Proposal for coal classification

Abstract

Several critiques to the ‘International Classification of Hard Coals by Type’ (ECE, Geneva, 1956) have been made in the past and a revision of its usefulness is currently being carried out by several investigators. The principal drawback of this classification is that it is not applicable to coals of variable maceral composition, especially those displaying a high content of inertinite. Furthermore, the parameters hitherto used in the International Classification and in some other national systems to define degree of coalification (rank), i. e. volatile matter and calorific value, are dependent on variable maceral composition. On the other hand, the parameters used in the International Classification to determine the agglutinating and coking properties of coals are competing parameters, instead of following a hierarchy. The proposed classification scheme is based on two primary parameters determined with microscopic techniques: (1) mean maximum reflectance of vitrinite, which is a good single measure of rank; and (2) petrographic composition (vitrinite and exinite) as an indication of the type of coal. A third parameter is chosen to qualify the different classes of coal: volatile matter for anthracitic coals; dilatation for semianthracitic and bituminous coals; and calorific value for subbituminous coals and lignites. The scheme is expressed by mean of a code number of four digits, which refers to the rank (first digit), type (second and third digits) and qualification (fourth digit) of coal.