s 2^\ \~Lo C.z. STATE OF ILLINOIS I) WIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief URBANA REPORT OF INVESTIGATIONS- NO. 120 CORRELATION OF DOMESTIC STOKER COMBUSTION WITH LABORATORY TESTS AND TYPES OF FUELS II. COMBUSTION TESTS AND PREPARATION STUDIES OF REPRESENTATIVE ILLINOIS COALS Roy J. Helfinstine and Charles C. Boley \%*c xfr PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1946 LIBRARY. STATE OF ILLINOIS HON. DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION HON. FRANK G. THOMPSON, Director BOARD OF NATURAL RESOURCES AND CONSERVATION HON. FRANK G. THOMPSON, Chairman NORMAN L. BOWEN, Ph.D., D.Sc, LL.D., Geology ROGER ADAMS, Ph.D., D.Sc, Chemistry LOUIS R. HOWSON, C.E., Engineering CARL G. HARTMAN, Ph.D., Biology EZRA JACOB KRAUS, Ph.D., D.Sc, Forestry GEORGE D. STODDARD, Ph.D., Litt.D , LL.D., L.H D. • President of the University of Illinois GEOLOGICAL SURVEY DIVISION M. M. LEIGHTON, Chief (24454— 2500— 9-4G) ^S^ 2 ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 7319 M. M Enid Townley, M.S., Assistant to the Chief Veld a A. Millard, Junior Assl. to the Chief SCIENTIFIC AND TECHNICAL STAFF OF THE STATE GEOLOGICAL SURVEY DIVISION 100 Natural Resources Building, Urbana LEIGHTON Ph.D., Chief Helen E. McMorris, Effie Hetishee, B.S., Secretary to the Chief Geological Assistant GEOLOGICAL RESOURCES Ralph E. Grim, Ph.D., Pelrographer and Principal Geologist in Charge Coal G. H. Cady, Ph.D., Senior Geologist and Head R. J. Helfinstine, M.S., Mech. Engineer Charles C. Boley, M.S., Assoc. Mining Eng. Robert M. Kosanke, M.A., Assl. Geologist Robert W. Ellingwood, B.S., Asst. Geologist Jack A. Simon, B.A., Asst. Geologist Arnold Eddings, B.A., Asst. Geologist John A. Harrison, B.S., Asst. Geologist Raymond Siever, B.S., Research Assistant Mary E. Barnes, B.S., Research Assistant Margaret Parker, B.S., Research Assistant Walter E. Cooper, Technical Assistant Oil and Gas A. H. Bell, Ph.D., Geologist and Head Frederick Squires, B.S., Petroleum Engineer David H. Swann, Ph.D., Assoc. Geologist Virginia Kline, Ph.D., Assoc. Geologist Paul G. Luckhardt, M.S., Asst. Geologist Wayne F. Meents, Asst. Geologist Richard J. Cassin, B.S., Research Assistant Sue R. Anderson, B.S., Research Assistant Industrial Minerals J. E. Lamar, B.S., Geologist and Head Robert M. Grogan, Ph.D., Assoc. Geologist Mary R. Hill, B.S., Research Assistant Clay Resources and Clay Mineral Technology Ralph E. Grim, Ph.D., Petrographer and Head Henry M. Putman, B.A.Sc, Asst. Geologist William A. White, B.S., Research Assistant Groundwater Geology and Geophysical Exploration Carl A. Bays, Ph.D., Geologist and Engineer, and Head Robert R. Storm, A.B., Assoc. Geologist Arnold C. Mason, B.S., Assoc. Geologist (on leave) Merlyn B. Buhle, M.S., Assoc. Geologist M. W. Pullen, Jr., M.S., Asst. Geologist Gordon W. Prescott, B.S., Asst. Geologist Margaret J. Castle, Asst. Geologic Draftsman Robert N. M. Urash, B.S., Research Assistant George H. Davis, B.S., Research Assistant Engineering Geology and Topographic Mapping George E. Ekblaw, Ph.D., Geologist and Head Richard F. Fisher, M.S., Asst. Geologist Areal Geology and Paleontology H. B. Willman, Ph.D., Geologist and Head Chalmer L. Cooper, Ph.D., Geologist C. Leland Horberg, Ph.D., Assoc. Geologist Heinz A. Lowenstam, Ph.D., Assoc. Geologist Subsurface Geology L. E. Workman, M.S., Geologist and Head Elwood Atherton, Ph.D., Asst. Geologist Paul Herbert, Jr., B.S., Asst. Geologist Marvin P. Meyer, B.S., Asst. Geologist Elizabeth Pretzer, M.S., Asst. Geologist Physics R. J. Piersol, Ph.D., Physicist Mineral Resources Records Vivian Gordon, Head Ruth R. Warden, B.S., Research Assistant GEOCHEMISTRY Frank H. Reed, Ph.D., Chief Chemist Carol J. Adams, B.S., Research Assistant Coal G. R. Yohe, Ph.D., Chemist and Head Eva O. Blodgett, B.S., Research Assistant Industrial Minerals J. S. Machin, Ph.D., Chemist and Head Tin Boo Yee, M.S., Research Assistant Fluorspar G. C. Finger, Ph.D., Chemist and Head Oren F. Williams, B.Engr., Asst. Chemist Chemical Engineering H. W. Jackman, M.S.E., Chemical Engineer and Head P. W. Henline, M.S., Assoc. Chemical Engineer James C. McCullough, Research Associate James H. Hanes, B.S., Research Assistant (on leave) Leroy S. Miller, B.S., Research Assistant (on leave) Earl C. Noble, Technical Assistant X-ray and Spectrography W. F. Bradley, Ph.D., Chemist and Head Analytical Chemistry O. W. Rees, Ph.D., Chemist and Head L. D. McVicker, B.S., Chemist Howard S. Clark, A.B., Assoc. Chemist Lewis E. Moncrief, B.S., Research Assistant Emile D. Pierron, B.S., Research Assistant John C. Gogley, B.S., Research Assistant Elizabeth Bartz, A.B., Research Assistant Albertine Krohn, B.S., Research Assistant Phyllis K. Brown, B.A., Research Assistant MINERAL ECONOMICS W. H. Voskuil, Ph.D., Mineral Economist Douglas F. Stevens, M.E., Research Associate Nina Hamrick, A.B., Research Assistant Ethel M. King, Research Assistant EDUCATIONAL EXTENSION Gilbert O. Raasch, Ph.D., Assoc. Geologist LIBRARY Regina Yoast, B.A., B.L.S., Librarian Ruby D. Frison, Technical Assistant PUBLICATIONS Dorothy E. Rose, B.S., Technical Editor Meredith M. Calkins, Geologic Draftsman Beulah F. Hopper, B.F.A., Asst. Geologic Draftsman Willis L. Busch, Principal Technical Assistant Leslie D. Vaughan, Asst. Photographer Consultants: Ceramics, Cullen W. Parmelee, M.S., D.Sc, and Ralph K. Hursh, B.S., University of Illinois Mechanical Engineering, Seichi Konzo, M.S., University of Illinois Topographic Mapping in Cooperation with the United States Geological Survey. This report is a contribution of the Coal Division. Aug. 1, 1946 ILLINOIS GECtOGICAL SURVEY LIBRARY APR 2 6 !?«3 CONTENTS PAGE Introduction 7 Acknowledgments 7 Objectives 7 Scope 7 Equipment 8 Combustion 8 Preparation 10 Procedure 12 Source of samples 12 Preparation * 13 Chemical analysis 14 Petrographic analysis 14 Combustion testing schedule 14 Combustion rating factors 15 Cost of heat 15 Attention required 16 Ability to maintain desired temperature in the home 16 Smoke emitted 18 Ability to maintain fire at low rates of operation 18 Appearance of fuel bed and fire 18 Results 19 Correlation of combustion results with chemical and petrographic analyses 19 Heat obtained 19 Uniformity of combustion 25 Responsiveness 30 Pickup 32 Overrun 32 Clinker rating 32 Correlations between combustion characteristics 35 Ranking of coals 35 Effect of cleaning upon quality of coal 36 Effect upon chemical characteristics 39 Effect upon petrographic constitution 46 Effect upon combustion characteristics 47 Conclusions 52 Appendix — Complete data on all test coals 53 TABLES Table Page 1. Source and description of samples 12 2. Relationship between cost of heat, heating value of coal, and cost of coal 24 3. Numerical ranking of combustion and chemical properties of coals tested 36, 37 4. Changes in heating value, mineral matter, ash, sulfur and pyritic sulfur due to cleaning 40 5. Change in quality, classified by methods of cleaning 41 6. Changes in vitrain caused by cleaning 46 7. Summary of changes in vitrain content caused by cleaning 47 8. Percentages of the banded ingredients in the test coals 48 9. Changes in combustion characteristics caused by cleaning 50 10. Summary of changes in combustion characteristics caused by cleaning 51 ILLUSTRATIONS Figure Page 1 . Stoker-boiler unit 9 2. Concentrating table and auxiliaries 10 3. Location of mines from which samples were obtained 13 4. Heat output during continuous stoker operation with a coal which burned non-uniformly . . . 16 5. Heat output during continuous stoker operation with a coal which burned uniformly 17 6. Heat obtained vs. heating value 19 7a. Efficiency vs. heating value 20 7b. Efficiency vs. ash 20 7c. Efficiency vs. volatile matter. , 20 8. Heat obtained vs. carbon 21 9. Heat obtained vs. fixed carbon 22 10. Heat obtained vs. ash 22 11. Heat obtained vs. 0.713 heating value -0.8 ash - 1000 : 22 12a. Heat obtained vs. fixed carbon X heating value 23 12b. Heat obtained vs. carbon / (oxygen -f- ash) 23 12c. Heat obtained vs. ash + oxygen + nitrogen 23 13. Relative cost of heat, as affected by heating value and cost of coal 25 14. Uniformity vs. ash 26 15. Uniformity vs. mineral matter 26 16. Uniformity vs. sulfur 26 17. View of fuel bed with large amount of clinker 27 18. View of fuel bed with considerable amounts of coke and clinker 27 19. Uniformity vs. British swelling index 28 20. Mineral matter vs. ash 28 21. Uniformity vs. vitrain 29 22. Responsiveness vs. ash 30 23. Responsiveness vs. volatile matter 30 24. Pickup vs. ash 31 25. Pickup vs. AI2O3 in ash 31 26. Pickup vs. volatile matter 31 27. Overrun vs. ash 33 28. Overrun vs. heating value 33 29. Clinker rating vs. ash 33 30. Heat obtained vs. uniformity 34 31 . Heat obtained vs. responsiveness 34 32. Responsiveness vs. pickup 34 33. Uniformity vs. pickup 38 34. Uniformity vs. overrun 38 35. Overrun vs. pickup 38 36. Uniformity vs. minimum/average rates of heat release 39 37. Changes in heating value, mineral matter, ash, sulfur, and pyritic sulfur caused by cleaning. 42, 43 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/correlationofdom120helf CORRELATION OF DOMESTIC STOKER COMBUSTION WITH LABORATORY TESTS AND TYPES OF FUELS II. COMBUSTION TESTS AND PREPARATION STUDIES OF REPRESENTATIVE ILLINOIS COALS Roy J. Helfinstine and Charles C. Boi.ey INTRODUCTION IN 1942 the Illinois State Geological Survey issued the first report 1 of a series on stoker combustion studies designed to explore the influence of coal on the perform- ance of typical domestic stokers. The first investigation, which was carried out in coop- eration with the University of Illinois Engi- neering Experiment Station, described the testing of six Illinois and two West Vir- ginia coals. Performance characteristics, as determined primarily from the observed formation of coke in the fuel bed, the smoke emission, and the nature of the clinker, appeared to have some correlation with rank, petrographic constitution, and British swell- ing index number. The present report, the second of the series, describes the results of more compre- hensive work along the same lines. Acknowledgments This investigation was made under the supervision of Gilbert H. Cady, Head of the Coal Division, for whose continuing interest and many helpful suggestions the writers are indebted. Grateful acknowledgment is extended to O. W. Rees, Geochemical Section, who directed the many routine and specialized chemical tests, to B. C. Parks, Coal Divi- sion, who was responsible for the petro- graphic analyses, and to S. Konzo of the University of Illinois Engineering Experi- ment Station for assistance and advice throughout the investigation. 1 McCabe, L. C, Konzo, S., and Rees, O. W., Correla- tion of domestic stoker combustion with laboratory tests and types of fuels. I. Preliminary studies: Illinois Geol. Survey, Rept. Inv. 78, 20 pp., 1942. Most of the coal samples were contrib- uted by the coal companies whose coopera- tion at all times is sincerely appreciated. OBJECTIVES The primary objective of the tests de- scribed in this report was to determine the degree of correlation existing between the combustion characteristics of Illinois coal in domestic stokers and their chemical prop- erties and petrographic composition. An essential preliminary objective was the de- velopment of suitable criteria by which the relative combustion behavior of coal could be evaluated. As a study of the entire range of Illinois coal quality was desired, several methods of cleaning the coal were employed. The action and effectiveness of these methods formed a secondary objective. SCOPE There are many factors that govern the suitability of coals for domestic stokers. Included are: 1) cost of heat; 2) attention required by the heating plant, including related cleanliness; 3) the ability to main- tain the desired temperature in the home; 4) the smoke emitted during combustion; 5) the ability to maintain fire at low rates of operation; 6) the appearance of the fuel bed and fire; 7) the odors given off by clinkers during their removal; and 8) the quietness of operation. These factors vary in relative importance, depending upon the heating system being used and also upon personal preferences of the operator. Some indicators of all the factors listed (except the odors given off by the clinker [7] s DOMESTIC STOKER COMBUSTION and the quietness of operation) were de- vised and are included in this report. The rating factors are discussed in a separate section (pp. 15-18). As the present project was concerned only with factors influenced by the combustion properties of the fuel, the appearance and cleanliness of the coal before firing were not considered. Forty-three Illinois coals, prepared from fifteen major samples, were tested. Chemi- cal tests of each coal included the proxi- mate analysis, the ultimate analysis, heating value, ash fusion temperatures, British swelling index, and some measure of plastic- ity. Additional determinations were made for the varieties of sulfur for 20 of the 43 coals, the chemical constituents of the ash for 22 coals, a measure of ignitibility for 21 coals, and chemical fusain for 16 coals. Analysis for petrographic constitution involved a determination of the percentages of vitrain, clarain, durain, and fusain, 2 and of non-coal material, defined as material exceeding 1.5 in specific gravity. Quantitative correlations of combustion characteristics and the data on chemical nature and petrographic composition were sought and are presented, together with an analysis of the effects of the cleaning pro- cesses on the quality and quantity of the coals. In addition, a basic fund of informa- tion regarding the combustion behavior of a group of Illinois coals has been obtained. EQUIPMENT Combustion All the tests included in this report were made in a stoker-fired cast-iron boiler, rated at 570 sq. ft. of equivalent direct radiation (136,800 B.t.u. per hour). A maximum feeding rate of 28 pounds per hour was also indicated by the boiler manufacturer. The unit was operated as a conventional forced- circulation hot-water boiler. The boiler inlet water was maintained at approximately 160° F. by automatic control of the quan- 2 Cady, Gilbert H., Nomenclature of the megascopic de- scription of Illinois coals: Econ. Geol. vol. 34, No. 5, pp. 475-94, 1939; Illinois Geol. Survey Cir. 46, 20 pp., 1939. tity of cooling water to a heat exchanger in the boiler-water circuit. The entire stoker-boiler unit, including the heat exchanger, was mounted on a scale with dial graduations of 1/2 pound. All external connections were made highly flex- ible; in fact a 2-ounce weight placed on the unit would cause an observable movement of the scale pointer. A photograph of the test unit is shown in figure 1. A two-pen mercury-actuated recording thermometer provided a continuous record of the temperatures of the water entering and leaving the boiler. This recorder had 12-inch round charts, with a temperature range of 80-220° F. and 1° scale divisions. A check indicated the accuracy of the instru- ment to be about ± \/ A ° F. This instru- ment error would be proportionately large during tests with low rates of operation if the maximum temperature difference be- tween the inlet and outlet water were lim- ited to 20° or 30° F., which is common practice in home installations. Therefore the maximum difference between the inlet and outlet boiler-water temperature was allowed to exceed 20° on many occasions. The quantity of water flowing in the boiler-water circuit was indicated by a hot- water meter. The meter was checked by occasionally weighing the quantity of water {Kissing through, although no appreciable variation was ever found. The rate of water flow was kept constant during the tests, irrespective of the opera- tion of the stoker. This is contrary to usual home practice, but seemed to be neces- sary if the measurements were to be accu- rate. Intermittent flow would result in increased errors of flow measurement, re- quiring knowledge of the instantaneous rate of flow and the difference between inlet and outlet boiler-water temperatures at cor- responding times. Such coordination would be extremely difficult. Therefore the water was circulated at a constant rate and as the same procedure was used for all tests, com- parable results were obtained. The temperatures of the air' entering the stoker fan and of the stack gas were recorded by means of a multipoint potentiometer (0 to 40 millivolt range) and thermocouples. EQUIPMENT Fig. 1. Stoker-boiler unit. A chemical-type meter, which was fre- quently checked with a hand-operated Orsat analyzer, recorded the percentage of C0 2 in the stack gas. The static pressure in the stoker air duct was recorded by a pressure gage. A wattmeter, to show the power required by the stoker, and inclined tube manometers, to show the draft in the stack and combustion chamber, were provided. The multipoint potentiometer also re- corded the opacity of the stack gases. This was done by projecting a beam of light across the smoke pipe upon a photoelectric cell. The current generated, which is approximately proportional to the illumina- tion on the face of the photoelectric cell, was passed through a fixed resistance. The voltage drop across this resistance was re- corded by the potentiometer. Since the illu- mination falling upon the photoelectric cell is governed by the "density" of the smoke in the stack, the desired record was made by the potentiometer. A 16-mm. motion picture camera was used for taking pictures of the fuel bed by one arrangement and of the scale dial by another. A special timer allowed the pic- tures of the fuel bed to be taken at any interval from ]4 to 6 seconds per frame. One frame every 2j/^ seconds was adopted as standard for the tests to date. When not being used for taking pictures of the fuel bed, the camera was mounted and controlled in such a manner that it automatically took single frame pictures of the scale dial and a clock at appropriate regular intervals, thereby furnishing a record of the loss in weight of the unit without continuous atten- tion. The weight at the indicated time could be determined rapidly and conveni- ently by viewing the film through a low- power microscope. 