Low-temperature pyrolysis of coals with different coking pressure characteristics

Low-temperature pyrolysis by means of the Gray-King test was carried out with ten coals of different coking pressure characteristics. The final pyrolysis temperature was selected taking into account the beginning and end of the coking pressure development. The soluble fraction in dicloromethane obtained from the tars was analysed by gas chromatography using flame ionization detection (GC-FID) and high performance liquid chromatography (HPLC). The coking pressure generated by the coals was assessed by means of a movable wall oven. Furthermore, the contraction/expansion of the coals during thermal treatment was measured by using the Koppers-INCAR and sole heated oven tests. The primary tar composition was studied in relation with contraction/expansion and the coking pressure generated by the coals. Although not conclusive, there is strong evidence to suggest that the relative amount of heavy compounds in the primary tars is related to the coking pressure generated by the coals studied.