Investigating the impact of N2 concentration on ternary gas hydrate formation for CH4 production and CO2 storage

This study was conducted to explore the intricacies of gas hydrate formation behavior in CH₄ + CO₂ + N₂ mixtures, focusing on the impact of N₂ inclusion from both kinetic and thermodynamic perspectives. The three-phase equilibria of CH₄ + CO₂ + N₂ hydrates were measured, and gas consumption experiments were conducted to determine the selectivity of guest molecules in the mixed hydrates. The results indicated that the inclusion of N₂ led to decreased gas uptake, hydrate conversion, and formation kinetics, which could be attributed to the thermodynamic inhibition effect resulting from N₂ enrichment in the vapor phase during hydrate formation. The guest compositions in the hydrate phase and the amount of enclathrated guests were quantitatively assessed during and after hydrate formation. The findings showed that the quantity of N₂ trapped within the hydrates increased with its initial vapor phase concentration, but this did not significantly influence the enclathration behaviors of CO₂ and CH₄. Consequently, the ratio of CO₂ and CH₄ remained consistent in both the vapor and hydrate phases, irrespective of the N₂ concentration during and after hydrate formation. This study conclusively demonstrated the consistent enclathrating behaviors of CO₂ and CH₄, even with the addition of N₂. The findings provide valuable practical insights for hydrate-based CO₂ sequestration and natural gas production.