Assessing the technological value of coal in coking

Abstract

Coking coal of the same rank from different countries and fields may be distinguished in terms of use value by rating on the basis of seven technological and petrographic characteristics that determine the coke yield and properties: the ash content A ^d; the total sulfur content S _t ^d; the yield of volatiles V ^daf; the plastic-layer thickness y; the vitrinite reflection coefficient R _o; the content of vitrinite-group macerals Vt; and the basicity index B _b. A range of values and a rating (on a scale from 1 to 10) are established for each of these parameters. Each rating corresponds to a particular score (from 0.1 to 1.0). Ranges of A ^d, S _t ^d, Vt, and B _b are established for the whole metamorphic series, while ranges of V ^daf, y, and R _o are established for individual ranks and groups of ranks. Altogether, 105 coking coals from Ukraine, Russia, the United States, Australia, and Canada that are used at Ukrainian coke plants are investigated. The range of rating scores and their mean values are determined for individual coal ranks and groups. As an example, three bituminous coals from Ukraine, the United States, and Australia are compared by the proposed method. This method permits objective assessment of the technological value of coal within a single rank and the selection of the best purchase option.