Experimental and process simulation of hydrate-based CO2 capture from biogas

This study experimentally investigated the effects of operation conditions for the CO2 capture from biogas by clathrate hydrate formation. The experiments were tested at 3.0 MPa and 278 K in the present of 5.0 wt % tetran-butylammonium bromide (TBAB). In addition, the dissociation enthalpies of CH4/CO2 hydrates in TBAB solution was calculated for energy consumption. The hydrate process simulation with Aspen Plus was carried out at the same experimental conditions to simulate the actual hydrate-based CO2 capture (HBCC), and the energy consumption of this process was analyzed. Experimental results show that the CH4 fraction in the residual gas phase increased with the decrease of gas liquid volume ratio (R-v). R-v decreased from 35.93 to 3.61 while the concentration of CH4 in residual gas increased from 80.5 mol % to 92.76 mol %. The CH4 concentration in residual gas phase was enriched from 67.00 mol% to 97.00 mol% by two stages of HBCC. Process simulation results showed that the energy cost was 1.17 kWh/kg (CH4). According to the handing capacity of the feed gas, the energy cost was 0.390 kWh/kg (biogas), which was lower than that by chemical absorption method. After adjusting the process parameters and increasing exhaust gas energy recovery, the energy consumption was reduced to 0.357 kWh/kg (biogas). The energy consumption could be decreased to 0.204-0.223 kWh/kg (biogas) by using static hydration enhancement technology.