Field studies on the formation of sinking CO2 particles for ocean carbon sequestration:: Effects of injector geometry on particle density and dissolution rate and model simulation of plume behavior

We have carried out the second phase of field studies to determine the effectiveness of a coflow injector which mixes liquid CO2 and ambient seawater to produce a hydrate slurry as a possible CO2 delivery method for ocean carbon sequestration. The experiments were carried out at ocean depths of 1000-1300 m in Monterey Bay, CA, using a larger injector than that initially employed under remotely operated vehicle control and imaging of the product. Solidlike composite particles comprised of water, solid CO2 hydrate, and liquid CO2 were produced in both studies. In the recent injections, the particles consistently sank at rates of similar to 5 cm s(-1). The density of the sinking particles suggested that similar to 40% of the injected CO2 was converted to hydrate, while image analysis of the particle shrinking rate indicated a CO2 dissolution rate of 0.76-1.29 mu mol cm(-2) s(-1). Plume modeling of the hydrate composite particles suggests that while discrete particles may sink 1070 m, injections with CO2 mass fluxes of 1-1000 kg s(-1) would result in sinking plumes 120-1000 m below the injection point.