aspirating bulb, m, is now worked,
drawing gas from the sample tube, n, in the setting and forcing
it out through h. When sufficient gas has been forced through to
clean out the air and dead gas from the sample tube, the cock, c, is
30
ILLINOIS ENGINEERING EXPERIMENT STATION
turned so that b is closed, and a is in communication with the
burette, e. The sample is then pumped into the burette, thus driv-
ing the water into the leveling bottle and more than filling the
burette. The leveling bottle is then raised until the water in the
burette stands exactly at 100 cc., the rubber tubing between the
leveling bottle and the burette is clamped between the thumb and
finger so that no change in the level at 100 cc. can take place and the
cock, c, momentarily opened to the atmosphere through b and then
closed to the burette. If this has been done correctly, when the two
FUEL ECONOMY IN HAND FIRED POWER PLANTS
31
surfaces, e and /, are brought to the same level, e should stand at
100 cc. An alternate method of obtaining 100 cc. at atmospheric
pressure is to have the 3-way cock open through a to c and closed to
b. The gas may now be forced out through the liquid in the leveling
bottle, /. The water -at / and e may now be brought to the same
level and the cock closed to the burette, e. The cock, d, is now
opened and the gas driven into the pipette, h, by raising the level-
ing bottle. It should be driven back and forth between the burette
and pipette several times, and then the liquid in the pipette brought
back to the mark, o, and the cock, d, is closed. The surfaces, / and
e, are again brought to the same level, and the amount of C0 2 in
the gas sample is read from the burette at e. This operation is
easily performed and a fireman of ordinary intelligence can analyze
a sample in about two minutes.
There are several precautions which should be observed in tak-
ing samples. There must be no leaks in the rubber tubing or con-
nections. If air leaks in during the analysis, it invalidates the
result. The sole object in making an analysis is to determine
what the fire is doing at the time the sample is taken; hence the
apparatus should be hung on the setting at a point as near as possible
to the point where the sample is taken in order to reduce the amount
of piping and rubber tubing between the sampling tube and the
analyzer, and to insure a sample representative of conditions at
the time. If the sample is conveyed through tubes of considerable
size and length, as is usually the case with a C0 2 recorder or even with
a C0 2 indicator, the analysis is made from 5 to 15 minutes after the
sample is taken. Thus a hole in the fire may be disclosed by the
analyzer 5 or 10 minutes after its initial occurrence and even after its
disappearance by filling up. The C0 2 recorder, therefore, is useful
for giving an idea of the average operation over a long period, but
is not satisfactory as a means of determining the proper relation
between load, draft, fuel bed thickness, and other conditions. The
determination of such relations involves simultaneous readings.
Precautions must be observed in inserting the sampling tube.
An elaborate sampling apparatus used in the hope of obtaining an
average sample is not to be recommended. Such apparatus consists
mainly of a double tube arrangement having a series of small
holes drilled into the tubes, the tubes extending across the gas
passage. These do not accomplish the desired result, however, be-
32
ILLINOIS ENGINEERING EXPERIMENT STATION
cause the holes become clogged with soot and ash making it impossible
to know the point in the flue from which the sample is drawn.
Another reason why these tubes are not reliable for procuring an
average sample lies in the fact that the gas stream varies across the
flue in all directions, while the sampling tubes can at best give an
average in only one direction. In order to obtain an exact average
Fig. 6. Sketch Showing the Proper Location for Gas Sampling Tubes to
Avoid Damper Pockets for Both Front and Rear Take-off
Point 2 is in the center of the main gas stream and indicates correct position of the sampling
tube. Points 1 and 3 show locations of pockets in which representative samples
cannot be secured.
it would be necessary to fill the flue with a network of sampling
tubes so arranged that each might take a quantity of gas propor-
tional to the velocity of the stream at its point of sampling. For
all practical purposes, therefore, it is best to take a sample through
the end of a straight tube consisting of a piece of ^-incli pipe so
that the point of sampling may be known with accuracy. A sample
taken from the center of the main gas stream where the gas lias
FUEL ECONOMY IN HAND FIRED POWER PLANTS
33
the greatest velocity has been found to yield an accurate indication
of the condition of the fuel bed at the time of sampling, slight vari-
ations in the condition of the fire being reflected immediately in
the sample. In placing the tube, care should be taken to have the
end in the center of the main gas stream at point No. 2, Fig. 6, and
not in any of the dead gas pockets as indicated by points 1 and
3. Otherwise low C0 2 values not representative of the actual con-
ditions will be obtained. The tube should be inserted at the point
where the gases leave the heating surfaces of the boiler for the last
time as indicated by point 2 in Fig. 6, and not further out in the
flue. An iron tube should not be used if the temperature at the
point of sampling is sufficient to raise it to a red heat, because the
character of the sample may be affected by part of the oxygen in
the sample uniting with the red hot iron. A small cotton filter, con-
tained in a glass tube, should be inserted between the sampling tube
and the aspirator bulb. In using the apparatus shown on page 30,
care should be taken to prevent a draft of cold air striking the burette
during a reading. A material change in temperature during a reading
will invalidate the result.
11. Losses of Heat Value . — The losses in the boiler plant may
be divided into two classes:
(1) Those due to the loss of green coal in handling.
(2) Those resulting in the process of combustion. Losses
of the first class are usually small and easily detected ; hence
they will not be discussed further.
The principal losses are those entailed in the process of com-
bustion. These may be divided into the following classes :
(1) Loss due to excess air and air leakage through the setting.
(2) Loss due to combustible in ash.
(3) Loss due to C0 2 formed.
(4) Loss due to soot on the tubes.
(5) Loss due to moisture carried in with the coal and air.
(6) Loss due to heat carried out by the escaping gases.
(7) Loss due to radiation.
Losses included under classes 1 to 4, inclusive, are largely pre-
ventable, while those under classes 5, 6 and 7 are more or less inevit-
able, although they may be reduced to a minimum with proper care.
34
ILLINOIS ENGINEERING EXPERIMENT STATION
Excess Air and Air Leaks
Losses due to excess air and to air leaks are discussed together
because they may both be detected by the same means, i. e., by analysis
of the flue gas. Under the head of excess air may be included all air
which goes through the combustion zone in excess of the amount
required for perfect combustion. Air leakage includes all air going
through holes in the setting and other places besides the fuel bed.
The space inside the average boiler setting is at less than atmos-
pheric pressure; hence if there are any openings in the setting, air
will leak through from the outside. This cold air not only takes no
part in the combustion, but its temperature must be raised to that
of the rest of the gas, a process which requires heat and lowers the
temperature of the other gases. Some of this heat is given back to the
water in the boiler, but all that indicated by the difference between
the temperature of the flue gas and that of the air in the boiler room
represents a dead loss. This is also true of the excess air carried
through the fuel bed. While these losses cannot be detected with the
naked eye, like that due to green coal in the ash, they are by far the
most serious of all losses occurring in the average plant.
Leaks in the setting may occur in the metal work around doors
and joints as well as in the brickwork. When leaks are found they
should not only be stopped with asbestos or stove putty, but should
be calked with waste or asbestos fiber soaked with fireclay in such
manner as to prevent cracking off or falling out as soon as dry.
The last of the leaks may best be found by building a smoky fire
and shutting the damper. Smoke may then be seen to issue where-
ever there is a leak. When the setting has been made as tight as
possible, air will still seep in because the bricks and the mortar are
porous. This leakage may be reduced to a minimum by tacking metal
lath to the setting and applying a coat of plaster one inch or so in
thickness made of a mixture of about 80 per cent magnesia and 20
per cent old magnesia pipe covering. In order to secure a satisfac-
tory surface 85 per cent magnesia should be mixed with cement to
form a thin grout, spread on the surface, troweled to a smooth finish,
and painted. This makes a good lagging not affected by temperature
changes and also serves to reduce the radiation loss listed under class
(7). If the setting is too hot to permit touching it with the hand
without discomfort, the radiation loss is excessive.
After the setting has been made absolutely tight it will pay to
FUEL ECONOMY IN HAND FIRED POWER PLANTS
35
give attention to the excess air loss, but it is well to emphasize
that the former should be done first. There exists a very definite
relation between capacity, draft, fuel bed thickness, and air passing
through the fuel bed with a given grade of coal. For Illinois coal
a draft of approximately .01 inch of water is required to burn one
pound of coal per square foot of grate surface per hour. This ratio
is slightly increased for rates of combustion above twenty-five pounds
of coal per square foot per hour.
In order to determine these relations in any given plant, a time
should be chosen when the load on the boilers will remain constant
for several hours. The fire should be clean, of uniform thickness,
and free of holes, and the surfaces of the tubes should be free of soot.
A draft and fuel bed thickness sufficient to maintain the load without
loss of pressure should then be chosen. Simultaneous readings of the
draft and analyses of the flue gas should now be made as rapidly
as possible and repeated at brief intervals to insure permanence of
conditions, and a watch should be kept on the fire to see that holes
do not develop. Care must be taken not to open the furnace doors
during a reading. Records should be kept of the drafts, C0 2 , and
fuel bed thickness. Thickness of fuel bed should then be varied and
the draft adjusted to carry the load without pressure drop, or
without blowing the safety valves. When sufficient time has elapsed
to allow conditions to become constant, another set of readings
should be taken. If too thin a fuel bed were used at the start, it will
be found on comparing the readings that as the thickness of the fuel
bed is increased, the draft increases, and the percentage of C0 2 also
increases. Finally a point will be reached at which the C0 2 does not
increase further as the thickness of the fuel bed and the draft increase.
The draft and fuel bed thickness to give this C0 2 reading represent the
proper values for the given load on the boiler, under which the suggested
changes in operating conditions have been made. This process should
then be repeated for a number of different loads on the boiler. Upon
doing this it will be found that with a given thickness of fuel bed,
certain more or less well defined limits of draft over the fire will
give a maximum C0 2 reading. The draft then becomes the key for
controlling the whole situation. If the load on the boiler is such as
to require drafts between certain limits, then the thickness of fire
which should be used is immediately known, provided there are no
holes in the fire and the tubes and fire are clean. These latter
36
ILLINOIS ENGINEERING EXPERIMENT STATION
conditions will be indicated by the differential draft gage, Fig. 4,
readings of which should also have been taken during the tests when
the tubes were known to be clean and the fire in good condition. A
table or chart should be laid out for the use of the fireman, which,
as soon as the approximate draft necessary to maintain boiler pres-
sure is known, gives the thickness of fire to be carried and the cor-
responding differential draft gage reading. If the furnace draft
and thickness of fire are correctly maintained and the differential
is then too low, it indicates either that the fire is dirty or that some
of the baffling has fallen. A too high reading of the differential
indicates that there are holes in the fire, or that soot is clogging the
passages through the tubes.
The thickness of the fire should not be left to the judgment
of the fireman, but definite marks should be placed on the inside
door liners, or at some points where they may be seen. In any
case, it should be thoroughly understood that the cooperation of
the fireman is necessary, and unless the fires are kept clean, and
the firing is done in such manner as to maintain a uniform fuel bed
without holes the other precautions suggested are useless.
Since air leakage through the setting tends to increase as the
draft increases, it is good policy to run on the mi minium draft which
will carry the load without pressure drop. The C0 2 readings are a
direct indication of the total loss due to both excess air and to air
leakage when taken just below the damper. A curve # is presented
in Fig. 7 which has been plotted from flue gas readings when
burning Illinois slack on a chain grate. It gives the percentage of
excess air represented by different percentages of C0 2 in the gas.
From this curve it may be seen that 12 per cent of C0 2 represent
about 35 per cent excess air. This is the maximum C0 2 reading
obtainable with this coal when burned on grates of approximately
93 per cent grate efficiency without danger of incomplete combus-
tion and a corresponding loss due to carbon monoxide. If this value
is not exceeded, it will not be necessary to analyze for carbon monox-
ide and the determination for C0 2 is sufficient.
It has been mentioned in a preceding paragraph that the proper
position for the sampling tube is at a point where the hot gases leave
the heating surfaces for the last time. The reason for this may now
* Kratz., A. P., “A Study of Boiler Losses.” Qniv. of 111. Eng. Exp. Sta., Bui. 78,
p. 33, 1915.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
37
be made clear. The C0 2 in the sample at this point is an indication
of all the excess air and leakage which has diluted the gas and
absorbed heat which should have gone into the water. After the
gases leave the heating surfaces there is no longer any chance of
heat being absorbed and it is not important, so far as efficiency is
. concerned whether it is lost in a small amount of gas at a high tem-
Percent excess a/r
Fig. 7. Curve Showing Relation between Excr Air and C0 2 in Flue Gas
(See “A Study of Boiler Losses,’ ’ Univ. of 111. F Exp. Sta., Bui. 78, 1915.)
perature, or in a large amount of air and g t a lower temperature.
Any air leakage beyond this point, there l-. e, does not lower the
efficiency. The harmful effect, however, h shown on the capacity.
