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

Abstract

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. © 2025 Elsevier B.V.