Coal structure and coal science: overview and recommendations

As unifying, underlying concepts, type and rank certainly can be validly employed to envision why coals have the properties that they do. However, it is time for a re-evaluation of coal classification concepts. A scientific classification should be based first on the fundamental properties of the vitrinite in coals. This means, at the very least that element concentrations and molecular structure configurations must be assessed. The structural properties of most importance to classification and process responses appear to be: (1) the nature of hydrogen bonding and physical entanglement that cohere molecular moieties, (2) the nature of cyclical structures (e.g., ring condensation index, aromaticity, heteroatoms), (3) amount and distribution of hydroaromatic hydrogen, (4) scissle bridging structure (e.g., ether, sulfides, polymethylenes), (5) functional group characteristics (esp. oxygen - and sulfur-containing), and (6) organic/inorganic interactions. To develop the basis of a scientific classification, these determinations need to be made on a large number of vitrinite-rich coal samples spanning a wide range of rank. Because coals are sensitive to oxidation and moisture changes during handling, the samples must be carefully collected, prepared and preserved. It is fairly evident that because of the complex interactions of depositionally-influenced and metamorphically-influenced properties, the fundamental chemical/structural properties willmore » need to be related to each other in a complex statistical fashion.« less