It not only adds its own bulk to the gases tl ? chimney must carry,
but also, due to its cooling effect on the ho ^ases, lessens the draft
available to produce the flow. In many case , the mere stopping of
the leaks in setting and breeching has enable ' toilers to carry over-
load, while previously it had been impossible i. oAain rated capacity.
The draft should be controlled by meaiu- of the dampers at the
flue, and not by the ashpit doors. Closing the ashpit doors prevents
air from going through the fuel bed, causes cum er and hot grates,
38
ILLINOIS ENGINEERING EXPERIMENT STATION
and also increases the air leakage loss. Each boiler should be
equipped with a separate damper and the position of maximum and
minimum damper opening should be determined. The damper should
then be operated between these limits. The points of maximum and
minimum opening should be found by noting the reading of the draft
gage while the damper is moved from one extreme position to the
other. These points of maximum and minimum draft gage reading
may not coincide with the points at which the damper is mechani-
cally open or closed. A position will usually be found at which the
draft is maximum, and a further opening of the damper will not
change the reading. It may also be found that the damper can be
opened quite appreciably before the draft gage begins to read.
In many plants of large and medium size automatic draft control
has proved economical and it is also of advantage in maintaining
constant steam pressure. If automatic control of the draft is used,
it is important to have the damper adjusted for the range of travel
determined by experiment as suggested, so that the draft will be
proportional to the opening. An automatic damper regulator, when
used, should preferably be of the type which responds to small
decreases or increases in steam pressure by causing a corresponding
movement of the damper, and not of the type which either com-
pletely opens or completely closes the damper in response to small
decreases or increases of pressure. If there are several boilers in
the plant, the best plan is to adjust the individual dampers so that
each boiler is carrying its share of the load under the most economi-
cal draft, and then, if the total load changes, to regulate with a
master damper in the main flue.
Loss Due to the Presence of Combustible in the Ash
The loss due to partly burned coal in the ash should not, with
very careful handling of the fire, exceed more than about three per
cent of the heat value of the coal. Excessive carbon in the ash with
stoker fired furnaces usually indicates too rapid feed for the rate
of combustion used. In hand fired furnaces it may indicate that the
grate openings are too large for the size of coal used or that the fire
is worked too much, or both. So far as possible the fire should be
operated without much working except at times of cleaning. Too
much working does two things; first, it shakes the green coal down
into the ash and allows it to pass through the grate bars, and
FUEL ECONOMY IN HAND FIRED POWER PLANTS
39
secondly, it brings the ash up into the hot part of the fire where it
fuses and causes clinker. Partly burned coal is fused in with the
clinker and is lost when the clinker is removed, and the coal which
is shaken through the grates during the additional working required
to remove the clinker adds further to the loss. The possible loss
due to firing green coal into holes in the fire and thus permitting it
to pass through the grate has not been considered in detail because
it is obvious that the holes should be filled up by leveling the fire
before adding a fresh charge of green coal. In working a fire, it should
be sliced from the bottom in such a manner as to avoid or minimize
the possibility of forcing ash up into the fuel bed. This applies to
stoker firing as well as to hand firing.
Loss Due to the Presence of Carbon Monoxide
in the Flue Gases
Carbon monoxide is formed if too thick a fire or an insufficient
draft is used. With central bituminous coals there is little possibility
of large loss from this source if the C0 2 reading is not more than 12
per cent.
Loss Due to Soot
The largest part of the loss due to smoke does not result from
the fact that the particles of carbon floating in the gas stream have
passed out before giving up their heat value, but it comes from the
deposit of soot on the tubes. The actual heat value of this deposit of
soot is small when compared with the amount of coal fired in pro-
ducing it, but its power of preventing the heat in the gases from
reaching the tubes and being absorbed is a factor of considerable
importance. Soot makes an excellent heat insulator, about five times
as effective as asbestos. Under normal working conditions and with
the normal amount of air, the temperature of the gases leaving the
boiler should be somewhere near 550 degrees F. If they leave at a
much higher temperature and the fire and drafts are normal, it
signifies that the tubes need blowing. The soot deposited on the
heating surfaces is keeping the heat in the gas from reaching the
water and the gases consequently are not cooled. Where automatic
blowers are installed the tubes should be blown every four or five
hours. In all cases they should be blown at least once for every shift.
A pyrometer placed at the point where the gases leave the tubes
for the last time will give a fairly good indication of their condition,
provided of course that low temperature is not due to excess air.
40
ILLINOIS ENGINEERING EXPERIMENT STATION
Loss Due to Moisture in the Coal and Air
The loss due to moisture in the air is very small and need not be
considered. That due to moisture in the coal may be larger. The
coal may carry 13 or 14 per cent of moisture, and the heat required
to evaporate this must be furnished by the coal itself, thus decreasing
the amount available to heat water in the boiler. Fine coal tends to
pack if fired dry. This prevents the proper amount of air getting
to the fuel, and results in the formation of carbon monoxide and in
cold fires. Sometimes very dry coal burns out unevenly, and will
not stay on the grates without allowing holes to form. For these
reasons, it is advisable to wet down the smaller sizes of coal just
before firing because the other losses mentioned are greater than
that due to the water. With larger sizes wetting is not necessary and
is not advisable. This, however, must be decided for each individual
plant. In no case should more water be added than is absolutely
necessary.
Loss Due to Heat in the Escaping Gases
Every pound of flue gas passing up the stack represents a loss
of about .24 heat units per degree F. above the temperature of the
steam in the boiler. This loss cannot be entirely eliminated. For
plants operating on natural draft, a temperature of about 500 degrees
F. is required in the stack to produce the draft necessary to operate
the boilers at full capacity. An average of 550 degrees F. is good
practice. For forced draft and four-pass boilers, it may run lower
than this temperature. An indicating pyrometer should be used on
each boiler and if the temperature in the flue becomes abnormally
high it may be accepted as an indication of an excessive deposit of
soot upon the tubes or of a draft greater than is necessary for the
load.
Loss Due to Radiation
Uncovered surfaces and other surfaces which are too hot to touch
without discomfort represent a serious loss of heat. This loss can be
decreased by covering the setting as previously suggested.
12. Significance of Smoke. — Smoke, depending upon its cause,
may or may not indicate a loss in efficiency. The loss is largely due
to the soot deposit, and not to the heat value of the fine particles
of floating carbon. The three principles of smokeless combustion
FUEL ECONOMY IN HAND FIRED POWER PLANTS
41
have already been stated. The question concerning whether there is
sufficient air for combustion can be answered with the C0 2 analyzer.
If the C0 2 reading is normal and smoke still appears, the trouble is
due either to a faulty mixture of the air and combustible gases, or
to a too small combustion chamber. Increasing the air supply may
decrease the smoke, but it also decreases the efficiency. In this case
smokeless combustion does not indicate high efficiency. If the fire is
hot and there is much oxygen in the gas, together with high carbon
monoxide, the trouble is due to poor mixing of the gas and air over
the fuel bed. Mixing piers or arches will eliminate the smoke which
in this case is an indication of loss of efficiency. If the fire is white
hot, and the C0 2 normal, without any indication of carbon monox-
ide in the gas the trouble is due to a too small combustion chamber.
In most plants this is the cause of smoke, and in such cases it does
not indicate poor furnace efficiency. The loss is due to soot rather
than to smoke.
13. Methods of Hand Firing . — There are two general methods
advocated for hand firing, (1) Coking, (2) Spreading. The first
involves the placing of a considerable amount of green coal on some
convenient part of the fuel bed where the heat will pass into it and
will slowly distil the volatile gases. These gases then mix with air
above the bed and in passing over the white hot bed are burned
before they reach the cold surfaces. The method usually adopted is
to pile the green coal at the front of the bed. After 10 or 15 minutes,
during which the coal has become well coked, this pile is broken up and
spread over the back part of the fuel bed, and a fresh charge is piled
at the front. This method accomplishes satisfactory results so far
as smokeless combustion is concerned, but it does not promote
efficiency. The keynote of efficiency lies in the maintenance of a
uniform fuel bed, while with the coking method of firing the bed
burns unevenly. The bed is usually too thick at the front, and burns
out and develops holes at the rear, and although it is less liable to form
clinker, this practice is not to be recommended as highly as some
form of spreading.
In the spreading method, small quantities of coal are fired at
frequent intervals. In alternate spreading, a thin layer of coal is
spread on one side of the furnace. As the gases distil, they mix with
the air, and the white hot surface on the other side maintains the
42
ILLINOIS ENGINEERING EXPERIMENT STATION
mixture at the ignition temperature. After a period of about five
minutes, when the distillation is complete, another charge of fresh
coal may be spread on the other side of the bed. By this method the
fire may be kept in a more nearly uniform condition than by coking.
Where the coal is spread over any considerable area, however, there
is still a tendency for the resistance at different parts to vary, and
for holes to develop.
The best method is to fire very often and in small quantities.
Holes should not be permitted to develop ; to prevent holes, small
amounts of coal should be placed on the thin parts of the bed. Thin
places may be recognized from the fact that they appear brighter
and hotter than the rest of the bed. This method requires more
attention on the part of the fireman, but it pays in the long run. It
is possible to maintain a uniform bed for long periods without barring
or working the fire. Where the coal is fired in small quantities, the
volume of combustible distilled at one time is small and may be
easily consumed over the hot part of the fuel bed without forming
smoke.
In any case, in hand firing, it is necessary that some auxiliary
air be taken in over the fuel bed for several minutes immediately
after firing. This should be admitted across the fire close to the
surface of the fuel bed, preferably from the front through auxil-
iary dampers in the fire door, which should have an area of at least
four square inches per square foot of grate surface. This admission
of air may be accomplished either automatically or under the control of
the fireman. The automatic device opens small supplementary damp-
ers when the fire door is opened, and then closes them gradually
after the door is shut. The time of closing is usually about three
minutes. The same result can be accomplished by the fireman regu-
lating the dampers in the fire door by hand. In some cases the use
of a steam jet immediately after firing has proved advantageous,
since it not only carries in the air necessary for the combustion of the
volatile gases, but also serves thoroughly to mix the air and gases.
14. Stoker Firing . — It is not within the scope of this discus-
sion to give detailed instructions for the use of different types of
stokers. All the statements, however, concerning tight settings,
determination of proper fuel bed thickness, draft, soot, etc., apply to
stoker firing as well as to hand firing. Most stokers accomplish one
FUEL ECONOMY IN HAND FIRED POWER PLANTS
43
prime requisite for good combustion, i.e., a uniform supply of coal
and air, but they require as intelligent attention as does hand firing.
Stokers should be inspected regularly to see that all ledge plates,
baffles, and other devices designed to decrease air leakage are per-
forming their functions properly. The grate should be kept uni-
formly covered with fuel and the rate of feed adjusted so as to mini-
mize the amount of unburned coal carried over into the ashpit. The
chain grate stoker is probably more generally used for Illinois coal
than any other type, and it has usually proved satisfactory. It is
used largely for burning slack, or screenings, and for this purpose
a fuel bed of about six inches gives the best results, particularly
when natural draft is used. Detailed instructions for the operation
of any particular type of stoker may be obtained from the company
building it.
44
ILLINOIS ENGINEERING EXPERIMENT STATION
IY. Features of Boiler Installation in Relation
to Fuel Economy
15. Boiler Bettings . — The boiler setting consists of the founda-
tion and such parts of the furnace and gas passages as are external
to the boiler shell. The setting must furnish a proper support for the
boiler and at the same time provide the necessary passages for the
products of combustion as well as a pit for the ashes.
Foundation
A good solid foundation resting on a firm footing is absolutely
necessary to insure a boiler setting which will remain tight and free
from any tendency to crack. The depth of the foundation and the
width of the footings necessary for a given installation depend upon
the character of the soil. In the case of good solid soil capable of sup-
porting heavy loads, the excavation need not be made very deep, but
where the ground is soft it is well to excavate the entire space occupied
by the setting and to construct a bed of concrete about two feet thick
upon which the walls may be supported.
When boilers are supported on steel columns, as is usually the
case with water tube boilers and as is desirable for fire tube boilers
also, the footings at the base of the columns must be enlarged, since
with such means of support the loads are concentrated and not dis-
tributed as in the case of horizontal return tubular boilers supported
by a series of lugs resting on the walls of the setting. In general, the
foundation for all types of boilers should be very rigid ; a weak found-
ation will always cause the setting to crack no matter how well the
brick in the walls may be set. Weak foundations may, furthermore,
tend to produce severe stresses at pipe connections to the boiler which
are likely to cause trouble.
