Influence of N(2) on Formation Conditions and Guest Distribution of Mixed CO(2) + CH(4) Gas Hydrates

In this contribution, a method based on a solid solution theory of clathrate hydrate for multiple cage occupancy, host lattice relaxation, and guest-guest interactions is presented to estimate hydrate formation conditions of binary and ternary gas mixtures. We performed molecular modeling of the structure, guest distribution, and hydrate formation conditions for the CO(2) + CH(4) and CO(2) + CH(4) + N(2) gas hydrates. In all considered systems with and without N(2), at high and medium content of CO(2) in the gas phase, we found that CO(2) was more favorable in occupying clathrate hydrate cavities than CH(4) or N(2). The addition of N(2) to the gas phase increased the ratio concentration of CO(2) in comparison with the concentration of CH(4) in clathrate hydrates and made gas replacement more effective. The mole fraction of CO(2) in the CO(2) + CH(4) + N(2) gas hydrate rapidly increased with the growth of its content in the gas phase, and the formation pressure of the CO(2) + CH(4) + N(2) gas hydrate rose in comparison to the formation pressure of the CO(2) + CH(4) gas hydrate. The obtained results agreed with the known experimental data for simple CH(4) and CO(2) gas hydrates and the mixed CO(2) + CH(4) gas hydrate.