Pyrolysis of Coal Liquefaction Vacuum Residue

Abstract

In order to improve the pyrolysis efficiency in utilization of a coal liquefaction vacuum residue (CLVR) from the NEDOL process, the characteristic of the CLVR and the conditions of its pyrolysis and required apparatus were experimentally studies.
Concerning the characteristics, it was clarified that the amount of volatile matter of CLVR is closely related to the softening point of CLVR rather than the degree of coalfication of raw coal. More over, the solvent insoluble composition of CLVR was related to raw coal properties, and the softening point depended on the amount of toluene insolubles of CLVR.
Pyrolysis experiments of three kinds of CLVR were carried out by using ordinary pressure thermo-balance, high pressure thermobalance, slot oven type (metallurgical coke oven type) and two types of flash pyrolysis apparatuses. Pyrolysis experiments by slot oven type, high pressure thermobalance and flash pyrolysis apparatus showed higher oil yield in that order. Aromaticity and molecular weight of all recovery oils were higher than those of the recycle solvent in the NEDOL process. In the case of the pyrolysis by slot oven type, the yield of products such as oil, char and gas changed with the softening point of CLVR, and the properties of recovery oil were depended on the raw coal properties.
Separation of solvent insoluble components, sulfur and nitrogen removement from CLVR and handling of CLVR in its utilization process will be important subjects in future for improving of the utilization efficiency of CLVR.