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Coal Mining (1978)

Chapter: COAL RESERVES AND QUALITY

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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Suggested Citation:"COAL RESERVES AND QUALITY." National Research Council. 1978. Coal Mining. Washington, DC: The National Academies Press. doi: 10.17226/18766.
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Ill COAL RESERVES AND QUALITY Those coal reserves from which production at substantially increased rates may be most realistically expected during the next 10 to 50 years exist in well- identified areas with mining conditions similar to those in areas now being mined. Additional reserves also exist but their mining characteristics are less well known and they may be thinner, deeper, or further removed from the market. Table 1 presents basic data from which conclusions can be drawn concerning the most probable areas for expanded production in 13 separate states or groups of states in which types of reserves and mining conditions are relatively similar. (Although data on coal resources have been published for many years, they have not always been compiled using the same definitions. Even when common definitions have been applied over broad areas of the country, data of uniform quality commonly were unavailable for different states or areas. The Panel believes, however, that the quantitative data on recoverable reserves presented in this report are realistic.) The first three columns in Table 1 present 1974 underground and surface (including auger) production data.1 In 1974 total production frorr surface mines, excluding auger mining, exceeded total production from underground mines for the first time. The proportion of surface to underground mining ranged from 50 to 100 percent in 19 of the 26 coal-producing states (considering eastern and western Kentucky separately because of their great dissimilarity). Coal production from the western states averaged from 5 to 10 percent of national production for many years, it exceeded 10 percent of national production for the first time in 1973 (11.3 percent) and further increased to 13.8 percent in 1974 and 17.1 percent in 1975. Column 4 lists recoverable underground coal reserves as adapated from U.S. Geological Survey (USGS) data.* These amounts represent 50 percent of the underground "in place" reserves reported in each state modified to reflect production through 1971. The Panel believes that these amounts represent the best available estimates of well- defined reserves recoverable by underground mining methods in each state and in total. Column 5 is adapated primarily from U.S. Bureau of Mines (USBM) data.3 Intensive exploration in the western states

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since 1968 has resulted in much greater knowledge of available surface minable coal, and some more recent estimates* show considerably greater reserves than those indicated by the USBM for Montana, South Dakota, North Dakota, and Wyoming; these estimates are reflected in Table 1. Column 8, percent depletion, is calculated by dividing Column 7, total production (which represents "recoverable" coal that has been mined), by Column 7, total production, plus Column 6, remaining recoverable reserves. Percent depletion ranges from 30.5 to 58.8 percent in all parts in the Appalachian area (including eastern Kentucky) except Ohio. In Ohio and in Illinois, Indiana, western Kentucky, Iowa, Arkansas, and Oklahoma, it ranges from 13.1 to 27.4 percent. The index for Kansas (44.8 percent) is ananalous since there is no estimate of remaining underground reserves and that for Missouri (7.7 percent) seems too low, suggesting that estimates for remaining underground and surface-minable reserves may be somewhat overstated. Seme might question the identification of Colorado (7.2 percent), Utah (14 percent), and Washington (15.8 percent) as states in "relatively mature stages of depletion," but familiarity with past underground operations in those states indicates that remaining reserves, mostly recoverable only by underground mining, are less favorably situated and more difficult to mine. Figure 1s is a graphic representation of the data in Table 1 and generally reflects the inverse relationship between stage of depletion and remaining recoverable reserves. It shows a theoretical curve for production of an exhaustible resource with the area under the curve representing the amount ultimately recoverable. The shape and size of the curve is related to time and production rate and would vary depending on the assumptions made about the total recoverable reserves and production rate. The position on this curve of individual states with regard to depletion represents roughly their relative position with reference to ultimate recovery. States are grouped in convenient increments of stages of depletion. Data on recoverable reserves in incremental groupings are displayed by pie-diagrams that show recoverable reserves in each grouping as percentages of U.S. totals. The ultimate cumulative production curve superimposed on the figure is related only indirectly to the other data presented. In those states where substantial mining has occurred, the most accessible, lowest cost, and highest quality reserves invariably were recovered first, and remaining reserves are likely to be difficult to mine because of relative thinness of coal bed, greater depth of cover, locations behind or between previous mining operations, or other inferior conditions. The extent of such difficulties 10

