Kinetic enhancement of capturing and storing greenhouse gas and volatile organic compound: Micro-mechanism and micro-structure of hydrate growth

摘要

The use of hydrate-based technology for gas capture and storage is highly attractive for environmental mitigation, as it entails low energy penalties and provides gas storage density maximization and long-term storage stability. Although this method has been investigated in extensive researches, its development is restricted by the obscure underlying gas capture micro-mechanisms, elusive micro-structures of stored forms, and insufficient hydrate film growth rates. In this study, the Magnetic Resonance Imaging technique was employed to analyze the hydrate growth micro-processes for greenhouse gas (imitated by CO2, CH4, and various fractions of CO2-CH4 mixed gases) and volatile organic compound (simulated by C2H4 and C2H2 gases) capture and storage. The hydrate film growth was enhanced with the addition of 288 ppm sodium dodecyl sulfate (SDS), which significantly improved the hydrate growth in the cases of hydrocarbon gases, but not CO2 gas due to the competing adsorption of bicarbonate and dodecyl sulfate ions. With SDS, hydrocarbon gas hydrates grew via the patchy model at 65-105 mm/s, and 65-95% liquid water was converted into hydrates for gas capture and storage. However, only about 1.4% water was converted into CO2 hydrates with SDS, at 10.4 mm/s. Thus, a multi-pressure control mechanism for secondary hydrate growth was developed to promote CO2 capture and storage, based on a large amount of dissolved CO2 gas compared to the other investigated gases. The enhanced CO2 capture has important implications for the optimized harmful gas sequestration, due to preferentially patchy hydrate morphologies and associated impacts on permeability.