How Does CO2-Hydrate Influence Options For Deep Ocean Carbon Dioxide Deposition?

To reduce the large amount of C02 emitted to the atmosphere, several options for CO2 removal and deposition are considered. Three promising options are liquid CO2 disposed on the sea floor, liquid CO2 disposed in free water mass and shallow water dissolution. Since Corhydrate is thermodynamically stable at pressure higher than 4.45 MPa and temperatures less than 10.2 °c, it is expected to form naturally at depths larger than about 500 meters provided a source of high concentration C∼ is available. Hydrate formation is therefore expected to have significant influence on all deep ocean CO2 deposition options. In order to more quantitatively predict the influence of CO2 hydrates on various options for carbon dioxide deposition in the ocean, a comprehensive mathematical model for hydrate formation and stability has been developed. The model presented in this paper includes kinetics and thermodynamic phenomena relevant to the system high pressurized water and CO2, The microscale hydrate kinetics model is coupled with macroscale models for ocean disposal options, and simulation giving qualitative and quantitative indications of the effect of hydrate formation ∼n these options is done. Simulations indicate that formation of a thin hydrate film on the interface of liquid C02 and seawater on depths larger than 3500 meters will have a significant inhibiting effect on the spreading of C02 in the ocean, and thus a positive effect on long time storage feasibility. For intermediate depth C02 deposition option, as a descending C02 plume, hydrate formation will have a negative effect, by inhibiting dissolution of CO2 from the plume bubbles into the ambient ocean mass. The third option for ocean deposition, i.e. shallow water injection, will not be influenced by hydrate formation, since CO2 hydrate is not thermodynamically stable at the actual pressure and temperature.