Coal Structure and Coal Science: Overview and Recommendations

Abstract

A new procedure for classifying coals is needed. This procedure must recognize both coal type (proportions of various macerals and minerals) and rank (stage of metamorphic development). An integrated program must be instigated to study a large number of vitrinite-rich samples covering a broad range of ranks. Fundamental properties, including molecular structures, must be related to responses of the samples in conversion processes. Properties and responses of liptinite and inertinite, and interactions of inorganics, subsequently must be integrated with the data from vitrinites. Multivariate statistical treatment of the data will be required. Until such a unified classification system is devised, we shall continue to be limited to applying empirical tests to predict process responses, a procedure hardly deserving to be called a science.Coal is a sedimentary rock accumulated as peat, composed principally of macerals and subordinately of minerals, and containing water and gases in submicroscopic pores. Macérais (mas' er-als) are organic sub stances derived from plant tissues, cell contents, and exudates that were variably subjected to decay, incorporated into sedimentary strata, and then altered physically and chemically by natural (geological) processes.Coal is not a uniform mixture of carbon, hydrogen, oxygen, sulfur, and minor proportions of other elements; nor is it, as is often implied, simply a uniform, polyaromatic, polymeric substance.Rather, it is an aggregate of microscopically distinguishable, physically distinctive, and chemically different macérais and minerals.Coal is analogous to a fruitcake, formed initially as a mixture of diverse ingredients, then baked to a product that is visibly heteroge neous. The heterogeneous nature of coal is evident in Figure 1, a

The mobile phase in coals: Its nature and modes of release: Final report: Part 1, Structural inferences from dry catalytic hydrogenation of a subbituminous coal

“…Thus, the coals would be rendered less amenable to liquefaction and would require more severe conditions and higher I hydrogen availability to redress these adverse effects. These comments are consistent with the obsemed behavior of low-rank coals in processes where the feed coal is rapidly elevated to temperatures in excess of 400°C (Neavel, 1981). Tn t h e presence of an active hydrogenation catalyst and at low severity, thermally initiated cross-linking would be inhibited allowing the coal to be more readily liquefied.…”

“…This is attributed to their highly condens&, strongly bonded structures. It has been reported that low-rank coals convert more slowly than bituminous coals, requiring higher severity conhtions to attain high conversions (Neavel, 1981). However, research conducted in this laboratory has shorn that low-rank coals appear to convert more readily than bituminous coals in the presence of a catalyst and under mild conditions (Derbyshire et al, 1986a).…”

Understanding the chemistry and physics of coal structure (A Review)

“…Ar-OH + R4NOH --ArONR4 CH3I + H20 -ArOCH3 + R4NI, [1] and ArCO2H + R4NOH --ArCO2NR4 + .H20 CH31 -ArCO2CH3 + R4NI. [2] The hydroxide serves as a coal- The infrared spectra in Fig.…”

“…The design of this next generation of conversion processes will require a deeper understanding ofcoal's intrinsic properties and the ways in which it is chemically transformed under process conditions. Coal properties-such as the chemical form of the organic material, the types and distribution of organics, the nature of the pore structure, and the mechanical propertiesmust be determined for coals of different ranks (or degrees of coalification) in order to use each coal type most effectively (1).…”

High Temperature Carbonization of Turkish Bituminous Coals in Jenkner Retort

“…In cases of too many carboxyl groups, the proportion of CO 2 /CO increases accordingly. It is stated that H 2 , occuring in methyl, methylene and longer aliphatic groups, is released as gas and light oil and the hydrogen amount increases even more in the gas of high temperature carbonization (Neavel, 1979). The lower the degree of coaling, the larger the proportion of CO and the higher the coaling degree, the larger the amount of methans.…”