Multiscale analysis of the effect of the structural transformation of TBAB semi-clathrate hydrate on CO2 capture efficiency

Abstract

TBAB semi-clathrate hydrate is considered as an environmentally friendly way to capture CO2. This study explored the effect of TBAB hydrate structure transformation on CO2–CH4 separation efficiency under the action of concentration and driving force. The experimental results showed that the gas consumption increased with increasing subcooling for the 10 wt% TBAB system but decreased for the 20 wt% TBAB system to a value that was much lower than that for the 10 wt% TBAB system. At 3 MPa and 12 K subcooling, the separation factor was 16.1 ± 1.2, the CO2 recovery was 63.3 ± 0.6%, and the hydrate phase CO2 concentration increased to 81.3 ± 0.8 mol%. A comparison of the hydrate structure showed that in the 20 wt% TBAB system, only type A hydrates were observed, whose growth was only dependent on the driving force. The larger driving force accelerated the formation of pure TBAB hydrate and inhibited the diffusion of CO2–CH4 guest molecules, reducing the separation effect. In contrast, under the 10 wt% TBAB system, except for the high driving force system, all systems exhibited the coexistence of type A and B hydrates with high gas storage and separation capacity, which can be considered for commercial applications.