Petrographic composition of coals

Bend S.L. (1992) The origin, formation and petrographic composition of coal. Fuel 71, 851—70. 

In keeping with the theme of this present chapter, a brief discussion of the influence of the petrographic composition of coal in relation to the technological properties of coal is warranted, although more specific reference will, as the data allow, be made to the various processes throughout the chapter. 

Coal rank seans to play a more significant role in self-heating than the petrographic composition of coal. 

Another aspect of coal behavior in relation to liquefaction that has also received (and is stiU receiving) some attention is the relationship of liquid yield to petrographic composition (Chapter 4) (Gagarin and Krichko, 1992). For example, vitrinite can be converted to liquid products readily as can exinite, but fusinite is quite resistant to liquefaction conditions and, thus, the petrographic composition of coals (whatever the rank) may be an important variable in determining the yields of liquid products. 

Table III Petrographic Composition of the Coals Used (Mineral Matter Free Basis)...

In liquefactioni the additional properties of Importance are (a) the petrographic composition of the coal, and (b) Its oxygen content. 

Local and regional variation in petrographic character of specific coal beds have been investigated actively for more than forty years. Roos (9) initiated comprehensive studies demonstrating that the character and quality of a coal seam change from place to place and that detailed sections were necessary for insight into the composition of coal. This important type of study has been continued and extended by several workers (3, 4, 5, 8, 10). In the Australian coals, Taylor and Wame noted that changes in microlithotype... 

Table II. Petrographic Composition of Selected layers of Upper Freeport Coal...

Table III. Petrographic Composition of Beds in the Lower Kittanning Coal Complex, %...

Martin B. Neuworth In some prior work, which will be published, we analyzed the six coals for petrographic composition and found they contained from 73 to 87% vitrain. In the case of coal No. 1, we compared the petrographic composition of the residue with the original lignite. On the basis of these analyses we would conclude that the vitrinite, resinite, and exinite fractions will undergo depolymerization with the rupture of certain aliphatic linkages. The semifusinite, micrinite, and fusinite appear to be inert. 

Rollins, M. S., Cohen, A. D., and Durig, J. R. (1993). Effects of fires on the chemical and petrographic composition of peat in the Snuggedy Swamp, South Carolina. Int. J. Coal Geol. 22,101-117. 

Although granular micrinites and semifusinites of Carboniferous coals do not soften and swell when heated, and are therefore classified as un-reactive petrographic components, their equivalents in Cretaceous coals commonly display fairly pronounced plasticity (101,102). Established standard correlations that connect coke stability with the petrographic compositions of Carboniferous coals (103) can consequently not be applied to Cretaceous coals without some modification (104). 

Fecko, R, Pectova, I., Ovcari, R, Cahhk, V., and Tora, B. 2005. Influence of petrographical composition on coal... 

Thus, it is possible to deduce several preferred options in the solvent extraction of coals using the so-called specific solvents. For example, the yield of extract usually decreases (but may, on occasion, increase) with an increase in the carbon content of the coal over the range 80% to ca. 87% carbon. However, use of a solvent such as pyridine may produce anomalous results and the petrographic composition of the coal may also have an effect. For coals having more than approximately 81% carbon the yield of extract is diminished to such an extent that only negligible yields of extracts are noted for coals having more than approximately 93% carbon. 

In contrast, specific solvents, which dissolve a large fraction of the coal, do so nonselectively. Thus, while the differing solubility of the petrographic constituents will influence the composition of coal extracts, the extracted material may resemble the insoluble residue closely and, in fact, may be virtually indistinguishable from it. Indeed, material snch as waxes and resins, unless present in phenomenally large amounts, is entirely masked by the remainder of the coal substance. The elemental compositions of the extracts as well as the properties (especially those associated with the chemical aspects of the dissolved material, e.g., magnetic and spectroscopic properties) are all almost identical with those of the original coal. 

This chapter focuses on the enviromnental and human health issues related to coal production (mining) and coal utilization. Emphasis is placed on those issues that are related to the petrographic, chemical, and mineralogical composition of coal. 

It is established that the rank and chemistry of the parent coal strongly influence the optical textures of cokes. Several studies show that the development of anisotropy (size, shape, and intensity) during carbonization varies mainly with (1) coal rank (2) petrographic composition of the coals (3) plasticity of the parent coal (4) carbonization conditions such as rate of heating, soak time, and gas overpressure as well as (5) the nature of additives used in the coal blends. 

Three West Virginia coals were supplied by the West Virgmia Geological Survey (WVGS). The particular coals were chosen on the basis of rank, petrographic composition, and mineral matter content The coals were limited to the bituminous rank since these coals are the most amenable to the NMP solvent extraction process and are mdigenous to the Appalachian region. Some of the coal characteristics are listed in Table 2. 

Clarke, L. Storch, H.H., "Hydrogenation and Liquefaction of Coal, Part 2 - Effect of Petrographic Composition and Rank of Coal", Technical Paper 642, US Bureau of Mines, 1942. 

For example, Beynon and Cwm coals when digested in anthracene oil give extraction yields of 68% and 47% respectively. This variation can be explained by reference to the maceral composition of the coals. Beynon coal contains a lower concentration of inertinite than the Cwm coal (Table V). In experiments where relatively pure samples of petrographic species were digested in anthracene oil, exinite and vitrinite were shown to be highly soluble, whilst in comparison the inertinite was almost completely insoluble. Similar variations in reactivity of macerals have been reported from studies of solubility in pure organic solvents (1(3). 

The Antarctic coal beds are apparently less persistent, and locally may be thicker, than many of the beds in Paleozoic coal fields of North America. It is hazardous to generalize about petrographic composition from hand specimens that are available from many of the coal beds, but one obtains the impression that dull, moderately dull, and midlustrous attrital layers are more prevalent than in Paleozoic coal of the Northern Hemisphere. Vitrain bands tend to be relatively sparse and thin fusain chips and partings generally are present and may be abundant. Many coal specimens are relatively impure, apparently owing to well-dispersed detrital mineral matter. 

Peter H. Given Whereas Tschamler and Fuks, and Peover studied more or less pure vitrinites, Mazumdar apparently worked with whole coals. Moreover, Indian coals, being from Gondwanaland strata, are most probably of very different petrographic composition compared with European and North American coals (rich in exinites and inert macerals See p. 284). Quite apart from the question whether sulfur dehydrogenation really is free of side reactions, there may well be a spread of data at any level or rank because of petrographic differences. 

From the foregoing it is evident that the lithotypes of anthracite are different. Differences in adsorption characteristics, surface structure, physical properties, and chemical composition conclusively demonstrate that the anthracite lithotypes are unalike and are distinct entities. It is also evident that to interpret research results of anthracite coals correctly, a petrographic knowledge of the coal is necessary. Anthracite cannot be regarded as a homogeneous substance. 

Several approaches are being taken in an attempt to relate petrographic composition with combustion behavior. Figure 17 shows how R. along with FS1 and ash fusion data may be used to predict the burning rate of coals in a specific combustion type (cross-feed stoker). In general, as R and FSI increase and ash fusion temperatures decrease, coals require more grate surface to insure optimum burn-out and minimum loss of combustibles in the ash. 

L. L. Newman Dr. Mackowsky has already asked you if you related your studies on the kinetics of volatile matter release from Pennsylvania anthracites to the petrographic constituents of the coal. Can you not say in effect that the coals from the various collieries differ from each other quite significantly with respect to their petrographic composition and that identification of a coal by source may identify it petrographically to some extent How do the results of these studies relate decrepitation actually experienced in industrial operations ... 

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