Document 1QvjjEvx7RzRyKZy2VYLGaLed

318 CHAPTER 13 1951 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 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 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 per Lb Constituents, Peb Cent Rank Most, Mineralmatter- free8 Moist, as Received Oxygen Hydrogen Carbon Nitrogen Sulfur Ash 0*+ hch- Anthracite.___________ 14,600 12,910 5.0 2.9 80.0 0.9 0.7 10.5 87.9 Semi-Anthracite............. 15,200 13,770 5.0 3.9 80.4 1.1 1.1 8.5 89.3 Low-Volatile Bituminous...... ........ 15,350 14,340 5.0 4.7 81.7 1.4 1.2 6.0 91.4 Med ium-Volatile Bituminous_________ 15,200 13,840 5.0 5.0 79,0 1.4 1.5 8.1 89.0 High-Volatile Bituminous A_______ 14,500 13,090 9.2 5.3 73.2 1.5 2.0 8.8 87.7 High-Volatile Bituminous B_______ 13,500 12,130 13.8 5.5 68.0 1.4 2.1 9.2 87.3 High-Volatile Bituminous C__ ____ 12,000 10,750 21.0 .5.8 60.6 1.1 2.1 9.4 87.4 Sub Bituminous B____ 10,250 9,150 29.5 6.2 52.5 1.0 1.0 9.8 88.2 Sub Bituminous C.____ 9,000 8,940 35.8 6.5 46.7 0.8 0.6 9.6 89.0 Lignite_________ ._____ 7,500 6,900 44.0 6.9 40.1 0.7 1.0 7.3 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 is a clean, dense, hard coal which creates little dust in handling. It is comparatively hard to ignite, but it burns freely when well started. It is nonmaking, it bums 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.* 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 bums 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 . 319 distinctly different composition, properties, and burning characteristics, having an,,e {rom the high-grade bituminous coals of the East to the poorer coals The coau r cating properties range from coals which melt completely, to [ thefronl which the volatiles and tars are distilled without change of form, so that theyme fir"--1 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 MatUr. Btu - British thermal units. Cuss Group Limits op Fixed Carbon oh Btu Mlieral-Matter-Fbee Basis Requisite Physical Properties 1. Meta-anthracite. Dry F.C., 98 per cent or more (Dry ' V.M., 2 per cent or lees) 2. Anthracite. I. Anthracite---< Dry F.C., 92 per cent or more and less than 98 per cent (Dry V.M., 8 per Non-agglomerating6 cent or lessandmore than 2percent) 3. Semi-anthracite. Dry F.C., 86 per cent or more and leas than 92 per cent (Dry V.M.* 14 per cent or lessandmore than 8 per cent) ' 1. 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 than 14 per cent) U. Bituminous*. 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 ESther agglomerating6 cent) or non-weathering' 3. High volatile A bituminous ccaL 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* III. Sub-bituminous, 1. Sub-bituminous A ooal...--------2. Sub-bituminous B coal Moist Btu, 11,000 or more and less than 13,000* Moist Btu. 9500 or more and less than 11,000* Both weathering and non-agglomerating6 IV. Lignitic___ 3. Sub-bituminous 1. Lignite.-,----2. Brows coaL Moist Btu, 8300 or more and less than 9500* Moist Btu less than 8300 Moist Btu less than 8300 Consolidated Unconsolidated . This classification does not include a few coala which have onuauat physical and chemical properties and which oome within the iimita of fixed carbon or Btu of the high-volatile bitummona and sub-bituminous rank,. All oi these ooals either oontain less than 48 percent dry, minaral-matter-free fixed carbon, or have more 15,500 moist, mineral-matter-free Btu. 6 If npgirwTtwwktany, classify in low-volatile group of the bituminous class. c Moist Btu refers to coal its natural bed moisture but not including visible water on the sur face of the coal. * It is recognised that there may be non-caking varieties in each group of the bituminous class. * having 69 percent or mare fixed carbon on the dry, mineral-matter-free basis shall be classified fy^rirding to fixed carbon, regardless of Btu. / There are three varieties of coal in the high-volatile C bituminous ooal group, namely. Variety 1, agglom erating and non-weathering; Variety S, agglomerating and weathering; Variety 3, non-agglomerating and non-weathering. Adapted from A.S.TM. Standards, 1937, Supplement, p. 145, American Society for Toting Materials. and non-friable enough to permit the screened sizes being delivered free from fines. In general, they ignite easily and bum 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