Porosity and water retention in coarse coking coal

At two Queensland mines producing high-rank coking coals, seam borecores and corresponding samples of product from the coarse coal centrifuges of the preparation plants were examined by mercury porosimetry. The dull (inertinite) particles were found to be much more porous than the bright (vitrinite), and to show greater variability in properties. Optical micrographs suggest that some of the variation is due to clays deposited in the pores of some inertinite particles. The pore water content predicted by assuming that all the particle porosity is filled with water was in good agreement with the internal moisture value determined experimentally by a centrifuge technique. The total porosity was estimated from the sum of the volume occupied by equilibrium moisture (micropores) and volume measured by mercury porosimetry (meso- and macropores). The mercury porosimetry results must be corrected for the compressibility of the coal. (C) 1997 Elsevier Science Ltd.