CO_2 Capture by Injection of Flue Gas or CO_2—N_2 Mixtures into Hydrate Reservoirs: Dependence of CO_2 Capture Efficiency on Gas Hydrate Reservoir Conditions

摘要

Injection of flue gas or CO_(2)–N_(2) mixtures into gas hydrate reservoirs has been considered as a promising option for geological storage of CO_(2). However, the thermodynamic process in which the CO_(2) present in flue gas or a CO_(2)–N_(2) mixture is captured as hydrate has not been well understood. In this work, a series of experiments were conducted to investigate the dependence of CO_(2) capture efficiency on reservoir conditions. The CO_(2) capture efficiency was investigated at different injection pressures from 2.6 to 23.8 MPa and hydrate reservoir temperatures from 273.2 to 283.2 K in the presence of two different saturations of methane hydrate. The results showed that more than 60% of the CO_(2) in the flue gas was captured and stored as CO_(2) hydrate or CO_(2)-mixed hydrates, while methane-rich gas was produced. The efficiency of CO_(2) capture depends on the reservoir conditions including temperature, pressure, and hydrate saturation. For a certain reservoir temperature, there is an optimum reservoir pressure at which the maximum amount of CO_(2) can be captured from the injected flue gas or CO_(2)–N_(2) mixtures. This finding suggests that it is essential to control the injection pressure to enhance CO_(2) capture efficiency by flue gas or CO_(2)–N_(2) mixtures injection.