Side and End Walls
The side and rear walls are supported upon the foundation and in
the older designs of settings a two-inch air space is generally provided
in these walls. In many of the newer types of setting, however, this
air space has been omitted. As a result of a series of experiments
made by the United States Geological Survey, it has been found that
the two-inch air space provided in the walls of boiler settings has
FUEL ECONOMY IN HAND FIRED POWER PLANTS
45
practically no effect in preventing the flow of heat from the interior
of the setting. As a matter of fact the radiation losses for a wall with
an air space are greater than those for a solid wall. In order to
strengthen the side walls, buck-stays held together by long bolts are
used. The furnace, the bridge wall, and all parts of the side and rear
walls including the back arch which are exposed to the hot gases must
be lined with high grade fire brick capable of withstanding the high
temperatures. The fire brick should be backed with hard, well burned,
red bricks laid in a high grade mortar. All arches, piers, and wing
walls which may form a part of the combustion chamber should be
made entirely of fire brick.
Settings for Horizontal Return Tubular Boilers
In order to use soft coal economically it is desirable to obtain as
complete combustion as possible. Complete combustion also means
elimination of smoke. To obtain proper combustion sufficient air must
be introduced into the furnace to supply the necessary oxygen. The
air thus introduced must mix thoroughly with the gases given off by
the burning coal and the mixture thus obtained must be kept at a high
temperature until the process of combustion is completed. The old
Fig. 8. Hartford Setting for Return Tubular Boilers
This setting does not satisfy the conditions for smokeless combustion. In fact it is, for
Central Western coals, very unsatisfactory and should not be used.
The setting shown in the above figure is no
longer used or approved by the Hartford Steam
Boiler Inspection and Insurance Co. This com-
pany has made very material changes in the de-
sign of their horizontal return tubular boiler set-
tings in recent years.
m
ILLINOIS ENGINEERING EXPERIMENT STATION
Dimensions of Double -arch Bridgewall Jeff mg for Horizontal
Re turn Tubular Boilers. Dimensions in Inches .
*
~<m
M-
N-
'*'i
to
"“VI
Wb
Wb
>
Wo
7 'N
Wb
<3
NS
"''V
<3
NS
NS
tv
<0
0O
On
Si
N
02
02
02
NS
o>
ov
\l
5
5
5
\
tjj
K
V
NS
o>
53
NOi
Qo
-1^
JY
5
>
ns
to
5
Ay
ta
to
am
ns
'0
t\
Ay
5
V
5
vVN
tx
tx
$
AM
<0
5
CO
5
So
<0
02
02
(\
Sq
cv
ON
on
Ay
02
0;
Oi
>
02
$
jV
*
Ol
ft:
oi
NS
02
5
5
SO
01
02
02
02
NS
02
<0
02
Si
<v
M
02
02
02
>
02
3 ,
N 9
V
NS
02
ON
to
IV
Ay
tv
ov
SO
5
"l*V
>
02
oi
v tM
55
02
0<
Ol
"I'M
ON
02
ns>
of
02
Ol
'1m
NS
V
<\2
Nb
00
°0
°0
IV
Vi
V
3
Ofr
02
<&
02
{0
02
N
"0
02
‘O
no
02
$
o
02
oj!
NS
0|
M-
M;
M-
V
NS
02
£
00
(0
02
"b
Nb
<S
2$
JVi
NS
'0
no
N
Nb
02
r>
2t
3
NO
CD
<0
•D
*
AM
fti
IV
02
o
to
8
<0
<o
s
5?
Ay
<*>
"5
vS
n
M-
to
"A*
$
IV
°b
>
>
N 5 >
>
$
§
$
$
to
-fty
§
Avi
o
NS
$
?!
am
p>
to
Ay
55
<0
NS
N*
NS
On
NS
Oi
02
<0
02
Vh
§1
to
<D
'NJ-j
£
§
NS
N 9
O
NS
NS
NS
NS
N 9
ft!
ft!
8
ft!
8
-
3
$
5
§
NS
NS
ft!
8
§
<3
it
sj
SV
02
V;
vs
5;
N 9
ns
5
NS
So
<$
5
«o
5
Oj
Ol
V-
$
5
NS
NS
NS
ft!
8
N-
<0
Fig. 9. Double Arch Bridge Wall Setting for Smokeless Combustion
FUEL ECONOMY IN HAND FIRED POWER PLANTS
47
standard setting 1 for return tubular boilers (shown in Fig. 8) is fre-
quently used, but it does not satisfy the conditions stated and for this
reason should not be used when smokeless combustion is required. In
recent years several types of settings have been devised which if pro-
perly fired make possible the satisfactory combustion of bituminous
coal.
A type of horizontal return tubular boiler setting which has given
good results with soft coals is shown in Fig. 9. It was originated and
perfected by the engineers associated with the Department of Smoke
Inspection of the City of Chicago and is generally recommended for
boilers operating at a steam pressure of sixty pounds or more. This
setting differs from that illustrated in Fig. 8 in that a series of arches
are constructed over the bridge wall and in the combustion chamber.
A double-arch rests on the bridge wall and on a suitable pier built up
between the bridge wall and a single span deflection arch, the latter
being located from two to three feet back of the bridge wall. The
highest point of this deflection arch is at the elevation of the top of
the bridge wall or somewhat below it. So as to prevent the gases from
passing over the arches bulkheads extending up to the boiler are con-
structed above them.
It is evident from this brief description that the gases in passing
from the grate over the bridge wall are divided into two separate
streams by the central pier supporting the double-arch. In going
through the retorts formed by the double-arch and the side walls of
the setting the gases are thoroughly mixed and at the same time are
subjected to high temperatures. Having passed through the retorts
the gases are compelled to change their direction of travel so as to pass
under the deflection arch back of the bridge wall, thus promoting
further mixing and thereby insuring proper combustion. The setting
is also provided with the usual panel door for the admission of air over
the fire. The steam jets shown extending through the furnace front
are generally considered standard equipment and it is recommended
that they be freely used after each firing.
The arches used in connection with the setting shown in Fig. 9
produce a side pressure on the walls, and in order to prevent bulging
and cracking of the walls additional buck-stays and tie rods should be
installed. The floor of the combustion chamber is subjected to high
temperatures and for this reason should be paved with second-grade
fire brick laid on edge.
48
ILLINOIS ENGINEERING EXPERIMENT STATION
According to Osborne Monnett * the following general propor-
tions should be satisfied in order to obtain satisfactory service with
this type of setting.
(1) The free area through the double-arch above the bridge
wall should be made equivalent to at least 25 per cent of the
grate area.
(2) The area from the back of the bridge wall to the deflection
arch should be at least 45 per cent of the grate area.
(3) The area under the deflection arch should be at least 50 per
cent of the grate area.
For convenience of reference the dimensions indicated in Fig. 9
for various sizes of boilers are given in the table presented with the
illustration. These dismensions were obtained from a report submitted
by the Standards Committee at the eleventh annual convention of the
Smoke Prevention Association.
There are several patented settings in which the gases are main-
tained at a high temperature and are thoroughly mixed by the use of
piers and wing walls in place of the arches shown in the setting of
Fig. 9. Experience seems to indicate that the temperature in the com-
bustion chamber of such settings is sufficiently high to promote proper
combustion, and furthermore it is claimed that they burn coal with
good economy and are cheaper to construct than the double-arch
setting.
Settings for Water Tube Boilers
A large number of hand fired water tube boilers of the horizontal
type designed for the use of soft coal are installed with what is gener-
ally called the standard vertical baffling. This form of baffling compels
the gases to pass across the tubes, thus producing a rather short flame
travel in the first pass and rendering complete combustion impossible.
In order to improve combustion in hand fired water tube boilers of
the horizontal type when burning soft coal, it has been demonstrated
by the Chicago Department of Smoke Inspection that the setting
should be so arranged as to fulfill the following specifications:!
* “Hand Fired Furnaces for Water Tube Boilers — I.” Power, Vol. 40, p. 264, August
25, 1914.
t Ibid.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
49
(1) Some provision must be made so that the bottom row of
tubes will absorb some heat directly from the fire. This is
accomplished by the use of T -tiles, thus exposing the bottom
row of tubes to the fire for a short distance from the front
header.
(2) Over the bridge wall and for some distance back of it a
high temperature zone, through which the gases and air pass,
must be provided. This zone is obtained by using box-tiles
around the bottom tubes. The box-tiles extend from the end of
the T-tiles to a point several feet in front of the back header.
The area provided between the bridge wall and the box-tile
should be made equivalent to 25 per cent of the grate area.
(3) In order that the gases and air will thoroughly mix, a de-
flecting arch is provided a short distance back of the bridge
wall. The distance between the arch and the bridge wall
should be such that the area obtained between them is equiv-
alent to 40 per cent of the grate area. The height of the arch
must be sufficient so as to provide an area underneath it
equivalent to 50 per cent of the grate area.
(4) As in the case of the horizontal return tubular boiler set-
tings, excess air is provided through the panel doors in addi-
tion to a siphon steam jet located above the fire doors.
When water tube boilers are very wide, it may be necessary to
construct the deflection arch mentioned in (3) in two or three spans.
These spans should be supported on suitable piers in order to relieve
the strain on the side walls. In case the area over the bridge wall is
in excess of 25 per cent of the grate area, the desired area may be
obtained by introducing piers upon the bridge wall opposite the spans
in the deflection arch. Due to these piers the gases and air will be
more thoroughly mixed, thus promoting combustion.
In water tube boilers equipped with horizontal baffles it generally
happens that there are parts of certain tubes which are not acted upon
effectively by the gases. This is due to the fact that the gases become
trapped in the corners as shown at A in Fig. 10 and become inert.
Such a condition can be improved with a gain in the efficiency of the
boiler, by providing openings approximately one inch wide in alter-
nate rows of the tile B, Fig. 10.
50
ILLINOIS ENGINEERING EXPERIMENT STATION
One of the most serious defects found in brick settings is air leak-
age. The fire brick used on the interior of the setting must be selected
with great care as the life of the setting very largely depends upon the
quality of these bricks as well as upon the workmanship in laying
them. Generally the arches used in settings cause more trouble than
Fig. 10. Sketch Showing Effects of Baffling and Dampers in Causing
Pockets and Eddies in the Flue Gas Stream
Defects in Settings
any other part of the setting. In some cases arches fail because of
the use of a grade of brick not suited to the purpose, but more fre-
quently failures are due to poor workmanship in laying the bricks. Air
leakage through the setting can be reduced by pointing up the brick
work in the proper manner and by covering the entire setting with an
FUEL ECONOMY IN HAND FIRED POWER PLANTS
51
insulating material, as for example a high grade of asbestos or magnesia
covering. The exposed parts of the shell of horizontal return tubular
boilers and of the steam drums of water tube boilers should be covered
with an 85 per cent magnesia covering two or three inches thick. The
outer surfaces of all insulating materials should be finished off with a
thin coating of hard cement or covered with canvas and painted. If
the walls of the setting are constructed with air spaces these spaces
should be filled with sand or ashes. The baffles on the interior of the
setting should be kept tight so that the gases cannot be by-passed
through the heating surfaces. All steam and water leaks around a
boiler should be stopped immediately since water coming in contact
with heated brick work is likely to cause rapid disintegration of the
brick. The setting should be so constructed that the boiler is free to
expand without affecting the brick work.
52
ILLINOIS ENGINEERING EXPERIMENT STATION
V. Installation Features Affecting Draft
Conditions
16. Stacks and Breechings . — The purpose of a stack is, of course,
to supply air to the fuel which is burning on the grates of the boiler
furnace and then to remove the flue gases which are formed after they
have passed over the boiler surfaces and given up most of their heat
to the water and steam in the boiler. The stack may waste coal if the
fireman allows it to supply too much or too little air, or if he allows
the flue gases to leave the boiler at too high a temperature. Most
stacks supply too much air so that a large amount of heat is carried
away in the unnecessarily large volume of flue gases formed when this
air passes through the fuel bed, where it not only serves to burn the
coal but also takes up heat.
Fig. 11 . An Approved Form of Hinged Damper
The Stack Damper and Its Use
In order to control the amount of air and flue gas passing to a
stack, a damper (Figs. 10 and 11) should be installed at the point
where the flue gas leaves each boiler. This damper should fit tight
FUEL ECONOMY IN HAND FIRED POWER PLANTS
53
and true and should move easily. An approved form of damper, which
is tight fitting, is shown in Fig. 11. It should have a free opening
about 25 per cent greater than the area through the tubes. Long
narrow dampers are to be avoided wherever possible. For water tube
boilers the damper opening should be about 0.25 of the grate area.
The damper must be opened only enough to permit the stack to supply
the right amount of air to burn completely the fuel fired. When the
demand for steam increases, more coal must be burned and the damper
must be opened wider in order to supply more air. The air supply
should not be controlled by opening and closing the ashpit doors,
which should stand wide open practically all the time. If the stack is
not controlled by the damper, it will always exert its full power on the
setting which means that the tendency for air to leak in at any cracks
and joints will be as great at half load as at full load, and even with
the ashpit doors closed this leakage would be unchanged if the stack
damper remained open.
From what has been stated, it is evident that a stack must be cap-
able (at full damper opening) of supplying all the air that the boiler
may require when burning coal at the highest rate (pounds per hour)
necessary for the maximum load. At all other rates of burning coal
the damper must be partly closed, and in many plants, since the stack
is too powerful (supplies too much air) even for the highest rate of
burning coal, the damper must never be fully opened; otherwise too
much air will pass through the grates and fuel will be wasted.
