Continuous CO₂ Separation from a N₂ + CO₂ Gas Mixture Using Clathrate Hydrate: Insights into Sustainable Post-combustion Carbon Capture

Clathrate-hydrate-based CO₂ capture from a post-combustion N₂ + CO₂ gas mixture has been experimentally investigated for decarbonization. In this study, we performed hydrate-based continuous CO₂ separation experiments for N₂ + CO₂ + tetrahydropyran (THP) + water system. The experimental conditions were set at 280.1 K under 3.0 MPa with THP mass fractions w_THP of 0.22 and 0.11. For each experimental run, the time-dependent changes in compositions in the gas phase and the hydrate slurry were recorded hourly until the system reached a steady state. The cage occupancies of N₂ and CO₂ in the structure II 5¹² small cages were determined to be 43 and 24%, respectively, with the powder X-ray diffraction analysis. The obtained results showed that the continuous carbon capture is a practicable scheme, yet the CO₂ concentration rate and CO₂ recovery ratio are comparable to or lower than those of the pre-combustion systems reported in previous studies. Still, our investigation revealed that the development of an efficient hydrate formation method, such as the improvement of the geometry of mixing impellers, could enhance the CO₂ recovery ratio for the continuous operation.