10 DOMESTIC STOKER COMBUSTION Preparation The coal washing unit selected for the investigation was a laboratory-size concen- trating table, equipped with a diagonal lino- leum-covered deck and wooden riffles. The dimensions of the deck were 8 feet 8 inches by 4 feet 7 inches. The action of the concentrating table, in common with most coal washing processes, takes advantage of the fact that the specific Fig. 2. Concentrating table and auxiliaries. EQUIPMENT II gravity of clean coal is appreciably less than the specific gravity of any solid inert mate- rial associated with the coal. Thus any separation based upon specific gravity will also produce a relatively low-ash fraction and a relatively high-ash fraction. The concentrating table utilizes specific gravity differences by balancing two tenden- cies that are simultaneously brought to bear on the coal particles. The head motion imparts a non-symmetric reciprocation of the table along its long axis, in such a way that particles on it tend to move toward one end. At the same time a sheet of water flows across the table, tending to carry par- ticles toward one side. The coal to be cleaned is introduced at one corner, where the separation process begins. Particles of low specific gravity are affected more by the wash of water and less by the reciprocation of the deck and thus tend to be carried to the side, while the net tendency of motion for particles of higher specific gravity is toward the end. It is evident that the angles of cross-wise and longitudinal slope are important in their effect. The concentrating table is built with provision for adjusting the cross- wise slope during operation ; in these tests the table was modified to permit prompt adjustment of longitudinal slope also. Special provision was also made to change the speed of reciprocation of the table, nor- mally of the order of 270 strokes per min- ute. Length of stroke could be adjusted during operation up to a maximum of about 1]/?, inches. Coal from a bin of about 3500-pound capacity was fed to the table by a vibrating feeder controlled by a variable voltage auto- transformer. Water flow was metered, and a modified type of manometer was provided to indicate rate of flow. Because relatively small quantities of coal were available for the entire procedure of establishing equilibrium, beginning with an empty table and producing at least 1500 pounds of coal under stable conditions, a recirculating system was developed, which consisted of a flight conveyor, a bucket ele- vator, and appropriate launders and chutes. It was then possible to draw off a relatively small (200 to 300 pounds) quantity of coal from the feed bin and to experiment at length, without further loss of coal, in order to establish desired washing conditions. During this period, coal particles were sep- arated on the table, recombined by launders, and dropped into relatively quiet water in a large tank where they settled into the trough of the flight conveyor. They were then carried up a de-watering section and dropped into the boot of a bucket elevator, which lifted them to a point that permitted chuting them back to the feedbox of the table. A photograph of the table and auxil- iary equipment is shown in figure 2. When the desired washing conditions were established, a simple redisposition ot a launder and a deflector permitted the withdrawal of the separated products. At the same time, of course, the feeder from the main feed bins was cut in, and the recir- culation phase of the washing operation gave way to the production phase, which continued steadily as long as necessary. Sampling boxes were available for snap zone samples of the table products and for rapid estimation of percentage of reject being produced at any time. Variations of size also affect the direc- tion and rate of travel of particles across the deck of a concentrating table, so that separation is not solely based on differences in specific gravity. For separation on a true specific gravity basis, a bath of high-density liquid in which particles are free to sink or to float may be used. In this investigation, water solutions of zinc chloride were used, contained in 55-gallon barrels. Coal was lowered into the solution in a close-fitting wire-mesh basket, and after stratification had taken place, a "float" basket with a spe- cial damper-type bottom was lowered through the floating coal. By closing the bottom and raising the float basket, practi- cally all of the floating coal was removed at once, leaving only scattered particles to remove with a dipper. Sink material was of course left in the larger basket. A small tank filled with water to wash the zinc chloride solution from the coal, and an over- 12 DOMESTIC STOKER COMBUSTION Table 1.— Source and Description of Samples Lab. No. County Coal bed Mining district* County rank index b Rank, High volatile A, B, or C Description of coal 1 Franklin LaSalle. . . Vermilion 5 Macoupin Peoria . . Gallatin Wabash Herrin No. 6 Franklin- Williamson. . . . LaSalle No. 2 LaSalle Grape Creek Danville Herrin No. 6 Central Illinois Springfield No. 5 . Fulton-Peoria. . Harrisburg No. 5. .Eagle Valley. . . Friendsville Mt. Carmel 9 St. Clair Herrin No. 6. Belleville 10 Saline . . 11 Vermilion. 12 Sangamon Harrisburg No. 5. .Saline Danville No. 7 . . . . Danville . . . Springfield No. 5 . . Springfield. 13 Randolph Herrin No. 6 14 Christian . 15 Williamson 16 Knox 131 .Southwestern Illinois 126 Herrin No. 6 Central Illinois 123 Herrin No. 6 Franklin- Williamson . 133 Rock Island No. 1 Northwestern Illinois 123 Washed stoker, 7/16" by 10 mesh 122 C Raw \}4" stoker 122 C 134" screenings, dedusted 121 c V/i" screenings 122 c V/i" screenings 145 A Mine run 122 C Largely 2" or 3" screen- ings with some lump 126 C Mine run. Considerable fine coal included 137 B Stoker, V/i" by 10 mesh 125 C Small stoker, 1 " by 8 mesh 121 C Largely stoker, 1 " by 5/16", with some 5 16" byO C Crushed V/ 2 " by %» C V/2" screenings B V/z" dedusted screenings C Stoker, 1" by K" a Designation of mining di-iricts approximately as used in: Bement A., Illinois coal: Illinois Geol. Survey Bull. 56, p. 23, 1929. b Average heating value, expressed in hundreds of B.t.u. per pound on a moisl mineral matter free l>a^, l samples reported up to October, 1934. See: Cady, Gilbert H., Classification and selection of Illinois coals: Illinois Geol. Survey Bull. 62, 354 pp., 1935. head track, trolley, and chain hoist simpli- fied the hoisting and moving operations. A three-surface vibrating screen, accom- modating wire-mesh screens 17 by 32 inches in size, was used for the screening operations, and a small jaw crusher and a 12 by 10-inch smooth surface double-roll crusher were used for crushing. and petrographic analyses, so that a mass of data relating to the combustion, chemical, and petrographic characteristics of all the test coals was built up. Salient details of the source of the sam- ples, methods of preparation, and nature of chemical and petrographic analyses arc given below. PROCEDURE In brief, the flow of work involved obtaining a truck-load of coal from a selected mine, sizing the coal, preparing from it two lots of improved quality (reduced mineral matter content), and testing a lot of sized but otherwise untreated coal and the two improved lots with standardized tests in a stoker-boiler unit. At the same time, sam- ples w r ere obtained for subsequent chemical Sourci- of Coal Samples Fifteen shaft mines throughout the State of Illinois, producing coal from all commer- cially important seams and in all major mining districts (excluding strip mines), were selected (table 1 and fig. 3). The county average of rank index 3 of the coals tested ranged from 121 to 145, as 8 Heating value, moist mineral-matter-free basis, ex- pressed in hundreds of B.t.u. per pound. PROCEDURE 13 DAVIESS STtPMlNSON WINNEBAli )T:r~ McHENRY )| LAKE *Zs IDEKALB j '| DU .? I WARREN | "tf / "I '-'V.NGSTON I £ j 5" , C PEORIA/ WOOOFOBD I <-L^^J kL|" I FORD I I "L, I McLt " 1 BROWN ^Wji^i -j MORGAN "NgIKoW^ T J f tH, \ f L-t ^oultr.elJ, I A ' ^ •"<«■•» r Icuar, J Jl-ttOMi.'MWGWI.r 7 ^UMBERLANDI ( 1^ I r A — 4 — t -, \* RICHLAND LAWRENCE/ WASHINGTON .* 7T' ,UNE Gal Fig. 3. Location of mines from which samples were obtained. noted in table 1. This represents nearly the complete range of rank index variation for Illinois coal, extending from 112 to 145. The only coal available with rank index lower than 121 is strip-mine coal, which was avoided throughout because of possible effects due to weathering. Preparation A fixed size range of one-half inch square hole by 8 mesh was selected and used throughout the tests. A study of the effect of size on combustion is the objective of a separate investigation. The selected size was well adapted to the concentrating table, and discrepancies due to sampling and seg- regation in handling were minimized by the small absolute size and the narrow size range. With the exception of test coal 1A, all sizing was done with the vibrating screen. The nominal size of coal 1A as obtained was 7/16-inch by 10 mesh, and it received no further preparation. The other test coals were passed over a one-half inch screen, and the oversize was crushed and passed over the screen a second time, this being repeated if necessary. Minus 8-mesh particles were sampled, weighed, and dis- carded. The concentrating table was used to pro- duce a coal of reduced mineral matter con- tent (identified by the suffix letter B) from the raw coal (identified by the suffix letter A). This operation was carried out in such a way that there was a commercially rea- sonable recovery, usually of the order of 80 to 90 percent. The adjustments of the concentrating table were varied during an initial trial period as appeared to be necessary for the coal being prepared. The recirculation equipment (p. 11) permitted experimenta- tion for any desired length of time. When a visually satisfactory separation was ob- tained, with approximately the desired amount of recovery, preparation of the test coal was begun and carried through with- out further change in the adjustments. In most cases a coal of still lower min- eral matter content (identified by the suf- fix letter C) was then prepared, using the table or the zinc chloride solution, or both. This operation was carried out without regard to the maintenance of a commer- cially reasonable percentage of recovery; the major intent was to produce, from the quantity available, a coal with the greatest possible change in characteristics from the original. The only limitation was the need for approximately 1500 pounds for sam- pling and combustion testing. Each washed coal was surface dried, with- out heat, in an effort to produce a washed coal having a moisture content similar to that of the corresponding raw coal. Coals 5B and 5B 1 were exceptions; they were dried in a gas-fired oven, with resulting moisture contents less than half of that of coal 5A. 14 DOMESTIC STOKER COMBUSTION Coals 5B 1 and 6B 1 were substantial duplicates of coals 5B and 6B, respectively, with regard to preparation procedure and to resulting ash content. Coal 12A 1 was prepared by adding to coal 12C crushed and sized clinker produced in burning coal 12B in an amount calculated to bring the resulting ash content up to that of the raw coal, 12A. Chemical Analysis A sample of from 100 to 150 pounds from each of the 43 coals was crushed and riffled to a portion of about two pounds for the chemical tests, which were conducted under the direction of O. W. Rees, Head of the Analytical Chemistry Division of the Illinois Geological Survey. Standard meth- ods of the American Society for Testing Materials 4 were used for the proximate and ultimate analyses, and for the determi- nation of heating values and ash fusion temperatures. Varieties of sulfur were determined according to Powell and Parr." For the property of plasticity, the Gieseler test was used for the majority of the coals. For ignitibility, the procedure developed by the Coal Research Laboratory of Carnegie Institute of Technology 7 was used. Chem- ical fusain was determined by a method suggested by Fuchs and his associates. 8 Petrographic Analysis The petrographic work, in which the per- centages of vitrain, clarain, durain, and fusain were estimated, was conducted by B. C. Parks. The method used involved a microscopic examination of each of a number of closely sized fractions prepared 4 Standard methods of laboratory sampling and analysis of coal and coke: A.S.T.M. Designation D271-44. 5 Powell, A. R., with Parr, S. W., A study of the forms in which sulfur occurs in coal: Univ. of 111. Eng. Exp. Sta. Bull. Ill, 66 pp., April 1919. Brewer, R. E., Plastic and swelling properties of bitu- minous coking coals: U. S. Bur. Mines Bull. 445, pp. 109-111, 1942. 7 Sebastian, J. J. S., and Mayers, M. A., Coke reactivity determination by a modified ignition point method: Ind. Eng. Chem., vol. 29, p. 1118, October 1937. 8 Fuchs, Walter, Gauger, A. W., Hsaio, C. C., and Wright, C. C., The chemistry of the petrographic constitu- ents of bituminous coals. Part I, Studies on Fusain: Pa. State College, Min. Ind. Exp. Sta. Bull. 23, 43 pp., 1938. 8 Parks, Bryan C, Studies in the petrographic analysis of broken coal by the particle count method: Illinois Geol. Surv., Rept. Inv. In preparation. from a sample of the coal to be analyzed. A thorough review of the subject and de- scription of the technique has been prepared for separate publication. 9 Combustion Testing Schedule The combustion testing schedule included tests with the stoker operating 60, 45, 30, and 15 minutes out of each hour. Approx- imately 300 pounds of coal were burned during each of these tests. The intermit- tent test with the stoker operating 15 min- utes out of each hour was followed by a hold-fire test of two days with the stoker operating about three minutes out of each one and three-fourths hours, and then a two-hour test with continuous stoker oper- ation. The test with the stoker operating contin- uously was started on a clean hearth. Only the clinker was removed before all tests with intermittent stoker operation. All coal, clinker, and ash were removed at the end of the series of tests with a given coal. About 50 pounds of coal were burned be- fore starting the actual test after changing the stoker operation rate and removing the clinker. Moving pictures of the combus- tion chamber were taken for approximately one-half hour at a definite time during each rest with a given operation rate. The chronological test schedule follows: Tuesday 7:00 a.m. Start fire on clean hearth. Cause stoker to operate continuously. 10:00 a.m. Beginning of test period for continuous stoker operation. 3:45 p.m. Start taking motion pictures of fuel bed. 4:25 p.m. Stop taking motion pictures of fuel bed. 8:00 p.m. End of test period with continuous stoker operation. Remove clinker, fill hopper and change stoker operating rate to 45 minutes on and 15 minutes off. 10:15 p.m. Beginning of test period with stoker operating 45 minutes out of each hour. Wednesday 10:50 a.m. Start taking motion pictures of fuel bed. 11:05 a.m. Stop taking motion pictures of fuel bed. 1 1 :13 a.m. Start taking motion pictures of fuel bed. 1 1 :40 a.m. Stop taking motion pictures of fuel bed. COMBUSTION RATING FACTORS 15 1:15 p.m. End of test period with stoker oper- ating 45 min. out of each hour. Re- move clinker, fill Kopper and change stoker operating rate to 30 minutes on and 30 minutes off. 4:30 p.m. Beginning of test period with stoker operating 30 minutes out of each hour. Thursday 10:45 a.m. Start taking motion pictures of fuel bed. 1 1 :05 a.m. Stop taking motion pictures of fuel bed. 1 1 :28 a.m. Start taking motion pictures of fuel bed. 1 1 :45 a.m. Stop taking motion pictures of fuel bed. 2:30 p.m. End of test period with stoker oper- ating 30 minutes out of each hour. Re- move clinker, fill hopper and change stoker operating rate to 15 minutes on and 45 minutes off. 6:30 p.m. Beginning of test period with stoker operating 15 minutes out of each hour. Friday 8 :43 a.m. Start taking motion pictures of fuel bed. 9:05 a.m. Stop taking motion pictures of fuel bed. 9:43 a.m. Start taking motion pictures of fuel bed. 9:55 a.m. Stop taking motion pictures of fuel bed. Saturday 10:30 a.m. End of test period with stoker oper- ating 15 minutes out of each hour. Remove clinker and change stoker operating rate to hold-fire (3 minutes out of each 1% hours). Monday 11:45 a.m. Start stoker operating continuously. 1 :45 p.m. Stop stoker. Quench fire, remove clinker and ash from hearth, and fly ash from boiler passages. Remove coal from hopper, worm, and retort. The weights of all coal placed in the hop- per, and of the coal, clinker, fly ash, and refuse removed were recorded. The refuse was sampled and analyzed for percentage of ash. This information enabled the cal- culation of the average relationship between the loss in weight of the stoker-boiler unit and the coal burned. 