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 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 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 2t 3 NO CD <0 •D * AM fti IV 02 o to 8 <0 "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 s i^0.45 &