Understanding coal quality and the critical importance of comprehensive coal analyses

Coal is a remarkably complex combination of macerals and minerals and inorganic elements in organic associations plus liquids, gases, and semi-solid organics, all overprinted by coal metamorphism. The proper characterization of coal is necessary for academic research on coal origins and utilization and for the current and future industrial utilization of coal and coal by-products. A coal analysis scheme must be comprehensive because no one petrographic or chemical analysis stands alone. Coal rank, for example, can be expressed as vitrinite reflectance, a petrographic parameter, or by a number of chemical parameters, such as heating value or carbon content. No one parameter is reliable from lignite to meta-anthracite and, even at a single rank level, variations due to the maceral content and aspects of the organic chemistry imply that a view of more than one parameter is necessary to determine the coal rank.