10 The average difference between the inlet and outlet boiler-water temperature was determined for 20-minute intervals for the test with continuous' stoker operation, and for each hour for the three tests with inter- mittent stoker operation. Overall averages of these temperature differences for each operation rate were determined. Overall averages for each operation rate were also obtained for "density" of smoke, pressure in the stoker windbox, temperature of the room, temperature of the stack gases dur- ing stoker operation, percentage of C0 2 in stack gases during stoker operation, rate of water flow through the boiler, boiler out- put, and coal burning rate. COMBUSTION RATING FACTORS As stated in the discussion of the scope of the investigation, some indicators were devised for all listed performance charac- teristics (p. 7), except odor given off by the clinker and quietness of operation. These indicators were all based upon objec- tive measurements, with the exception of clinker characteristics. A brief description of these indicators follows. Cost of Heat The cost of heat can be readily computed if the amount of heat that can be obtained from a pound of coal and the cost of the coal are known. The former can be deter- mined by fairly standard laboratory proce- dures, which were followed for all reported tests. With these standard tests, the heat output of the boiler, which is called "heat obtained" in this report, is the product of the difference in temperature between the inlet and outlet water and the quantity of water flowing through the boiler. It should be recognized that the actual quantity of heat obtained per pound of coal will be dependent upon the heating plant used for the tests. Therefore the values for heat obtained should be considered as relative, and are given in absolute terms only as a convenience. In fact, the figures do not represent the total amount of heat that would be given up to the house with the unit because of radiation from the heat- ing plant, including the chimney. A discus- sion of these losses is given in University of Illinois Experiment Station Bulletin No. 189. 11 10 Ratio: coal fed — (clinker removed -f- ash in refuse -(- ash in boiler passages) coal fed into combustion chamber 11 Willard, Arthur C, Kratz, Alonzo P., and Day, Vin- cent S., Investigation of warm air furnaces and heating systems, Part IV: Univ. 111. Eng. Exp. Sta. Bull. 189, pp. 46-55, 1929. 16 DOMESTIC STOKER COMBUSTION Attention Required The attention required by a stoker-fired heating plant depends upon many things. One major item is the frequency of required cleaning periods, which is generally related to the quantity of ash. Another is the quantity of clinker to be removed, which is equal to the quantity of ash, if it is a good stoker coal. Thus the percentage of ash in a coal is one index of the amount of atten- tion required. Other factors include the characteristics of the clinker. It is generally considered desirable for clinkers to have a high density (to minimize volume removed) and to be tough (to enable removal without shatter- ing). However, the clinker should not be so hard that it is difficult to break it into pieces that are easy to handle. The clinker should not stick to the hearth or combustion cham- ber walls, nor tend to form within the stoker retort. A major requirement is that the ash fuse into a clinker so that none must be removed in loose form. It is evident that judgment concerning clinkering characteristics is largely based upon personal opinions and that such char- acteristics do not readily lend themselves to objective tests. A subjective ranking vary- ing from (unsatisfactory) to 5 (ideal) was made at the time of clinker removal. In common with all subjective rankings, its value is limited. Ability to Maintain Desired Tempera- ture in the Home The ability of a heating plant to maintain the desired temperature within a home is generally thought to be governed by the heating plant and its controls. Neverthe- less, the fuel burned may exert a powerful influence. For example, if the coal does not burn uniformly it is possible that too little heat will be supplied during a period of poor combustion to maintain the desired tempera- ture, even though the stoker operates con- tinuously. The magnitude of the variation of the instantaneous rate of heat release is fre- quently not realized. Figure 4 shows this variation in rate of heat release with one of the coals tested that did not burn uni- formly. The stoker was operating continu- ously throughout the period illustrated. Even the most uniformly burning coal varied somewhat in rate of heat release, as shown by figure 5. An indicator of the magnitude of this variation is the ratio of minimum rate of heat release to the average rate of heat release. Therefore the heat release for each 20-minute interval of the test with continu- ous stoker operation was determined, and the minimum value was divided by the aver- age to give the required ratio. The ratio of the minimum to average rates of heat release was also determined for the tests 275 250 225 175 ■ilili 7 8 9 Hours after fire was started Fig. 4. Variation in heat output during continuous stoker operation with coal 9A, a rela- tively non-uniformly burning coal. COMBUSTION RATING FACTORS 17 275 250 £ 100 o 50 5 Fig. 6 7 8 9 Hours after fire was started 5. Variation in heat output during continuous stoker operation with coal 15C, a rela- tively uniformly burning coal. with 45, 30, and 15 minutes of stoker oper- ation per hour. The cycle of operation for these tests was considered to be 60 minutes. It is recognized that the determination of absolute minimum value requires tests of infinite length. However, each test had a sufficient number of cycles to furnish a fairly reliable indicator of this combustion characteristic. The ability of a heating plant to main- tain uniform temperatures will probably be influenced by the constancy of the heat re- lease at any one operation rate. This char- acteristic was expressed as the average per- centage variation of the rate of heat release, for relatively short intervals of time, from the average rate of heat release for the test. The intervals arbitrarily selected were 20 minutes for the test with continuous stoker operation, and 60 minutes for the other three rates. The responsiveness of the fire is an impor- tant factor when quick heat is desired after a prolonged hold-fire period, such as occurs when the, house temperature is reduced dur- ing the night. "Responsiveness" in the present report is the average rate of heat release from the boiler for the first 30 min- utes of stoker operation following the 50- hour hold-fire period. Only one test was made for each coal, because the time required for duplicate tests was not thought to be warranted. The values indicated should not be considered as representative, but as single examples. Another factor closely connected with the responsiveness of the fire after a prolonged "off" period is the respon- siveness after a shorter "off" period, such as caused by thermostatic control during normal operation. This factor was meas- ured by determining the amount of heat released during the first five minutes of stoker operation following a 45-minute "off" period, and was classified as "pick- up." The values given are averages of 40 cycles. Some stoker-fired heating systems occa- sionally release sufficient heat after the stoker is shut off (by thermostatic or other type of control) to cause the temperature to rise above that desired. If so, the home owner would favor a coal furnishing the least amount of heat after the stoker shuts off. A measure of this tendency was made by determining the amount of heat released during the first five minutes after the stoker is shut off during the test period with 15 minutes of stoker operation per hour. The value given is the average for 40 cycles, and is called "overrun." Overrun is also an indicator of the responsiveness of the fire to control. 18 DOMESTIC STOKER COMBUSTION Smoke Emitted It is difficult to measure the quantity of smoke that passes out the stack during com- bustion. However, a record of the opacity of the stack gases can be made fairly con- veniently with the apparatus described (p. 9). It should be recognized that the rec- ord obtained does not give a quantitative measure of "smoke" for several reasons. Included is the fact that the velocity of the smoke particles through the beam of light is not constant. For example, with other factors constant, a drop in stack tempera- ture from 1000° F. to 635° F. results in a 25-percent decrease in velocity of the stack gas. If the velocity of the smoke particle is considered equal to that of the gas, only three-fourths the amount of smoke would pass out the stack at the lower temperature for the same reading of the smoke density indicator. This range in stack temperature could readily occur when testing poor coals. With intermittent stoker operation, the possible variation between smoke density and weight of the solid particles can be even greater, for the stack temperature not only drops a greater amount when the stoker shuts off, but the actual flow by weight of stack gas is reduced to a very small amount. Thus the volume of gas passing out the stack is extremely low, and a rather limited amount of "smoke" by weight passing out the stack per unit of time will result in a relatively opaque gas. This fact should always be remembered when records show that with a domestic stoker, the smoke density is greatest just after the stoker stops. This does not necessarily mean that the rate of the "smoke" emission during this off period is greater than during opera- tion. In any event the smoke produced when using a properly adjusted domestic stoker is not a serious problem, so elaborate equip- ment and highly accurate measurements were not considered warranted. Ability to Maintain Fire at Low Rates of Operation A satisfactory stoker coal must provide a responsive fire without giving off an appreciable quantity of heat. The most desirable coal in this respect would be the one that maintained the most responsive fire with the lowest combustion rate. As the length of time required to determine the lowest operation rate for each coal w r ould be prohibitive, it was arbitrarily decided that any coal that would maintain a respon- sive fire with the stoker operating approxi- mately 3 minutes out of each 1)4 hours would be considered excellent in this respect. All coals were thus checked. APPEARANCE OF FUEL BED AND FIRE Some householders may judge the suita- bility of a coal for domestic stokers by the appearance of the fuel bed and fire. This is rather unfortunate since the appearance may be very misleading. A level fuel bed, burning uniformly across the hearth, so often pictured, seldom exists in practice. Although visual inspection alone is not an adequate basis for judging stoker coal performance, it may aid in assigning the cause for non-uniform combustion. Thus, motion pictures of the fuel bed furnish a useful record. Such pictures are not amen- able to presentation in a written report ex- cept for enlargement of isolated frames. RESULTS 19 RESULTS Correlation of Combustion Results with Chemical and Petrographic Analyses Before discussing the results of the tests, it seems desirable to point out that the exact duplication of any single test can not be expected for several reasons. Included among these is the fact that coal is not a homogeneous substance, and no two loads, or even pieces of coal, are exactly alike. Consequently different results may be well expected, w T ith the amount of variation dependent upon the uniformity of the coal. Errors of measurement also prevent the exact duplication of results. These errors are quite small with the present equipment, but still exist. The results of a few dupli- cate tests indicate that 200 or 300 B.t.u. per pound is the least variation in heat obtained that should be considered signifi- cant. The least significant variations for the other combustion rating factors are probably two percentage figures for uni- formity, 3,000 B.t.u. per hour for respon- siveness, 2,000 B.t.u. per hour for pickup, and 3,000 B.t.u. per hour for overrun. The results discussed are all based upon tests of Illinois coals Although the range in characteristics is quite large, the coals are limited to the high volatile bituminous group. The conclusions reached are meant to apply to Illinois coals, and no extrapola- tion of results to out-of-state coals has been attempted. The data reported were obtained from the tests on the stoker-boiler unit pre- viously described. However, it is thought that the coals would exhibit the same rela- tive performance characteristics in other domestic heating units of this general type. Several tests on duplicate coals with a stoker-furnace unit that was available sup- ported this conclusion. Reference in the following discussion to degree of correlation existing between vari- ous items is based upon judgment of the usefulness of the graphs from the stand- point of estimation of one item from knowl- edge of another. The use of statistical methods to evaluate degree of correlation, while possible, did not appear to be war- ranted. The data are presented in full in the appendix. 1. heat obtained The amount of heat that was obtained from each coal was very nearly directly pro- portional to the heating value of the fuel, on the as-fired basis, as determined in a cal- i i.o a A 8.0 6 • _ "•" -- ^2 • %- ~- ' ■"•?■ • V _*- - —• «> — •— ^*« ..*— -* "•" • r^ ^ _».#• II.000 II, 800 12,600 Heatmq value, as - fired basis, B.t.u. per lb. Fig. 6. Relationship of heat obtained per pound of coal to heating value, on the as-fired basis. 20 DOMESTIC STOKER COMBUSTION 7o • • • > • • • • • e % s 4* • • • • • % • • • • • • • •• • • • • • 1 9400 10,200 11,000 11,800 12,600 Heating value, as-f''red Dosis, B.Tu per lb. 1 7b 1 • • • • • • • 1 • • 1 1 % 4 >c • • • • * 1 ► • i > • • • • • 8 10 12 I' Ash, as-fired basis, percer 7c 72 64 • • • • » e a .• > 4 ' ^ .• • • * • • 56 • • • • • • i ■ 40 10 ?>? 33 35 37 Volatile matter, os-firea basis, percent Fig. 7. Relationship of efficiency of stoker-boiler to (a) heating value, (b) ash, and (c) volatile matter, on the as-fired basis. orimeter (fig. 6). The solid line appears to be the best single line to represent the points shown. All points falling within the dotted lines are within 5 percent of the value indicated by the solid line. It will be observed that most of the points plotted are within the ± 5-percent lines. No evidence of unusual test or sampling errors could be found that would account for the variations exceeding 5 percent. Thus while the heat that will be obtained from Illinois coals can generally be closely pre- dicted from knowledge of the heating value, exceptions are quite probable. RESULTS 21 10.0 X 4.0 8 « -*- „ r" ■ " •r i • i — ■• --"•*' .• — 1 — • —- — — "" — ""• — ■ — "1 r — •" — -« -• — ^ •"% i ^___ -— ■ - -~C -— —■% O6.0 ^^=-—+r^ ^ . » — - 53 61 63 65 67 Carbon, as-fired basis, percent Fig. 8. Relationship of heat obtained per pound of coal to percentage of carbon, on the as-fired basis. Attention should be directed to the fact that the line indicated as the best for the points plotted is not an exact proportional- ity, owing to a slight increase in efficiency 12 of the heating plant with an increase in the heating value of the coal, as indicated by figure 7a. The increase in efficiency for the range of heating value represented was about 5 percent, although the coal with the lowest heating value (coal 8A) actually burned with a higher efficiency than did the coal with the greatest heating value (coal 7C). This emphasizes the risk in making all-inclusive generalizations. Figures 7b and 7c also show the relation- ships between efficiency and the percentages of ash and volatile matter as determined by chemical analysis. No marked trends are indicated. It might be well to emphasize that as far as cost of heating is concerned, the product of efficiency and heating value, which is called "heat obtained" in this report, is the governing factor. In addition, the term efficiency has several meanings, which often lead to misunderstandings, so its use is min- imized in this report. 12 The term efficiency as used in this report is the ratio of the heat absorbed by the boiler water to the heat of complete combustion, per unit weight of fuel burned. The heat obtained from the coals tested was also nearly directly proportional to the percentage of ultimate carbon, on the as- fired basis (fig. 8). There were actually fewer points outside the ± 5-percent lines with the carbon curve than with the heating value curve. However, this correlation with carbon is not as useful as that with heating value, because the former is more difficult to determine by present methods used in the chemical laboratory. Pleat obtained also exhibited a strong correlation with fixed carbon (fig. 9) although not quite as good as with heating value (fig. 6) or ultimate carbon (fig. 8). The correlation of heat obtained with the percentage of ash should probably be 'con- sidered as only fair, but it is a useful one because it is easily determined in the labo- ratory. Figure 10 shows that most of the values obtained fall within the ± 10-per- cent lines. Some of the chemical items that furnished relatively poor correlations with heat ob- tained may be of interest. Although graphs are not shown in this report, little or no useful correlation was found to exist be- tween the heat obtained and the British swelling index, volatile matter, moisture or vitrain. 