Phase conversions and coking properties of certain coal components during coking

The liquid non-volatiles form during coking as a result of thermal breakdown of the organic coal substance. The breakdown itself comprises a thermal stage forming lower molecular weight products and a thermal synthesis which forms more extensively cross-linked structures. Thermal synthesis is dominant up to 280 C, after which thermal breakdown takes over. Breakdown and synthesis co-exist between 500 and 550 C in the plastic region so that the soluble and liquid phase products finally go over into insoluble and solid-phase conditions. Research indicated that the caking capacity of the soluble part of a gas coal is appreciably lower than the caking capacity of the coal as a whole. This is due largely to the extensive cross-linking which takes place during heating and which inhibits plastic mass formation and retards any caking tendencies.