In order that the approximate capacity of a stack may be checked
against the load it should carry, Table 3 has been arranged in con-
venient form for ready reference. Thus, if a certain boiler plant is
burning 2,800 pounds of coal an hour at its maximum capacity and the
stack is 100 feet high, the diameter should be 60 inches,
Table 3 is a modification of William Kent’s stack table and is re-
liable for the ordinary rates of combustion with bituminous coals.
The values in the table give the pounds of coal burned per hour. With
coal of fair grade it is necessary to burn about five pounds per boiler
horse-power, but with low grade bituminous coal it is necessary to
burn from six to eight pounds per boiler horse-power. . For example,
in the boiler plant already considered, burning 2,800 pounds of coal an
hour, a stack 100 feet high and 60 inches in diameter would provide
only for 400 boiler horse-power, if a poor grade of middle western coal
was used requiring seven pounds per boiler horse-power.
54
ILLINOIS ENGINEERING EXPERIMENT STATION
Table 3
Stack Sizes Based on Kent’s Formula
Diameter
Inches
Area
Square Feet
Height
OF STACK IN FEET
Side of Equivalent
Square Stack, In.
Diameter
1 Inches
50
60
70
80
90
100
110
125
150
175
Pounds of Coal Burned per Hour
33
5.94
530
575
625
665
705
745
30
33
36
7.07
645
705
760
815
865
910
32
36
39
8.30
775
845
915
980
1040
1095
1145
1225
35
39
42 _
9.62
915
1000
1080
1155
1225
1290
1355
1445
1580
38
42
48
12.57
1230
1345
1450
1555
1650
1740
1825
1945
2130
2300
43
48
54
15.90
1590
1740
1880
2010
2135
2245
2360
2515
2755
2975
48
54
60
19.64
2000
2185
2365
2525
2680
2825
2965
3160
3460
3740
54
60
66
23.76
2450
2685
2900
3100
3290
3470
3640
3800
4245
4590
59
66
72
28.27
2955
3230
3490
3735
3960
4175
4380
4670
5115
5525
64
72
78
33.18
3500
3830
4140
4425
4695
4950
5190
5535
6060
6550
70
78
84
38.48
4090
4480
4840
5175
5490
5785
6070
6470
7090
7655
75
84
Height
of Stack in
Feet
100
110
125
150
175
200
225
250
Pounds of
Coal Burned
per Hour
90
44.18
6690
7015
7480
8195
8850
9465
10040
10580
80
90
96
50.27
7660
8080
8565
9380
10135
10835
11490
12115
86
96
102
56.75
8695
9120
9720
10650
11500
12295
13045
13750
91
102
108
63.62
9795
10270
10950
11960
12960
13850
14695
15490
98
108
114
70.88
10960
11495
12255
13425
14500
15500
16440
17330
101
114
120
78.54
12190
12785
13630
14930
16130
17240
18285
19275
107
120
126
86.59 •
13485
14145
15080
16515
17840
19070
20230
21325
112
126
132
95.03
14850
15570
16605
18185
19645
21000
22275
23480
117.
132
144
113.10
17770
18630
19865
21760
23505
25130
26655
28090
128
144
156
132.73
20950
21965
23420
25655
27710
29625
31425
33120
138
156
168
153.94
24390
25
575
27270
29870
32270
34495
36590
38565
150
168
“Draft” is in Reality a Pressure
It must be remembered that air enters the ashpit, or rushes
through the open fire door, or through any cracks or crevices in the
setting or breeching because the surrounding outside air is always
FUEL ECONOMY IN HAND FIRED POWER PLANTS
55
heavier than the hot flue gas in the stack and setting, and hence exerts
an inward pressure at all points. The so-called “ draft” over the
grate as shown by a draft gage (Figs. 3 and 4) is an indication of this
difference in pressure or tendency for the outside air to crowd its way
into the furnace and boiler setting. In order to understand why this
tendency exists and why draft is a true pressure and not a suction
\
M
v;
Fig. 12. Isometric Sketch Illustrating the Principle that Light Fluids or
Gases are Pushed Upward when in Contact with Heavier Fluids or Gases
In this case the lighter fluid, oil (shown in red), is pushed up by the heavier fluid, water
(shown in green). The force pushing the oil up the tube is 0.086 pounds per square inch.
refer to Fig. 12. It will be evident that, since the column of water
two feet high weighs more per square inch than a similar column of
oil, the water will push the oil up the tube in the same way that the
56
ILLINOIS ENGINEERING EXPERIMENT STATION
cold outside air pushes through the grates of a boiler furnace and
forces the hot flue gas up the chimney. If there is a fire burning on
the grate the action is continuous, and outside air will continue to
Note: The inward air
pressure aga/nst ttr*
setting at th/s po/nt
is egu/va/ent to the
cotumn(c) on gage board.
See gage No e
Gaqe doard
Draft gages read m inches
Water column a
b
c
d
e
f
g
= Total draft avai/ab/e at damper
- Loss of draft through boiler tubes.
- Draft available at rear arch
= Loss of draft between furnace and '
- Draft over fire in furnace.
- Loss of draft through grates and fuet bed
- Loss of draft through ash pit door opening.
Fig. 13. Sketch Showing Variations in Draft at Different Points and
Indicating Tendency Toward Air Leakage
enter the ashpit (Fig. 13) and push its way through the bed of fuel
on the grate, thus promoting the combustion of the fuel.
Air Leaks Affect the Draft and Waste Coal
If cold air leaks into the setting at any point, it will result in two
forms of fuel waste. First, it will cool the gases in the setting and in
the chimney and will make the draft less. This may make it difficult
to burn the fuel properly. Secondly, the air which has leaked in must
be warmed up, thus taking heat away from the boiler and wasting it
through the chimney, and finally this air will so increase the volume
of flue gas that it may be difficult for the chimney to handle the in-
creased volume of flue gas even with the damper wide open.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
57
Breechings for a Battery of Two or More Boilers
Many breechings serving more than one boiler are condemned as
being too small because so much unnecessary air is leaking into the
various settings that the breeching cannot handle both the leakage
and the necessary flue gas. By systematically stopping all the leaks
such a breeching will often easily handle the flue gases resulting from
the minimum air supply actually required for burning the fuel.
Breechings should be at least from 10 to 15 per cent greater in area
than the stack to which they connect.
The individual boiler dampers in the throat or uptake connections
opening into a breeching should fit accurately and close tightly, other-
wise it will be impossible to prevent cold air from entering the main
breeching through the damper of a “dead” boiler. This will often
seriously affect the operation of all the other boilers by “checking”
the draft of the stack which serves the boilers connected to this breech-
ing.
Breechings should be as short and straight as possible, and should
have no sharp angles around which the flue gases may swirl and eddy
in their passage to the stack. The bad effect of sharp angles is shown
in the stack connection marked “B” in Fig. 14. The method of cor-
recting this difficulty is shown at “A” in the same figure. Breech-
ings should be covered with a good heat insulating material or lined
with a refractory brick or vitrified material.
All boiler dampers should be “calibrated,” that is, should have
the operating lever or chain so marked and set that the draft for boiler
No. 1, nearest the stack (Fig. 14), will be no greater than for boiler
No. 3, farthest from the stack, when both boilers are clean and have
the same thickness of fuel bed. To accomplish this result it may be
found that the damper on the nearest boiler must be nearly closed most
of the time. If all dampers are set at the same angle without regard
to their location with reference to the stack, too much air will go
through the nearest boiler or the farthest boiler will get too little air
and suffer a loss in capacity.
Conditions Under Which a Stack Will Operate Economically
If fuel is to be used economically, the stack must supply the fur-
nace with just enough air to burn the fuel completely. This can only
be done when the following conditions are observed :
FUEL ECONOMY IN HAND FIRED POWER PLANTS
59
(1) The setting must be made air tight.*
(2) All doors and door frames opening into setting and breech-
ing must be made to fit air tight.
(3) The breeching and stack should likewise be made air tight
and should be well insulated to prevent heat loss from the
flue gases so that all the heat in the gases may be available
for creating draft.
(4) The air used for burning the fuel should all enter through
the ashpit, except a limited and carefully regulated air supply
which should be admitted through the fire door after firing
fresh coal.
(5) When natural draft is employed, the control of the air
should be accomplished by operating the stack or breeching
damper according to the rate of burning coal and never by
opening and closing the ashpit doors.
* A candle flame is commonly used to detect air leaks into a setting since it will be
drawn into any crevice through which air is entering.
GO
ILLINOIS ENGINEERING EXPERIMENT STATION
VI. Feed Water Heating and Purification as Factors
in Fuel Economy
17. Feed Water Purification . — The majority of waters used for
boiler feeding purposes contain more or less impurities which are
deposited in the boiler. Such deposits of foreign matter tend to de-
crease the evaporative capacity of the boiler and, if they are not re-
moved, will frequently cause overheating of tubes and sheets. To
overcome these difficulties the impurities in the feed water should be
removed before feeding into the boiler.
For convenience of reference, the impurities most often found
in feed water and their effects upon the sheets and tubes if permitted
Table 4
Impurities in Feed Waters, their Effects and Remedies*
Impurities
Effects
Remedies
1
2
3
Sediment, mud, clay, etc.
Bicarbonates of lime, magnesia
Sulphates of lime and magnesia
Incrustation and the for-
mation of sludge
Settling tanks, filtration, blowing
down.
Blow down.
Heat feed water. Treat by adding
lime.
Treat by adding soda. Barium
carbonate.
Chloride and sulphate of magnesia
Acid
Dissolved carbonic acid and oyx-
gen
Grease
Organic matter
Corrosion
Treat by adding carbonate of soda.
Soda or lime.
Heat feed water. Keep air from
feed water. Add caustic soda
or slacked lime.
Filter. Iron alum as coagulant.
Neutralize with carbonate of
soda. Use the best of hydro-
carbon oils.
Filter. Use coagulant.
Sewage
Readily soluble salts in large
quantities
Carbonate of soda in large
quantities 2
Priming
Settling tanks. Filter in con-
nection with coagulant.
Blow down.
Barium carbonate. New feed
supply. If from over treat-
ment, change or modify.
Steam,” published by Babcock & Wilcox Company.
2 May cause brittleness in plates. See Bulletin 94, Eng. Exp. Sta. Univ. of 111., “The Embrittling
Action of Sodium Hydroxide on Soft Steel,” by S. W. Parr.
to enter the boiler are given in columns 1 and 2 of Table 4. In the
last column of this table are given the usual remedies employed to
FUEL ECONOMY IN HAND FIRED POWER PLANTS
61
neutralize or to prevent to a certain degree the effects produced by the
various impurities. Some of the impurities found in feed water cause
the formation of scale on the sheets and tubes, others cause corrosion
of the metal, and still others produce priming, or the carrying over of
particles of water with the steam as the latter leaves the boiler.
18. Treatment of Feed Waters . — One of the best ways of deter-
mining the remedy to be applied in overcoming the injurious effects
of the impurities contained in the feed water is to submit a sample of
the water to a reliable chemist for analysis and prescription. After
such an analysis has been made it is possible to ascertain which one of
the following treatments should be applied, chemical treatment, heat
treatment, or combined heat and chemical treatment.
Chemical Treatment
The chemical treatment of feed water involves the use of either
the lime or the soda process or a combination of these two. The first
of these processes in which slacked lime is used is well adapted for
precipitating the bicarbonate of lime and magnesia contained in the
feed water. In the soda process carbonate of soda or caustic soda ,
either separately or together, is used for converting the sulphates of
lime and magnesia into carbonates or chlorides which may be disposed
of by occasional blowing off. The combination of the lime and soda
processes, however, is most frequently used. It is satisfactory for
treating water containing sulphates of lime and magnesia, carbonic
acid, or bicarbonates of lime and magnesia. In this process the sul-
phates are broken down by the use of sufficient soda, and the necessary
lime is added to absorb the carbonic acid not taken up in the soda re-
action.
Heat Treatment
The bicarbonates of lime and magnesia so often found in natural
waters may be partially precipitated by preheating the feed water in
some form of apparatus commonly called a heater. The sulphates of
lime and magnesia, however, require high temperatures for complete
precipitation and it is impossible to remove these impurities by the
simple process of preheating in the ordinary heater using exhaust
steam. Instead, live steam heaters and economizers are required for
removing them.
62
ILLINOIS ENGINEERING EXPERIMENT STATION
Combined Chemical and Heat Treatment
Since preheating of feed water removes the carbonates of lime
and magnesia, many water purification systems combine the chemical
and heat treatments discussed in the preceding paragraphs, the chem-
ical treatment being used merely for reducing the sulphates.
