Ocean Disposal of CO2: Conditions for Producing Sinking CO2 Hydrate

Abstract Carbon dioxide sequestration at intermediate ocean depths in the form of a sinking CO2 stream has been shown to be technically feasible. Buoyancy characteristics of CO2 hydrate particles obtained from a coflow reactor operating under conditions that produce negatively buoyant CO2 hydrate composite particles were studied. Using a simplified process model, the limiting ratios of CO2 to water to produce sinking hydrate composite streams were established for pressure and temperature conditions of intermediate ocean depths. A kinetic model involving a mass transfer step and a reaction step was proposed to explain experimental data using a seafloor process simulator. Results suggest that the reactor operates under mass‐transfer controlled conditions. Although the density of freshwater is only a few percentage units less than that of seawater, operating conditions derived from freshwater‐based studies are significantly different for ambient seawater. Owing to the higher density of seawater, greater conversion of CO2 to hydrate is needed to obtain a sinking CO2 composite stream than at the same depth of freshwater.