o tn )n <r w U) UJ DC 2 z u a o 0) 00 fO 4J CO o 4J 00 O u a <d en 0) 4-i a> a s <d o o 0) rH •s o o 0) 4-i in o at CO M •H QJ n a> >. a) 11

varies substantially from one mining area to another. Appendix A describes each of the areas identified on Table 1 in detail and served as the basis for the regional analysis that follows. A. REGIONAL ANALYSIS OF RESERVES Certain critical elements require consideration before the potential for expansion of coal production from recoverable reserves in various areas can be assessed. The analysis of remaining reserves is oriented entirely to future availability of coal as a source of supply for power generation, general industrial use, gasification, and liquefaction. While calorific values and quality are important factors, the facilities that utilize coal in these ways generally can be modified to handle whatever type of coal is selected as the dominant source of supply. (A brief discussion of the chemical and physical properties of coal and the sulfur content of reserves is presented in Section B.) Coal is mined for metallurgical purposes and for export, usually in special areas where coal quality is particularly high. The Panel does not believe that future increases in the production of these types of coal will be comparable in volume to those in the production of coal required to meet major domestic energy demands. Significantly increased production might be expected to come from existing mines, from large numbers of relatively small new mines, from fewer numbers of relatively large new mines, or from a combination of all of these. Most existing mines already are being operated at relatively high efficiencies, which means that increased production would require additional mining units at new locations within the existing mine reserve confines, mining on an additional number of days per year, or both. Such possibilities frequently are limited or impractical and, if possible, may decrease efficiencies and reduce the projected lives of any such mines. Under most economic conditions, the installation of relatively large new mines results in better efficiencies, higher outputs per mining unit and per man, and lower costs than the installation of relatively small new irines. The installation of large mines, however, requires the acquisition of larger blocks of reserves and greater capital, and there is a limit to the "economies of scale" and increased efficiencies that can be derived from large mines—strip or underground. The relative availability of one or more blocks of reserves of sufficient size to support new operations is of primary importance. Areas in which adequate reserves occur 12

in one or at most two or three principal coal beds are irore likely to contain reasonably large blocks of unirined reserves than areas where the reserves are distributed among three or more beds. In regions of relatively rugged topography, where the coal beds generally outcrop at varying locations within a unit area and at varying elevations in the slopes formed by the drainage system, the assembling of large blocks of reserves is less feasible than in areas of less rugged terrain. The result is the opening of more small mines. Where three or more minable beds occur in a vertical sequence, the bed or beds having the most favorable characteristics in terms of quality or production cost frequently are mined first. Thus, the beds with less favorable mining characteristics represent large portions of the remaining reserves. Depending on depth, nature of strata, mining system, and interval between beds, prior mining of a lower bed might preclude or make difficult the subsequent mining of a higher bed. Although existing mines range from relatively new to old, they all have finite limits established by the boundaries of original acquisition, the topographic constraints, or the cost of mining. Consequently, a number of active mines are closed each year, and equivalent production from new mines is required to maintain the existing production rate. The nationwide rate of such annual depletion is estimated by the National Coal Association to be 3 percent of total production and is significant in any attempt to delineate areas from which expanded production may be expected during the next 10 years. 1. Appalachian Region Coal production in the Appalachian Region (Areas 1-4, Table 1) may be characterized as being in the advanced stages of maturity (i.e., having annually supplied 60 percent or more of total national production ever since coal mining began in the United States). It is obtained from a large number of mines of widely varying sizes and from a large number of coal beds, many of which occur in areas of steep terrain. This region provides nearly 90 percent of the coal used for coke production in the United States (80 million tons of the total 93 million tons in 1974) and about 95 percent of the coal exported (56 million tons of the total 59 million tons in 1974). The remaining recoverable underground reserves in the region are large (totalling 52.45 billion tons), but substantial portions occur between inaccessible, highly depleted areas and may remain unmined or in less depleted 13