19. Boiler Compounds. — So-called boiler compounds are used
rather extensively for treating feed water and no doubt in many cases
the results obtained are satisfactory. According to reliable authori-
ties the use of compounds is recommended for the prevention of new
scale rather than for the removal of old scale. In general, no com-
pound should be used until the proper advice has been obtained to in-
sure the selection of the right compound for the particular feed water
to be treated. In no event should the use of boiler compounds be re-
garded as a suitable substitute for regular cleaning and inspection.
20. Feed Water Heaters . — In any power plant of considerable
size cold water should not be fed into the boilers, since all steam boilers
are more or less seriously affected by the resulting unequal expansion
and contraction. If cold water is forced into the boiler, the tubes of
water tube boilers are very likely to become troublesome while in re-
turn tubular boilers the seams are liable to develop leaks. Further-
more the feed water cannot be converted into steam until its temper-
ature is raised to the point controlled by the steam pressure, and to do
that requires fuel. If the temperature of the feed water can be raised
by means of heat which otherwise would be wasted, it is good economy
to do so. The preheating of feed water also increases the steaming ca-
pacity of the boiler, because of the reduction in the amount of heat to
be supplied by the boiler per pound of water evaporated. With-certain
types of feed water heaters a considerable portion of the scale forming
ingredients are precipitated before the water enters the boiler, thus
increasing the efficiency and capacity of the boiler as well as effecting
a saving in the expense of cleaning out the boiler. In general, it may
be stated that one per cent of fuel is saved for every eleven degrees
rise in the feed water temperature, provided the heat producing this
rise in temperature would otherwise be wasted.
In steam power plants there are two main sources of waste heat,
the first being the exhaust steam of the various units, and the second
the products of combustion which pass from the boiler to the chimney.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
63
The heat contained in the drips from the high pressure piping system
is also a source of loss in many small plants, although its extent is not
great. Condensation in the high pressure system, which includes all
piping under pressure practically equivalent to boiler pressure, is
free from oil and should be returned to the feed water heater by means
of pumps or traps. If desired the condensed steam may be returned
directly to the boiler. In steam power plants, high pressure steam
traps are generally used for automatically draining the condensation
from the high pressure lines.
Exhaust Steam Heaters
Heaters using exhaust steam for heating the water may be either
of the open or closed type.
An open heater is one in which the exhaust steam and water
mingle, the steam in condensing giving up its heat directly to the
water. In general an open heater consists of a shell the upper part of
which contains a number of removable trays. The function of these
trays is to break up the incoming feed water into thin streams or
layers. In passing over the trays, the water mingles with the exhaust
steam, and if sufficient steam is supplied temperatures as high as 210
degrees F. may result. It is evident that in an open heater only those
scale forming ingredients which will precipitate below 210 degrees
F. will be deposited in the heater. Below the trays, the heater is
provided with a bed of coke or charcoal through which the water is
filtered before the feed pump sends it into the boiler. The function
of the coke or charcoal filter is to remove the precipitates and other
suspended impurities coming into the heater. Open heaters should
always be supplied with a suitable oil separator for removing any oil
contained in the exhaust steam.
Closed Heaters
In a closed heater the exhaust steam and feed water do not come
into actual contact with each other, the steam giving up its heat to the
water by conduction. In one type of closed heater the exhaust steam
surrounds tubes through which the water passes. In a second type,
the steam passes through tubes which are surrounded by the water.
Closed heaters are recommended only for installations where the feed
water is free from scale forming ingredients, since there is a tendency
for the tube in these heaters to become coated with a deposit of scale,
thus materially decreasing the efficiency of the apparatus.
64
ILLINOIS ENGINEERING EXPERIMENT STATION
Advantages and Disadvantages of Exhaust Steam Heaters
The advantages of an open heater are as follows :
(1) The feed water may reach approximately the temperature of
the exhaust steam provided sufficient steam is supplied.
(2) Scale and oil do not effect the transmission of heat.
(3) The pressure in an open heater is low, practically atmos-
pheric.
(4) Scale and other impurities precipitated in the heater may
easily be removed.
(5) An open heater is well adapted to heating systems in which
it is desired to pipe the returns direct to the heater.
(6) The initial cost of an open heater is generally less than that
of a closed heater.
(7) With the open heater all the condensed steam is returned to
the system.
The disadvantages of an open heater are as follows :
(1) Some provision must be made for removing oil from the ex-
haust steam. In modern open heaters this is accomplished
by effective oil separators attached directly to and forming
a part of the heater.
(2) “ Sticking” or clogging of the back pressure valve may sub-
ject the open heater to excessive pressure.
(3) If the feed water supply is under suction, open heaters may
require the use of two pumps, one for hot and one for cold
water.
The advantages of a closed heater are as follows :
(1) The closed heater will safely withstand any ordinary boiler
pressure.
(2) Oil does not come in contact with the feed water.
(3) It is the only type of heater which may be used in the ex-
haust main between a prime mover and its condenser.
(4) Since it is customary to locate a closed heater on the pressure
side of the feed pump, only one pump, and that for cold
water, is necessary.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
65
The disadvantages of a closed heater are as follows :
(1) Scale and oil deposits on the tubes lower the heat trans-
mission.
(2) The temperature of the feed water will always be from four
to eight degrees below the temperature of the incoming ex-
haust steam.
(3) Scale in the tubes is removed with difficulty.
21. Economizers . — An economizer is an arrangement of vertical
water tubes arranged in nests, located in the flue between the boiler
and the stack. Its purpose is to heat the feed water. The adjacent
nests of tubes are connected together by means of expansion bends.
To prevent deposits of soot, the tubes are provided with automatic
scrapers which are kept moving up and down by means of a suitable
mechanism driven by a motor or a small steam engine. Since the
temperature of the flue gases is generally about 550 degrees F., it is
evident that considerable heat escapes through the chimney. In gen-
eral, the load factor, the size of the plant, and the cost of fuel are
factors which should be considered in determining the advisability of
installing an economizer.
22. Live Steam Heaters . — Live steam heaters use steam at boiler
pressure and, as mentioned in a preceding paragraph, are primarily
intended for purifying the feed water. Such heaters are generally not
installed unless scale forming impurities are found in the water. At
temperatures less than 300 degrees F. the sulphates of lime and mag-
nesia do not entirely precipitate; hence a feed water containing these
impurities will not be thoroughly purified by preheating with exhaust
steam at atmospheric pressure. Reports of tests tend to show that live
steam heaters do not increase boiler efficiency, but merely act as puri-
fiers. Live steam heaters should always be by-passed and so located
that the bottom of the shell is at least two feet above the water level
in the boiler, thus permitting the purified water to gravitate into the
boiler.
23. Feeding Boilers . — Water is fed to the boiler by means of an
injector or a pump depending upon the size of the plant. The use of
an injector does not permit preheating the feed water by means of
an open heater; hence relatively cold water is introduced into the
boiler, thus decreasing the economy of the plant. It is possible to
66
ILLINOIS ENGINEERING EXPERIMENT STATION
install between the injector and the boiler a closed heater, but in such
an installation the effectiveness of the heater is decreased because of
the heat supplied by the injector. Frequently it is claimed that an
injector considered as a combined pump and heater has an efficiency
of one hundred per cent since all the heat in the steam used for operat-
ing the injector is returned with the water forced into the boiler. Con-
sidered as a pump the injector is very inefficient since it requires much
more steam to force a given amount of water into the boiler than is re-
quired by a pump to do the same amount of work. Furthermore when
a pump is used for feeding boilers, the exhaust steam from the pump
may be used for preheating the feed water. According to tests, a
direct acting steam pump, feeding water through a heater in which
the exhaust steam of the feed pump is utilized, shows a much greater
saving of fuel than an ejector with or without a heater. In general
the feed pump must be located below the water level in the heater,
preferably about three feet below, since hot water cannot be lifted
by suction.
In order that it may be possible to check the efficiency of the
boiler as well as that of the fireman or to determine the most
economical fuel, the feed water system should include some form of
metering device for measuring the water fed to the boilers. There
are a number of metering devices on the market some of which are
permanently accurate and some of which must be checked up at fre-
quent intervals. There are now several manufacturers of feed water
heaters who are prepared to furnish heaters equipped with water
measuring devices.
In addition to measuring the amount of water fed to a boiler,
provision should be made for weighing the coal used by each boiler,
thus affording a means of determining for each boiler the evapora-
tion per pound of fuel. This will also make it possible to compare
the performance of any two boilers in the plant.
For the majority of small boiler plants the feed water should
be introduced into the boiler at a constant rate rather than intermit-
tently as is too frequently done.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
67
VII. Steam Piping Requirements for Fuel Economy
in Small Plants
24. Possibility of Fuel Loss in the Transmission of Steam. — In
order to promote the economical use of coal, the steam generated
should be transmitted to the point of use with as little loss of both
heat and steam as practicable. This means that the piping system
should be as simple as possible and well insulated. Only short direct
runs should be used in connecting boilers, engines, and other appa-
ratus.
All branch lines not in use should have the valves closed so that
steam cannot enter them and wrnste heat by condensing in these dead
ends, and the stop valves should be located (Fig. 15) so as to accom-
plish this purpose. If the engine shown in Fig. 15 is shut down for
any length of time tlie valves at both ends of the engine lead should
be closed to prevent steam from condensing in and filling up this
lead.
25. Value of High Pressure Drips as Hot Feed Water. — Each
high pressure header and steam separator should be dripped (Fig. 15)
and the hot water returned to the feed-water heater, which should
be included in the equipment of every power plant since each 11
degrees F. increase in the feed-water temperature will effect a sav-
ing of nearly one per cent in the coal burned. In no case should cold
water be fed direct to the boilers, even if live steam has to be used
for heating it.
The oily drips from the exhaust steam header (Fig. 15) should
be discharged to the sewer or wasted since the oil they carry has an
injurious effect upon the boiler tubes and shell, and may do much
more harm than the fuel value of the heat contained in these drips
is worth.
26. Leakage Losses at Valves and Fittings. — The boiler blow-off
cock or valve must be perfectly tight to prevent the escape of any
hot water to the sewer or other waste channel. If the end of this
line cannot be readily inspected to make sure that all blow-off valves
are tight, then a tell-tale connection (Fig. 15) with valve should be
68
ILLINOIS ENGINEERING EXPERIMENT STATION
placed in the blow-off line beyond the main cock so that by opening
it a leak at the blow-off will at once be apparent.
Leaks of hot water or steam which appear in any line either at a
valve, flange, or other fitting should be stopped immediately; other-
wise a serious waste of fuel may result in making up the heat so lost.
An even more serious condition may result if a leak is so located
that it discharges water or steam over any part of the boiler or over
another pipe since corrosion is very rapid in such a case. In fact,
such leaks have started corrosion which later resulted in boiler
explosions.
27. Size of Steam and Exhaust Mains— The size and length
of steam and exhaust mains may adversely affect the fuel consump-
tion of a plant if these lines are either, (1) too small, or (2) too
large for the proper handling of the steam they have to carry. Gen-
erally, the lines are too small, but this is not always the case.
If the steam main between boiler and engine is too small or too
long, it will be necessary to carry a much higher pressure at the
boiler than would otherwise be necessary in order to get the required
pressure at the engine. The excessive friction in small steam lines
causes this loss in pressure, and if the main is also very long the
loss will be still more pronounced. Steam gages at the boiler and at
the engine throttle should not show a difference, or a drop in pres-
sure of more than five pounds when the engine is running at full
capacity. Should it be necessary to carry a much higher pressure
at the boiler than at the engine in order to get a satisfactory opera-
ting pressure, some unnecessary coal must be burned since all the
heat losses will be slightly increased and leaks will be somewhat
more likely to develop.
On the other hand, if this main is too large (which is not so
serious) the pressure at the engine throttle will be almost the same
as that at the boiler when running at full capacity. The heat losses
from oversize pipes and fittings are greater and the first cost of
installation is higher than for mains of the proper size.
In the case of the exhaust main, the size is most important since
the steam has now expanded and occupies a much greater volume
than when it left the boiler. This exhaust steam must be discharged
from the engine at the lowest possible back pressure if the engine is
to get the most work out of each pound of steam supplied to it and
THE. LIB8ABK
OF THE
raESsmf c: : n
FUEL ECONOMY IN HAND FIRED POWER PLANTS
73
hence develop the greatest power. With exhaust piping which is too
small, a steam gage on the line will show a back pressure of more than
two pounds which means that more steam is being taken into the
engine to do the work than is necessary. This in turn means coal
wasted. Exhaust mains are almost never too large, but in such cases
the excess heat loss due to radiation from large exhaust mains is not
so serious as in the case of high pressure steam mains since the tem-
perature of exhaust steam is very much less than that of live steam.
28. Heat Insulating Materials Required on Piping , Boilers, and
Breechings . — The desirability of covering or insulating all high tem-
perature surfaces around a boiler and power plant, when fuel is as
expensive and as difficult to obtain as at present, is self evident. It
can be shown that by covering all steam and hot-water pipes, fit-
tings, flanges, and valves enough heat can be saved as compared with
the loss from bare pipe to pay for the labor and covering material in
a very few months. This, of course, applies to the ordinary com-
mercial coverings ranging from one to two inches in thickness. Table
5 shows the saving per year for 100 feet of covered pipe in pounds
of coal and in dollars with coal at $5.00 per ton (2,000 pounds).
