Permeability measurements of raw and briquette coal of various porosities at different temperatures

Temperature is one of the main factors influencing the parameters describing the phenomena of sorption, diffusion and filtration of gases occurring in the pore space of coal. While the influence of temperature on sorption capacity and the diffusion coefficient of coal is known, changes in the coal permeability coefficient due to temperature changes are undetermined. The main objective of this work was to study and explain the influence of temperature on the permeability of raw and briquette coals with various porosities. In order to describe coal permeability, the Klinkenberg equation was used, as it takes into consideration the slippage effect, typical of porous media characterized by low permeability. The experiments on coal permeability to helium and nitrogen were carried out using an original measurement stand. They were performed on five samples prepared from the same bituminous coal material (two raws and three briquettes samples) from Budryk coal mine, located in the Upper Silesian Coal Basin in Poland. On the basis of the obtained results, it was established that as the temperature rises, the value of absolute permeability of raw coal to nitrogen and helium drops significantly. The influence of temperature changes on briquette coal permeability changes could be neglected, and it could be compensated by the changes in the value of the dynamic viscosity factor, which is present in the Darcy permeability equation. The results show that in the case of raw and briquette coals, the influence of temperature on permeability is ambiguous.