Selective adsorption of ethane, ethylene, propane, and propylene in flammable gas mixtures on different coal samples and implications for fire hazard assessments

Sorption studies of gaseous mixtures of ethane, ethylene, propane, and propylene allowed us to obtain a better understanding of flammable gas behavior during flow through a coal seam. The dynamic sorption method was used to characterize the behavior of the multi-component gas mixtures. In these experiments, a gas mixture was released during a simulated heating process for coal and was then flown through a fixed bed of coal with particle sizes of 0.5-0.7 mm. The composition of gaseous effluent flow at the inlet and outlet of the sorption column was analyzed by gas chromatography (GC). The mixture composition influenced the amounts of sorbed gas, and variations occurred as a result of differences in the coal permeability. Both the high content of ethane in the mixture and its mechanism of sorption resulted in faster retention times for this gas. Propylene, which was characterized by low concentrations, was sorbed in the largest amounts and had the least steep adsorption curves compared to the other gases. The coal adsorbent with the largest surface area as determined by micropores and mesopores sorbed the largest amount of gases. These findings suggest that sorption measurements in which only a single gas is considered are not reflective of the real conditions in coal mines. Therefore, studies on flammable gas mixtures under dynamic states have great significance in terms of fire hazard assessments.