Precombustion CO2 capture using a hybrid process of adsorption and gas hydrate formation

In this study, a fixed bed of pulverized coal particles was employed to enhance the precombustion CO2 capture from fuel gas (40 mol% CO2/H2). The performance of the HAHF (hybrid adsorption-hydrate formation) process occurred in the fixed bed was evaluated at different liquid saturations and operation pressures. The experiments were carried out at 274.2 K with the pressure varying from 3.0 MPa to 6.0 MPa. 1.0 mol% THF (tetrahydrofuran) solution instead of liquid water was used to saturate the fixed bed and reduce the hydrate phase equilibrium conditions. The results indicated that gas hydrate nucleation in the fixed bed was quickly induced by gas adsorption in coal particles. The HAHF process was dominated by hydrate formation as the fixed bed saturation increased, and the CO2 recovery and separation factor were increased. Gas consumption during the HAHF process was promoted with the increase of operation pressure, but the CO2 recovery and separation factor decreased. In the fixed bed of coal particles saturated by 1.0 mol% THF solution the highest gas uptake obtained was 51.9 mmol of gas/mol of water, which was comparable with that obtained in the fixed bed of silica sand in the presence of 5.53 mol% THF. Therefore, compared with the hydrate based gas separation process, the hybrid adsorption-hydrate formation process proposed in this study could be a viable option for CO2 capture from fuel gas.