coal beds that are comparatively thin, deep, inferior in quality, or difficult to reach. Relatively large-scale surface mining presently is being practiced in a small number of areas in Pennsylvania, northern West Virginia, and eastern Kentucky; in thin, deep beds in Alabama; and in a number of areas in Ohio. The Panel believes future surface mining in the Appalachian area probably can continue at the present rate of production for no longer than approximately 10 years. While coal production in the Appalachian Region will remain high for many years, the Panel believes this region as a whole will be hard-pressed to achieve a net percentage increase of as much as 30 to 40 percent despite higher demands. Such an increase, however, would be of significance in meeting 1985 demands, particularly for coal to be used for the manufacture of metallurgical coke (including increased export demands for such coal). 2. Eastern Interior Region Coal production in the Eastern Interior Region (Area 5, Table 1) involves a small number of individual irines with relatively high annual production rates and may be considered to be moderately mature (i.e., Indiana, western Kentucky, and Illinois have annually supplied from 20 to 25 percent of total national production for many years). While moderate amounts of the total remaining recoverable underground reserves (35.5 billion tons) occur in relatively thin to moderately thick beds, the greatest portion occurs in areas underlain by remaining unmined reserves in the two or more principal beds that extend throughout much of the region. With respect to remaining recoverable surface-minable reserves, coal production has remained essentially constant for a number of years. This probably means that surface mining of the principal beds has advanced into irore mature stages of depletion than is the case for underground mining. Since surface topography is generally favorable for large- scale surface mining, it is likely that this method will be further pursued (although at reduced annual rates from individual mines) in thinner beds as reserves in the principal beds become exhausted. The Panel believes that prospects for substantial expansion of production from underground mines in the Eastern Interior Region may be considered favorable. Surface mines should be able to maintain their present rate for many years, but the Panel does not anticipate any significant increase.

3. Western Interior Region Coal production in the Western Interior Region (Areas 6 and 7, Table 1) is difficult to characterize in terms of maturity since underground production has entirely ceased in Arkansas, Kansas, Missouri, and Oklahoma and has been very limited for many years in Iowa. While surface production has remained approximately constant in recent years, the amount produced is not significant (i.e., ranging from about 200 thousand tons in Iowa to 5,638 thousand tons in Missouri in 1975). The coal beds are persistent but thin throughout the region except in Iowa and the southern portion of Oklahoma where there are some beds of moderate thickness. Were it not for local markets, it seems doubtful that iruch coal would be mined in this region. Some coal in the southern portions of Oklahoma and Arkansas is of metallurgical and foundry grade and is being mined and shipped out of the region although mining conditions are difficult. The Panel does not expect production in this region to increase significantly in the near future. 4. Western Regions a. Surface-Minable Reserves The western states of Montana, North Dakota, Wyoming, New Mexico, Texas, and Alaska contain the largest quantities of recoverable surface-minable reserves (72.02 billion tons) and are virtually untouched (except for a few large active operations). The beds generally are thicker than beds being suface-mined anywhere else in the country (excluding Pennsylvania anthracite). In Washington and Arizona, surface-minable reserves are essentially those remaining in the single surface mines now active in each state; in South Dakota and Utah, surface-minable reserves are irinor in amount; and in Colorado, surface-minable reserves are confined largely to the two northwestern counties. The sparsity of surface mining in these states has been due to their remote geographic location with respect to large markets. In anticipation of future need, intensive prospecting and acquisition by leasing or purchase was initiated about 10 years ago, and many unit areas capable of supporting large individual mines already have been blocked out. Contracts for large annual shipments froir some of these unit areas to existing or contemplated new power plants have been negotiated while other units have been set aside for prospective gasification or liquefaction plants. Plans for new or connecting transportation facilities have been completed or are being developed. 15

