CO₂ Capture by Injection of Flue Gas or CO₂–N₂ Mixtures into Hydrate Reservoirs: Dependence of CO₂ Capture Efficiency on Gas Hydrate Reservoir Conditions

Abstract

Injection of flue gas or CO₂-N₂ mixtures into gas hydrate reservoirs has been considered as a promising option for geological storage of CO₂. However, the thermodynamic process in which the CO₂ present in flue gas or a CO₂-N₂ mixture is captured as hydrate has not been well understood. In this work, a series of experiments were conducted to investigate the dependence of CO₂ capture efficiency on reservoir conditions. The CO₂ 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 CO₂ in the flue gas was captured and stored as CO₂ hydrate or CO₂-mixed hydrates, while methane-rich gas was produced. The efficiency of CO₂ 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 CO₂ can be captured from the injected flue gas or CO₂-N₂ mixtures. This finding suggests that it is essential to control the injection pressure to enhance CO₂ capture efficiency by flue gas or CO₂-N₂ mixtures injection.