Thermogravimetric Analysis of Coal Liquefaction Residues and Their Solvent Extracts

Pyrolysis of four coal liquefaction residues and their solvent extracts was carried out by a thermobalance. Weight losses by pyrolysis are relating to the yields of solvent extracts. Weight loss of Illinois No. 6 coal liquefaction residue was the largest among the four coal liquefaction residues since the fraction of the light volatile matter in both oil + asphaltene and preasphaltene was larger than that of other three residues. Weight loss of Wandoan coal liquefaction residue was the smallest due to the large amount of extraction residue. From kinetic analysis, it was found that activation energies for pyrolysis of coal liquefaction residues were lower than the mean values of coals. This is because distillation of the relatively light volatile matter is dominant for the residues. Activation energy increased at smaller heating rate since cross-linking reactions and condensation were promoted. Weight loss curves calculated with the activation energies and frequency factors obtained from experiments agreed well with the experimental ones. In pyrolysis of the coal liquefaction residue, the weight loss was large at relatively low temperature region compared to that of coal and most fractions of the volatiles can be extracted by solvents. Therefore, it is considered to be one of the effective utilizations of coal liquefaction residues to gasify the extraction residue after the solvent extraction.