PORE-SIZE DISTRIBUTION OF COALS AND CHARS FROM WESTERN CANADA

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