1 1.0 0.0 9 8.0 • ■* • ^^•"^T! ■"""""ii • , • — ' • . — t • .— — • _•- • --*-"" «i— H 7.0 *-f 'V — — \ 1-^ • • f— ■ > 6.0 5.0 -••"* 4.0 34 36 38 40 42 44 46 48 50 52 54 56 58 Fixed carbon, as-fired basis, percent 0.0 3 8.0 §6.0 10 • — « t ~~2 • • « -- -^. •• • • « to ~~* • • « 1 """-I r^- a • • • • — • • ^« 4 l. •""*" ■ -•__ -— . 2 4 6 3 10 12 14 16 Ash, as-fired basis, percent 20 22 1 1 1 0.0 9 11 • — -"• .--— •-*•"" • — 8 ^>"Y 1 — — • — -—•*■ • •^s ■"" 7 .-•-' .•— ■ """" -•' " — 'mT~ — \~ • 6 _ • ■ 5.0 4 5700 6500 6900 7300 0.713 Heating value -0.8 ash - 1000 7700 Fig. 9 (Top). Relationship of heat obtained per pound of coal to percentage of fixed carbon, on the as-fired basis. Fig. 10 (Middle). Relationship of heat obtained per pound of coal to percentage of ash, on the as-fired basis. Fig. 11 (Bottom). Relationship of heat obtained per pound of coal to the best fitting linear expression involving heating value and ash, on the as-fired basis. RESULTS 23 Combinations of a few items given by chemical analysis were selected and the best co-efficients for a linear equation (equated to heat obtained) were calculated. The im- provements in correlation over that obtained with heating value alone are very slight. Figure 1 1 is a graph of one of the combina- tions calculated. Three other combinations I2a • . ■- ^* » «> — . • •_^ ■""• 5v • • • , -11 ~~* • _ -- — *" •~~~ , _•■ --- - •"• — • __ s^ • • —- 12 46 50 54 58 62 Fixed carbon X heating value 12 D __ _ — — - ( • i > » 1 • j i „ ^,— '^/-« i ► -""" — * « — ^33 i u •— # ss r^ r «^ < — • ' i " 'gen + ash as-fired basis 0.0 9.0 I2c #~~~ ^"~ ►- — . -— - 7.0 6.0 5.0 40 4 -« • — i __ --«. -•_^_ 1 ( • ~" ""-* • • ••- • 4 » i _ ► -,- - t_ "~— • l __ 1 f" ~- ~ — ^ -^ 23 25 27 29 31 33 35 ,sh + oxygen + nitrogen, os-fired basis, percent Fig. 12. Relationship of heat obtained per pound of coal to (a) fixed carbon X heating value; (b) ratio of carbon to oxygen plus ash; (c) percentage of ash -f- oxygen -f- nitrogen ; all on the as-fired basis. 24 COMBUSTION RATING FACTORS Table 2. — Relationship between Cost of Heat, Heating Value of Coal, and Cost of Coal Heating value of coal, B.t.u. per lb. Cost of coal, dollars per ton 9600 10000 10400 10800 11200 11600 12000 12400 12800 13200 Relative cost of heat obtained 3.00 27 26 25 24 23 22 21 20 19 19 3.25 30 28 27 26 24 23 23 22 21 20 3.50 32 30 29 28 26 25 24 23 22 22 3.75 34 32 31 29 28 27 26 25 24 23 4.00 36 35 33 31 30 29 28 27 26 25 4.25 39 37 35 33 32 31 29 28 27 26 4.50 41 39 37 35 34 32 31 30 29 28 4.75 43 41 39 37 36 34 33 32 30 29 5.00 45 43 41 39 38 36 35 33 32 31 5.25 48 45 43 41 39 38 36 35 34 32 5.50 50 47 45 43 41 40 38 37 35 34 5.75 52 50 47 45 43 41 40 38 37 36 6.00 55 52 49 47 45 43 42 40 38 37 6.25 57 54 51 49 47 45 43 42 40 39 6.50 59 56 53 51 49 47 45 43 42 40 6.75 61 58 56 53 51 49 47 45 43 42 7.00 63 60 58 55 53 50 49 47 45 43 7.25 66 63 60 57 54 52 50 48 47 45 7.50 68 65 62 59 56 54 52 50 48 46 7.75 70 67 64 61 58 56 54 52 50 48 8.00 73 69 66 63 60 58 55 53 51 50 8.25 75 71 68 65 62 59 57 55 53 51 8.50 77 73 70 67 64 61 59 57 55 53 8.75 79 76 72 69 66 63 61 58 56 54 9.00 82 78 74 71 68 65 62 60 58 56 9.25 84 80 76 73 70 67 64 62 59 57 9.50 86 82 78 75 71 68 66 63 61 59 9.75 88 84 80 77 73 70 68 65 63 60 10.00 91 86 82 79 75 72 69 67 64 62 10.25 93 89 84 81 77 74 71 68 66 64 10.50 95 91 87 83 79 76 73 70 67 65 10.75 98 93 89 85 81 78 75 72 69 67 11.00 100 95 91 87 83 79 76 73 71 68 which also give good correlation with heat obtained are : 1 ) the product of fixed car- bon and of heating value (fig. 12a) ; 2) the ratio of carbon to oxygen-plus-ash (fig. 12b) ; and 3) ash plus oxygen plus nitro- gen (fig. 12c). The product of fixed car- bon and heating value will probably prove to be the most useful of this group. The home owner is not primarily inter- ested in the actual amount of heat that can be obtained from a pound of coal. His prob- lem is one of relative costs. The relative cost of heat can be fairly readily calculated, if the cost of the coals and the amount of heat that is obtained per pound are known. As the heat that can be obtained from a pound of coal can be closely predicted as indicated by figure 6, it is possible to approximate the cost of heat directly from knowledge of the heating value. Such cal- culations are given in table 2. The base cost of heat given in the table is that obtained with coal of 9600 B.t.u. per pound, on the as-received basis, and costing $11.00 per ton, which is assigned a value of 100. The figures for all other heating values and coal cost give the cost of heat relative to this arbitrarily selected base coal. The same general information contained in table 2 is given in figure 13. RESULTS 25 9600 10,000 11,200 12,000 12,800 Heating value, as-firea basis, B.t.u. per lb. Fig. 13. Relative cost of heat, as affected by heating value and cost of coal. For an example of the use of table 2, assume that information is desired regard- ing the relative cost of heating with two coals, called A and B. Coal A has a heat- ing value of 11,600 B.t.u. per pound and costs $8.50 per ton. From the table it is found that its relative cost is 61. Coal B has a heating value of 10,400 B.t.u. per pound and costs $5.75 per ton. The table indicates its relative cost is 47. In other words, the ratio of heating costs would be 61 to 47, or approximately 23 percent less with coal B than with coal A. The same values can be obtained from figure 13. 2. UNIFORMITY OF COMBUSTION Uniformity of combustion, expressed as the percentage variation from the average rate of heat release, correlated about equally well with chemically determined values for ash, mineral matter, 1 ' 5 and sulfur on the as- fired basis. The general tendency was for more uniform combustion with a decrease in the percentage of these chemical items. The 13 Tri the present report, mineral matter is assumed to be 1.08 X (Ash) + 0.55 X (Sulfur). relationships are shown in figures 14, 15, and 16. Exceptions to the general trend were numerous. The most notable exception in case of ash vs. uniformity was with coal 8A (20.8 percent ash) from Wabash County which had an average variation of only 8.3 percent. One possible explanation is that this coal did not exhibit very strong coking tenden- cies, hence "coke tree" formation did not cause irregular combustion. The motion pictures taken of the fuel bed point to this explanation. Figure 17 is one view of the fire showing the lack of coke. The immense clinker which is shown certainly checked the fire, but did so in a fairly uniform man- ner as indicated by the relatively low per- centage of variation. Coal 9A had approxi- mately the same percentage of ash (19.3 percent) as 8A, but did not burn as uni- formly (20.5 percent variation). Although the black and white picture of the fuel bed with coal 9 A (fig. 18) does not differenti- ate coke and clinker, the original colored film makes possible definite identifications 26 DOMESTIC STOKER COMBUSTION 24 4- 14 • • • • • « | • • • ! • ^«» ' ' € **^ • »• • • **'! • i 1 • s > • • • • • • • 8 10 12 14 Ash, as-fired basis, percent 20 22 o 24 15 o • 20 c^ o % 16 D • • • • a e • • • 2 1 2 • c o « ^ . • • o U • • »^- 'I r • > • • •-*" •• •• • « ■ • c • • . » 1) a -•' 6 8 10 12 14 16 18 20 22 24 26 Mineral matter, as-fired basis, percent 16 • — IT"" " 1 1 • n __• • _!_ -^l_*.-, *-^- ! • • « •• • •_ • " • • • (i < • ii • , . . _• •_!! . t • 0.6 1.0 1.4 1.8 2.2 2.6 3.0 3.4 3.8 4.2 4.6 5.0 5.4 Sulfur, as-fired basis, percent Fig. 14 (Top). Relationship of uniformity of combustion to percentage of ash, on the as-fired basis. Fig. 15 (Middle). Relationship of uniformity of combustion to percentage of .mineral matter, on the as-fired basis. Fig. 16 (Bottom). Relationship of uniformity of combustion to percentage of sulfur, on the as-fired basis. l 1v ,!'S /* t ^ # Fig. 17. View of fuel bed with large amount of clinker. : W§Btmm Fig. 18. View of fuel bed with considerable amounts of coke and clinker, 28 DOMESTIC STOKER COMBUSTION 24 19 £ £ i < ii «-„. 12 Co 4) flO (i 4 1; *■ 8 « ' If 1 :: !_ (i c o • < British swelling index Fig. 19. Relationship of uniformity of combustion to British swelling index. of the large solid mass in the foreground as clinker, and the two spires at the top of the picture as coke. The lower portions of the pieces of coke are hidden by the clinker. It is obvious that the amounts of both coke and clinker would influence the uniformity of combustion. Hence the more uniform combustion with coal 8 A than with coal 9 A might be attributed to the difference in coking tendencies, since their percentages of ash are comparable. The British swelling index is commonly considered to be an indicator of coking tendency, and so an attempt was made to combine the percentage of ash and this swell- ing index in a manner that would give a use- ful correlation with uniformity of heat release. However, no systematic relation- ship could be found. The correlation of uniformity of combus- tion and British swelling index alone is very poor, as indicated by figure 19. This figure 26 /. 'lO 24 / 1-22 c \ V X '* r — Q. ** s* •" w I 8 o I i • *^ y*» I 2 4) I I ,j k 1 W 8 o « /' c 6 2 4 /"• 2 n 2 4 6 8 10 12 14 16 18 20 2 Ash, as-fired basis, percent Fig. 20. Relationship of percentage of mineral matter to percentage of ash in coals tested, on the as-fired basis. RESULTS 29 also indicates that the great majority of Illinois coals have a British swelling index in the 3 to 5 range, which is indicative of intermediate to weak coking tendency. The uniformity vs. mineral matter graph (fig. 15) exhibits very nearly the same characteristics as the uniformity vs. ash graph, with coals 8A, 3A, 8B, 2A, 16A, 8C, 1 IB, 11C, and 7C still exhibiting the great- est variation from the curve drawn. This might be expected, because the percentages of ash and mineral matter in the Illinois coals tested exhibit a strong correlation as shown in figure 20. When the percentages of sulfur were plotted against uniformity (fig. 16), it was found that the Wabash County coals (8 series) followed the indicated trend quite closely. Coals 2A, 16A, 11C, 11B, and 7C varied considerably from the general trend, as they did on the uniformity vs. ash graph, and also coals 11A and 9 A. The uniformity of combustion correlated fairly well with the percentage of vitrain (fig. 21) with the exception of the Wabash County coals. However, the maximum per- centage of vitrain reported for any coal burned was less than 30 percent. Within the range of coals tested, those with the higher percentages of vitrain tended to burn more uniformly. Numerous other single chemical items were plotted against the uniformity of com- bustion. Included were ultimate carbon, fixed carbon, moisture, Gieseler plasticity, heating value, oxygen, volatile matter, ini- tial deformation temperature of the ash, softening temperature of the ash, and fluid temperature of the ash. The correlations were considered to be poor or non-existent in every case. Several combinations including ash and sulfur; ash, sulfur and carbon-hydrogen ratio; and ash and ash-softening tempera- ture were tried. Little or no improvement in correlation over that found with ash alone was evident. 24 21 £ 2« • a .2* • • S*. 16 « ° D «• • s » • » • - - £ 4 c o • • 20 24 4 8 12 16 Vitrain, as — fired basis, percent Fig. 21. Relationship of uniformity of combustion to percentage of vitrain. ?8 30 DOMESTIC STOKER COMBUSTION 3. RESPONSIVENESS The responsiveness of the fire after a prolonged hold-fire period correlated fairly well with the percentage of ash in the coals (fig. 22). No definite reason could be found to explain the wide deviation of the group of six coals with approximately 9 per- cent ash that released heat to the boiler at a rate well above the apparent trend. As coal was fed into the combustion chamber faster than it burned during the period when the responsiveness of the coal was measured, it would seem that there might be a useful correlation with some measure of ignitibility. However, the igni- tion temperatures reported were very nearly constant, and no correlation was evident. The volatile matter is driven off rapidly after the coal comes into the combustion chamber, so that correlation between respon- siveness and volatile matter seemed possi- ble. However, the data (fig. 23) did not reveal such a correlation. The value given as an index to respon- siveness is not a measure of the amount of heat released by the coal, but of the rate of heat absorption by the boiler water. Be- cause the clinker, ash, and fuel in the com- 2 22 • • • 4 • • • • • • • • • • • • • • • • • • • • • •* • • • • 8 10 12 14 Ash, as-fired basis, percent 22 23 • • • 1 • • • • • • • • • < • i ' 1 . • • • • • • • • • • • 1 33 Volatile 35 37 -fired basis, percent 39 Fig. 22 (Top). Relationship of responsiveness of the fire after a prolonged hold-fire period to percentage of ash, on the as-fired basis. Fig. 23 (Bottom). Relationship of responsiveness of the fire after a prolonged hold-fire period to percentage of volatile matter, on the as-fired basis. RESULTS 31 32 24 *■•*. — • "^***« ■^^^ -- ^"*-4l 4 I * >» • T"*- « «► — ■"-»« , • '•*»*. "•^ ">. • • i » • "' % • •* ^. V t «- ^ ^^ • • « "^«^^ "**•« ^;-\ • ^-^v. -^ ^. 52 3 10 12 14 Ash, as-fired basis, percent 20 22 25 • # • ... """ • 4 • • • • • 20 22 l 2 3 in ash, percent 26 • * • 1 1 « • • 4 • 41 • • ► « 4 » » .' • • • • • • • — • 41 f 36 29 31 33 35 37 39 41 Volatile matter, as-fired basis, percent Fig. 24 (Top). Relationship of pickup rate after a 45-minute "off" period to percentage of ash, on the as-fired basis. Fig. 25 (Middle). Relationship of pickup rate after a 45-minute "off" period to percentage of A1 2 2 in the ash. Fig. 26 (Bottom). Relationship of pickup rate after a 45-minute "off" period to percentage of volatile matter, on the as-fired basis. 32 DOMESTIC STOKER COMBUSTION bustion chamber are relatively cool after a prolonged hold-fire period, they will absorb heat during the early part of the operation period. The quantity of heat absorbed will be partially dependent upon the amount of clinker, ash, and fuel in the combustion chamber. It is therefore obvious that even if the rate of heat release were the same for all coals, the rate of heat absorption by the boiler would be less for the high-ash coals. With the exception of mineral matter, all the other chemical items tried furnished either poor or no correlation with the re- sponsiveness. Included were British swell- ing index, ultimate carbon, Gieseler plastic- ity, heating value, oxygen, sulfur, moisture, initial deformation temperature of the ash, softening temperature of the ash, and fluid temperature of the ash. Little or no corre- lation was evident between the percentage of vitrain and responsiveness. 4. PICKUP One of the better indicators of pickup (defined on p. 17) was the percentage of ash on the as-fired basis, shown in figure 24. Numerous points fall outside the ± 10-per- cent lines. It is evident that the correlation is far from excellent. Coal 8A again gave better performance than would be expected in view of its high ash content. In fact, its rate of pickup was greater than that of coal 16C which had less than 5 percent ash. Thus, while the pickup rate did generally increase with a decrease in ash, the performance of individ- ual coals can not be predicted. The heating value, sulfur, mineral mat- ter, and carbon, on the as-fired basis, fur- nish about the same degree of correlation with pickup as the percentage of ash. A graph of the percentage of aluminum oxide in the ash vs. pickup rate indicates a fair correlation, as shown by figure 25, with a general increase in pickup accompanying an increase in AUCX Coals 3C and 1A, which furnished the greatest rate of pickup, were not included among the 22 coals for which the composition of the ash was determined. Unless these coals had more than 26 per- cent AUOs in their ash, which would not be expected, their high rate of pickup must be assigned to other causes. Although during the pickup period the coal is fed into the combustion chamber faster than it is burned, the volatile matter is probably released as fast as the coal is fed. Thus, the volatile matter might be expected to serve as an indicator of pickup rate. How- ever, figure 26 indicates that there is little or no correlation. Other chemical and petrographic items that gave poor or no correlation with pickup rate were British swelling index, fixed car- bon, moisture, ash fusion characteristics, Gieseler plasticity, and vitrain. 5. OVERRUN The percentage of ash and the heating value of the coal, on the as-fired basis, give the best correlations with overrun (defined on p. 17) of those plotted. Neither is very good (figs. 27 and 28). The range in over- run for equal ash or heating value is quite large. The correlation of mineral matter, sulfur, and carbon, on the as-fired basis, with overrun rate was of the same general order as the correlations of overrun with ash and with heating value. The correla- tions between overrun rate and British swelling index, Gieseler plasticity, oxygen, volatile matter, ash fusion characteristics, and vitrain were either poor or non-existent. 