The best commercial coverings one inch in thickness will save
or prevent the escape of from 75 per cent to 85 per cent of the heat
lost from bare pipes. The thickness of the covering should be varied
with the temperature of the steam or water in the pipe line, but in
general it will pay to use not less than one inch on all lines which are
at 200 degrees F. and up to 300 degrees F. Above 300 degrees F.
and up to 400 degrees F. it is advisable to use iy 2 inch covering and
above 400 degrees F., not less than two inches.
The actual heat saving value of commercial pipe coverings now
on the market has been the subject of many investigations. The
latest work in this field has been done by L. B. McMillan * at the
University of Wisconsin and the charts (Figs. 16 and 17) have been
made from the results of his tests on bare and covered five-inch steel
pipe. These charts show how the heat transmitted by bare pipe com-
pares with the heat transmitted by the same pipe when insulated.
The values of only seven of the twenty or more coverings tested are
shown. Their efficiency as insulators is easily seen by reading the
* “The Heat Insulating Properties of Commercial Steam Pipe Coverings,” Journal,
A. S. M. E., Dec., 1915.
74 ILLINOIS ENGINEERING EXPERIMENT STATION
FUEL ECONOMY IN HAND FIRED POWER PLANTS
75
0.95
0.90
0.65
Carves taken from " The Meat l 'nsuiatmg Properties of Com-
mercial Of earn Pipe Coverings " LB.M c Millan A5M.E. Dec. 1915
' 0.65
£ ^
-Si 0..55
t>s
i^0.45
&
<p0.40
0.30
50 100 750 300 EDO 300 350 400 450 500
Temperature difference /n cfegreeo Fahrenheit
between pipe and room temperatures.
Fig. 16. Chart Showing Amount of Heat Transmitted by Steam Pipes In-
sulated with Commercial Coverings (See Fig. 17 for Bare Pipe.)
76
ILLINOIS ENGINEERING EXPERIMENT STATION
5 K'
^ k ■«
^ ^.4
O 50 100 150 200 250 300 350 400 450
Temperature difference in degrees rahrenhe/t
between pipe and room temperatures.
Fig. 17. Chart Showing Heat Lost by Bare Steam Pipe and Saving which
May be Secured by Using a Good Covering
scale at the left of the chart, which shows the heat lost or transmitted
per hour per square foot of pipe surface per degree difference of
temperature between the steam in the pipe and the air outside. The
heat loss is expressed in B. t. u.*
* For a definition of B. t. u. see foot-note, p. 17.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
77
The importance of covering steam lines operating at high pres-
sures and temperatures is emphasized by Fig. 17. It will be seen by
reference to the upper curve in this diagram that the heat loss per
square foot from an uncovered five-inch steam line increases very
rapidly as the temperature of the steam in the line increases. By
covering the line with a good insulator, not only is a large saving
effected by reducing the heat loss (see shaded area), but the increase
in the heat loss per square foot from such a covered line at high
temperatures is very much less than for a bare pipe.
In other words, it is most important to cover all high tempera-
ture surfaces which are in contact with the air.
The chart (Fig. 17) shows that with steam which is 300 degrees
F. above the temperature of the outside air a five-inch diameter
standard bare steel pipe transmits about 3.3 B. t. u. per square foot
per hour, while the same pipe covered with “Nonpariel High Pres-
sure Covering” transmits (Fig. 16) only 0.425 B. t. u. per hour or
thirteen per cent of the heat wasted by the bare pipe. In other
words about seven-eighths of the loss has been stopped by the cover-
ing.
29. Requirements for a Good Covering . — A satisfactory pipe
covering must be, (1) unaffected by heat or fire, (2) easily molded
and light in weight, (3) impervious to or unaffected by water and
steam, (4) non-corrosive in its effect upon metals (steel, iron and
brass), (5) structurally fairly strong or self sustaining, and (6)
sanitary and not attractive to vermin of any kind. The market
affords a great variety of materials at various prices which are used
for this purpose. But the purchaser must remember that he is buy-
ing heat insulation, not merely covering, and he must assure himself
that the material is a practical and effective insulator.
In this connection, it should be noted that the soot which col-
lects on the boiler tubes where no insulation is desired is several
times as good an insulator as asbestos, and that the fine ash which
also collects on the tubes is almost as good an insulator as soot. In
other words, if it is advisable and economical to cover steam pipes
with insulation, it is decidedly more economical and necessary to keep
boiler tubes absolutely clean and free from the insulating effects of
soot and ashes at all times. A similar argument applies to the scale
which collects on the water side of the tubes or shell as a result of
78
ILLINOIS ENGINEERING EXPERIMENT STATION
infrequent cleaning or failure to employ suitable treatment for the
feed water.
30. Bad Effects of Water of Condensation in Steam Lines . —
Not only does an uncovered steam line waste heat by transmission
to the outside air, but it greatly increases the condensation , require
ing the boilers to furnish more steam than would be necessary in a
covered line. It also adds to the amount of water to be handled by
the traps, and results in excessive wear on the valve seats and
through the steam ports of the engines. If a trap fails to operate
properly, the accumulated water may travel along with the steam at
high velocity and develop a “water hammer” which will loosen or
break some fitting.
31. Uncovered Pipes Waste Steam as Well as Coal. — The owner
of a power plant should realize that an uncovered steam main wastes
heat and that it should therefore be covered. The loss of heat means
a loss of steam by condensation and the generation of steam by the
boiler plant which cannot be used.
That this loss is serious and that it requires the boilers, the feed
pumps, and the traps to handle much more water than would be
necessary if the steam mains were properly covered is shown by
Fig. 18. The simple computations necessary to prove this statement
for a typical case are given below. The plant shown in Fig. 18 is
operating 24 hours per day for 365 days per year. A five-inch steam
main, which is uncovered, carries steam at 150 pounds gage pres-
sure to an engine 100 feet away. The air around the main averages
70 degrees F. and the feed water enters the boiler at 200 degrees F.
(1) Actual tests show that each square foot of pipe loses
3.25 B. t. u. per hour for each degree of difference in tem-
perature between steam inside and air outside (Fig. 17).
(2) The outside surface of 100 feet of five-inch pipe amounts to
145.6 square feet.
(3) The total heat loss from the pipe per hour is:
3.25 X 145.6 X (366-70) = 140,000 B. t. u.
(The temperature of saturated steam at 150-pound gage is
366 degrees F.)
(4) This heat is obtained by condensing not by cooling some
of the steam in the pipe. One pound of steam gives up
FUEL ECONOMY IN HAND FIRED POWER PLANTS
79
Note: Each tank car con fa ins 10,000 ga/s. of wafer
80
ILLINOIS ENGINEERING EXPERIMENT STATION
858 B. t. u. when it condenses at 150 pounds gage pressure, or
the uncovered pipe condenses ^^’^^ =163 pounds per hour. -
o5o
(5) In one year, 163 X 24 X 365 = 1,428,000 pounds of steam
wasted; that is, this much steam never reaches the engine.
At 8 1-3 pounds per gallon, 171,200 gallons of water have
been needlessly handled.
(6) Expressed in another way, this plant has evaporated and
sent over 17 tank ears (of 10,000 gallons capacity per car)
of water into this line which did not perform useful work.
This represents an absolute waste of coal, of steam, and of
boiler capacity. At least 75 per cent of this waste could
have been prevented by covering the line.
(7) To evaporate each pound of this water from feed water at
200 degrees F. took 168 -|- 858 = 1,026 B. t. u. or a total of
1,026 X 103 = 167,300 B. t. u. per hour.
(8) At 60 per cent efficiency each pound of coal (heat value
taken as 12,000 B. t. u. per pound) gives to the boiler 7,200
B. t. u. or the plant is wasting 23.2 pounds of coal per
hour to supply the condensation loss.
(9) The coal required per year is:
23.2 X 24 X 365 = 203,000 pounds or 101.5 tons.
(10) This means that this plant has to burn about 2 y 2 cars
of coal (holding 40 tons each), in order to provide for this
annual heat loss. A good covering would stop 75 per cent
of this waste and save two whole cars or 80 tons of coal a
year. Bare steam pipe is a very expensive luxury in any
power plant.
The cost of labor and material for covering 100 feet of the five-
inch main referred to, including two valves and six fittings, is esti-
mated at about $160. This is based on present day conditions with
the plant located within 150 miles of Chicago, using the best 85 per
cent magnesia sectional covering, of IV 2 inches in thickness. The use
of asbestos sponge felted covering would not add more than four or
five per cent to this estimate, and if this work could be executed as
part of a large covering job the cost could be reduced about twenty-
five or thirty per cent.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
81
VIII. Record of Operation
32. Purpose of the Record . — The maintenance of such records
of operation as may be necessary to enable the superintendent or
owner of a plant to determine with reasonable reliability the cost of
operation, the relative efficiency of the plant, and the improvement
from time to time is essential. For practical purposes, the index
to the performance of any steam generating plant lies in the relation
between the number of pounds of water evaporated, and the number
of pounds of coal fired less the weight of the ash. The record must
therefore give the information on the basis of which this relation
may be determined at any time, and it should also contain such other
data as may be required for detecting and remedying any defects in
operation which indicate loss.
33. Character of the Record . — It must be recognized that no
satisfactory record of operation is possible unless the plant is equipped
with certain checking and recording devices which have been recom-
mended in the preceding pages of this discussion. These may be re-
counted as follows :
(1) Means of weighing the coal fired for each boiler.
(2) Means of weighing the ash removed from the pit.
(3) Some device for weighing or measuring the water fed to
the boiler or the steam delivered by the boiler.
(4) A thermometer for indicating the temperature of the feed
■water.
(5) A draft gage connected into the space above the fuel bed
and into the ashpit.
(6) A differential draft gage connected into the space above
the fuel bed and into the flue gas passage near the point
of discharge from the boiler.
(7) A C0 2 analyzer.
(8) A pressure gage at the boiler (pressure gages should also
be supplied at the ends of all live steam lines).
(9) A pyrometer for indicating the temperature of the flue
gases leaving the setting.
Some of these devices are already part of the equipment of most
82
ILLINOIS ENGINEERING EXPERIMENT STATION
plants and the others may be secured at so slight a cost in proportion
to the saving to be effected as easily to warrant their installation.
The weighing of the coal does not present any difficulties. The
weighing of the ashes, however, is not so easy owing to the fact that
in most plants the ash is wetted down to facilitate handling and to
the possibility of a certain amount of unconsumed coal being present
in the ash.
The function to be performed by each item of equipment
included in the foregoing list has already been explained. The first
four items are necessary for arriving at the relationship :
Number of pounds of water evaporated
Number of pounds of ash free coal fired
The last five items of equipment listed are needed to indicate
the source of any defects in operation or troubles which may be
leading to losses.
The daily record of operation should include the items shown in
the form given on page 83.
Items 1, 2, and 3 of this record should cover the entire shift
of the firemen for each boiler. Items 4 to 9, inclusive, should con-
- tain readings taken for each boiler at regular intervals (the sug-
gested form provides for hourly readings) throughout the shift as
frequently as may be practicable. The choice of the individual to
be charged with the responsibility of maintaining this record is a
matter which will depend largely upon the character and size of the
existing organization of each plant. In some cases it may be found
satisfactory to entrust the matter to the fireman; in others it may
be desirable to assign it to some other employe. It should be recog-
nized in any case that unless the record is maintained with reason-
able care and accuracy its value is not great. If carefully kept the
record will prove a means of stimulating the interest and coopera-
tion of employes concerned with the operation of the plant as well
as the basis for effecting economies the extent of which will in most
cases be material.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
83
NAME OF FIRM
DAILY 'RECORD OF POWER PLANT OPERATION
ILLINOIS ENGINEERING EXPERIMENT STATION
84
34. Profit Sharing or Bonus Systems . — In some plants the
practice is followed of permitting firemen and other employes to
share in the savings which result from their efforts. Without under-
taking either to commend or to condemn the profit sharing system as
applied to power plant operation, the suggestion is offered that in
any event no such system should be inaugurated until the plant is
put in proper condition, i. e., until the setting has been made tight
and is well covered, until live steam pipes are covered, and until
such other changes have been made and devices installed as have been
herein discussed. Having made these mechanical changes and im-
provements, the importance of which will be reflected in the results
of operation, the earnest cooperation of employes concerned with
the plant is essential in securing the maximum benefits, and the
application of a profit sharing plan may in some cases prove the
means of enlisting this cooperation.