b. Underground Reserves Excluding Washington, New Mexico, and Alaska where significant recovery of underground reserves is considered dubious and North Dakota and Texas where the lignite beds are considered unsuitable for underground mining, the western states of Colorado, Utah, Montana, and Wyoming contain over 55 billion tons of recoverable underground reserves. Although important portions of the coal fields of Utah, Colorado, and Wyoming have undergone substantial depletion, there are still many relatively unmined areas. Some of these may be comparatively difficult to mine because of the degree of dip or the excessive thickness of overlying cover, but mining conditions in many areas are relatively favorable. In addition to the extensive interest in suface-minable reserves in western states, there has been considerable recent interest in underground reserves in Utah and Colorado, and significant increases in underground production in these two states can be expected in the next few years. The Panel sees no reason why similar interest in the underground reserves in Wyoming and Montana should not also develop although underground recovery of as much as 50 percent of the thicker beds may be difficult with present technology, which generally is limited to bed thicknesses not exceeding 15 feet. If or when additional production becomes necessary, there is no reason why underground production could not be conducted simultaneously with or subsequent to surface mining. B. COAL QUALITY Coals vary considerably in chemical and physical properties that determine their quality in relation to intended use. Complete appraisal of coal reserves therefore includes consideration of these factors. 1. Pank Rank is a measure of the degree of metamorphism that was caused by heat and/or pressure during geologic time. The classification ranges are from the lowest rank, lignite, through the highest rank, meta-anthracite. Formal limits for the various ranks of coal are defined by Airerican Society of Testing and Materials (ASTM) Standard D-388 and are based on heating value (Btu per pound) on a moist, mineral-matter-free basis in high-volatile B-bituminous and lower ranks and on fixed carbon and volatile matter on a dry, mineral-matter-free basis in higher ranks (Table 2). High-volatile bituminous coals have agglomerating characteristics (tendency to fuse when heated) as do higher ranks of coal generally. The lowest rank coals, subbituminous and lignite, are nonagglomerating. In 16