6. CLINKER RATING It is recognized that the subjective ratings of the clinker may not be strictly compara- ble because more than two years elapsed be- tween removing the first and last clinker for the series of tests reported, and the suc- cessive ratings were probably biased in each case by comparison w T ith the clinker last seen. In other words, the tendency would be to give the clinker a higher rating than proper if the clinkers recently removed had been very poor, and a lower rating if the previous ones had been excellent. Some correlation is evident between the subjective clinker rating and percentage of ash (fig. 29), but the points are widely scat- tered from the general trend. One coal RESULTS 33 IC4 I j j 2 60 f 27 • 1 • • 4 > • • • • 4 • • • • • • » • • : • • « • • ■ • • • • • » • • • • 3 10 12 \A Ash. as-fired basis, percent 28 • 4 < • • « • •• • • • • • •• • • • • • • • • • • • • • • • • • • • 11,000 11,800 12,500 Heating value, as-fired basis, B.t.u. per lb. 29 •-* — • • — » — 2 4 6 8 10 12 14 16 18 20 22 Ash, as-n'red basis, percent Fig, 27 (Top). Relationship of overrun rate after a 15-minute "on" period to percentage of ash, on the as-fired basis. Fig. 28 (Middle). Relationship of overrun rate after a 15-minute "on" period to heating value, on the as-fired basis. Fig. 29 (Bottom). Relationship of subjective clinker rating to percentage of ash, on the as-fired basis. 34 DOMESTIC STOKER COMBUSTION 30 30 • ,♦ / • «• • • • • • • • • » • • t • • • • • • • • • 4 6 8 10 12 14 16 Uniformity, percent voriatiort from average heat release 3 < 1 _ it ii i> < li ( > I I I • • O II 40 44 48 Average pickup rate, M B.tu. per hr 60 Fig. 30 (Top). Relationship of heat obtained per pound of coal to uniformity of combustion. Fig. 31 (Middle). Relationship of heat obtained per pound of coal to responsiveness of the fire after a prolonged hold-fire period. Fig. 32 (Bottom). Relationship of responsiveness of the fire after a prolonged hold-fire period to pickup rate after a 45-minute "off" period. RANKING OF COILS 35 with a clinker rating of four had an ash content approximately equal to another with a rating of one. This overlapping is even more evident in intervening ratings. The clinker rating was also plotted against the initial deformation, softening, and fluid temperatures of the ash. Little or no correlation was evident. Correlations Between Combustion Characteristics Little if any apparent definite relation- ship exists between the heat obtained from a coal and the uniformity with which it burns (fig. 30). Only one coal furnished more heat than the Gallatin County coals (7 series), but they were among the poorer coals in respect to uniformity. Several coals that furnished very low quantities of heat burned quite uniformly. However, the Franklin, Saline, and Williamson County coals ranked high in both categories. The responsiveness of the fire to heat demand after a prolonged hold-fire period appeared to have only a slight correlation with the heat obtained as shown in figure 31. A slightly better correlation is shown in figure 32 between responsiveness and pickup. Figures 33 and 34 show that there is little correlation between uniformity of combustion and pickup or overrun. How- ever, an increase in pickup is generally ac- companied by an increase in overrun, as indi- cated by figure 35. Figure 36 shows that there is a very good correlation between the uniformity of combustion and the minimum rate of heat release divided by the average rate of heat release. RANKING OF COALS As has been stated, the coals can be ranked according to individual characteristics, but these individual characteristics can not be combined into a single overall rating, be- cause their relative importance is not con- stant. Table 3 lists some of the combustion and chemical properties of the coals tested in numerical order from good to poor. Although the coals from southern Illinois are generally superior in most of the char- acteristics listed, frequently the prepared coals from other fields, and occasionally a raw coal from the northern districts, are included with the superior coals. Coal 15C furnished the greatest amount of heat per pound of coal of any tested. This coal was the float coal in a solution of approximately 1.3 specific gravity, and rep- resented the lightest 44 percent of coal 15 A. This low recovery, although not commer- cially practical, was of laboratory interest in an endeavor to secure an extreme improvement. It may be noted that the softening temperature of the ash was 250° F. less than with coal 15B. Nevertheless, some improvement over 15B occurred in nearly all the combustion characteristics. This was not true with coal from Knox County (16 series). The lightest fraction did not in general perform more satisfac- torily than the first upgrade, although its lower ash would be desirable. The coals from La Salle County (2 series) ranked rather poorly from the stand- point of heat obtained, but remarkably high in uniformity of combustion. The chief point of interest about the Gal- latin County coals (7 series) was the lack of improvement resulting from the cleaning operations. Although all three of the series ranked high as far as heat obtained per pound was concerned, they were in the lower ranks for most of the other combus- tion characteristics. The moisture content of these coals is quite low in comparison with other Illinois coals. Care needs to be exercised when using table 3 for a comparison of coals. For example, one of the poorer performing coals (6A) has the lowest percentage of volatile matter. This is a result of a high percent- age of inerts, and the relative position of this coal would be shifted considerably if the volatile matter ranking were made on a moisture-and-ash-free basis. 36 DOMESTIC STOKER COMBUSTION Table 3. — Combustion and Chemical Properties of Coals Tested. Heat obtained Uniformity Responsive- ness Pickup Overrun Ash Volatile matter Fixed carbon Coal M Coal Vari- Coal M Coal M Coal M No. B.t.u. No. ation No. B.t.u. No. B.t.u. No. B.t.u. Coal Per Coal Per Coal Per per per per per per No. cent No. cent No. cent lb. cent hr. hr. hr. 15C 8.48 2C 2.9 13C 39.5 3C 56 5A 63 15C 2.8 6A 29.9 15C 57.1 7A 8.19 15C 2.9 1A 38.5 1A 54 2A 64 16C 4.6 1A 30.2 15B 54.9 15B 8.17 3C 3.6 5B 1 37.9 15C 49 11A 64 9C 4.9 15B 31.1 1A 54.0 7B 8.16 16B 4.2 6B 1 37.3 2B 48 6B 65 2C 5.2 15A 31.4 10C 53.8 7C 8.09 2B 4.3 6B 35.3 3B 47 3B 69 IOC 6.0 2A 32.1 10B 53.2 10B 8.05 16C 4.4 3B 34.0 7C 47 9A 69 3C 6.7 3A 32.5 7C 52.9 15A 8.03 14C 4.9 8C 29.7 3A 45 12 A 1 70 15B 6.9 12A 32.8 15A 52.5 1A 8.02 3B 5.0 13B 29.4 7A 45 8A 73 1A 7.2 15C 32.9 7B 51.7 IOC 8.01 1A 5.2 14B 28.0 15B 45 lie 73 10B 7.2 13A 33.0 10A 50.9 16B 7.86 2A 5.4 15C 27.2 7B 44 12A 73 14C 7.3 10A 33.2 7A 49.4 16C 7.73 15B 5.4 15B 27.1 15A 44 16C 73 15A 7.9 6B 1 33.5 5B 1 49.2 3C 7.68 16A 5.6 16C 25.8 8B 42 11B 74 2B 8.0 12A 33.7 9C 48.7 10A 7.63 8C 5.7 3C 25.2 9B 42 7A 75 3B 8.0 6B 1 33.9 2C 47.3 9C 7.63 8B 5.7 9B 23.7 13C 42 12B 75 16B 8.1 7A 33.9 16C 47.1 2C 7.47 10C 6.3 14C 23.7 5B 1 41 13A 75 14B 8.2 8A 34.0 13C 46.9 5B 1 7.45 15A 6.4 15A 21.9 8C 40 2B 76 11C 8.4 5A 34.3 3B 46.1 5B 7.39 10B 6.4 7C 20.6 10A 40 6B 1 77 5B 1 8.8 9A 34.4 3C 45.2 13C 7.31 5B 1 6.7 2B 20.4 14A 40 16B 78 6B 9.2 10B 34.5 5B 44.9 14C 7.22 3A 6.8 16B 20.3 16B 40 3A 79 13C 9.2 3B 34.7 13B 44.4 11C 7.22 6B 1 6.9 3A 20.2 2A 39 7C 79 5B 9.3 2C 34.8 16B 44.4 9B 7.21 6B 6.9 12B 19.8 6B 39 9C 79 6B 1 9.6 IOC 34.9 11C 44.2 13B 7.12 5B 7.1 10B 19.5 6B 1 39 16A 80 7C 9.8 13C 34.9 12B 44.2 2B 7.09 9C 7.9 14A 19.3 10B 39 6B 81 10A 9.8 14A 34.9 6B 44.1 14B 7.07 13C 8.0 9C 19.1 IOC 39 7B 82 12B 9.9 11A 35.0 14C 44.1 12B 6.90 14B 8.2 16A 19.1 13B 39 8C 82 7B 10.4 7C 35.2 14B 43.7 16A 6.89 13B 8.2 8B 18.8 14C 39 14A 82 11B 10.5 12B 35.3 6B 1 43.3 8B 6.75 8A 8.3 13A 18.6 5B 38 14C 82 13B 11.5 3C 35.4 12A 1 43.1 6B 6.74 12 A 1 8.4 5B 18.4 8A 38 8B 83 16A 11.5 7B 35.4 2A 42.9 8C 6.71 12B 8.6 10A 18.2 9C 38 14B 83 8C 11.7 5Bi 35.8 11B 42.6 11B 6.67 9B 8.6 8A 18.0 14B 37 5B 84 9B 12.0 13B 35.8 2B 42.3 6B 1 6.65 10A 8.9 7B 17.6 16C 37 5B 1 84 14A 12.1 16A 35.8 14A 41.4 3B 6.60 14A 10.6 10C 16.2 11C 36 10A 84 12 A 1 12.4 8B 36.4 13A 41.3 12 A 1 6.57 12A 11.1 6A 15.7 16A 36 10B 86 2A 12.5 14C 37.1 9B 41.2 3A 6.53 7B 11.8 12A 15.4 5A 35 9B 87 8B 13.5 14B 37.3 8C 41.1 13A 6.25 5A 12.9 12A 1 15.0 9A 35 13B 87 7A 13.9 8C 37.6 6A 40.3 2A 6.21 6A 13.4 2A 14.6 11B 35 13C 88 12A 13.9 16B 38.1 8B 40.0 9A 6.18 11C 13.8 5A 14.6 12A 34 3C 90 3A 15.0 11B 38.4 16A 40.0 14A 6.11 7C 15.4 11C 13.7 12B 34 15B 90 6A 15.5 9B 38.6 12A 39.8 11A 6.09 7A 15.5 11B 12.6 11A 32 15C 90 13A 15.9 16C 38.6 3A 38.9 12A 6.04 11B 15.7 7A 11.7 12A 1 32 IOC 91 5A 16.6 9C 38.8 11A 36.6 8A 5.98 13A 16.8 11A 9.3 13A 32 15A 93 11A 17.4 2B 38.9 5A 36.5 6A 5.96 11A 17.8 9A 9.2 6A 30 1A 99 9A 19.3 11C 39.6 9A 36.4 5A 5.71 9A 20.5 8A 20.8 5B 40.6 8A 34.6 EFFECT OF CLEANING UPON QUALITY OF COAL The production of coals with character- istics appreciably different from those of the raw coals was the primary purpose of the coal cleaning work. The examination or the degree of change in quality resulting from the cleaning operation was an objec- tive of secondary importance. It was not considered advisable nor with- in the scope of the investigation to stand- ardize on some one element of the cleaning operation, such as percentage of reject, per- centage of reduction in mineral matter, per- centage of final mineral matter, or, in the case of the concentrating table, the setting of the various operating variables. Such a selection and its numerical value would have been arbitrary, and no single choice could be expected to be applicable to all Illi- nois coals. The criterion for the tabling which pro- duced the "B" coals was the establishment of an optimum degree of separation of coal EFFECT OF CLEANING 37 Each Property is Listed in Numerical Order from Good to Poor Sulfur Carbon Oxygen I.D. of Ash S.T. c jf Ash F.T. ( >f Ash Carbon ■*■ available Heating value Hydrogen Coal Per Coal Per Coal Per Coal op Coal op Coal op Coal Ratio Coal No. B.t.u. No. cent No. cent No. cent No. No. No. No. per lb. 15C .79 15C 73.4 7A 5.4 15B 2460 15B 2550 15A 2650 1A 20.2 7C 13220 1A .80 7C 73.2 7B 6.4 15A 2320 15A 2530 15B 2650 15A 20.1 15C 13100 15B .85 7B 73.0 7C 7.0 1A 2190 15C 2300 8A 2620 15B 20.0 7B 13080 15A .91 10C 73.0 10B 11.7 8B 2180 1A 2260 16C 2570 15C 19.2 10C 12990 3C 1.41 10B 72.1 10C 11.7 8C 2180 8C 2250 8B 2530 3A 19.1 10B 12880 3B 1.59 15B 70.7 10A 11.8 15C 2130 JB 2230 15C 2530 14A 19.1 9C 12530 IOC 1.74 1A 69.6 5B 14.2 3A 2120 3A 2170 16B 2530 14B 18.9 15B 12460 10B 1.95 9C 69.0 11C 14.2 3B 2110 16C 2170 8C 2510 14C 18.7 16C 12360 3A 2.09 7A 68.9 15B 14.6 8A 2070 3B 2160 1A 2460 3A 18.6 10A 12330 8C 2.10 15A 68.9 11B 14.7 13C 2060 16B 2160 3A 2420 13C 18.6 7A 12300 8B 2.12 10A 68.8 9A 14.8 16B 2060 3C 2140 13C 2400 9C 18.5 11C 12260 10A 2.47 16C 67.9 11A 15.2 14C 2050 13C 2130 13B 2390 3B 18.4 15A 12200 2C 2.56 11C 67.3 1A 15.4 16A 2040 2A 2110 lie 2380 5B 1 18.4 1A 12160 16C 2.65 5B 66.2 5B 1 15.4 16C 2040 7B 2110 3C 2370 8C 18.4 5B 11940 13C 2.72 5B 1 65.5 8A 15.4 3C 2030 8A 2110 3B 2370 12 A 1 18.3 16B 11890 8A 2.77 3B 64.9 15A 15.4 14B 2030 14C 2110 14A 2360 5B 18.2 5B 1 11830 6B 2.93 16B 64.9 9B 15.5 5B 2020 7C 2100 14B 2360 10B 18.2 11B 11830 13B 2.93 2B 64.8 15C 15.7 14A 2020 16A 2100 5A 2350 13B 18.2 2C 11650 6B 1 2.98 11B 64.8 9C 16.0 5A 2000 14B 2090 5B 2340 2C 18.1 2B 11630 11C 3.00 2C 64.7 13B 16.2 13B 2000 2B 2080 6B 2340 8B 18.1 13C 11600 9C 3.09 3C 64.7 13A 16.4 5B 1 1980 5B 2080 11A 2340 9B 18.0 3C 11490 11B 3.28 13C 64.2 16B 16.5 2A 1970 13B 2080 14C 2340 13A 18.0 14C 11490 14C 3.26 14C 63.1 2A 16.9 6B 1970 5B 1 2060 6B 1 2330 10C 17.9 3B 11450 2B 3.32 9B 62.7 2B 17.0 7B 1970 5A 2050 12A 2330 12A 17.8 14B 11430 9B 3.32 13B 62.7 13C 17.0 6A 1960 14A 2050 5B 1 2320 12B 17.8 9B 11360 7C 3.35 14B 62.4 8B 17.1 6B 1 1960 2C 2040 9B 2320 11C 17.7 13B 11330 16B 3.40 8C 62.0 8C 17.2 7C 1950 6B 2040 10A 2290 2B 17.6 12B 11320 7B 3.46 12B 61.6 5A 17.4 9C 1940 6B 1 2040 10C 2290 6B 1 17.6 8C 11110 14B 3.48 6B 61.5 12 A 1 17.5 7A 1930 9C 2010 16A 2290 16C 17.3 6B 11070 6A 3.54 6B 1 60.9 12B 17.6 2B 1920 6A 2000 10B 2280 2A 17.1 12A 1 10920 12 A 1 3.55 8B 60.3 16C 17.6 9B 1920 7A 2000 7C 2260 7C 17.1 16A 10920 5B 3.68 12 A 1 59.9 12A 17.7 10A 1920 13A 2000 7B 2250 10A 17.0 6B 1 10900 13A 3.69 2A 59.3 16A 17.9 2C 1910 11A 1990 9C 2250 6B 16.9 8B 10750 5B 3.76 16A 59.2 6A 18.0 11B 1910 11B 1990 11B 2240 8A 16.9 2A 10740 14B 3.77 14A 58.6 15B 18.3 12 A 1 1910 9B 1980 9A 2230 11B 16.9 14A 10720 11A 3.88 13A 57.7 14A 19.0 11 A 1890 10C 1980 6A 2220 6A 16.8 13A 10510 12B 4.01 12A 57.6 14B 19.0 11C 1890 11C 1970 2A 2210 5A 16.6 12A 10350 12A 4.37 11A 57.1 3A 19.2 9A 1880 10B 1960 13A 2210 9A 16.5 11A 10300 16A 4.55 3A 57.0 6B 19.3 13A 1880 9A 1950 2C 2200 16B 16.3 3A 10150 2A 4.77 6A 56.2 14C 19.4 10B 1870 12 A 1 1950 7A 2160 11A 16.1 6A 10100 5A 4.79 5A 54.8 6B 1 19.5 12A 1870 10A 1940 2B 2130 16A 16.1 9A 9990 9A 4.97 9A 54.8 3C 20.0 12B 1870 12A 1940 12 A 1 2120 7B 16.0 5A 9960 7A 5.21 8A 54.5 2C 20.4 10C 1860 12B 1920 12B 2080 7A 15.7 8A 9660 from impurities as judged visually. Differ- ent coals produced varying percentages of reject and of improvement, but it is felt that a reasonable simulation of commercial cleaning was achieved. Indeed, it is proba- ble that the results were conservative com- pared to those obtainable in a commercial installation, using unlimited coal, unlimited time, and larger equipment. As has been mentioned the "C" coals were produced in an endeavor to achieve an ex- treme change in characteristics from the "A" coals and a significant change in char- acteristics from the "B" coals, without regard to the percentage of reject in the process. In general, the procedure thus provided coals of the same size range at three quality or grade levels. Percentage of reject was considered to be the ratio of material rejected to the sum of material rejected and cleaned coal, disre- garding the substantially constant quantity 38 DOMESTIC STOKER COMBUSTION 36 28 04 33 • a i i • • • • • 4 > • 8 < • ' •' «9 « » a • e • • » • • • • ■c 100 a 96 ? 6! c ioo S 96 BO 2 4 6 8 10 12 14 16 I Uniformity, percent variation from average heat release 34 ft • < o e • • • • • • * 4 6 8 10 12 14 16 If Uniformity, percent variation from average heat release ?z 35 — i > i » • • • < > • • 5 I • •• 4 i » < i 1 < • i • • 4 i < i < > • < 9 • < > • • < » e 23 32 36 40 44 48 52 56 60 Average pIcKup rate, M B.t.u. per hr. Fig. 33 (Top). Relationship of uniformity of combustion to the pickup rate after a 45-minute "off" period. Fig. 34 (Middle). Relationship of uniformity of combustion to the overrun rate after a 15-minute "on" period. Fig. 35 (Bottom). Relationship of overrun rate after a 15-minute "on" period to pickup rate after a 45-minute "off" period. EFFECT OF CLEANING 39 £ .8 5 £ X-7 5 £.6 36 V5 V s • ft m \ "• •v s 4 V s • ^ • • . • • » < • V ^« • 2 4 6 8 10 12 14 16 18 20 22 Uniformity percent variation from average heat release Fig. 36. Relationship of uniformity of combustion to the minimum rate of heat release divided by the average rate of heat release for all stoker operation rates except hold-fire. of coal remaining on the table and in the conveying equipment at the end of the clean- ing run. The changes in quality characteristics resulting from the coal cleaning work in this investigation are discussed in the fol- lowing sections. The summaries apply only to the coals actually cleaned and should not be considered as necessarily representative of all cleaned and all raw Illinois coal. Effect upon Chemical Characteristics Tables 4 and 5 summarize the data re- lating to type of cleaning, amount of reject, and extent of improvement in quality in the 28 coals cleaned in the course of the pres- ent investigation, as reflected in changes in mineral matter, ash, sulfur, and heating value. Figure 37 illustrates certain of the data shown in table 4. Unless otherwise stated, all data are reported on the dry basis and in terms of raw coal. a). Mineral /natter content. — The major purpose and effect of any coal clean- ing process is reduction of mineral matter, defined for the purposes of the present re- port as 1.08 X(Ash) + 0.55 X (Sulfur). In table 5 the changes in mineral matter are summarized and classified by method of cleaning. The majority of coals were pre- pared by tabling, with the operating adjust- ments such that no more than a commer- cially reasonable amount of raw coal was rejected. This was arbitrarily taken as a maximum of 25 percent, although for any given coal and process, the percentage of reject most financially attractive depends upon a variety of market considerations. In Illinois cleaning plants, the proportion of reject averages about 16 percent of raw coal, 11 and in at least one plant it is under- stood to be about 25 percent. For the 1 7 coals cleaned by the use of the table alone, so operated that less than 25 percent of raw coal was rejected, mineral matter was reduced an average of 33.9 per- cent, varying from 13.5 to 47.7 percent (table 5, column 1). On the basis of per- centage points the average reduction was 7.2, varying from 1.3 to 11.7. Variations in degree of improvement in the up-grading of coals are due primarily to differences in specific gravity distribu- tion. A raw coal containing a relatively large proportion of particles composed of both high- and low-gravity material bound together is much more difficult to separate sharply on the basis of specific gravity than 14 Young, W. H., Anderson, R. L., and Isaac, L. H., Bituminous coal and lignite; table 52. U. S. Bur. Mines Minerals Yearbook, 1943. 