FUEL ECONOMY IN HAND FIRED POWER PLANTS
85
IX. Summary of Conclusions
35. Conclusions . — To enable the plant owner to determine
whether or not his installation conforms with the requirements of
practice promoting fuel economy and to check up his methods of
operation, the essential features discussed in the preceding pages
are summarized as follows :
Coal
(1) Practically the only fuel available for power plant use
in Illinois under present conditions is bituminous coal from
the central fields of Illinois, Indiana, and western Ken-
tucky.
(2) The care with which coal is “prepared,” and separated
into different sizes is an important factor affecting its value
in the power plant.
(3) The B. t. u. value and the percentage of ash furnish a
general guide to the relative values of Illinois coals. Gen-
erally the coals having the lowest ash content have the
highest B. t. u. value.
(4) The storage of bituminous coal is both practicable and
desirable. Certain precautions, however, must be observed.
These are set forth in detail on page 18.*
Principles to be Observed in Firing
(5) The three fundamental conditions necessary for complete
and smokeless combustion of bituminous coal are:
(a) A sufficient amount of air must be supplied.
(b) The air and fuel must be intimately mixed.
(c) The mixture must be brought to the ignition tem-
perature and maintained at this temperature until
combustion is complete.
(6) Since bituminous coal from the central field is practically
the only fuel available at present for power plant use in
Illinois the boiler setting and the plant in general should
be adapted to the economical use of this fuel.
* See also Univ. of 111. Eng. Exp. Sta. Circular 6, entitled, “The Storage of Bituminous
Coal,” by H. H. Stoek.
ILLINOIS ENGINEERING EXPERIMENT STATION
(7) Every boiler should be equipped with two draft gages,
one connected directly in the space over the fire, and one
connected both into the space over the fire and into the gas
passage below the damper. For every given load, the draft
necessary to carry it and the proper thickness of fuel bed
with the grade of coal used should be determined.
(8) In many plants of large and medium size automatic draft
control has proved economical, and it is also of advantage
in maintaining constant steam pressure.
(9) Every plant should have some simple type of C0 2 analyzer
for obtaining a knowledge of conditions existing within
the furnace. (See page 30.)
(10) Air leakage through the boiler setting should be pre-
vented by properly calking and covering the setting.
(11) Losses due to the presence of unconsumed coal in the
ash should be avoided by seeing that the fire is properly
worked and that the grate openings are not too large for the
size of fuel fired.
(12) Sooty deposits on the heating surfaces should be removed
frequently. Should the temperature of the gases leaving
the boiler exceed 550 degrees F., it probably indicates that
the tubes need blowing.
(13) Scale on the water surfaces of the boiler should not be
allowed to accumulate.
(14) The spreading method of firing in which small quantities
of coal are fired at frequent intervals is regarded as a sat-
isfactory method for hand fired plants. (See page 41.)
Features of Boiler Installation
(15) The foundation for a boiler setting should rest on a firm
footing in order to insure a setting which will remain tight
and free from any tendency to crack.
(16) For the complete combustion of bituminous coal boiler
settings must provide for the introduction of sufficient air
into the furnace, for the proper mixing of this air with the
gases given off by the burning coal, and for the mainte-
nance of a high temperature until the process of combustion
is complete. This is to be accomplished by means of arches,
baffles, and other devices as hereinbefore described. (See
page 44.)
FUEL ECONOMY IN HAND FIRED POWER PLANTS
87
(17) The brick work in setting should be properly pointed
up and covered with an insulating material to prevent air
leakage. The exposed parts of the shell of horizontal
return tubular boilers and of the steam drums of water
tube boilers should be covered with a high grade of asbestos
insulating material at least two inches thick, or with an
85 per cent magnesia covering two or three inches thick,
and the outside finished off with a thin coat of hard cement
or covered with canvas and painted. Air spaces in the
walls of the setting should be filled with sand or ashes.
Stacks and Breechings
(18) In order to control the amount of air and flue gas passing
to the stack a damper installed at the point where the flue
gas leaves the boiler should be regulated so as to permit the
stack to supply the right amount of air to burn completely
the fuel fired. The air supply should be controlled by this
damper and not by opening and closing the ashpit doors,
which should stand open practically all the time. Each
boiler should have its individual damper.
(19) The individual boiler dampers should fit accurately and
close tight, otherwise it will be impossible to prevent cold
air from entering the main breeching through the damper
of a “dead” boiler.
(20) The breeching and stack should be made air tight and
should be insulated to prevent heat loss from the flue gases
so that all the heat in the gases may be available for creat-
ing draft.
Feed Water and Fuel
(21) If the feed water used causes scale, corrosion, or priming
it should be analyzed by a reliable chemist and treated in
such manner as he may prescribe.
(22) It is necessary and economical to heat the feed water.
One per cent of fuel is saved for every eleven degrees rise
in the feed water temperature.
(23) For the majority of small boiler plants the feed water
should be introduced into the boiler at a constant rate
rather than intermittently. The feed water system should
include some form of metering device for measuring the
water fed to the boiler or the steam delivered by it.
88
ILLINOIS ENGINEERING EXPERIMENT STATION
(24) Means should be provided for weighing the coal fired to
each boiler and the ash removed.
Steam Piping Requirements
(25) The piping system should be as simple as possible and
well insulated. Only short direct runs of live steam pipes
should be used in connecting boilers, engines, and other
steam using apparatus.
(26) Each high pressure header and steam separator should
be provided with drips and the hot water returned to the
feed water heater.
(27) Leakage losses at valves and fittings in all steam and
water lines should be stopped at once.
(28) If a steam main is either too small or too long it will be
necessary to carry a higher pressure at the boiler to get the
required pressure at the engine. Steam gages at the boiler
and at the engine throttle should show a drop in pressure
of not more than five pounds when the engine is running
at full capacity. If a steam main is too large the pressure
at the engine throttle will be almost the same as that at
the boiler. The heat losses from oversize pipes and fittings
are somewhat greater and the cost of installation is higher
than for mains of the proper size. The exhaust piping
should be of such size that a gage near the engine will
show a pressure of not more than two pounds.
(29) All steam and hot water piping, fittings, flanges, and
valves should be covered with an insulating material. The
saving to be affected by such covering is sufficient to repay
the cost in the first few months. (See page 76.)
Record of Operation
(30) A suitable record of operation should be maintained upon
the basis of which the superintendent or owner of the plant
may determine with reasonable reliability the cost of opera-
tion, the relative efficiency of the plant, and the improve-
ment from time to time. From the record of operation it
should be possible to determine whether the individual
boilers are operating at their rated capacities. In cases in
which boilers are operating at less than capacity condi-
tions should be so changed as to require each unit to carry
FUEL ECONOMY IN HAND FIRED POWER PLANTS
89
its full load or an overload. In cases in which it is not pos-
sible to balance the load with the combined capacity of
units, it is economical to operate as many boilers as pos-
sible at capacity and to throw the excess on an extra unit.
(31) Special emphasis is to be laid upon the problem of the
plant owner and upon the part he must play in the program
of saving fuel. The economical utilization of fuel in power
plants is vital, not so much because it means a cash saving to
the owner, but rather because conditions are fast approaching
a point at which the owner who does not conserve his fuel
may find himself unable to maintain continuous operation.
LIST OF
PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION
Bulletin No. 1. Tests of Reinforced Concrete Beams, by Arthur N. Talbot, 1904. None available.
Circular No. 1. High-Speed Tool Steels, by L. P. Breckenridge. 1905. None available.
Bulletin No. 2. Tests of High-Speed Tool Steels on Cast Iron, by L. P. Breckenridge and Henry
B. Dirks. 1905. None available.
Circular No. 2. Drainage of Earth Roads, by Ira O. Baker. 1906. None available.
Circular No. 3. Fuel Tests with Illinois Coal (Compiled from tests made by the Technological
Branch of the U. S. G. S., at the St. Louis, Mo., Fuel Te'sting Plant, 1904-1907), by L. P. Breckenridge
and Paul Diserens. 1908. Thirty cents.
Bulletin No. 3. The Engineering Experiment Station of the University of Illinois, by L. P.
Breckenridge. 1906. None available.
Bulletin No. 4- Tests of Reinforced Concrete Beams, Series of 1905, by Arthur N. Talbot.
1906. Forty-five cents.
Bulletin No. 5. Resistance of Tubes to Collapse, by Albert P. Carman and M. L. Carr. 1906.
None available.
Bulletin No. 6. Holding Power of Railroad Spikes, by Roy I. Webber. 1906. None available.
Bulletin No. 7. Fuel Tests with Illinois Coals, by L. P. Breckenridge, S. W. Parr, and Henry B.
Dirks. 1906. None available.
Bulletin No. 8. Tests of Concrete: I, Shear; II, Bond, by Arthur N. Talbot. 1906. None
available.
Bulletin No. 9. An Extension of the Dewey Decimal System of Classification Applied to the
Engineering Industries, by L. P. Breckenridge and G. A. Goodenough. 1906. Revised Edition
1912. Fifty cents.
Bulletin No. 10. Tests of Concrete and Reinforced Concrete Columns, Series of 1906, by Arthur
N. Talbot. 1907. None available.
Bulletin No. 11. The Effect of Scale on the Transmission of Heat through Locomotive Boiler
Tubes, by Edward C. Schmidt and John M. Snodgrass. 1907. None available.
Bulletin No. 12. Tests of Reinforced Concrete T-Beams, Series of 1906, by Arthur N. Talbot
1907. None available.
Bulletin No. 13. An Extension of the Dewey Decimal System of Classification Applied to Archi-
tecture and Building, by N. Clifford Ricker. 1907. None available.
Bulletin No. 14- Tests of Reinforced Concrete Beams, Series of 1906, by Arthur N. Talbot.
1907. None available.
Bulletin No. 15. How to Burn Illinois Coal Without Smoke, by L. P. Breckenridge. 1908
None available.
Bulletin No. 16. A Study of Roof Trusses, by N. Clifford Ricker. 1908. None available.
Bulletin No. 17. The Weathering of Coal, by S. W. Parr, N. D. Hamilton, and W. F. Wheeler.
1908. None available.
Bulletin No. 18. The Strength of Chain Links, by G. A. Goodenough and L. E. Moore. 1908.
Forty cents.
Bulletin No. 19. Comparative Tests of Carbon, Metallized Carbon and Tantalum Filament
Lamps, by T. H. Amrine. 1908. None available.
Bulletin No. 20. Tests of Concrete and Reinforced Concrete Columns, Series of 1907, by Arthur
N. Talbot. 1908. None available.
Bulletin No. 21. Tests of a Liquid Air Plant, by C. S. Hudson and C. M. Garland. 1908. Fifteen
cents.
Bulletin No. 22. Tests of Cast-Iron and Reinforced Concrete Culvert Pipe, by Arthur N. Talbot.
1908. None available.
Bulletin No. 23. Voids, Settlement and Weight of Crushed Stone, by Ira O. Baker. 1908.
Fifteen cents.
* Bulletin No. 24 ■ The Modification of Illinois Coal by Low Temperature Distillation, by S. W. Parr
and C. K. Francis. 1908. Thirty cents.
Bulletin No. 25. Lighting Country Homes by Private Electric Plants by T. H. Amrine. 1908.
Twenty cents.
*A limited number of copies of bulletins starred is available for free distribution.
91
92
PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION
Bulletin No. 26. High Steam-Pressures in Locomotive Service. A Review of a Report to th
Carnegie Institution of Washington, by W. F. M. Goss. 1908. Twenty-five cents.
Bulletin No. 27. Tests of Brick Columns and Terra Cotta Block Columns, by Arthur N. Talbot
and Duff A. Abrams. 1909. Twenty-five cents.
Bulletin No. 28. A Test of Three Large Reinforced Concrete Beams, by Arthur N. Talbot.
1909. Fifteen cents.
Bulletin No. 29. Tests of Reinforced Concrete Beams: Resistance to Web Stresses, Series of
1907 and 1908, by Arthur N. Talbot. 1909. Forty-five cents.
* Bulletin No. 30. On the Rate of Formation of Carbon Monoxide in Gas Producers, by J. K. Cle-
ment, L. H. Adams, and C. N. Haskins. 1909. Twenty-five cents.
* Bulletin No. 31. Tests with House-Heating Boilers, by J. M. Snodgrass. 1909. Fifty-five
cents.
Bulletin No. 32. The Occluded Gases in Coal, by S. W. Parr and Perry Barker. 1909. Fifteen
cents.
Bulletin No. S3. Tests of Tungsten Lamps, by T. H. Amrine and A. Guell. 1909. Twenty cents.
* Bulletin No. 3J+. Tests of Two Types of Tile-Roof Furnaces under a Water-Tube Boiler, by J. M.
Snodgrass. 1909. Fifteen cents.
Bulletin No. 35. A Study of Base and Bearing Plates for Columns and Beams, by N. Clifford
Ricker. 1909. Twenty cents.
Bulletin No. 36. The Thermal Conductivity of Fire-Clay at High Temperatures, by J. K. Clement
and W. L. Egy. 1909. Twenty cents.
Bulletin No. 37. Unit Coal and the Composition of Coal Ash, by S. W. Parr and W. F. Wheeler.
