Co-pyrolysis Behavior of Low-grade Coal and Binder Using High Temperature Solvent Fractionation

Abstract

The authors have proposed a high temperature solvent fractionation method that can separate coals into several fractions having different molecular weight without destroying coal structure. In this study the method was applied to characterization of low-grade coals and binder during their co-pyrolysis to clarify chemical interaction between them. When a sub-bituminous coal or a slightly-caking coal was co-pyrolyzed with asphalt pitch (ASP), it was found that smaller-molecular weight compounds less than 800 in molecular weight which were abundant in ASP could be added by appearance as can be expected from the calculation assuming no interaction between the coals and ASP. The added smaller-molecular weight compounds contributed to the reduction of viscosity of the pyrolyzing coal. The possibility was also suggested that part of smaller-molecular weight compounds in ASP were converted to heavier compounds whereas some smaller-molecular weight compounds were formed from coals to compensate the loss of such compounds derived from ASP. It was also shown that oxygen existent in the heaviest fraction of the low-grade coals was removed to form H2O and CO2 by chemical interaction with ASP. This interaction was found to contribute to the reduction of shrinkage of low-grade coals during carbonization.