Geologic ranking process

Strict numerical site rankings should be considered only as approximations of site characteristics and geologic expertise should be substituted where appropriate. The system described here requires knowledgeable decisions to be made for each of the "presumed effects" and the ranking process should be done by an individual with hydrogeologic background. 

The heterogeneity of coal, exemplified by Figure 1, is inherited from the diversity of source materials that accumulated in a peat swamp. Coals may be compared, contrasted, and classified on the basis of variations in the proportions of these microscopically identifiable components. Such a classification is referred to as a classification according to type. Coals may also be classified according to how severely geological alteration processes, referred to collectively as metamorphism, have affected their properties this is classification according to rank. These two classification methods are independent and orthogonal therefore, within certain limits, any type of coal can be found at any rank. 

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. 

Another proof of the importance of temperature is the fact that there is often a strict relationship between the run of isovols and the run of isotherms in deep profiles, both being influenced no doubt by the varying thermal conductivity of the different rocks. The strong influence of temperature on the rank of coal is obvious in the case of contact-metamorphic coals, whose rank increases distinctly when approaching the intrusive body. Apart from these geological observations, all experiments on artificial coalification have shown that temperature is the decisive factor in the coalification process. Thermodynamic and reaction kinetic considerations (9) also support this opinion. 

Whereas the degree of coaliflcation generally determines the rank of the coal, the process is not a series of regular, or straightforward, chemical changes. Indeed, complexity is the norm insofar as the metamorphosis of the plant debris relies not only on geological time but also on other physical factors, such as temperature and pressure. Thus, the occurrence of a multitude of different and complex chemical reactions (no matter how simple they appear on paper or how simply they occur in laboratory simulations) is inherent in the coaliflcation process. 

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