CO2 storage behavior via forming hydrate from N2/CO2 gas mixtures in the presence of initial SI CO2 hydrate seeds.

Schematic diagram for N 2 /CO 2 gas enrichment process during hydrate growth process. Blue sticks and spheres: N 2 in the gas phase; yellow spheres: CO 2 in the gas phase or hydrate phase; red sticks: hydrate seeds. [Display omitted] • Proper subcooling can improve the hydrate growth rate and final occupancy of CO 2 molecules. • Mass transfer process could impact the hydrate growth rate, with a higher pressure improving the concentrations of N 2 and CO 2 in the free water. • Higher pressure decreased the selectivity of CO 2 for 51262, and lower subcooling assisted CO 2 in entering 51262 cages easily. The climate system is changing and becoming warmer due to the consumption of fossil energy, which results in a large quantity of CO 2 emitted into the atmosphere. The hydrate formation process can encapsulate guest molecules in hydrate cages, enabling a promising storage of CO 2 in the form of hydrate under the seafloor. Here, we performed molecular dynamics (MD) simulations to validate the hydrate-based gas storage method for low-concentration flue gas. The direct phase method was applied at four target pressures to obtain the melting temperature of mixed gas hydrate in the presence of SI hydrate seeds that are fully occupied by CO 2 molecules. Hydrate growth simulations showed that a proper subcooling can improve the hydrate growth rate and final occupancy of CO 2 molecules in newly formed hydrate cages. The mass transfer process could impact the hydrate growth rate, with a higher pressure improving the concentrations of N 2 and CO 2 in the free water. This enhanced the hydrate growth at both 260 K and low subcooling temperatures. The influence of pressure and subcooling on cage selectivity presented a different tendency for CO 2 and N 2. A higher pressure decreased the selectivity of CO 2 for 51262, and lower subcooling assisted CO 2 in entering 51262 cages easily. Interestingly, the CO 2 occupancy at 260 K is larger than that of the simulations at the melting temperature. The results could be of help in revealing the behavior of case filling during hydrate formation from a gas mixture. [ABSTRACT FROM AUTHOR]