Ol Ol c c iO S- JL >, M 8- IO ^ t- QJ QJ +J •— Ol "c S c E Ol E u 0i c Ol c ra)4J Ol •r- ^- t- ro C IO E 0> )O 0> C 2 CT-C o s- O Ol S- Ol o <*0 O <£ CU «£ 0i o O O 000 0 O O 0 0 0 O 000 co co t/> C ^3 -o CO C o o )n )n )n In -!-) 3 '- l/l 10 CU -C i i i I I I «!. co r— r— 0 0> co oo 0 E Q. -r- •r- -r- t/l i4- _J S- i— ra •r- tt) -*-) iO S- CO L. "o o o o o o o o o CD m )n 000 O o co '- OJ CL m U 0) O 3 •r- QJ 4-* a> IO IO C CU o o o In )n co I — I — 3 O C 4-* IU 3 <U IO i i i ! ! ^*roVo" cr 0> co IO i IO rO 4-> 21 •i~ iO S- cr s- s- .c i i i t_j ^* co *••- •• y y LI_ -iJ O CD \-- C0 IO W> C CM co ^r CM r— i i i • ) ) ) ) i CO 3 CO iO CM co ) ) I ) ) ) ) ) i 4-) IO o- S- a) .c CU Q- S- CU S- ro CO UJ O _l t— r- O •— CU u •r- S- CO ro S- QJ 4-) O) 4-> S- Ll_ t) C i CM CO •9- CM r— -i i ' ) t ) ) .— 4J E C C 4- 4) ro i r— CM CO i i ) I ) ) ) O IO -r- CU -r- CU !- -C* > s: _) u z: 4-) |C3l- _ co C i CO CM vo co en ) ) ' ) I I ) )/) CO ro on r-.. I.o I ) 1 ) ) I ) C i CO • r- a) J= i CT> CT! O i 4-) IO JD S- IO CO ra Q_ &_ CU t > C3 r- CU 1. -O 4^ S- U- co ro S- CU CO CM l£3 CO 01 i i i ) ) ) I ) CU -r- 4J CU ro ro C Ol Ol CO ) ) x E c C s- 3 CO ro r^ v0 ) ) ) ) ) ) •r- -r - Ol •r- CU cr s_ s_ j= U i U Z 4-) UJ O C3 I— ^r— r— r— CO o o o o CO I — U U U U IO i O l/l CO l/l l/l o O 3 n 3 3 O 0 0 0 E co C = C C CO O E E E E C 3 3 3 3 '- .— •— . ., •r- 4-) 4-> 4-) +J iI3 (O (C E '^ ''~ '•*" 'r~ o o o 3 3 -Q -O -Q -Q u u u c CU •I- CU ^ C5 O ^ (VJ S_j * 4-) CU /^ r- ••- CU CU CU O£ •r- 4J I/I Ul CO O •<- 0) 4-) •— r— r— 333 ^ ra U r- ro ••- -r- -r- O O O .Q i_ OJ ro •r- .— 4J 4J 4J C C C a. -C 4-) S- 4-) O IO IO IO •r- «p- «r- •q; CQ )n 4J -I- _C ro > I— I— r- E E E o c u *-) .— O O O 333 CU CU tO C3 > 3 o i '- ro •r- -r- •(- •i- -i- ro .C 'r- •r- .C ^ ^ c c 4-J 4-) E S T3 Ol O) Ol ^3 .a _Q Ol Ol n CU C CU O CU •— -r- •r- 333 O S < CO CO CO CO _1 _J c r— CM rO •— CM ro »r In r— CM co r— CM iC CO c 3 !£ O CU C0 .,_ 4J 3 E CU y IO «p* O 3 4-) 'TJ CO U c 4-) ^j ro IO •r- J3 C G c n 31 CM c J. CO i U. CO 5 I— . _ either contain less than 48 percent dry mineral-matter-free tter-free British thermal units per pound. 4) i- IO pally nonberded varieties, which have unusual physical and fixed carbon or calorific value of the high-volatile isture but not including visible water on the surface of , mineral -matter- free basis shall be classified according tt) l_ CU J= 4J •o c IO CO V) ra u CO 3 O c 4-) J3 CU -C 4-) <t- O W bituminous class. Q. 3 0 ' Ol CD CO CU .c tJ c CU tt) T- 4- CO ro 0 ^is• ' • u o ^B E E 4) '.- ra O- ^3 ^ 3 c IO 1 4-> 0= O ^ 4J o IO C CU 01 )_ 'i Ol a. i CU j; c 4-* ai CU S- O •^ CO CO CO C 0 ^J 3 4) Q. g- IO r_ ^- •r - E c o s_ 0 ro 3 • c O a; 4_) ff 0 CU cu U ^ A t. C 3 •^ <*. O ~ E — ' 01 3 5 a X2 IO CO ra ^ cu c • p™ t- 4) ^_ 3. Ol 4- ' <«- 3 O Ol _Q c- I — Z= -W •r- U u ro ra 4-) «s ra c T_j 0 •o L^_ o .•- c IO a) x 0 o • pw c 4) •a m V) O X ,- 3 . <«- o CU en s^ I .a "u c ,rm X ro •r- 4-) c ^ IO 01 0 CU U ^ IO L. s- c c IO O ^1 ro o 4_ E [ * u CO c C E O > o 4-) 4) 3 trm s- c .£ 0 ra u) t _c a) ^ 0 Ol C . 4-J (4_ CO CU l/l c CU -E .r - 4J • ^ CU ^g -C 0 C o •. C •a 4_* 4J u l/> C 4J 13 (O CU CO OJ c -Q ro i. ra ro C l/l ra U CD Ol 4J o .1 JD ra 0 CU C0 u Q. c: 4_) 4_) CO Ol •o 0 ^, i. o Ol ra a) c c CU u •0 0 .*_> 4J 0 N 4_) Q. C Q. c^ O ro c CO ro £-) ^ J^ 4) .^ - o i. S C ro Ol U CO a. CO .a 0i CD U o X 3 S- V- • 5 p u CD ny ^ O IO cU — 13 CD 4) ^_ IO u '- ra X ^_ U u -~ 0 ^-) I— § 4J U CO CO -S CO 1 T3 4) X •t- cu S .- V) -C .^ (fr- ~ O 4-9 O 1+- y 4_) ^j t- (_) ^i c_ ' *^ c 3 -^ I~l -J 17

