Enhanced separation of carbon dioxide from a CO2Â + CH4 gas mixture using a hybrid adsorption-hydrate formation process in the presence of coal particles

In the present study, CO2 separation from a simulated shale gas (40 mol% CO2 and 60 mol% CH4) was experimentally investigated in a fixed bed reactor (FBR) filled with mesoporous coal particles. The experiments were conducted at a fixed temperature of 277.2 K and in the pressure range of 3.7-5.2 MPa. It was found that a hybrid adsorption-hydrate formation process occurred when liquid water was added to the fixed bed of coal particles, and the gas uptake was enormously enlarged as compared to that obtained in the fixed bed reactor without water. The effects of driving force (overpressure) and bed height on CO2 selectivity were also studied. The results indicated that a higher driving force led to the increase of gas uptake but the CO2 separation efficiency was compromised. A higher CO2 selectivity was obtained when increasing the fixed bed height from 4.0 to 6.0 cm, and the highest CO2 separation factor (37.6) obtained in the fixed bed of coal particles was 4.3 times larger than that in a stirred tank reactor (STR). Therefore, low driving force and large bed height would be optimum conditions for CO2 capture in the fixed bed of mesoporous coal particles.