Permeability and Porosity Development during the Carbonization of Coals of Different Coking Pressures

To obtain a better understanding of the development of coking pressure during the carbonization process, the plastic and semicoke layers of nine coking coals were investigated. The permeability of the plastic layer to the passage of gas and the porosity of the semicoke were analyzed at two temperatures, 500 and 800 °C. In the case of dangerous coals, there was a wide zone of low permeability covering most of the plastic layer and part of the semicoke, whereas safe coals had a very narrow permeability zone that affected only a small part of the plastic layer. It seems that dangerous coals have a higher porosity and a lower Hg apparent density than safe coals. In addition, the semicokes obtained at 800 °C from the dangerous coals had a higher macropore volume with pore size between 50 nm and 12 μm but a lower suprapore volume (pore size between 12 and 250 μm).