Pre-combustion capture of CO2 by gas hydrate formation in silica gel pore structure

摘要

This study presents an efficient hydrate-based CO2 separation process from a binary mixture consisting of 40.3 mol% CO2 and balanced H2, which is a simulated fuel gas from the integrated gasification combined cycle (IGCC), in the presence of porous silica gel particles containing water. According to our previous work (Y. Seo, S.P. Kang, Enhancing CO2 separation for pre-combustion capture with hydrate formation in silica gel pore structure, Chem. Eng. J. 161 (2010) 308-312), the cage occupancy of CO2 in mixed gas hydrates with H2 is enhanced by the use of a silica gel pore structure containing water. Based on that result, a simulated fuel gas is applied to form gas hydrates, and a richer CO2 containing gas stream is thereby retrieved through dissociation of the hydrates from a single-stage reactor. Equilibrium dissociation pressures of CO2 + H2 gas mixtures were measured with silica gel particles with pore sizes of 25,100, and 250 nm. The effect of CO2 concentration on equilibrium dissociation pressures was also investigated at a silica gel pore diameter of 100 nm. The results indicate that when a simulated fuel gas has formed in 100 nm silica gel pores, a gas stream containing more than 96 mol% of CO2 is achieved by one-stage gas hydrate formation in a silica gel pore structure, which is comparable to the result (88-92) from hydrate formation in bulk water. In addition to demonstrating enhanced distribution of CO2 in coexisting phases, gas hydrate formation in a fixed-bed type reactor charged with silica gel particles containing water in pores is investigated. The formation of gas hydrates in silica gel pores occurred to a high extent and at a high rate, and the proposed method is thus expected to be a promising CO2 capture tool for pre-combustion.