Modeling descending carbon dioxide injections in the ocean

Abstract

An integral double plume model is used to explore the fate of solid CO2 hydrate particles released continuously into a quiescent ocean for the purposes of CO2 sequestration. Such a release is desirable because hydrate particles are negatively buoyant and dissolution of CO2 enhances this negative buoyancy through the solute density effect. Plume depth and thickness are shown to increase with CO2 mass loading and initial hydrate particle diameter, and exceed the equivalent rise height and thickness associated with positively buoyant droplet releases. The depths also greatly exceed those associated with a single particle release, highlighting the importance of the “plume” effect. Plumes initially composed of multiple particle sizes produce greater maximum plume depth, but similar average plume depth and dilution compared with plumes composed of homogeneous particles, suggesting that adequate simulations can be made using a single particle size. Although the model is valid only for discharge to quiescent receiving water, analysis shows the effects of an ambient current decrease with increasing mass flow rate or decreasing particle size, making results relevant for most likely release scenarios.