40 DOMESTIC STOKER COMBUSTION (LI "3 u «-< "rt (-> ti (L) C c a o3 "" OS oo " O 4^ 1— I V c CO c -e (U -H Sh 0, (Li Wi CX ri Loss in cleaning, percent a '5 u w*_ o oh> on wo on »o n ^ oo o ^ ^ COCO wo wo oo ON i— ir) ON O i— ' — rN o •* O u-> ■^ co itr- 00 — O O T^ CO n o CN O CO Tf CO 01 CO n OO OO O CO ^D CN CN i— i i— i CO CO CO •* CN CN Tf on CO co H O CN co O ^ co (X) vOh wo o OO CO r-l r-H O no no oo on o oo n co on U-iON 0 CO wo O i— i "^ CN O o n ^fn co wo os n -— oo ^ CO ON U-) VON — CO ON Tf >o CO r-H CO -co — r- Tf ^o co co TJH O OO CN <^> r-H O "*! CN O CO ^ Tf rf wo OO CN O >om oo On On ON O o N ■<*< co "+< rfcN ooh ,-h -* 1 OO o ^ N N CO'* 1 OOO OO O OJ ^ OO O vivO wo N wo wo Ol O Tc o co co *o CO •>* t^. OO XTf r-H LO NO ON no O oo ^ O ^o (Ob O ^O ^O ON nOCN OOio N ~* NO O^^C OOt^ OlsC 1^-ON ^hO On— nOON tjh sO —N t^CN oico co^^ Oco con ui »o woOn r^sC coco u-> *-< oooo r^o oo Tf ^h^h r-JON NO ^^t - OICI ON N N CO — -^ Cl-f Tfu-, CO^- OCO N*- 1 OOO —(OO NO — CO OO oo oi OO OO — CO on o O ooo Th Tf O O ON OO O O ^ Ol N CO u-> CN "^ N OO u-) O i— i o b — « ON u-, OO O .-H — O O CN oo r- OO OO N N o ^ c O OO ""f WO CN CO co CO ^ CO o N ON wo wo wo CO OO rf o o CO wo O Tt< Tf WO wo N o> o CO CO CN CO ~r co CO T^ CO r-H CO N O OO CN CO ON O co ^ OO if OJ CO N O IN Tf 0^ O OJ CO CO CN — o —I OO CO wo ON r- N ^ CN CO <■*< o N CN OJ ->f WO ON OO N O wo CO O CN ON -1- c CO OO oi oo N ON oc O oo N O OJ CO OJ CO — wo On Tt< ON o o ON — O -< OO N Tj< WO ON — O oo CO -* ON 1-H wo O wo OO wo O r-H O WO ON CN Tf OO ON Tf i— i O On CO O O oo — O^S OJOJ NO OJOJ COO OJwo ^H O co oo r-H O co O ~f o oo co r-H TtH r-H CO — T»H — Tf r-H WO i-H UN bjj on b/j be bfj bD bt>.~ bfj bfi oil orj « a, _Q _q -O -O _Q -Q rtrt rtrt rtrt c-jro HH HH HH hh _Q -Q _Q _D _Q _C S -Q h -Q „ -Q 3 -O .3-C .S - .rH.tn iss iss iss _o2 io5 _oii sis rt O 30 I 2 I0B IOC MB IIC I2B I2C I3B I3C I4B I4C I5B I5C I6B I6C 10 20 30 50 60 70 Fig. 37b. Changes in heating value, mineral matter, ash, sulfur, and pyritic sulfur, on the dry basis, caused by cleaning. percentages of reject referred to the raw coal (table 5, column 3) ; and 3) float-and- sink procedures (table 5, column 4). Three coals were produced by the first method, with an average reduction of mineral mat- ter of 52.8 percent and an average reject of 36.7 percent. For the five coals produced by the second method, the reduction in min- eral matter averaged 40.2 percent, with an average reject of 43.9 percent Three coals 44 DOMESTIC STOKER COMBUSTION were produced by the third method, using zinc chloride solutions of such low specific gravities (of the order of 1.30) that rejects of over 50 percent were produced in each case. The average reduction in mineral matter was 64.0 percent. However, no single coal was cleaned by more than one of the three methods, so a direct compari- son of the methods is not possible. b). Ash content. — Quantity of ash is more easily determined and hence more commonly used than quantity of mineral matter in evaluating quality of coal, even though it is less exact theoretically. Ash, or inert material in its burned state, is gener- ally about fifteen percent less than mineral matter, which approximates inert material (dry basis) in its unburned state. How- ever, the relative reductions of ash and of mineral matter from raw to cleaned coal are of similar magnitude, and the foregoing comments on the effect of cleaning on min- eral matter apply \cr\ closely to the effect of cleaning on ash. Tables 4 and 5 and figure 37 set forth the data. c). Sulfur content. — Reduction of sul- phur on a moisture-free basis is not usually as high, on a percentage basis, as reduction in mineral matter and ash (tables 4 and 5, fig. 37). For the 17 tabled coals prepared at the expense of less than 25 percent reject, the average reduction in sulfur was about 1 percentage point, or 23 percent. For the coals prepared at the expense of higher per- centages of reject, the reductions averaged 1.2 percentage points, or 2 C ) percent. Sulfur occurs in three distinct forms in coal, but only pyrite (iron disulfide), with a specific gravity of about 5.0, is reduced in percentage by a cleaning process that de- pends upon differences in specific gravity. Neither sulfur organically combined with, the coal substance nor that occurring as a sulfate compound is appreciably affected by such a process. Data on the percentage reduction in pyritic sulfur are presented for thirteen cleaned coals (table 4, fig. 37). They tend to be somewhat higher than the percentage reduction in mineral matter, ranging from 36.1 to 65.1 percent. d). Heating value. — For the 17 coals cleaned by the use of the table alone, so operated that less than 25 percent of raw- coal was rejected (table 5, column 1), heat- ing values were increased an average of 887 B.t.u. per pound, varying from 111 to 1494 B.t.u. per pound. The average percentage increase in heating value was 7.6 with a range from 0.8 to 13.9. For the eleven coals cleaned by means of the table or float-and-sink methods, or both, with percentages of reject more than 25 percent (table 5, columns 2, 3, 4, and 5), the increases in heating value were some- what greater. They had an average of 1200 B.t.u. per pound and ranged from 589 to 2466 B.t.u. per pound. On a percentage basis, the average increase in heating value was 10.1, with a range from 4.5 to 22.2. The heating value of a given coal may be considered approximately proportional to the percentage of heat-producing material, with inert or non-heat-producing material acting as a diluent. For purposes of com- putation, satisfactory accuracy may usually be obtained by defining inert material (dry basis) simply as ash. This leads to the familiar dry ash-free heating value as a basis for computing heating value for any cleaned product, the ash content of which is known. The heating values of the 28 cleaned coals, so computed, have an average variation from the heating values, as deter- mined in a calorimeter, of 84 B.t.u. per pound. More complex definitions of inert mate- rial have been proposed, one being mineral matter, previously defined as (1.08 X Ash + 0.55 X Sulfur), and another a modifi- cation of this (1.1 X Ash + 0.1 X Sul- fur). These do not always yield better results in computing heating value. As a matter of fact, for the 28 cleaned coals, the average difference between computed and determined heating values is 147 B.t.u. per pound using (1.1 X Ash + 0.1 X Sulfur) as the diluent, or 204 B.t.u. per pound using (1.08 X Ash + 0.55 X Sulfur) as the diluent. Correcting for the heat of combustion of sulfur, as recommended by EFFECT OF CLEANING 45 Parr, 16 reduces the latter average difference to 127 B.t.u. per pound. Dry mineral-matter-free heating value with correction for sulfur (unit heating value) is a concept widely accepted as an estimate of the heating value of the pure coal substance. For the present data, unit heating value averages 153 B.t.u. per pound lower in the cleaned coal than in the raw coal, a value larger than can be accounted for by sampling fluctuations. The cleaning process thus appears to have reduced the heating value of the coal substance, insofar as this is given by unit heating value, by approximately 1.0 percent. Possible expla- nations are : 1 ) accelerated oxidation of the coal due to the wetting and drying cycle suffered in the washing process; or 2) a selective action in the washing process whereby particles of a prevailingly lower unit heating value concentrate in the cleaned-coal product. e). Volatile matter and fixed carbon. — On any comparable moisture basis the re- duction of ash in a coal by a known amount obviously increases by an equal amount the percentage of coal material represented by the sum of volatile matter and fixed carbon. Ordinarily, but not always, both volatile matter and fixed carbon share in this in- crease. For the 27 cleaned coals for which data are available, the average increase in volatile matter was 2.3 percentage figures, and in fixed carbon, 4.7 percentage figures, on the dry basis. In three cases the entire increase due to reduction in ash was absorbed by fixed carbon and in one case by volatile matter. The possibility of selective action in the cleaning process, whereby particles having prevailingly higher or lower fixed carbon are concentrated in the clean coal, may be investigated by comparing the ratio of fixed carbon to volatile matter before and after cleaning. These ratios are, respectively, 1.25 and 1.30 on the average for the data of this report. In other words, the average 10 Parr, S. W., The classification of coal: Univ. 111. Eng. Exp. Sta. Bull. 180, 59 pp., 1928. raw coal had a fixed carbon content 25 per- cent greater than volatile matter, while the average cleaned coal had a fixed carbon content 30 percent greater than volatile matter. This difference is greater than could be attributed to sampling fluctuations, and it may be inferred that a slight selective action existed in the cleaning processes, pos- sibly due to low-ash particles having a pre- vailingly higher ratio of fixed carbon to volatile matter than high-ash particles in most of the coals tested. f). Items of the ultimate analysis. — Reduction of non-combustible material re- sults in a corresponding increase in the coal substance and hence usually in increases in the percentages of carbon, hydrogen, oxygen, and nitrogen. However, the increases in these elementary components are rarely pro- portionately alike, the tendency being toward appreciably higher oxygen in the cleaned coals than might be expected. On the mois- ture-and-ash-free basis, the average cleaned coal has 1.4 percentage figure more oxygen than the average raw coal, a difference greater than may be attributed to sampling fluctuations. On the same basis the differ- ences in carbon, hydrogen, and nitrogen appear to be insignificant. Sulfur, of course, is reduced, as has been discussed previously. g). Ash fusion temperatures. — The aver- age difference in ash softening temperature between the raw coals and the cleaned coals was an increase of 30° F. Although this is less than the usual laboratory tolerance of 54° F. between duplicate samples, the trend exceeds reasonable sampling fluctuations, and a tendency toward slightly higher ash softening temperature in the washed coals prepared in the present investigation seems evident. No significant change in either initial deformation temperature or fluid tempera- ture is apparent. h). Other chemical tests. — Washing appeared to reduce chemical fusain, but changes were small in absolute amount. No significant effects due to washing on British swelling index, Gieseler plasticity, or ignition temperature appear to be dem- onstrated. 46 DOMESTIC STOKER COMBUSTION Table 6. — Changes in Vitrain Content Caused by Cleaning Coal County and coal bed Method of cleaning Loss in cleaning, percent Ash content (dry), percent Vitrain, percent Vitrain, percentage figure change Vitrain, percentage change in cleaned coal re- ferred to raw coal 1A 3A 3B 3C 5A 5B 5B 1 6A 6B 6B 1 7A 7B 7C 8A 8B 8C 9A 9B 9C 10 A 10B IOC MA 1 IB 11C 12A I2B 12C 13A 13B 13C 14A 14B 14C 15A 15B 15C L6A 16B 16C Franklin — No. 6. -Grape Vermilion- Creek. . Vermilion — Grape Creek Vermilion — Grape Creek Tabling Tabling Macoupin — No. 6 Macoupin — No. 6 Macoupin — No. 6 Peoria — No. 5 Peoria — No. 5 Peoria — No. 5 Tabling Tabling Tabling Tabling Gallatin— No. 5. Gallatin — No. 5. Gallatin— No. 5. Wabash — Friendsville . Wabash — Friendsville Wabash — Friendsville . Tabling Tabling Tabling Tabling St. Clair— No. 6 St. Clair — No. 6 Tabling St. Clair- No. 6 Float-and-sink Saline — No. 5 Saline— No. 5 . . Saline — No. 5. . . . . Tabling . . . Retabling Vermilion — No. 7 Vermilion — No. 7 . . .Tabling Vermilion No. 7 Retabling Sangamon No. 5 Sangamon No. 5 Sangamon No, 5 Randolph No. 6 Randolph— NO. 6 Randolph— No. 6. Christian — No. 6 Christian — No. 6 Tabling. . Christian — No. 6 Retabling Tabling Retabling Tabling Retabling Williamson — No. 6 Williamson — No. 6. . Tabling Williamson — No. 6. . Float-and-sink Knox — No. 1 Knox — No. 1 Tabling Knox — No. 1 Float-and-sink 7.9 17.4 26.5 12 28.6 9.0 16.3 +3.5 + 27 40.6 7.6 14.2 + 1.4 + 11 9.1 11.2 19.0 9.8 9.4 9.8 12.3 13.2 + 2.5 -3.4 +26 +35 7.4 4.8 18.1 10.6 111 10.8 12.4 13.4 +2.6 +2.6 + 15 +24 7.9 24.4 14.3 10.7 10.0 5.7 5.2 5.1 -0.5 -0.6 - 9 -11 10 1 20.6 23.3 15.0 12.9 1.50 1.68 1.87 +0.18 +0.37 + 12 +25 8.9 61.3 21.5 13.1 5.3 7.2 6.8 12.3 -0.4 + 5.1 - 6 +71 L2.6 60.3 10.4 7.6 6.3 14.5 17.7 17.9 +3.2 +3.4 +22 +24 14.0 40 6 19.5 11.4 9.1 7.4 10.7 9.4 +3.3 +2.0 +45 +27 13.2 38.2 16.1 11.1 10.1 7.9 8.2 10.2 +0.3 +2.3 + 4 +29 11.7 40.0 17.6 12.6 10.1 8.6 8.6 11.4 +2.8 +33 13.2 40.2 13.7 9.2 8.2 11.2 11.5 14.1 +0.3 +2.9 + 3 +26 14.3 56.0 8.6 7.4 3.0 14.5 18.1 19.2 +3.6 +4.7 +25 +32 18.2 53.5 13.2 8.9 5.1 7.4 9.5 9.4 +2.1 +2.0 +28 +27 Effect upon Petrographic Constitution a). Jitrain content. — Owing to its low ash content and low specific gravity, vitrain is ordinarily considered to concentrate in a washed coal. The data of the present re- port indicate a minor trend in that direction. Table 6 sets forth the percentages of vitrain and dry ash for 40 test coals, of which 14 were raw and 26 were cleaned coals. The percentage change in vitrain and the per- centage of raw coal rejected in the cleaning EFFECT OF CLEJNING 47 process are also listed. Petrographic data on the coal from La Salle County (2 series) were not obtained. It will be observed that of the 16 tabled coals prepared at the expense of less than 25 percent reject, 12 showed an increase, three showed a slight decrease, and one showed no change. The average change was an in- crease of 1.4 percentage figures or 15 per- cent (table 7). Table 7. — Summary of Changes in Vitrain Content Caused by Cleaning Percentage of reject Number of coals Per- centage figures Per- centage Less than 25 percent Exceeding 25 percent All coals 16 10 26 1.4 3.0 2.0 15 33 21 In the ten coals cleaned by tabling, reta- bling, or float-and-sink methods, with per- centages of reject exceeding 25 percent, the increases in vitrain were somewhat greater, averaging 3.0 percentage figures or 33 per- cent. The average increase in vitrain for the entire 26 cleaned coals was 21 percent or 2.0 percentage figures (table 7). A por- tion of this increase is attributable, of course, to the upward adjustment of the vitrain percentages of the raw coal due to decrease in 1.5 sink material, considered for petrographic purposes to be non-coal. The effect of washing (exclusive of this effect) is given by a comparison of the percentage of vitrain on a 1.5-float basis, as reported in table 8. From this it will be seen that of the 26 prepared coals for which data are available, 15 show an increase, 4 show a decrease, and 7 show no change, where a change of 1.0 percentage figure is regarded as the minimum for significance. The aver- age change was an increase of 1.0 percentage figure on a 1.5-float basis. Although tests on coals containing 70 percent or more of vitrain were described both in the first report of this series and in an earlier exploratory study, 17 none of the coals tested during this phase of the general investigation was reported to approach that quantity of vitrain. All but one contained less than 20 percent, despite preparation procedures which were expected to increase vitrain markedly. The coal richest in vitrain was a cleaned 7/16-inch by 10-mesh coal from Franklin County, with a vitrain content of only 26.5 percent. The reason for the wide discrepancy between this figure and the 70-percent figure obtained in a sim- ilar coal in the earlier work is not known. Certain possible explanations are being investigated. b). Clarain content. — Percentage of clarain (table 8) for the coals reported varied between 67 and 89 percent, on the as-fired basis, with a rather distinct trend in the direction of increased clarain con- tent in the cleaned coals. The average increase was 8.3 percentage figures. How- ever, this is primarily due to an adjustment in the percentage figure resulting from a decrease in 1.5-sink material rather than to a selective concentration of clarain. The percentages of clarain on a 1.5-float basis show no consistent trends associated with washing. c). Duraln and fusain content. — The percentages of both durain and fusain (table 8) were uniformly low, ranging from zero to 3.0 percent for the former, and from 0.1 to 1.4 percent for the latter, as-flred basis. In each case the trend was toward reduction with washing, but changes were small in absolute amount. Effect upon Combustion Characteristics a). Heat obtained per pound of coal — Of the 27 cleaned coals for which compa- rable data were obtained, 23 showed in- creases in heat obtained per pound and four showed no change (table 9), where a differ- ence of 200 B.t.u. per pound was estab- lished as the minimum to be regarded as significant. The average increase was 810 11 McCabe, L. C., Illinois coals — constitution important with reference to their utilization: Mech. Eng., vol. 60, No. 3, pp. 217-21, March 1938. 48 DOMESTIC STOKER COMBUSTION • K a. -fired asis, rcent _^ c/} _Q 0> c rt & i^ r- 1 « W o lO^ jj T-H ft £ < [J ta "S » S i CQ »h WJ3 JJ ps a, 4-1 rt ti ° « ?, , c/5 O in rt £- : _o jj r-H Ch y. < ei Q V CO ? r_r-j C/> O CO_Q <" o.2 5 "3^: v, u i « u ^-° a % < < J U £ <*? a a f/l _Q U rt CX float sis, cent ^_2 ^ z < > l) IB C u .22 _r> © cn w> Tt< r~~oCS voc^ui m cO •<*< CO ^O ^i i— i CN oo p-OiO 'O CO -h _' r-^ CO CO V-^ CO OS r~-^ Os ■<+< co OOO i^oco O'trv ^Dw)^o (Shh r^ >n co u~> © os osooi— oooooooo oo^h- ^ ,-i ,-h -h hh'o odd odd odd ddo »-! — <' o ddo dodo odd CO rnrlO Tf ON l— CO ■* O co o o T-H C^tSH T-H CN r- rf ^D o od w-)u-)vo ri-H-H u-)Tf*co TfONO r — • i — r-~ r-^ r^- oo r-^ o-^r- odd odd odd ^'00 odd dood dod OOO vOO'* CN CN ON cOOOrf (NMtJ< ON — O CN © ON ON —,_<,- odd cn —i ri — <' d d © on 00 00 ,-h rir-.