Study of CO2/CH4 exchange sorption in coal under confining pressure conditions

The study examined the effect of confining pressure on the properties of sorption and CO2/CH4 exchange sorption in coal. An increase in confining pressure, corresponding to different depths of coal seams, reduces the coal sorption capacity in relation to CH4. The maximum decrease was 1.2% of the sorption capacity per 1 MPa increase in confining pressure. Confining pressure had an effect on the kinetics of sorption processes, but did not affect the balance of CO2/CH4 exchange sorption. There was also no effect of confining pressure on CO2/CH4 sorption selectivity. The maximum efficiency of CO2/CH4 sorption exchange was approx. 90% for all samples tested at various confining pressures. The results showed that bituminous coal has good sorption properties and is suitable for technologies related to CO2 storage and simultaneous CH4 capture, but the confining pressure to which this rock is subjected in situ may significantly limit the applicability of these processes.