Document 8Ry86zqBg54ZpOKMk0q3qZrkk

326 CHAPTER 16 1949 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 for Coals BtupbbLb Constituents, PbrCent Rant Moist, Mineralmatter- free** Moist, as Received Oxygen Anthracite_____ _________ 14,600 12,910 5.0 Semi-Anthracite!.............. 15;200 13,770 5.0 Low-Volatile Bituminous___ ........... 15,350 14,340 5.0 Medium-Volatile Bituminous................... 15,200 13,840 5.0 High-Volatile Bituminous A____ __ 14,500 13,090 9.2 HighrVolatile 13,600 12,130 13.8 High-Volatile Bituminous ___ 12,000 10,750 21.0 Sub Bituminous'S______ 10,250 9,150 29.5 Sub Bituminous C.._!__ 9,000 8,940 35.8 Lignite.^.-.________ ______ 7,500 6,900 44.0 Carbon Nitrogen Sulfur ' Ash 2*+ V 2.9 80.0 0.9 0.7 10.5 87.9 3.9 80.4 1.1 1.1 8.5 89.3 4.7 81.7 1.4 1.2 6.0 91.4 5.6 79.0 1.4 1.5 8,1 89.0 5.3 73.2 1.5 2.0 8.8 87.7 5.5 68.0 1.4 2.1 9:2 87.3 6.8 60.6 1.1 2.1 9.4 87.4 6.2 52.5 1.0 1.0 9.8 88.2 6.5 46.7 0.8 0.6 9.6 89.0 6.9 40.1 0.7 1.0 7.3 91.0 * (lOO-1" A0 (BtUa3reCelTOd). nized that there are no distinct lines of demarcation between the kinds, and that they graduate into each other. Anthracite ia a.cle&n, dense, hard coal which creates 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 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, its properties are similar to those of anthracite. ./ Semi-bituminous coalis soft and friable, and fines and dust are created by handling ,itv It ignites somewhat slowly and burns with a medium length of flame. Its caking .properties .increase as the volatile matter increases, but tlw coke formed is relatively weak. Having only half the volatile matter content of the more abundant bitumi- Fuels and:Combustion 327 nous coals, it can be burned with less production of smoke, and it is sometimes called smokeless coal. The term bituminous coal covers a large range of coals and includes many, types having distinctly different composition, properties, and burning characteristics. Table 2. Classification of Coals by Rank Legend: F.C. Fixed Carbon. V.M. -- Volatile Matter. Btu ** British thermal units. Class Group Louts op Faso Carbon on Btu Mineral-Matter-Fee* Basis Requisite Pan . - Properties 1. Meta-anthracite. Dry F.C., 98 per cent or mow (Dry V.M., 2 per cent or less) ` I. Anthracite------ < 2. Anthracite_____ Dry F.C., 92 per cent or more and lees than 98 per cent (Dry V.M., 8 per Non-ogglomerat oentor lessand morethan 2 per cent) 3. Semi-anthracite. Dry F.C.. 86 per cent or more and less than 92 per cent (Dry V.M., 14 per centor leaandmore than8 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) II. Bituminous*__J 2. Medium volatile bituminous eoal Dry F.C., 69 per cent or more and less th*n 78 percent (Dry V.M.,31 per cent or less and more than 22-pcr Either agglomera cent) . or non-weather 3. High volatile A bituminous coaL Dry F.C., less than 69 per dent (Dry V.M., more than 31 per cent): and moist* Btu, 14.000* or more, i. 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* Ul. Sub-bituminous, 1. Sub-bituminous A coal..,,___ __ 2. Sub-bituminous B coal------------- Moiat Btu, 11,000 or more and less than 13,000* Moist Btu, 9500 or more and less than 11,000* Both weathering Doo-egglomerat -!IV. Lignitio_____ 3. Sub-bituminous C coaL----------- 1. Lignite____ 2. Brown coaL Moist Btu, 8300 or more and less than 9500* Moist Btu less than 8300 -Consolidated Moist Btu less than 8300. Unconsolidated * This classification doesnot 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 sub-bituminous ranks. All of these coals either contain less than 48 per cent dry, mineral-matter-free fixed carbon or have more 15,500 moist, mineral-matter-free Btu. * If agglomerating, classify in low-volatile group of the bituminous class. Moist Btu refers to coal containing 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. ' Coals having 69 per cent or more fixed carbon on the dry, mineral-matter-free basis shall be classified according to fixed carbon; regardless of Btu. ' f There are three varieties of coal in the high-volatile C bituminous coal group, namely. Variety 1, agglomj erating and non-weathering; Variety 2, agglomerating and weathering; Variety 3, non-agglomerating and non-weathering. Adapted from A&.TM. Standards, 1937, Supplement, p. 145, American Society for Testing Materials, Philadelphia. 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 completely melt, 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 and non-friable enough to permit of the screened sizes being delivered free from fines. In general, they ignite easily and bum freely; the length of flame varies with different