general, moisture and volatile content decrease and fixed carbon increases with increased rank. The moisture content of higher rank coals varies but is not a parameter for determining rank. The moisture content in lower rank coals generally is higher than in high rank coals. 2. Coking Coal Characteristics Higher rank bituminous coal has a higher heating value than lower rank coals, and its physical characteristics at elevated temperatures are particularly significant. All bituminous coals are agglomerating (fuse and adhere on heating). Optimum agglomerating characteristics for producing metallurgical coke generally are found in the upper ranks although some lower rank coals can be blended successfully with higher ranks to produce metallurgical coke. 3. Utility Coal Characteristics Utility boilers can be built to burn almost any coal, and the character of coal to be used is a significant factor in how the plant is designed. The need to utilize coals markedly different in character from those for which a plant was designed causes substantial problems, particularly when low-sulfur western subbituminous coal is substituted for midwestern coal. The western coals have a lower heating value (higher moisture) than midwestern coals, and greater fuel input is required to obtain an equal heat value output. The ash characteristics of the coals also are markedly different, and electrostatic particulate precipitators are adversely affected by the low sulfur content of some of the western coals. Other factors that affect substitution are grindability and boiler corrosion and fouling tendencies. <». Mineral Matter Content in Coal Determination of coal rank is independent of mineral content, which may vary widely in all ranks of coal. Mineral content produces ash when coal is burned, and the quantity of ash-forming minerals influences the heat content (Btu per pound) of the fuel. Many coal preparation techniques, particularly coal washing at the mine, reduce the mineral content. The quantity of ash-forming minerals may be of little importance in an electric power generating facility equipped to dispose of ash; however, in the manufacture of metallurgical coke, low ash content is desirable. The characteristics of the mineral matter in coal may be of much more significance than its quantity in electric power generating plants because boiler fouling and corrosion problems are related to the character of the mineral matter. Combustion chambers in large boilers are designed to remove 18

ash as dry material or as a molten slag, and, although boilers may be designed to burn any coal, technical problems can and do occur when the fuel for a particular plant is changed to one with significantly different ash characteristics. Western and eastern coals generally have a higher ash fusion temperature than midwestern coals. Sulfur in coal is found commonly in the inorganic mineral pyrite and in organic combination. Soire sulfur occurs in sulfate form, but the amount normally is very minor in fresh coals. Pyritic sulfur, which normally ranges from well under 0.5 percent to 6 percent (and sometimes as much as 10 percent), occurs as nodules, bands, cementing material, facings on fractures, and finely disseminated crystals in the coaly material. Reduction of pyritic sulfur in coal by gravity separation (washing) may remove from about 10 percent to 90 percent, the average being about 50 percent. The remainder of the pyritic sulfur is finely disseminated in the coaly material and cannot be removed using conventional washing techniques. Organic sulfur content, which may range from under 0.5 percent to more than 2 percent, is not separable by gravity methods, and no generally applicable commercial method has yet been devised for removing it from large volumes of coal other than by first converting coal to liquids or gases. The sulfur content of coal has become very important because of limits on combustion emissions imposed by the Clean Air Act Amendments of 1970. New power plants generally are limited to emissions of 1.2 pounds of sulfur dioxide (SO2) per million Btu of input. Maximum sulfur in coal to meet this emission standard without other controls is approximately 0.6 percent for a coal with a heating value of 10,000 Btu per pound. For each 1,000 Btu per pound higher or lower, the allowable sulfur content is changed by about 0.06 percent (i.e., the sulfur limit for coal with 12,000 Btu per pound would be about 0.72 percent [Figure 2 ]). «• Since most of the available coal in the eastern United States and even significant tonnages of low-rank western coals cannot meet these standards (Table 3),7 new reliable, economic, and efficient methods of combustion and/or removal of SO2 from flue gases will have to be demonstrated adequately before the direct use of these coals may be substantially increased. Sulfur content in coals also is critical for production of metallurgical coke. The current economics of sulfur removal from iron generally limit coking coals to those containing less than 1.5 percent sulfur. Most coals with sufficiently low sulfur content and desired physical properties are found in the Appalachian states, particularly West Virginia and eastern Kentucky; a much smaller amount of recoverable reserves suitable or satisfactory in blends for coke making are found in the central and western states. 19