-H ,_ _< _ -h © © 000 t— t-h cn —'do co t-h — © — © t-hooo 1^ cou-^t-h nroh- ■<*' r^ ■<*« o > u-, cn o rf r^ on 00 s . > lo r- ^f o cn co nn ^C ON vOiCHO t-h^hCN ON t"^- CN in OO OO (>rH O^, ON OO © O © ON t-h m OO CO CN CO CO CN OO -^H -rf CN cn vc -r CT- r 1 CO Criro r^cir— ' iai^on rJoon i^r-cj\ -^r^rf oncncn^o 0^)^ UT)U-)W-) r-Hr^^H r^OC^I ^H|N|N hOON t^OOO<^ OOCOt-H < odd r-i o o OhO »ot^n c^oooo ^h _* _ odd odd ON J^. d d d d OO CO Tf CO OO r-i i-h' ^ HO I (Nhh loco^jh cn r-- O'f^o ,_ _ ^ _ ^ J ^ H 1-i MV>H OOO^O CN On O on oo Tfnn on ^l -1 ^ CN o ^o co *o cN loooin CO CN Tp i^OO(J\ CO OS On ^O VO 11 o ,-H < n i— i TJ C fS»OH W"i ,-h CN -f UO *f o o J3 "o X < CN o> R Pi CN ,-. ,-H -^ ■"f OO 0"\ r~- On On 1-1 T3 c 25% Uniformity, percentage figures Reject Reject <25% >25% Responsive- ness, M B.t.u./hr. Reject Reject <25% >25% Pickup, M B.t.u./hr. Reject Reject <25% >25% Overrun, M B.t.u./hr. Reject Reject <25% >25% 2B 2C. 3B. 3C. 5B 5B 1 6B. 6B 1 7B 7C. 8B. 8C. 9B. 9C. 10B. IOC. 11B 11C. 12B. 13B. 13C. 14B. 14C. 15B. 15C. 16B. 16C. Averages 40.8 28.6 40.6 9.1 11.2 7.4 4.8 7.9 24.4 10.1 20.6 8.9 61.3 12.6 60.3 14.0 40.6 13.2 11.7 40.0 13.2 40.2 14.3 56.0 18.2 53.5 +0. 4-1.68 4-1.74 4-0.78 4-0.69 -0.03 -0.10 4-0.77 +0.73 + 1.03 +0.42 +0.58 +0.86 +0.87 +0.96 +0.11 +0.97 + 1.26 +0.09 + 1.17 + 1.45 +0.38 + 1.13 + 1.06 + 1.11 +0.45 +0.84 1.1 - 5.8 - 6.2 - 6.5 - 6.5 - 3.7 - 0.1 - 2.6 - 2.6 - 11.9 - 2.5 - 2.1 - 2.5 -8.6 - 2.4 - 1.0 - 1.4 2.5 1.8 3.2 12.6 - 2.6 4.0 8.8 5.7 3.5 1.2 + 5. + 3.8 +23.3 + 19.6 +21.6 + 5.9 + 8.9 + 0.8 + 11.7 + 14.5 + 1.3 + 3.3 + 4.4 + 10.8 + 8.7 + 5.2 + 1.2 ( a ) + 13.8 + 5.0 + 9.9 2.0 + 4.4 +20.9 + 4.4 + 5.3 + 6.7 +9 + 3 + 6 +9 +9 -1 +2 +4 +2 +7 -1 +3 +7 + 1 +4 ( a ) + 2 + 11 + 3 - 1 + 4 + 10 - 1 + 5 + 1 + 12 +21 +21 + 16 + 12 + 7 + 4 + 10 + 9 + 18 + 2 + 10 + 2 + 12 + 1 - 3 - 2 ( a ) -10 + 11 + 10 + 7 + 9 + 13 - 3 - 7 Averages for coal all cleaned +0.76 +0.89 +0 81 4 - 4.6 -4.2 + 8.9 + 7.6 + 8.4 + 3.6 +3. +3.7 + 8.9 + 3.3 +7.0 a Not obtained. B.t.u. per pound on the as-fired basis (table 10). Improvement due to washing is to be expected, inasmuch as washing increased the heating value and carbon and decreased the ash and sulfur, both types of change having been shown to exert a positive influ- ence on the heat obtained. The decreasing advantage of cleaning with heavy reject losses is illustrated by com- paring the results obtained with smaller and with larger reject. For the 17 coals cleaned at the expense of less than 25 percent reject, the average increase in heating value was 760 B.t.u. per pound and the average reject was 12.4 percent (table 10). For the 10 coals cleaned at the expense of reject ex- ceeding 25 percent, the average increase in heating value was 890 B.t.u. per pound and the average reject was 46.2 percent. Hence, a further gain of only 130 B.t.u. per pound EFFECT OE CLEANING 51 Table 10. — Summary of Changes in Combustion Characteristics Caused by Cleaning Reject loss in cleaning Number of tests Average loss Heat in cleaning, obtained, percent M B.t.u. lb. Uniformity, percentage figures Responsive- ness, M B.t.u. /hr. Pickup, M B.t.u./hr. Overrun, M B.t.u./hr. Less than 25% 17 12.4 4-0.76 -4.0 + 8.9 +3.6 +9 More than 25% 10 46.2 +0.89 -4.6 +7.6- +3.8* +3* All cleaned coals 27 24.9 +0.81 -4.2 + 8.4 +3.7 +7 Nine comparisons only. was obtained at the expense of a reject loss nearly four times as great. The heat obtained per pound from the stoker combustion tests for a cleaned coal may be fairly closely computed from the heat obtained from the raw coal by correct- ing for the change in the amount of heat producing material per pound. Values so computed for the cleaned coals, using whole coal minus the moisture and ash as the equiv- alent of heat producing material, have an average difference from stoker test results of 130 B.t.u. per pound, a difference charge- able to sampling fluctuations. b). Uniformity. — The cleaned coals tended to burn more uniformly than the raw coals, as measured by the average vari- ation from the mean burning rate of each coal (p. 17). Of the 27 cleaned coals for which comparable data were obtained, 21 showed decreases in average variation and six showed no change (table 9), where a change of at least two percentage figures was arbitrarily selected as the minimum to be considered. The average change was 4.2 (table 10) and the maximum 12.6 percent- age figures, the latter representing a reduc- tion in variation of 61 percent referred to the raw coal. Comparing coals cleaned at the expense of more than and of less than 25 percent reject, the average improvements in uni- formity were 4.6 and 4.0 percentage points respectively (table 10), a difference which is not regarded as significant. c). Responsiveness. — The cleaned coals tended to be more responsive than the raw coals, as measured by the average rate of heat release during the first 30 minutes of operation after a prolonged hold-fire period (p. 17). Of the 26 cleaned coals for which comparable data were obtained, 22 showed increases in responsiveness and four showed no change (table 9), where a change of at least 3000 B.t.u. per hour w r as arbi- trarily selected as the minimum to be con- sidered. The average change was 8400 B.t.u. per hour (table 10) and the maxi- mum 23,300 B.t.u. per hour. Although a trend toward greater responsiveness might be expected, due to the increased heating values of the cleaned coals, the observed increase was generally much more than could be attributed to this factor. Refer- ring to the raw coal in each case, the aver- age percentage increase in responsiveness was 57 percent, while the average increase in heating value, as-fired basis, was only 1 1 percent for the same 26 cleaned coals. The coals cleaned at the expense of greater percentages of reject (table 10) had a slightly smaller average increase in responsiveness than coals cleaned at the expense of lesser percentages of reject. The respective figures are 7600 and 8900 B.t.u. per hour. d). Pickup. — The cleaned coals showed a pronounced trend toward increased pick- up over the corresponding raw coals, where pickup is based upon the average rate of heat release during the first five minutes of operation following an "off" period of 45 minutes (p. 17). Of 26 cleaned coals for which comparable data were obtained, 18 ILLINOIS GEOLOGICAL SURVEY LIBRARY APR 2 6 1993 52 DOMESTIC STOKER COMBUSTION showed an increase, one showed a decrease, and seven showed no change (table 9), where a change of at least 2000 B.t.u. per hour was arbitrarily taken as the minimum to be considered. The average increase was 3700 B.t.u. per hour (table 10). The aver- age improvements in pickup for the coals cleaned at the expense of greater and of lesser percentages of reject were practically the same, the respective figures being 3800 and 3600 B.t.u. per hour (table 10). e). Overrun. — The cleaned coals tended toward increased overrun over the corre- sponding raw coals, where overrun is based upon the average rate of heat release dur- ing the first five minutes of an "off" period following an "on" period of 15 minutes (p. 17). Of 26 cleaned coals for which com- parable data were obtained, 17 showed an increase, four showed a decrease, and five showed no change (table 9), where a change of at least 3000 B.t.u. per hour was arbitrarily taken as the minimum to be con- sidered. The average increase was 7000 B.t.u. per hour (table 10). The average change in overrun for the coals cleaned at the expense of greater percentages of reject was considerably less than that for those with smaller percentages of reject, the re- spective figures being 3000 and 9000 B.t.u. per hour (table 10). However, because of the wide variations in the individual coals, the difference is not regarded as significant. f). Other criteria.— Both hold-fire abil- ity and smoke-producing tendency were at satisfactory levels for all coals, whether raw or cleaned. CONCLUSIONS 1). The heat obtained from the coals tested was very nearly directly proportional to the heating value and to percentage of ultimate carbon, on as-fired basis. 2). A slight increase in efficiency of about \]/i percent for each 1000 B.t.u. per pound increase in heating value was obtained from the tests. However, exceptions to this general tendency were numerous. 3). A general improvement in all per- formance characteristics measured, except overrun, accompanied a reduction in the per- centage of ash. 4). An increase in vitrain was generally accompanied by more uniform combustion. 5). None of the following chemical characteristics furnished useful correlations with any of the measured performance char- acteristics of the coal: British swelling in- dex ; Gieseler plasticity ; volatile matter ; initial deformation, softening, or fluid tem- peratures of the ash. 6). The southern Illinois coals tested are generally superior in most of the per- formance characteristics measured. Several of the cleaned coals and a few of the raw coals from the central and northern fields are also included in some of the superior groupings. 7 ) . By the use of the concentrating table so adjusted as to produce a commercially reasonable percentage of reject, not to ex- ceed 25 percent, a reduction of roughly one- third in mineral matter and in ash was obtained for most of the raw coals. Reduc- tion in total sulfur was generally somewhat less, whereas heating value was increased an average of 7.6 percent. The percentages of both vitrain and clarain were increased for most coals. Performance characteris- tics were generally improved, excepting for overrun. 8). Cleaning by tabling or float-and-sink procedures in such ways that percentages of reject in excess of 25 percent were produced resulted in further reductions in mineral matter, ash, and total sulfur, and slight further increases in heating value. For most coals, the percentages of vitrain and clarain were also slightly increased. Per- formance characteristics were not appreci- ably different from those of coals produced at the expense of lower percentages of reject. 9). Quality changes not caused directly by reduction in mineral matter, observed in most of the cleaned coals, were increases in the ratio of fixed carbon to volatile mat- ter, in oxygen (dry ash-free basis), and in vitrain (1.50-float basis); and a decrease in heating value (unit-coal basis). Each of these was minor in magnitude. APPENDIX 53 APPENDIX COMPLETE DATA ON ALL TEST COALS 54 DOMESTIC STOKER COMBUSTION Analy- sis No. SOURCE PROXIMATE ANALYSIS Coal No. County Seam As-fired Moisture-free Moisture and Ash Free Dry Mineral- Matter-Free Mosture, % Ash, % Volatile Matter, % Fixed Carbon, % Ash, or 70 Volatile Matter, % Fixed Carbon, % Volatile Matter, % Fixed Carbon. % Volatile Matter. % Fixed Carbon. % 1A C-2507 Franklin 6 8.6 7.2 30.2 54.0 7.9 33.0 59.1 35.9 64.1 35.2 64.8 2A 2B C-2527 C-2529 C-2577 C-2556 C-2617 C-2721 LaSalle LaSalle 2 2 2 6 6 6 12.7 10.8 12 7 13 . 6 11.2 12.7 12.5 8.0 5.2 15 .0 8.0 6.7 32.1 38.9 34.8 32.5 34.7 35.4 42.7 42.3 47 .3 38.9 46 1 45.2 14.3 8.9 5.9 17 4 9.0 7.6 36.8 43.6 39.9 37.6 39.0 40.5 48.9 47.5 54 2 45 52.0 51 9 42.9 47.9 42.4 45.6 42.9 43.9 57.1 52.1 57.6 54.4 57 1 56.1 41 46.9 41.6 44 1 42.1 43.2 59.0 53.1 2C LaSalle 58.4 3A 3B 3C Vermilion Vermilion Vermilion 55.9 57.9 56.8 5A 5B 5Bi C-2697 C-2768 C-2775 Macoupin Macoupin Macoupin 6 6 6 12.6 5 2 6.2 16.6 9 3 8.8 34.3 40 .6 35.8 36.5 44.9 49 2 19.0 9.8 9.4 39.2 42.9 38.2 41.8 47 3 52 4 48 4 47.5 42 1 51.6 52 5 57.9 46.4 46.5 40.9 53 6 53 5 59.1 6A 6B C-2776 C-2873 C-2895 C-2912 C-2920 C-2921 Peoria. . 5 5 5 5 5 5 14 .3 13 2 13 2 2 8 2 5 2 1 15 5 '.1 .» 9.6 13 9 10.4 9 8 29.9 33.5 33.9 33.9 35 4 35 2 40.3 44 1 43 .3 49 4 51 7 52.9 18.1 10.6 11.1 14 3 10.7 10.0 34.9 38.6 39.1 34 9 36.3 35.9 47.0 50.8 49.8 50.8 53.0 54 1 42.7 43.2 43.9 40.7 40.7 39.9 57 3 56.8 56.1 59.3 59.3 60.1 40 7 41 9 42.8 38.7 39.3 38.6 59.3 58 1 6Bi 57.2 7A Gallatin 61.3 7B 7C Gallatin Gallatin 60.7 61.4 8A 8B 8C C-2932 C-2939 C-2943 Wabash Wabash Wabash * 111 ti 10 1 9 ii 23 8 13.5 11.7 34 36 4 37.6 34 6 40.0 41 1 23.3 15.0 12 9 38 1 40.5 41 ti 38.6 44 5 45 5 49.6 47.6 47 7 50.4 52.4 52.3 47.9 46.5 46.8 52 1 53 5 53.2 (»A 9B 9C C-2953 C-2998 C-3032 St. Clair St. Clair St. Clair 6 6 6 9 9 8 2 7.6 19 :; 12.0 4 9 34 4 38 (i 38.8 36 4 41 2 is 7 21 5 13 1 5 3 33 1 42 42.0 40 4 44 9 52.7 48 6 48 3 44.4 51 4 51.7 55.6 46.4 47 1 43.5 53 6 52.9 56.5 10A 10B IOC C-3024 C-3048 C-3072 "Saline Saline Saline 5 5 5 6.1 5 1 5 3 9 8 7 2 6.0 33 .2 34 5 34 9 50.9 53 2 53.8 10 4 7.6 ti 3 35 4 36.3 36.8 54.2 56 1 56.9 39 5 39.3 39.3 60.5 60.7 60.7 38.4 38 5 38.6 61 . 6 61.5 61.4 11A 11B 11C C-3079 C-3088 C-3113 Vermilion Vermilion Vermilion 7 7 7 11.0 8 5 7 8 17.4 10 5 8.4 35 .0 38 4 39 ti :;., 6 42.6 44 2 19.5 11.4 9 1 39 3 41.9 42 9 41 2 46.7 48.0 48.9 47.4 47.2 51 1 52.6 52.8 47 1 46.2 46.3 52 9 53.8 53.7 12A 12A 1 12B 12C C-3132 C-3183 C-3151 C-3181 Sangamon Sangamon Sangamon Sangamon 5 5 5 5 13 5 10 8 10 ti 11 .8 13 9 12 4 9 9 8.9 32.8 33 7 35 3 39 8 43.1 (4 2 16 1 13 9 11 1 13.9 38.0 37.8 39.4 45 9 48 3 49.5 45.2 43 9 44.4 54.8 56.1 55.6 43.4 42.4 42.9 56 ti 57.6 57.1 115 A 133 1 ;c C-3204 C-3229 C-3246 Randolph Randolph Randolph 6 6 6 9.8 8.3 9.0 15 9 11 5 9.2 33 35 8 34 it 41.3 11 1 Hi 9 17 6 12 6 10.1 36 ti 39 38 3 45 8 48.4 51.6 44.4 44.6 42.6 55.6 55 4 57.4 42.6 43.4 41 5 57.4 56.6 58.5 14 A 14B 14C C-3257 C-3286 C-3304 Christian Christian Christian 6 6 6 11.6 10.8 11 5 12.1 8.2 7.3 34 9 37 3 37 1 41 1 43.7 44 1 13.7 9.2 8.2 39 5 41.8 41.9 46.8 49.0 49.9 45.7 46 1 45.7 54.3 53.9 54.3 44.3 45.0 44.6 55 7 55.0 55.4 15A 15B 15G C-3319 C-3389 C-3462 Williamson Williamson Williamson ti (i 6 8.2 7.1 7-2 7 9 6.9 2 8 31 4 31.1 32 '.t 52.5 54 9 57 1 8.6 7.4 3 34 3 33.5 35 5 57.1 59.1 61 5 37.5 36 2 36.6 62.5 63.8 63.4 36.8 35.6 36.2 63.2 64.4 63.8 1CA 16B 16C C-3463 C-3507 C-3520 Knox Knox Knox 1 1 1 12 7 9 4 9 7 11 5 8.1 4 ti 35.8 38.1 38.6 40.0 44.4 4/ 1 13.2 8.9 5.1 41.0 42.0 42.8 45.8 49.1 52.1 47 .3 46 1 45 1 52.7 53 9 54 9 45.7 45.0 44.4 54 3 55.0 55.6 *Friendsville APPENDIX 55 PROXIMATE ANALYSIS Sulfur Heating Vai UE Ash Fusion Characteristics Moist, Mineral- Matter-Free Coal Mois- ture, Crr /o Volatile Matter, % Fixed Carbon, /o As- fired, % Mois- ture free, % Mois- ture and Ash-free, % As-fired, B.t.u./lb. Moisture free B.t.u./lb. Moisture and Ash-free, B.t.u./lb. Mineral-matter-free Initial Deform. Soften- ing, °F Fluid, op No. Dry, B.t.u./lb. Moist, B.t.u./lb. 9.4 31.9 58.7 .80 .87 .95 12,160 13,306 14,446 14,576 13,205 2188 2258 2462 1A 15 1 12 1 13.7 34 8 41 2 35 9 50 1 46 7 50 4 4.77 3.32 2.56 5.47 3 72 2.93 6 38 4.09 3.12 10,741 11,628 11,650 12,309 13,035 13,341 14,357 14,315 14,181 14,758 14,545 14,339 12,521 12,802 12,392 1969 1918 1912 2105 2078 2040 2209 2128 2202 2B 2B 2C 16.5 12 4 13 8 36.9 36 9 37.3 46 6 50.7 48.9 2.09 1.59 1.41 2.42 1.79 1 61 2.92 1.97 1.75 10,148 11,448 11,490 11,748 12,886 13,163 14,224 14,154 14,253 14,556 14,330 14,391 12,151 12,563 12,414 2115 2113 2033 2167 2160 2140 2415 2370 2368 3A 3B 3C 15.9 5.9 7.0 39.1 43.6 38.0 45 .0 50.5 55.0 4.79 3.76 3.68 5.47 3.97 3.92 6.76 4.40 4 33 9,955 11,935 11,833 11,387 12,594 12,618 14,058 13,957 13,923 14,533 14,209 14,165 12,230 13,366 13,167 1996 2020 1984 2048 2075 2060 2346 2344 2320 5A 5B 5B' 17.6 14.9 15 33.5 35.7 36.3 48.9 49.4 48.7 3.54 2.93 2.98 4.13 3 37 3 44 5.05 3.77 3 87 10,095 11,074 10,895 11,776 12,763 12,552 14,383 14,275 14,115 14,798 14,526 14,375 12,197 12,354 12,212 1960 1972 1963 200,2 2040 2040 2215 2338 2328 6A 6B 6Bi 3.4 2.9 2.4 37.4 38.2 37.8 59.2 58.9 59.8 5.21 3.46 3.35 5.35 3.54 3.42 6.25 3.97 3 80 12,297 13,075 13,223 12,649 13,408 13,505 14,760 15,008 15,009 15,170 15,296 15,270 14,657 14,854 14,907 1927 1969 1951 2002 2105 2100 2155 2251 2256 7A 7B 7C 13.9 12.0 11 1 41 1 40.9 41.6 45.0 47.1 47.3 2.77 2.12 2.10 3.09 2.36 2.33 4 03 2.78 2.67 9,655 10,746 11,108 10,794 11,953 12,290 14,067 14,065 14,102 14,547 14,345 14,357 12,518 12,629 12,763 2065 2177 2184 2113 2229 2247 2618 2529 2514 8A 8B 8C 13.0 9.6 8.2 40 4 42.6 40 .0 46 6 47.8 51.8 4.97 3.32 3.09 5.52 3.62 3.35 7.03 4.16 3.54 9,989 11,358 12,531 11,090 12,362 13,556 14,123 14,225 14,321 14,665 14,525 14,483 12,744 13,136 13,306 1883 1924 1937 1948 1981 2005 2231 2319 2254 9A 9B 9C 6 9 5.6 5.7 35.7 36.3 36.4 57 4 58.1 57.9 2.47 1.95 1.74 2.63 2.06 1.84 2.93 2.23 1.97 12,333 12,876 12,993 13,136 13,573 13,725 14,666 14,685 14,655 14,894 14,851 14,786 13,865 14,019 13,943 1920 1873 1857 1940 1958 1983 2287 2280 2291 10A 10B 10C 13.9 9.8 8.7 40.5 41.8 42.2 45 6 48.4 49.1 3.88 3.23 3.00 4.36 3.53 3.25 5.42 3.98 3.57 10,299 11,825 12,259 11,574 12,925 13,290 14,382 14,596 14,613 14,844 14,867 14,852 12,775 13,416 14,561 1892 1911 1888 1985 1985 1970 2338 2236 2380 11A 11B 11C 16.3 12.8 12.2 36.2 37.0 37.8 47.5 50.2 50 4.37 3.55 4.01 3.67 5.06 3.98 4.49 4.16 6.02 4.63 5.05 4.63 10,354 10,915 11,317 11,332 11,970 12,236 12,659 12,851 14.260 14,216 14,234 14,297 14,666 14,543 14,538 14,565 12,269 12,688 12,767 12,616 1873 1906 1868 1935 1950 1922 2327 2119 2077 12A 12A1 12B 12C 12 .1 9.7 10.2 37.4 39.2 37.3 50.5 51 1 52.5 3.69 2.93 2.72 4.08 3.20 2.99 4.96 3.66 3.32 10,506 11,332 11,601 11,644 12,360 12,753 14,128 14,134 14,180 14,521 14,404 14,409 12,766 13,011 12,940 1880 2003 2058 1995 2081 2131 2213 2389 2396 13A 13B 13C 13.7 12 1 12.7 38.2 39.5 39.0 48 1 48.4 48.3 3.77 3.48 3.26 4.26 3.90 3.68 4.94 4.30 4.01 10,720 11,430 11,491 12,132 12,816 12,978 14,064 14,122 14,136 14,395 14,363 14,356 12,419 12,620 12,541 2016 2026 2048 2054 2094 2106 2359 2357 2339 14A 14B 14C 9.0 7.7 7.5 33.4 32.8 33.5 57.6 59.5 59.0 .91 .85 .79 .99 .92 .86 1.09 .99 .88 12,202 12,458 13,101 13,296 13,407 14,113 14,546 14,484 14,548 14,691 14,604 14,612 13,363 13,480 13,528 2321 2463 2130 2530 2550 2304 2653 2650 2532 15A 15B 15C 