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304 CHAPTER 13 1950 Guide 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 per cent 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 coals and in lignite.: The percentage of ash and its fusion temperature do not indicate the composition or distribution of its constituents. 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- Table 1. Typical Ultimate Analyses fob Coals Btu kb La CONSTTTTJXNTS, PkB CENT Ranx Moist, Mineralmatter- free Moist, as Received Oxygen drogca 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 Medium-Volatile 4.7 81.7 ' 1.4 1.2 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 6.8 60.6 1.1 2.1 Sub Bituminous B_____ 10,250 9,150 29.5 6.2 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 Anh 10.5 8.5 6.0 8.1 8.8 9.2 9.4 9.8 9.6 7.3 &+ ffCrt- 87.9 89.3 91.4 y 89.0 87.7 87.3 87.4 88.2 89.0 91.0 * (Btu as received) X 100 (100 -- 1.1 Ash) nized that there are no distinct lines of demarcation between the kinds, and. that they graduate into each other. Anthracite ia a clean, dense, hard coal which created little dust in handling. It is comparatively hard to.ignite, but it burns freely when well started; It is non-caking, it burns uniformly and smokelessly with a short flame, and it requires no attention to the fuel bed between firings. It is capableof 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.9 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 handling it. It ignites somewhat slowly and burns with a medium length of flame. Its caking properties increase as the volatile matter increases, but the coke formed is relatively weak. Having only half the volatile matter content of the bituminous coals, it can be burned with less production of smoke, and is sometimes called a smokeless coal. The term bituminous coal covers a large range of coals and includes many types Fuels and Combustion 305 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 caking properties range from coals 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 bt Rank* Legend: F.C. " Fixed Carbon. V.M. *=* Volatile Matter. Btu D British thermal Class I. Anthracite----- < II. Bituminous4 4 III. Sub-bituminous, IV. Lignitie_____ j Group Limits op Fixed Carbon or Btu Mineral-Matter-Free Bass RiQciarrB Pan ' Properties I. Meta-anthracite_____________ Anthrnrit* Dry F.C.. 98 per cent or more (Dry V.M., 2 per cent or less) Dry F.C., 92 per cent or more and lees than 98 per cent (Dry V.M.. 8 per centor lessandmorethan 2 per cent) Non-agglomerat 3. Semi-anthracite. Dry F.C., 86 per cent or more and less than 92 per cent (Dry V.M., 14 per centorless and morethan8percent) 1. Low volatile bituminous ooaL__ Dry F.C.. 78 per cent or more and leas than 86 per cent (Dry V.M., 22 per cent or less and more than 14 per cent) 2. Medium volatile bituminous coal Dry F.C., 69 per cent or more and less than 78 per cent (Dry V.M., 31 per cent or less and more than 22 per cent) Either agglomem . or. non-weather 3: High volatile A bituminous coaL Dry F.C., less than 69 per cent (Dry V.M., more than 31 per cent); and moist* Btu. 14.000* or more 4. High volatile B bituminous coaL Moist*- Btu, 13.000 or more and less than 14,000* 5. High volatile C bituminous CoaL Moist Btu, 11,000 or more and less than 13,000* 1. Sub-bituminous A 2. Sab-bituminous B coal Moist Btu, 11,000 or more and less than 13,000*' than 11,000* Both weathering non-agglomerat 3. Sub-bituminous C coal_______ Moist Btu; 8300 or more and less than 9500* 1. Lignite___________ :__ Moist Btu less than 8300 -Consolidated 2. Brown coaL.......... - Moist Btu less than 8300. Unconsolidated . * This-classification does not include a few ooala which have unusual physical and properties and which oome within the limits of fixed carbon or Btu of the high-volatile bituminous and suhrbituminous ranks. Ail of these coals either contain lees than 48 per cent dry, mineral-matter-free carbon, or have more than 15,500 moist, mineral-matter-free Btu. 9 If agglomerating, classify in low-volatile group of the bituminous class. e Moist Btu refers to coal containing its natural bed moisture but not including visible water on the sur face of the ooal. * It is recognized that there may be non-caking varieties in each group of the bituminous * Coals having 69 per cent or more fixed carbon on the dry, mineral-matter-free basis according to fixed carbon, regardless of Btu. be.classified ^ There are three varieties of coal in the high-volatile C bituminous coal group, namely, Variety 1,-agglom erating and non-weathering; Variety .2, agglomerating and weathering; Variety 3, nnw-ftpflnmrrating non-weathering. Adapted from A.8.TJI. Standards, 1937, Supplement, p. 145, American Society for Testing Material*. and non-friable enough to permit the screened sizes being delivered free from fines. In general, they ignite easily and burn freely; the length of flame varies with different coals, but it is long. Much smoke and soot are possible, if improperly fired, especially at low rates of burning. Sub-bituminous coals occur in the western states; they are high in moisture when mined and tend to break up as they dry or when exposed to the weather; they are