TP 32.5 YF HI UC-NRLF GIFT OF ; THE NATIONAL RESEARCH COUNCIL Washington, D. C. Clean Coal THE EFFECT OF HIGH ASH upon Thermal Efficiency Amount of Boiler Plant Amount of Transportation Equipment Reprinted by THE J. G. WHITE ENGINEERING CORPORATION New York with the permission of THE NATIONAL RESEARCH COUNCIL Washington, D. C. fcrk City. Number ofSOO HP. Boilers required fo generate 30O, OOO pounds steam per Hour. / 2345 6 78 9 10 /I 12 13 14 /5 /6 /7 /8 /9 2O 00 oo 00 oo a o oo OO OO OO OO ao OO an OO oo /8 oo oo oo po po po OO oo ge oo oo 00 oo oo gg oo oo oca OQ aa aa 00 aa =_a OO aa OO 03 o a oo pobo tool OQ oo OO OO OQ OO on OO ao 00 00 00 00 oo oo 00 oo DO too po sHis cj; 8 no nn 00 on 00 00 OO OO 00 nn no aa aa aa 00 OD oo o a DO D O 3D oo a a aa O on o a 00 00 po po pD an 00 OO OO 00 OQ 00 88 Number of Boilers. CHART -V ;-i- : i U pcO ' practice to operate central station boilers at 2CC$ to 250$ of their rated capacity during peak periods. In the same stations it is now difficult to operate the boilers at more than 150$ to 160$ of their rating, and sometimes at even less. It is, therefore, necessary for these stations to place more boilers on the line, and in many cases they have been compelled to purchase additional boiler units at unusually high prices. This phase of the subject is illustrated on Chart Ho. 3, which shows the number of 500 horsepower boilers required to generate 300,000 pounds of steam, equivalent to a peak load of 15,000 to 20,000 k.w. With coal containing $ ash or less eight boilers can be made to do this work. If the ash runs higher than 6^ nine boilers must be operated, above 10$ eleven boilers would be required, and above 18$ nineteen or twenty boilers are required. This situation is so bad that practically every large central station today has no spare boiler capacity, unless spare boilers have been purchased and installed within the past two years. They are compelled to refuse new business and must often keep boilers in service that should be undergoing cleaning and furnace repairs. The effect upon industrial plants is similar to that experienced by the central stations, but in a different degree. Industrial plants do not operate their boilers at the high ratings experienced in central station practice, but they do not as a rule carry so large a percentage of spare boiler equipment as do the central stations. They, therefore. 90 080 find it necessary to operate their entire boiler equipment, or curtail production, and their boilers are kept in service for longer periods than is good practice. It is impossible to take the boilers out of service long enough to properly clean them from scale and to properly repair baffles and brick work in the furnaces. The consequence is that the boiler efficiency is seriously reduced until they are in such poor condition that they must be shut down for cleaning, at the expense of production. With reasonably clean coal this situation would not exist. IHCKEA3E IN TBAKSPOBTATIOff SQUIPMSHT PEE TO HIGH ASH. There is a difference between preventible and non-preventible non-combustible in coal. The non-preventible ash is so thoroughly incorporated with the structure of the coal that it cannot be separated mechanically. This minimum ash content differs in each mine. By preventible ash is meant the slate and other impurities which can be separated by careful, preparation. This minimum ash varies from as low as 2$ in some cases to as high as 33$ in other cases. The average for the country is probably about 9$ or 10$. The percentage of ash in the coal from various States, together with the output for the year 1915 is given in Table I. Over half the coal mined shows an ash analysis of <$ or better. The percentage for the country if averaged in proportion to each State* s production is about 9.9$. We may, there- fore, consider 10$ as a fair average for clean coal for the entire country. fjCt> i . -7- TABLE I TONS OP COAL MIKED IB 1915 AND THE PER CENT. OP ASH IN THE COAL 1 PRINCIPAL COAL Coal mined per annum. Tona (2000 Average per oent. of unavoidable ash Pennsylvania West Virginia Illinois OMo Kentucky Indiana Alabama Colorado Virginia Iowa Kansas Wyoming Tennessee Other States 158,000,000 77,000,000 59,000,000 22,500,000 21400,000 17,000,000 15,000,000 8,600,000 8,100,000 7,600,000 6,800,000 6,500,000 5,700,000 29,500,000 AVEKAGE FOR THE COUHTBY 1255 The J. G. White Engineering Corporation New York City. Incr&as c d Cars A/b c Gssary for Transportation of rf/gf) Ash Coa/. Useful Freight Unnecessary freight 4 6 7 / 9 /O // /2 /J /* /S /6 /7 O O o o o D B o b ' o v o o o o o o o C Comparative Number of Cars. . ft f* ft't f"! W 'ft PI PI PI There will be mined this year probably six hundred million tons of coal. 85$ of this coal will be transported by the railroads; hence for each per cent, above the average 10$, the excess ash will add to the work of the overburdened railroads 5,000,000 tons of useless freight. Chart No. 4 illustrates diagranmatically the increased transportation equipment necessary for handling coal with a high per- centage of ash. The number of cars shows the relative number of cars necessary to carry coals of varying degree of ash. The shaded cars represent the percentage of carrying capacity which has heating value, the light cars, the useless freight. It will be noted that in some shipments as much as 40$ of the cars carry worthless material, or in other words coal containing 21$ ash requires 65$ more cars than coal containing 10$ ash. In all these charts it will be noted that the trouble from ash is not excessive until we pass 10$ to 12$ content. If, therefore, we might limit the percentage of ash to the average of 10$, we would reduce our transportation equipment to a practical minimum; we would be able to operate all boilers at a reasonable efficiency and would reduce the number of boilers operated to a little over one-half of the number required for the dirty coal (that is l8$ ash or over) besides making a saving in money that cannot be accurately estimated. Very truly yours, THE J.G. WHITE ESGIHEEfflnU} CORPORA! IOK. WAS:HD:9: , ' ''."-' --.,-. " : e*io >.uc4s .. - - t^ad v . -. . . :.-.' ' . . "- ' ' ;i ' . dw {sassrj - . . - . JJ1< an cos t 464148 UNIVERSITY OF CALIFORNIA LIBRARY UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. This book is DUE on the last date stamped below. LD 21-100m-ll, '49(B7146sl6)476