Continuous CO₂Separation from a N₂+ CO₂Gas 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 wTHP 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.