1909. Thirty-five cents.
* Bulletin No. 38. The Weathering of Coal, by S. W. Parr and W. F. Wheeler. 1909. Twenty-
five cents
* Bulletin No. 39. Tests of Washed Grades of Illinois Coal, by C. S. McGevney. 1909. Seventy-
five cents.
Bulletin No. 40. A Study in Heat Transmission, by J. K. Clement and C. M. Garland. 1910.
Ten cents.
Bulletin No. 41. Tests of Timber Beams, by Arthur N. Talbot. 1910. Thirty-five cents.
* Bulletin No. 4%- The Effect of Keyways on the Strength of Shafts, by Herbert F. Moore. 1910.
Ten cents.
Bulletin No. 43. Freight Train Resistance, by Edward C. Schmidt. 1910. Seventy-five cents.
Bulletin No. 44 • An Investigation of Built-up Columns Under Load, by Arthur N. Talbot and
Herbert F. Moore. 1911. Thirty-five cents.
* Bulletin No. 46. The Strength of Oxyacetylene Welds in Steel, by Herbert L. Whittemore. 1911.
Thirty-five cents.
* Bulletin No. 43. The Spontaneous Combustion of Coal, by S. W. Parr and F. W. Kressman.
1911. Forty- five cents.
* Bulletin No. 47. Magnetic Properties of Heusler Alloys, by Edward B. Stephenson, 1911. Twen-
ty-five cents.
* Bulletin No. 48. Resistance to Flow Through Locomotive Water Columns, by Arthur N. Talbot
and Melvin L. Enger. 1911. Forty cents.
* Bulletin No. 49. Tests of Nickel-Steel Riveted Joints, by Arthur N. Talbot and Herbert F. Moore.
1911. Thirty cents.
* Bulletin No. 50. Tests of a Suction Gas Producer, by C. M. Garland and A. P. Kratz. 1912.
Fifty cents.
Bulletin No. 51. Street Lighting, by J. M. Bryant and H. G. Hake. 1912. Thirty-five cents.
* Bulletin No. 62. An Investigation of the Strength of Rolled Zinc, by Herbert F. Moore. 1912.
Fifteen cents.
* Bulletin No. 53. Inductance of Coils, by Morgan Brooks and H. M. Turner. 1912. Forty cents.
* Bulletin No. 64 ■ Mechanical Stresses in Transmission Lines, by A. Guell. 1912. Twenty cents.
* Bulletin No. 55. Starting Currents of Transformers, with Special Reference to Transformers with
Silicon Steel Cores, by Trygve D. Yensen. 1912. Twenty cents.
* Bulletin No. 56. Tests of Columns: An Investigation of the Value of Concrete as Reinforcement
for Structural Steel Columns, by Arthur N. Talbot and Arthur R. Lord. 1912. Twenty-five cents.
* Bulletin No. 57. Superheated Steam in Locomotive Service. A Review of Publication No. 127
of the Carnegie Institution of Washington, by W. F. M. Goss. 1912. Forty cents.
*A limited number of copies of bulletins Btarred is available for free distribution.
PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION
93
* Bulletin No. 58. A New Analysis of the Cylinder Performance of Reciprocating Engines, by
J. Paul Clayton. 1912. Sixty cents.
*Bulletin No. 59. The Effect of Cold Weather Upon Train Resistance and Tonnage Rating, by
Edward C. Schmidt and F. W. Marquis. 1912. Twenty cents.
*Bulletin No. 60. The Coking of Coal at Low Temperatures, with a Preliminary Study of the
By-Products, by S. W. Parr and H. L. Olin. 1912. Twenty-five cents.
* Bulletin No. 61. Characteristics and Limitation of the Series Transformer, by A. R. Anderson
and H. R. Woodrow. 1913. Twenty-five cents.
Bulletin No. 62. The Electron Theory of Magnetism, by Elmer H. Williams. 1913. Thirty-five
cents.
Bulletin No. 68. Entropy-Temperature and Transmission Diagrams for Air, by C. R. Richards.
1913. Twenty-five cents.
* Bulletin No. 64- Tests of Reinforced Concrete Buildings Under Load, by Arthur N. Talbot and
Willis A. Slater. 1913. Fifty cents.
* Bulletin No. 65. The Steam Consumption of Locomotive Engines from the Indicator Diagrams,
by J. Paul Clayton. 1913. Forty cents.
Bulletin No. 66. The Properties of Saturated and Superheated Ammonia Vapor, by G. A. Good-
enough and William Earl Mosher. 1913. Fifty cents.
Bulletin No. 67. Reinforced Concrete Wall Footings and Column Footings, by Arthur N. Talbot.
1913. Fifty cents.
*Bulletin No. 68. The Strength of I-Beams in Flexure, by Herbert F. Moore. 1913. Twenty
cents.
Bulletin No. 69. Coal Washing in Illinois, by F. C. Lincoln. 1913. Fifty cents.
Bulletin No. 70. The Mortar-Making Qualities of Illinois Sands, by C. C. Wiley. 1913. Twenty
cents.
Bulletin No. 71. Tests of Bond between Concrete and Steel, by Duff A. Abrams. 1913. One
dollar.
*Bulletin No. 72. Magnetic and Other Properties of Electrolytic Iron Melted in Vacuo, by Trygve
D. Yensen. 1914. Forty cents.
Bulletin No. 73. Acoustics of Auditoriums, by F. R. Watson. 1914. Twenty cents.
*Bulletin No. 74. The Tractive Resistance of a 28-Ton Electric Car, by Harold H. Dunn. 1914.
Twenty-five cents.
Bulletin No. 75. Thermal Properties of Steam, by G. A. Goodenough. 1914. Thirty-five cents.
Bulletin No. 76. The Analysis of Coal with Phenol is a Solvent, by S. W. Parr and H. F. Hadley.
1914. Twenty-five cents.
* Bulletin No. 77. The Effect of Boron upon the Magnetic and Other Properties of Electrolytic
Iron Melted in Vacuo, by Trygve D. Yensen. 1915. Ten cents.
*Bulletin No. 78. A Study of Boiler Losses, by A. P. Kratz. 1915. Thirty-five cents.
*Bulletin No. 79. The Coking of Coal at Low Temperatures, with Special Reference to the Prop-
erties and Composition of the Products, by S. W. Parr and H. L. Olin. 1915. Twenty-five cents.
*Bulletin No. 80. Wind Stresses in the Steel Frames of Office Buildings, by W. M. Wilson and
G. A. Maney. 1915. Fifty cents.
*Bulletin No. 81. Influence of Temperature on the Strength of Concrete, by A. B. McDaniel.
1915. Fifteen cents.
Bulletin No. 82. Laboratory Tests of a Consolidation Locomotive, by E. C. Schmidt, J. M. Snod-
grass, and R. B. Keller. 1915. Sixty-five cents.
*Bulletin No. 83. Magnetic and Other Properties of Iron-Silicon Alloys. Melted in Vacuo, by
Trygve D. Yensen. 1915. Thirty-five cents.
Bulletin No. 84. Tests of Reinforced Concrete Flat Slab Structure, by Arthur N. Talbot and
W. A. Slater. 1916. Sixty-five cents.
*Bulletin No. 85. The Strength and Stiffness of Steel Under Biaxial Loading, by A. T. Becker.
1916. Thirty-five cents.
*Bulletin No. 86. The Strength of I-Beams and Girders, by Herbert F. Moore and W. M. Wilson.
1916. Thirty cents.
*Bulletin No. 87. Correction of Echoes in the Auditorium, University of Illinois, by F. R. Watson
and J. M. White. 1916. Fifteen cents.
Bulletin No. 88. Dry Preparation of Bituminous Coal at Illinois Mines, by E. A. Holbrook. 1916.
Seventy cents.
*A limited number of copies of bulletins starred is available for free distribution.
94
PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION
* Bulletin No. 89. Specific Gravity Studies of Illinois Coal, by Merle L. Nebel. 1916. Thirty
cents.
*Bulletin No. 90. Some Graphical Solutions of Electric Railway Problems, by A. M. Buck.
1916. Twenty cents.
Bulletin No. 91. Subsidence Resulting from Mining, by L. E. Young and H. H. Stoek. 1916.
One dollar.
* Bulletin No. 92. The Tractive Resistance on Curves of a 28-Ton Electric Car, by E. C. Schmidt
and H. H. Dunn. 1916. Twenty-five cents.
* Bulletin No. 93. A Preliminary Study of the Alloys of Chromium, Copper, and Nickel, by
D. F. McFarland and O. E. Harder. 1916. Thirty cents.
* Bulletin No. 94. The Embrittling Action of Sodium Hydroxide on Soft Steel, by S. W. Parr.
1917. Thirty cents.
* Bulletin No. 95. Magnetic and Other Properties of Iron-Aluminum Alloys Melted in Vacuo, by
Trygve D. Yensen and W. A. Gatward. 1917. Twenty-five cents.
* Bulletin No. 96. The Effect of Mouthpieces on the Flow of Water Through a Submerged Short
Pipe, by Fred B. Seely. 1917. Twenty-five cents.
* Bulletin No. 97. Effects of Storage Upon the Properties of Coal, by S. W. Parr. 1917. Twenty
cents.
* Bulletin No. 98. Tests of Oxyacetylene Welded Joints in Steel Plates, by Herbert F. Moore.
1917. Ten cents.
Circular No. 4- The Economical Purchase and Use of Coal for Heating Homes, with Special
Reference to Conditions in Illinois. 1917. Ten cents.
* Bulletin No. 99. The Collapse of Short Thin Tubes, by A. P. Carman. 1917. Twenty cents.
* Circular No. 5. The Utilization of Pyrite Occurring in Illinois Bituminous Coal, by E. A.
Holbrook. 1917. Twenty cents.
* Bulletin No. 100. Percentage of Extraction of Bituminous Coal with Special Reference to Illinois
Conditions, by C. M. Young. 1917.
* Bulletin No. 101. Comparative Tests of Six Sizes of Illinois Coal on a Mikado Locomotive, by
E. C. Schmidt, J. M. Snodgrass, and O. S. Beyer, Jr. 1917. Fifty cents.
* Bulletin No. 102. A Study 'of the Heat Transmission of Building Materials, by A. C. Willard
and L. C. Lichty. 1917. Twenty-five cents.
* Bulletin No. 103. An Investigation of Twist Drills, by Bruce W. Benedict and W. P. Lukens.
1917. Sixty cents.
* Bulletin No. 10 4- Tests to Determine tjie Rigidity of Riveted Joints of Steel Structures, by
W. M. Wilson and H. F. Moore. 1917. Twenty-five cents.
Circular No. 6. The Storage of Bituminous Coal, by H. H. Stoek. 1918. Forty Cents.
Circular No. 7. Fuel Economy in the Operation of Hand Fired Power Plants. 1918.
Twenty cents.
: A limited number of copies of bulletins starred is available for free distribution.
THE UNIVERSITY OF ILLINOIS
THE STATE UNIVERSITY
Urbana
Edmund J. James, Ph.D., LL.D., President
THE UNIVERSITY INCLUDES THE FOLLOWING DEPARTMENTS:
The Graduate School
The College of Liberal Arts and Sciences (Ancient and Modern Languages and
Literatures; History, Economics, Political Science, Sociology; Philosophy,
Psychology, Education; Mathematics; Astronomy; Geology; Physics; Chemis-
try; Botany, Zoology, Entomology; Physiology; Art and Design)
The College of Commerce and Business Administration (General Business, Bank-
ing, Insurance, Accountancy, Railway Administration, Foreign Commerce;
Courses for Commercial Teachers and Commercial and Civic Secretaries)
The College of Engineering (Architecture; Architectural, Ceramic, Civil, Electrical,
Mechanical, Mining, Municipal and Sanitary, and Railway Engineering)
The College of Agriculture (Agronomy; Animal Husbandry; Dairy Husbandry;
Horticulture and Landscape Gardening; Agricultural Extension; Teachers’
Course; Household Science)
The College of Law (three years’ course)
The School of Education
The Course in Journalism
The Courses in Chemistry and Chemical Engineering
The School of Railway Engineering and Administration
The School of Music (four years’ course)
The School of Library Science (two years’ course)
The College of Medicine (in Chicago)
The College of Dentistry (in Chicago)
The School of Pharmacy (in Chicago; Ph. G. and Ph. C. courses)
The Summer Session (eight weeks)
Experiment Stations and Scientific Bureaus: U. S. Agricultural Experiment
Station; Engineering Experiment Station; State Laboratory of Natural His-
tory; State Entomologist’s Office; Biological Experiment Station on Illinois
River; State Water Survey; State Geological Survey; U. S. Bureau of Mines
Experiment Station.
The library collections contain (December 1, 1917) 411,737 volumes and 104,524
pamphlets.
For catalogs and information address
THE REGISTRAR
Urbana, Illinois
■
UNIVERSITY OF ILLINOIS-URBANA
3 0112 067251923