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344 CHAPTER 14 1957 Guide a heat balance when required in testing of heating devices. Typical ulti mate analyses of the various kinds of coal are shown in Table 1.* Other important qualities of coals are the screen sizes, ash fusion tem perature, friability, caking tendency, and the qualities of the volatile matter. In considering these factors the following points are of interest. The volatile products given off by coals when they are heated differ mate rially in the ratios by weight of the gases to the oils and tars. No heavy oils or tars are given off by anthracite, and very small quantities are given off by semi-anthracite. As the volatile matter in the coal increases to as much as 40 percent of ash and moisture-free coal, increasing amounts of oils and tars are released. For coals of higher volatile content, the relative quantity of oils and tars decreases and is therefore low in the sub-bituminous Table 1. Typical Ultimate Analyses fob Coals Btu fsb Lb Constituents, Pxb Cent lUm Moist, Mineralmatter- free* Moist, SB Received Oxygen drogen Carbon Nitrogen Sulfur Anthracite-___________ 14,600 12,910 5.0 2.9 80.0 0.9 0.7 Semi-Anthracite............ 15,200 13,770 5.0 3.9 80.4 1.1 1.1 Low-Volatile Bituminous_________ 15,350 14,340 5.0 4.7 81.7 1.4 12 Medium-Volatile Bituminous.________ 15,200 13,840 5.0 5.0 79.0 1.4 1.5 High-Volatile Bituminous A______ 14,500 13,090 9.2 5.3 73.2 1.5 2.0 High-Volatile Bituminous B______ 13,500 12,130 13.8 5.5 68.0 1.4 2.1 High-Volatile Bituminous C______ 12,000 10,750 21.0 5.8 60.6 1.1 2.1 Sub Bituminous A--j._ Sub Bituminous B____ 10,250 9,150 29.5 62 52.5 1.0 1.0 Sub Bituminous C____ 9,000 8,940 35.8 6.5 46.7 0.8 0.6 Lignite____'.......... ........ 7,500 6,900 44.0 6.9 40.1 0.7 1.0 AbS 10.5 8.5 6.0 8.1 8.8 9.2 9.4 9.8 9.6 7.3 OH- 87.9 89.3 91.4 89.0 87.7 87.3 8T.4 88.2 89.0 91.0 * (Btu as received) X 100 4- (100 -- 1.1 Ash). coals and in lignite. The percentage of ash and its fusion temperature do not indicate the composition or distribution of its constituents. Classification of Coals A classification of coals is given in Table 2, and a brief description of the kinds of fuel is given in the following paragraphs, but it should be recog nized that there are no distinct lines of demarcation between the kinds, and that they graduate into each other. Anthracite is a clean, dense, hard coal which creates little dust in handling, It13 comparatively hard to ignite, but it bums freely when well started. It is non-caking; it bums uniformly and smokelessly with a short flame, and it requires no attention to the fuel bed between firings. It is capable of giving a high efficiency in the common types of hand-fired furnaces. A tabulation of the quality of the various anthracite sizes will be found in a Bureau of Mines Report.* Standard anthracite sizing specifi cations are shown in Table 3. '> Semi-anthracite has a higher volatile content than anthracite. It is not so hard, and ignites somewhat more easily. Otherwise their properties are similar. Semi-bituminous coal is soft and friable, and fines and dust are created by handhufi it. It ignites Bomewhat slowly and burns with a medium length of flame. Its caking properties increase as the volatile matter increases, but the coke formed is relativWweak. Having only half the volatile matter content of the bituminous coals, it c*? be burned with less production of smoke, and is sometimes called a smokeless coo*\ Fuels and Combustion 345 The term bituminous coal covers a large range of coals and includes many types having distinctly different composition, properties, and burning characteristics. The coals range from the high-grade bituminous coals of the East to the poorer coals of the West. Their calcine properties range from coalB which melt completely, to those from which the volatiles and tars are distilled without change of form, so that they are classed as non-caking or free-burning. Most bituminous coals are strong Table 2. Classification of Coals by Rank" Legend: F.C. = Fixed Carbon. V.M. = Volatile Matter. Btu = British thermal units. Class Group Limits op Fixe Carbon or Btu Minebal-Matteb- Requisite Physical Fbeb Basis PbOPEHTI 88 I. Anthracite. . II. Bituminous*1. HI Sub-bitumi nous IV. Lignitic.. 1. Meta-anthracite. . Dry F.C., 98 per cent or more (Dry V.M., 2 per 2. Anthracite......... cent or less) Dry F.C., 92 per cent or more and less than 98 per cent (Dry V.M., 8 per cent or leas and more 3. Sem i-anthracite. than 2 per cent) Dry F.C., 86 per cent or Non-agglome rating more and less than 92 per cent (Dry V.M., 14 j per cent or less and more than 8 per cent) 3. Low volatile .bituminous coal.. Dry F.C., 78 per cent or more and less than 86 per cent (Dry V.M., 22 per cent or less and more 2. Medium volatile bituminous coal than 14 per cent) Dry F.C., 69 per cent or more and less than 78 per cent (Dry V.M., 31 per cent or leas and more than 22 per cent) Either agglomerab ing* or non- 3- High volatile A bituminous j Dry F.C., less than 69 per coal 1 cent (Dry V.M , more weathering^ than 81 per cent); and moist* Btu, 14,000* or 4. High volatile B -bituminous coal 3. High volatile C bituminous Coal 1. Sub-bituminous A coal.............. more Moist6 Btu, 13,000 or more and less than 14,000* Moist Btu, 11,000 or more and less than 13,000* Moist Btu, 11,000 or more 2. Sub-bituminous B ooal.. 3. Sub-bituminous C coal. and less than 13,000* Moist Btu, 9500 or more and less than ll.OOO6 Moist Btu, 8300 or more Both weathering and non-agglomerating* 1. Lignite....... 2. Brown coal. and less than 9500* Moist Btu less than 8300 Moist Btu less than 8300 Consolidated Unconsolidated This classification does not include a few coals which have unusual physical and chemical properties and which come within the limits of fixed carbon or Btu of the high-volatile bituminous and aub-bitummous mnks. All of these coals either contain less than 48 percent dry, mineral-matter-free fixed carbon, or have more than 15,500 moist, mineral-matter-free Btu. If agglomerating, classify in low-volatile group of the bituminous class. ..............ot theMcooisatl.Btu refers to coal containing its natural bed moisture but not inoludh including visible water on the surface . rvjjt t*8pized that there may be non-caking varieties in each group o f the bituminous class. _vln* 69 percent or more fixed carbon on the dry, mineral-matter-free basis shall be classified to fixed carbon, regardless of Btu. eratin*a*1* varieties of ooal in the high-volatile C bituminous ooal group, namely, Variety 1, aggk>m- i^j^^^^Q'-weathering; Variety 2, agglomerating and weathering; Variety 3, non-agglomerating and Adapted from AJ5.T.M. Standards, 1937, Supplement, p. 145, American Society for Testing Materials. enough to permit the screened sizes being delivered free from fines coals KTM" *8Qite easily and burn freely; the length of flame varies with different at loi*>UVt >s long. Mach smoke and soot are possible, if improperly fired, especially *w rates of burning. mn ^luminous coals occur in the western states; they are high in moisture when liable! t,en<^ to break up as they dry or when exposed to the weather; they are and ht01a'*e apontaneously when piled or stored. They ignite easily and quickly, to bre wa medium length flame; are non-caking and free-burning; tne lumps tend reak into small pieces if poked; very little smoke and soot are formed. Sntte is of woody structure, very high in moisture as mined, and of low heating