CO 2 Sequestration by Hydrate Formation under Simulated Permafrost Conditions

Carbon Capture and Storage (CCS) is regarded as one of the critical technologies to achieve the goals of carbon peaking and carbon neutrality. As an emerging CCS method, storage of CO 2 as hydrates in permafrost has gained increasing attention. This approach benefits from the natural low-temperature, high-pressure, and porous environment of permafrost, which promotes the formation of CO 2 hydrate. In addition, CO 2 hydrates have high thermodynamic stability, robust mechanical integrity, and considerable gas storage capacity. This study evaluated the feasibility of CO 2 storage as gas hydrates in permafrost by simulating permafrost conditions in the Qilian Mountains. The optimal CO 2 storage depth was determined to be 200 m. At this simulated permafrost depth, an induction time of 39 min and a formation rate of 0.16 mmol·min –1 were observed, with the storage capacity reaching 109.28 V·V –1 after a single pressurization. CO 2 hydrates showed high stability, with a dissociation duration of 490 min and an average dissociation rate of 0.14 mmol·min –1 at room temperature and pressure. Multistage pressurization enhanced the peak hydrate formation rate by 84% and improved the CO 2 storage capacity to 413.81 V·V –1, with an overall enhancement of 278%. The study reveals that the formation of a CO 2 hydrate follows a cycle of nucleation, localized dissociation, and reformation governed by interfacial CO 2 concentration. Dissociation begins at CO 2 hydrate edges through the thermally triggered disruption of host–guest interaction. Subsequently, the dissociation front propagates radially inward. This study provides a theoretical foundation for the development of CO 2 hydrate-based storage technology in permafrost regions.