Sorption properties of hard coals with regard to gases present in the mine atmosphere

In this study, the sorption capacities of hard coals with reference to gases present in the mine atmosphere: carbon dioxide, methane, ethane, ethene, propane, propene, carbon monoxide and hydrogen were examined. For laboratory tests, 4 samples of hard coals collected from exploitable coal seams were selected. Among considered gases the mostly sorbed is carbon dioxide, in slightly smaller amounts are sorbed unsaturated hydrocarbons: ethene and propene. Their large sorption results from i.a. interactions of π electrons in the double bond between carbon atoms in the ethene or propene molecules with energetic centers of the coal surface. The amounts of the sorbed saturated hydrocarbons: ethane and propane are small, which is probably related to the adsorption mechanism of their sorption by coals. In the smallest amounts are sorbed hydrogen and carbon monoxide, the values of their sorption being maximum 5% of hard coals sorption capacity in relation to carbon dioxide. Based on the experiments it was found that the largest amounts of gases are sorbed by low-rank, highly porous coals with high oxygen content. The process of sorption of unsaturated hydrocarbons: ethene and propene can lead to a reduction in concentration of those gases in the mine atmosphere and thus may affect correctness of the self-heating phenomenon assessment.