00 uT D (9 z 14 i o 12 11 10 11J 1 9 O O 5b 0.3 0.4 0.5 0.6 0.7 0.8 0.9 SULFUR CONTENT OF COAL, wt-pct 1.0 FIGURE 2 Plot of maximum permissible sulfur content versus Btu content of coal commensurate with EPA air quality standards.6 20

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Many trace and minor elements in mineral matter in coal are being investigated as possible pollutants in air or other mining or processing wastes. Catalytic effects during liquefaction or gasification also may be important. Significant differences in trace element content have been recognized in coals from various parts of the country. 5. Pegional Evaluation Although coals with a broad range of physical and chemical properties are widespread in various parts of the country, the properties of the major recoverable coal reserves discussed in Section A can be generalized more simply. Most coal from the Appalachian states ranges from high-volatile through low-volatile bituminous. Anthracite production is essentially confined to the eastern Pennsylvania fields. The highest quality coking coals generally are found in the Appalachian fields (strong coke, low sulfur, low ash), which produced about 150 irillion tons of coking coal in 1975. Most other coals available for electric power generation in the Appalachian Pegion will not meet the emission limit of 1.2 pounds of SO2 per million Btu input. Coals in the Interior Regions are generally high- volatile bituminous in the B and C ranks. A significant percentage of reserves have sulfur content in the 3 to 5 percent range although some current production averages 1.5 percent or less; mineral content generally ranges from 5 to 15 percent but may be even higher. Some of the lower sulfur coal is utilized in blends with eastern coals to produce metallurgical coke. The largest recoverable coal reserves in the western states are of the subbituirinous and lignite ranks. Major increases in production projected for this area will come from the shallow and thick seams of the low-rank coals recoverable by surface mining. Although low in heat content, western deposits of subbituminous coal and lignite generally are relatively low in sulfur and mineral content, and it is the low sulfur content that has created markets for these coals as far as 1,500 miles away. In spite of its low sulfur content, much of this coal will not meet the emission limit of 1.2 pounds of SO2 per million Btu of input because of its low heating value. 22

REFERENCES 1. U.S. Bureau of Mines, Coal—Bituminous and lignite in 1974, Mineral Industries Surveys (Washington, D.C.: U.S. Bureau of Mines, 1976). 2. U.S. Geological Survey, Coal Peserves Base of the United States, January !_,. JjTT4, Bulletin 1412, (Washington, D.C.: U.S. Geological Survey, 1975). 3. U.S. Bureau of Mines, Strippable Reserves of Bituminous Coal and Lignite in the United States, Information Circular 8531, (Washington, D.C.: U.S. Bureau of Mines, 1971) . 4. Northern Great Plains Resources Program and the U.S. Department of the Interior, The Effects of Coal Development in the Northern Great Plains, NTIS Report No. PB 269863, (Springfield, Virginia: National Technical Information Service, 1975). 5. M. King Hubbert, Energy Resources -- A Report to the Committee on Natural Resources, Publication 1000-D, (Washington, D.C.: National Academy of Sciences, 1962). 6. U.S. Bureau of Mines, The Reserve Base of U.S. Coals by. Sulfur Content, Information Circular 8680 (Washington, D.C.: U.S. Bureau of Mines, 1975). 7. U.S. Bureau of Mines, The Reserve Base of U.S. Coals by Sulfur Content on January 1t J97*t, Mineral Industries Surveys, (Washington, D.C.: U.S. Bureau of Mines, 1975). 23

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