Coalification anthracite coals

Coalification. A process by which organic matter is converted into coal of increasingly higher rank. Brown coal, bituminous coal, and anthracite coal are coal ranks in order of increasing carbon content, from 69 to 95% carbon. 

The coalification process (coal-forming process) is, simply defined, the progressive change in the plant debris as it becomes transformed from peat to lignite and then through the higher ranks of coal to anthracite (Francis, 1961 Sunavala, 1990). 

Douglas S. Montgomery. Dr. Hacquebard stated that in his experience there was no more fusinite in anthracite than in low rank coals, and fusinite therefore did not, in his opinion, result from the coalification process. Could the same statement be made concerning the semifusinite ... 

Rank property of coal that is descriptive of degree of coalification (i.e., the stage of metamorphosis of the original vegetal material in the increasing sequence peat, lignite, subbituminous, bituminous, and anthracite) (ASTM D-388). Anthracite rank of coal such that on a dry, mineral-matter-free basis, the volatile matter content of the coal is greater than 2% but equal to or less... 

Contrary to H2S, the amount of S02 evolution remains constant with coal maturation. The peak temperature of S02 rises from about 350 C for the peat sample to about 650 C for the anthracite sample. This temperature increase with coal maturation could be due to a loss of inflammable volatile matter which accelerates the char oxidation, and a relative enrichment of the char in condensed aromatic nuclei more resistant to pyrolytic breakdown, as seen by PTP and Py-GC, but also to a reduction of the size of micropores during coalification which hampers oxygen penetration into the solid matrix. 

Finally, humic substances no longer play a role in coalification as the insoluble coal undergoes further diagenesis leading to bituminous coal, anthracite, and eventually graphite. 

Because of the complexity of the coalification processes, different measures are used to define different levels of rank (Table I) high moisture, low heating value, and nonagglomerating character of the coal define the rank (group) within the lignite and subbituminous classes and volatile matter (or fixed carbon) define the various groups of rank in the bituminous and anthracite classes. In addition to these properties, the reflectance of vitrinite, carbon content of the coal (dry, mineral matter free), and some other properties change proportionately as rank increases (Table I). 

All types of lignite and most bituminous coals, except those which have progressed too far in the coalification process, such as anthracite, are satis-factoiy raw materials for liquefaction. Young coals, which at present have the least value, are suitable for high-pressure hydrogenation. 

Where terrestrial vegetable matter accumulates, peat is formed which, after burial, is transformed in various steps into lignite, bituminous coal and, eventually, anthracite. The coalification process is initiated by anaerobic bacteria and continues under the action of temperature and pressure over a period of millions of years. Upon maturation, the volatile gaseous and liquid hydrocarbons are progressively lost, leaving only solid carbonaceous compounds. Consequently, coals are solid compounds with a relatively high carbon and low hydrogen content. 

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