Pore size distribution of coals and chars from western Canada

Abstract

The small angle X-ray scattering (SAXS) technique was used to determine the pore size distributions of some coals from western Canada and their resulting chars. Chars were prepared by pyrolysis at 930 °C in nitrogen until no further volatile matter was evolved. The distribution peak of the minerals was identified by acid treatment. Assuming that minerals dispersed in carbonaceous medium are not subject to sintering during pyrolysis, the mineral distribution peak was used as the internal standard to convert each pore size distribution of a coal sample and its char to the same scale. In this way, the changes in pore size distribution that occur during pyrolysis were compared. It was found that for highly reactive chars from low rank coal samples, the total pore volumes increased on pyrolysis. For poorly reactive chars from high rank coals, however, the total pore volumes decreased from their original coal counterparts.