14.9 10.5 13 4 38.9 40 4 39.7 46.2 49.1 49.9 4 55 3.40 2.65 5.21 3.75 2.94 6.00 4.12 3.10 10,919 11,889 12,362 12,501 13,123 13,693 14,403 14,409 14,432 14,769 14,650 14,586 12,566 13,111 13,010 2044 2055 2036 2099 2158 2173 2289 2534 2565 16A 16B 16C 56 DOMESTIC STOKER COMBUSTION ULTIMATE ANALYSIS Coal As Fired Moisture Free No. Hydrogen, Carbon, Nitrogen, Oxygen, Sulfur, Ash, Hydrogen, Carbon, Nitrogen, Oxygen, Sulfur, Ash, % % % /o % % % % % % % % 1A 5.37 69.64 1.58 15.37 .80 7.24 4.83 76.20 1.72 8.46 .87 7.92 2A 2B 2C 5.56 5.82 6.13 59.28 64.78 64.67 1 04 1.12 1.06 16.87 17.01 20.41 4.77 3 32 2.56 12 48 7.95 5.17 4.75 5.18 5 40 67.94 72.62 74.06 1 19 1.25 1.22 6.35 8.31 10.47 5.47 3.72 2.93 14.30 8.92 5.92 3 A 3B 3C 5.46 5 81 5.89 57.03 64 85 64.74 1.21 1.48 1 33 19.17 18.34 20.00 2.09 1 59 1.41 15 04 7.93 6.63 4 57 5.15 5.12 66.02 72.99 74.17 1.40 1.67 1.52 8.18 9.47 9.99 2.42 1.79 1.61 17.41 8.93 7.59 5A 5B 5Bi 5.48 5.42 5 41 54.76 66 17 65.47 .97 1.22 1 21 17.40 14.21 15.36 4.79 3.76 3.68 16.60 9.22 8 81 4.67 5.11 5.09 62.64 69.83 69.82 1 11 1.28 1.29 7.12 10 08 10.48 5 47 3 97 3.92 18.99 9.73 9.40 6A 6B 6Bi 5.61 6 05 5.89 56.20 61.50 60.86 1 04 1.05 1.16 18.04 19.32 19 45 3 54 2 93 2.98 15 57 9 15 9.66 4.69 5.28 5 10 65 55 70.88 70.11 1.21 1 21 1.34 6 26 8 71 8.88 4 13 3 37 3 44 18.16 10.55 11.13 7A 7B 7C 5.07 5.36 5.16 68.85 72.96 73.23 1 52 1.46 1 50 5 41 6.40 7.00 5.21 3.46 3 35 13.94 10 36 9.76 4 89 5 21 5 04 70.82 74 82 74.80 1.56 1.49 1.53 3 04 4.32 5 24 5 35 3.54 3.42 14.34 10.62 9.97 8A 8B 8C 5.16 5 47 5 51 54.45 60.31 62 02 1 39 1 49 1 57 15.42 17.05 17 15 2 77 2 12 2.10 20.81 13 56 11 65 4 46 4 84 4 93 60.87 67.08 68.62 1 55 1.66 1.74 6.76 8.98 •i 19 3 09 2.36 2.33 23.27 15.08 12.89 9A 9B 9C 5.16 5.41 5.73 54 75 (12 69 69.01 99 1.04 1 32 14 77 15.54 15 95 1 97 3 32 3 09 19.36 12 00 4 90 4.51 4 91 5.38 60.79 68.23 74.66 1 10 1.13 1.43 6.59 9.05 9.88 5 52 3 62 3.35 21.49 13 06 5.30 10A 10B IOC 5 31 5.42 5.53 68.78 72 10 72 99 1 91 1.62 2 01 11 77 11.71 11.68 2 47 1 95 1 74 9 76 7.20 6 05 4 93 5 11 5 22 73.26 76 00 77.10 2.03 1 71 2.12 6.75 7.53 7 33 2.63 2.06 1 84 10.40 7.59 6.39 11A 11B 11C 5 44 5 66 5.81 57.05 64.82 67 34 1 06 1.18 1 22 15 18 14.67 14 24 3 88 3.00 17 39 10.44 8.39 4 76 5 16 5 36 64 11 70 85 73.00 1 19 1.29 1.33 6.04 7.75 7.97 4.36 3 53 3.25 19.54 11.42 9.09 12A 12Ai 12B 5 45 5 46 5 66 57.58 59 85 til 60 1.07 1 18 1 22 17.65 17.53 17.58 4 37 3.55 4 01 13.88 12 43 9 93 4 57 4.77 5 01 66 57 67 09 68.90 1.24 1.32 1.36 7.51 8.91 9.13 5.06 3.98 4.49 16.05 13.93 11.11 13A 13B 13C 5 25 5.48 5 59 57 65 62 (i!» 64 21 1 14 1.17 1 25 16 42 Hi 22 17.03 3 69 2 93 2.72 15 85 11 50 9.17 4.61 4 97 5.04 63.90 68.38 70.61 1.26 1.28 1.37 8.58 9.63 9.91 4.08 3.20 2.99 17 57 12 54 10.08 14A 14B 14C 5.45 5 . 69 5 81 58 . 60 62.43 63.11 98 1 19 1 18 19.04 18.97 19.40 3 77 3.48 3.26 12.16 8 24 7 24 4.70 5 02 5.13 66.32 70 00 71.28 1 11 1.33 1.33 9.85 10.51 10.40 4.26 3.90 3.68 13.76 9.24 8.18 15A 15B 15C 5.34 5 35 5.78 63.90 70.71 73.38 1.62 1 63 1.65 15 36 14.58 15 67 .91 .85 .79 7.87 6.88 2.73 4.81 4.91 5.37 75.08 76.10 79.05 1 76 1.76 1.77 8.79 8.90 10.01 99 .92 .86 8.57 7.41 2.94 16 A 16B IOC 5 00 6.04 6.12 59 18 64.. 89 67.85 99 1 11 1.17 17.86 16.51 17.58 4.55 3 40 2 65 11.52 8 05 4.63 5.14 5.52 5.58 67.76 71.66 75.16 1 14 1 23 1.30 7.56 8.95 9.89 5.21 3.75 2.94 13.19 8.89 5.13 APPENDIX 57 ULTIMATE ANALYSIS Moistu re and Ash Free Coal No. Hydrogen, Carbon, Nitrogen. Oxygen . Sulfur, Si0 2 , A1-.0.3, Fe>0 3 , MgO, CaO, so 3 , Ignition loss, % 07 /o % 07 % % % 07 /o % % % % 5.24 82.73 1.87 9.21 .95 - - ~ - - ~ - 1A 5.54 5.69 5.74 79.25 79.74 78.73 1 39 1 37 1.29 7 44 9 11 11.12 6.38 4.09 3.12 — - — E - — 2A 23 2C 5.53 5.66 5.54 79.93 80 17 80.31 1 70 1.83 1.64 9.92 10.37 10.76 2.92 1.97 1.75 — — — — E — 3 A 3B 3C 5.76 5 . 66 5.62 77.32 77.38 77.03 1.37 1.42 1.43 8.79 11.14 11.59 6.76 4.40 4.33 — - — - E — 5 A 5B 5B 1 5.73 5.90 5.73 80.06 79.28 78.85 1 48 1.36 1.50 7.68 9.69 10.05 5.05 3.77 3.87 — - - — E — - 6A 6B 6B 1 5.70 5.83 5 60 82.64 83.75 83 13 1 82 1.67 1.70 3.59 4.78 5.77 6.25 3.97 3.80 — - - — - — 7A 7B 7C 5 81 5.70 5.66 79.33 78.94 78.74 2.02 1.95 2.00 8.81 10.63 10.93 4.03 2.78 2.67 - — — - — = — 8A 8B 8C 5.74 5.65 5.68 77.41 78.51 78.87 1.41 1.31 1.51 8.41 10.37 10.40 7.03 4.16 3.54 51.25 21.85 17.20 1.02 3.20 1.08 1.39 9A 9B 9C 5 50 5 53 5 57 81.79 82.23 82.33 2.27 1.85 2.26 7.51 8.16 7.87 2.93 2 23 1.97 39.99 41 57 44.16 23.05 21.88 23.49 24.35 23.59 22.02 .98 .78 .94 6.18 4.85 3.78 5.25 3.92 2.42 2.40 2.41 2.75 10A 10B 10C 5.91 5.83 5.89 79.66 80.01 80.27 1 48 1.46 1.46 7.53 8.72 8.81 5.42 3.98 3.57 41.88 38.59 38.39 19.96 18.51 18.01 21.62 24.33 26.68 .79 .93 1.00 6 05 6.62 5.62 5.79 6.68 5.68 3.28 2.10 2.97 11A 11B 11C 5 44 5.54 5.63 79.30 77.95 77.48 1.48 1.53 1.53 7.76 10 35 10.31 6.02 4.63 5.05 41.74 48 93 47.00 12.84 14.67 13.49 25.56 24.58 25.53 .78 .74 .63 5.81 5.06 5.55 5.45 3.42 5.43 1.07 1.10 .87 12A 12Ai 12B 5.60 5.66 5.61 77.53 78.20 78.51 1 53 1.46 1.52 10.38 11.04 11.04 4.96 3.66 3.32 48.90 51.53 51.78 19.93 20.94 21.46 18.83 14 12 13.97 1.00 .97 .97 4.17 4.05 3.62 4.10 4.18 3.80 2.17 2.75 3.25 13A 13B 13C 5.45 5.53 5.59 76.88 77.13 77.64 1.29 1.47 1.45 11.44 11.57 11.31 4.94 4.30 4.01 43.03 45.31 46.71 20.04 21.42 21.69 23.85 20.03 18.65 1.04 1.11 1.20 3.54 2.86 2.70 3.30 2.39 2.70 3.32 1.38 1.87 14A 14B 14C 5.27 5.30 5.54 82.14 82.21 81.49 1.93 1.90 1.83 9.57 9.60 10.26 1.09 .99 .88 58.07 58.84 50.52 25.37 25.90 26.21 9.20 8.59 13.18 .78 1.04 1.00 1.59 1.28 2.79 1.18 .72 1.83 1.58 .72 1.95 15A 15B 15C 5.92 6.06 5.88 78.06 78.65 79.21 1.31 1.35 1.37 8.71 9.82 10.44 6.00 4.12 3.10 . 36.40 36.42 34.95 18.67 23.09 25.56 34.71 29.82 26.25 .56 .63 .58 6.23 4.16 4.04 6.93 3.52 2.95 .37 .21 3.13 16A 16B 16C 58 DOMESTIC STOKER COMBUSTION VARIETIES OF SULFUR Coal As-Fired Moisture-Free Moisture and Ash Free No. Sulfate, % Pyritic, % Organic, % Total, % Sulfate, % Pyritic, Vo Organic, % Total, % Sulfate, % Pyritic, % Organic, % Total, % 2A 2B 2C 3A 3B 3C 5A 5B 5Bi 6A OB 6B 1 7A 7B 7C 8A 8B 8C 9A 9B .22 .19 .24 .34 .20 .11 .04 .23 .15 .03 .28 .30 .08 .00 .05 .08 .00 .00 .10 .08 3.20 2.13 1.20 1 18 .09 .70 2.88 1.33 1.27 2.04 1.05 .99 3.24 1.02 1.55 1.50 .04 .55 3.00 1.05 1.29 1.00 1 12 .57 .04 .00 1.87 2 20 2.20 1.47 1.00 1.69 1.89 1.78 1.75 1 13 1 42 1.49 1.87 1 59 4.77 3.32 2.56 2.09 1.59 1 41 4.79 3 76 3.08 3 54 2.93 2.98 5 21 3.40 3.35 2.77 2.12 2.10 4.97 3.32 .25 .21 .28 .39 .29 .13 .04 .25 .10 .04 .32 .35 .08 .00 .05 .09 .07 .00 11 .08 3.74 2.39 1.37 1.36 .77 .81 3.30 1 41 1.35 2.38 1.21 1 14 3 34 1.00 1.58 1 75 .71 .01 3 33 1.80 1.48 1.12 1.28 .67 .73 .67 2.13 2.31 2.41 1.71 1.84 1 95 1.93 1.82 1.79 1.25 1.58 1.66 2.08 1.74 5.47 3.72 2.93 2.42 1.79 1.61 5.47 3.97 3.92 4 13 3.37 3.44 5.35 3.54 3.42 3.09 2.36 2.33 5.52 3 62 .29 .23 .30 .47 .32 .14 .05 .27 .18 .05 .36 .39 .09 .07 .06 .12 .08 .07 .14 .09 4.36 2.62 1.45 1.05 .85 .87 4.07 1.50 1.49 2.91 1.36 1.28 3.89 1.86 1.75 2.28 .84 .70 4.24 2.07 1.73 1.24 1.37 .80 .80 .74 2.64 2.57 2.66 2.09 2.05 2.20 2.27 2.04 1.99 1.63 1.86 1.90 2.65 2.00 6.38 4.09 3.12 2.92 1.97 1.75 6.76 4.40 4 33 5.05 3 77 3.87 6.25 3.97 3.80 4.03 2.78 2.67 7.03 4 16 APPENDIX 59 GlESELER Plasticity Ignition Temperature Chemical fusain, moisture and ash free, % . British swelling index Mineral matter, % Carbon avail. H2 Fixed Carbon Volatile matter Fixed Carbon X heating value Recovery of washed coal, referred to raw coal, % Fusion, °C Maximum Fluidity, °C Solidifi- cation, °C Maximum fluidity, divisions per min. Tib °C T75 °C Coal No. * * * * 175 227 2.4 5.5 8.2 20.2 1.79 6566 - 1A * * 457 456 * * 169 170 167 189 191 188 2.2 1.9 1.1 4.0 4.0 3.5 16.0 10.5 7.0 17.1 17.6 18.1 1.33 1.09 1.36 4586 4919 5510 91.5 59.2 2A 2B 2C t t 454 t * t 166 169 167 187 187 189 4.2 2.1 2.1 3.5 1.0 4.0 17.3 9.4 7.9 18.6 18.4 19.1 1.20 1.33 1.28 3948 5278 5193 71.4 59.4 3A 3B 3C 398 408 370 377 440 433 433 .81 3.4 3.2 167 169 165 191 189 189 3.1 1.7 1.9 4.0 3.0 3.5 20.6 12.1 11.5 16.6 18.2 18.4 1.06 1.11 1.37 3634 5359 5822 90.9 88.8 5A 5B 5Bi 384 387 408 392 388 443 445 445 11.0 2.9 5.6 173 167 174 188 190 191 2.7 1.9 2.1 4.0 2.0 2.0 18.8 11.5 12.0 16.8 16.9 17.6 1.35 1.32 1.28 4068 4884 4718 92.6 95.2 6A 6B 6B' 379 382 380 415 421 415 467 458 459 9000 20300 12800 216 214 213 257 261 259 3.9 7.5 8.0 8.0 17.9 13.1 12.4 15.7 16.0 17.1 1.46 1.46 1 50 6075 6760 6995 92.1 75.6 7A 7B 7C 369 375 387 390 435 436 435 6.7 4.1 4.6 168 168 166 194 196 189 3.8 2.0 3.0 3.0 24.0 15.9 13.8 16.9 18 1 18.4 1.02 1.10 1.09 3341 4298 4565 89.9 79.4 8A 8B 8C 393 388 390 404 407 406 434 434 431 10.0 26.0 24.0 183 167 206 195 2.7 4.5 4.5 3.5 23.7 14.8 7.0 16.5 18.0 18.5 1.06 1.07 1.26 3636 4679 6103 91.1 38.7 9A 9B 9C 398 404 406 417 422 425 447 447 453 48 27 35.6 - — - 4.5 5.0 4.5 11.9 8.8 7.4 17.9 18.2 17.9 1.53 1.54 1.54 6277 6850 6990 87.4 39.7 10A 10B 10C 380 t t 409 t t 447 t t 700 t t — — — 4.0 3.5 4.0 20.9 13.1 10.7 16.1 16.9 16.7 1.05 1.11 1.12 3769 5037 5428 86.0 59.4 11A 11B 11C t t t t t t t t t t t t = 3.0 3.0 4.0 17.4 15.3 12.9 17.8 18.3 17.8 1.21 1.28 1.25 4121 4704 5002 86.8 61.8 12A 12A 1 12B 12C t t t t 410 t t 440 t t 4.0 - - - 3.5 4.0 4.0 19.2 14.0 11.4 18.0 18.2 18.6 1.25 1.24 1.34 4339 5031 5441 88.3 60.0 13A 13B 13C t t t t t t t t t t t t — — - 3.0 4 4.0 15.1 10.8 9.7 19.1 18.9 18.7 1.19 1.17 1.19 4438 4995 5068 86.8 59.8 14A 14B 14B 418 t 425 420 t 452 450 t 6.0 3.2 t - - - 4.0 4.0 3.5 9.0 7.9 3.5 20.1 18.2 19.2 1.67 1.76 1.73 6406 6839 7481 85.7 44.0 15A 15B 15C t t 1- t t t t t t t t t - - - 3.5 4.5 3.5 14.9 10.6 6.4 16.1 16.3 17.3 1.12 1.16 1.22 4368 5279 5823 81.8 46.5 16A 16B 16C * Plasticity characteristics of this coal were tested by other methods method. Data not reported. f Test inconclusive; rabble arms stirred through powdered coal. later concluded to be less useful than the Gieseler 60 DOMESTIC STOKER COMBUSTION UNIFORMITY RESPONSIVENESS PICKUP OVERRUN Coal No. Average Variation, % Minimum -T- average * First 30 min., M B.t.u./hr. First hr., M B.t.u./hr. Average Cycle Minimum Cycle Average Cycle Maximum Cycle M B.t.u./hr. Ratiot M B.t.u./hr. Ratiof M B.t.u./hr. Ratiof M B.t.u./hr. Ratiot 1A 5.2 .85 38.5 114 9 54 .28 46 .24 99 .52 120 .62 2A 2B 5.4 4.3 .86 .89 14.6 20.4 57.8 68.1 39 48 .28 .29 32 40 .23 .24 64 76 .46 .46 77 92 55 .56 2C 2.9 .91 — — — — — — — — — — 3A 3B 3C 6.8 5.0 3.6 .87 .89 .90 20.2 34.0 25.2 92.6 77.4 103.2 45 47 56 .29 .30 .32 33 33 42 .21 .21 .24 79 69 90 .51 .44 .51 108 88 104 .70 .56 .59 5A 5B 5Bi 12.9 7.1 6.7 .69 .83 .83 14.6 18.4 37.9 63.5 87.6 97.3 35 38 41 .25 .23 .26 18 26 25 .13 .16 .16 63 84 84 .45 .51 .53 81 115 109 .58 .70 69 6A 6B 6B' 13.4 6.9 6.9 .69 .85 .85 15 .7 35.3 37.3 68.0 113.2 30 39 39 .22 .25 .25 16 23 25 .12 .15 .16 65 81 77 .48 .52 .50 90 109 104 .66 .70 .67 7A 7B 7C 15 5 11.8 15 4 .63 .74 .64 11.7 17.6 20.6 34.2 70.0 81.7 45 44 47 .24 .23 .26 23 34 32 .12 .18 .18 75 82 79 .40 .43 .44 111 124 137 .59 .65 .76 8A 8B 8C 8.3 5.7 5.7 .72 .85 .84 18.0 18.8 29.7 78.1 65.8 101 38 42 40 .27 .27 .25 28 31 25 .20 .20 .18 73 83 82 .52 .54 .52 93 100 100 .66 .65 .63 9A 9B 9C 20.5 8.6 7.9 .58 .78 .80 9.2 23.7 19.1 32.8 102.5 86.4 35 42 38 .23 .24 .22 23 33 26 .15 .19 .15 69 87 79 .45 . 50 .46 117 106 121 .76 61 .71 10A 10B IOC 8.9 6.4 6.3 .76 .84 .85 18.2 19.5 16.2 80.2 90.5 86.6 40 39 39 .24 .21 .21 30 30 32 .18 .16 .17 84 86 91 .50 .46 .49 116 109 119 .69 .58 .64 11A 11B 11C 17.8 15.7 13.8 .62 .63 .73 9.3 12.6 13.7 23.0 56.4 74.9 32 35 36 .23 .23 .21 25 28 30 .18 .18 .18 64 74 73 .45 .48 .43 89 105 107 .63 .68 .63 12A 12A' 12B 11.1 8.4 8.6 .69 .79 .78 15.4 15.0 19.8 62.9 65.5 75.9 34 32 34 .23 .22 .21 27 22 28 .18 .15 .17 73 70 75 .49 .48 .46 100 96 94 .67 .66 .58 13A 13B 13C 16.8 8.2 8.0 .65 .80 .78 18.6 29.4 39.5 83.5 106.2 112.6 32 39 42 .22 .23 .24 24 29 34 .16 .17 .19 75 87 88 .51 .51 .50 91 113 108 .62 .66 .61 14A 14B 14C 10.6 8.2 4.9 .77 .75 .87 19.3 28.0 23.7 61.5 94.1 97.5 40 37 39 .27 .22 .23 31 28 31 .21 .17 .18 82 83 82 .56 .50 .48 99 106 98 .68 .64 .58 15A 15B 15C 6.4 5.4 2.9 .85 .85 .93 21.9 27.1 27.2 100.8 99.5 44 45 49 .24 .24 .26 31 34 43 .17 .18 .23 93 90 90 .50 48 .48 111 105 106 .60 .56 .56 16A 16B 1(»C 5.6 4 2 4.4 .87 .90 .89 19.1 20.3 25.8 59 8 77.4 89.2 36 40 37 .24 .26 .24 32 32 31 .21 .20 .20 80 78 73 .53 .50 .47 91 96 92 .60 .61 .60 * Average of all operation rates except hold-fire. t Ratio of rate of heat release during pickup or overrun period to the average rate with continuous stoker operation, APPENDIX 01 Heat Obtained Boiler Output With Continuous Stoker Coal Average efficiency % Clinker rating Windbox pressure in. of H 2 Coal fed, Ib./min. Operation No. 60** M B.t.u. lb. 45** M B.t.u., lb. 30** M B.t.u. 'lb. 15** M B.t.u. lb. Average M B.t.U.; 11). Average, M B.t.u./hr. Minimum, M B.t.u./hr. Minimum Average 1A 7.81 7.84 8.06 8.38 8.02 66.0 4 .60 .42 192 178 93 2 A 2B 2C 6.27 7.04 6.92 6.09 6.94 7.25 6.00 6.90 7.58 6.48 7.48 8.12 6.21 7.09 7.47 57.8 61.0 64.1 1 2 .84 .72 .62 .38 .40 .40 139 165 172 125 148 163 .90 .89 .95 3 A 3B 3C 6.22 6.70 7.35 6.25 6.76 7.46 6.66 6.66 7.61 6.98 6.28 8.30 6.53 6.60 7.68 64.3 57.7 66.8 2 3 3 .98 .65 .42 .39 .40 155 157 176 126 144 154 .82 .92 .88 5 A 5B 5Bi 5.47 7.31 7.58 5.85 7.42 7.39 5.74 7.47 7.44 5.77 7.35 7.40 5.71 7.39 7.45 57.4 61.9 63.0 1 2 1.07 .72 .68 .43 .36 .36 140 165 158 80 149 141 .57 .90 .90 6A 6B 6Bi 5.99 6.79 6.79 5.93 6.65 6.75 6.07 6.76 6.63 5.87 6.76 6.43 5.96 6.74 6.65 59.0 60.9 61.0 2 2 1.20 .70 .79 .39 .38 .38 136 156 155 116 145 145 .85 .93 .94 7 A 7B 7C 8.22 8.31 8.09 7.95 8.22 8.02 8.16 8.32 8.05 8.43 7.78 8.21 8.19 8.16 8.09 66.6 62.4 61.2 1 1 1.15 1.22 1 15 .40 .39 .39 188 191 180 134 136 138 .71 .71 .76 8A 8B 8C 5 74 6.50 6.69 5.68 6.60 6.61 6.05 6.77 6.72 6.43 7.12 6.80 5.98 6.75 6.71 61.9 62.8 60.4 1 2 2 1.20 .86 .68 .42 .41 .40 141 154 158 100 141 125 .71 .91 .79 9A 9B 9C 6.07 7 17 7.83 5 91 7.02 7.64 6.16 7 20 7.57 6.57 7.45 7.48 6.18 7.21 7.63 61.9 63.5 60.9 1 4 1 13 .92 .72 .43 .41 .37 154 174 171 71 118 150 .46 .68 .88 10A 10B IOC 7.64 8.20 8 18 7.48 7.88 8.08 7.49 8.02 7.99 7.93 8.08 7.81 7.63 8 05 8.01 61.9 62 5 61.6 2 3 4 .93 .83 .69 .38 .38 .38 169 188 186 132 151 158 .78 .80 .85 11A 11B 11C 6.16 6.71 7.46 6 09 6.63 7 17 6.06 6.54 7 15 6.06 6.80 7.09 6.09 6.67 7.22 59 1 56.4 58.9 2 3 1.09 .92 .81 .41 .39 .38 141 154 169 .63 78 113 .45 .51 .67 12A 12A» 12B 12C 6.17 6.61 7.12 5.86 6 51 6.88 6.02 6.49 6.82 6.12 6.66 6.79 6.04 6.57 6.90 58.3 60.2 61.0 1 1 3 .82 .86 .78 .42 .39 .41 149 145 163 97- 120 118 .65 .83 .73 13A 13B 13C 6.04 7.08 7.26 6.28 7.03 7.26 6.35 7.13 7.39 6.34 7.24 7.33 6 25 7.12 7.31 59.5 62.8 63.0 3 4 .97 .91 .90 .43 .42 .41 147 172 177 56 130 127 .38 .76 .72 14A 14B 14C 6 21 7.06 7 30 6.08 6.96 7.23 5 65 6.98 7.18 6.50 7.26 7 17 6.11 7.07 7.22 57.0 61.9 62.8 2 4 4 .89 .88 .58 .41 .40 .39 146 166 170 69 102 148 .47 .61 .87 15A 15B 15C 7.86 8.26 8.75 7.81 8 14 8 53 8.01 8 00 8.39 8.44 8.27 8.26 8.03 8.17 8.48 65.8 65.6 64.7 2 4 4 .81 .58 .39 .40 .38 .37 185 188 189 163 170 175 .88 .90 .93 16A 16B 16C 6.77 7.55 7.74 6.74 7.54 7.74 6.73 7.84 7.54 7.33 8.52 7.88 6.89 7.86 7.73 63.1 66.1 62.5 1 2 3 .78 .67 .57 .38 .35 .33 151 158 155 127 139 143 .84 .88 .92 Minutes of stoker operation per hour. 62 DOMESTIC STOKER COMBUSTION RESULTS OBTAINED WITH CONTINUOUS STOKER OPERATION Coal No. CO2 % Stack Tempera- ture, °F HEAT BALANCE Heat Absorbed Stack Loss Moisture Loss Hydrogen Loss Radiation and Unaccounted B.t.u./lb. % B.t.u./lb. % B.t.u./lb. % B.t.u./lb. % B.t.u./lb. % 1A 12.9 980 7810 64.2 3070 25.2 130 1.1 450 3.7 700 5.8 2A 2B 2C 9.6 10.7 10.4 880 970 930 6270 7040 6920 53.3 60.5 59.4 3080 3400 3400 28.7 29.2 29.2 180 160 180 1.7 1.4 15 440 480 460 4.1 4.1 4.0 770 548 690 7.2 4.8 5.9 3A 3B 3C 10.7 10.5 11 5 900 890 935 6220 6700 7350 61.2 58.6 64.0 2760 3140 3040 27.2 27.4 26.4 190 160 180 1.9 14 1.6 390 450 440 3.9 3.9 3.8 588 998 480 5.8 8.7 4.2 5A 5B 5Bi 9.5 10.6 9.8 880 915 915 5470 7310 7580 55.0 61.2 64.1 2870 3280 3500 28.8 27.5 29.6 180 75 84 1.8 .6 .7 420 460 456 4.2 3.9 3.8 1015 810 213 10.2 6.8 1.8 6A 6B 6B' 9.8 11 4 10.0 865 900 850 5990 6790 6790 59.3 61.3 62.3 2820 2760 2890 28.0 24.9 26.5 190 190 185 1.9 17 1.7 420 470 435 4 2 4.2 4 665 874 595 6.6 7.9 5.5 7A 7B 7C 11.7 12.0 10.0 965 990 945 8220 8310 8090 66 8 63.6 61.2 3320 3500 3960 27.0 26.7 29 9 40 40 30 .3 .3 .2 575 600 570 4 7 4.6 4.3 142 625 573 1.2 4.8 4.4 8A 8B 8C 8.9 10.1 10 3 895 965 980 5740 6500 6690 59.5 60 5 60.2 3110 3310 3400 32 2 30.8 30.6 150 150 140 15 14 13 415 440 440 4.3 4.1 4.0 240 346 438 2.5 3.2 3.9 9A 9B 9C 10 1 11.6 11 3 910 1000 910 6070 7170 7830 60.8 63.2 62.5 2820 3150 3210 28 2 27.7 25.6 140 120 110 1.4 11 .9 430 460 480 4.3 4.0 3.8 529 458 901 5.3 4.0 7.2 10A 10B IOC 11 3 12.6 11 3 920 960 7640 8200 61.9 63.7 3230 3190 26.2 24.8 90 70 .7 .5 500 520 4 1 4.0 873 896 7.1 7.0 11A 11B 11C 10.1 9.0 10.3 840 850 910 6160 6710 7460 59.8 56 7 60.9 2670 3480 3420 25.9 29.4 27.9 155 120 110 15 1.0 .9 450 480 520 4.4 4 1 4.2 864 1035 749 8.4 8.8 6.1 12A 12A' 12B 9.9 9.9 11.0 910 900 920 6170 6610 7120 59.5 60.5 62.8 3040 3110 2950 29.4 28.5 26.1 190 150 150 1.8 1.4 1.4 420 420 450 3.1 3.9 4.0 534 625 647 5.2 5.7 5 7 13A 13B 13C 9.8 12.0 865 975 940 6040 7260 57 5 62.6 2890 2890 27.5 24.9 140 130 1.3 1.1 405 450 3.9 3.9 1031 871 9.8 7.5 14A 14B 14C 9.5 10.8 11.0 900 900 895 6210 7060 7300 57.9 61.8 63.5 3200 2960 2900 29.9 25.9 25.2 165 150 160 1.5 1.3 1.4 390 425 430 3.6 3.7 3.8 755 835 701 7.1 7.3 6.1 15A 15B 15C 11.8 12.1 11 4 1015 960 920 7860 8260 8750 64.4 66 3 66.8 3400 3285 3370 27.9 26.4 25.7 120 100 100 1.0 .8 .8 450 510 490 3.7 4.1 3.7 372 303 391 3.0 2.4 3.0 16A 16B 9.5 900 885 6770 62.0 3140 28.8 180 1.6 470 4.3 359 3.3 16C 8.9 860 7740 62.7 3690 29.8 140 1.1 500 4.0 292 2.4