Modeling the release of CO 2 in the deep ocean

Abstract

In order to better understand the mechanics of ocean disposal of CO 2 captured from power plants, a comprehensive plume model was developed to simulate the dynamic, near-field behavior of CO 2 released in the water column as either a buoyant liquid or vapor. The key design variables in the model that can be controlled are: (1) release depth, z o (2) number of diffuser ports, N, and (3) initial bubble or droplet radius, r o. For a CO 2 stream from a 500 MW power plant with 100% capture and z o=500 m, N=10, and r o=1 cm, the model predicts that the plume will rise less than 100 m. This will result in CO 2 enrichment at depths greater than 400 m. Detailed predictions of local CO 2 concentrations near the plume are presented and discussed. The issue of the residence time of the captured CO 2 in the ocean is also addressed. We estimate a typical residence time of less than 50 years for releases of CO 2 less than 500 m deep and, for a release depth of 1000 m, a residence time from 200 to 300 years. These residence times may be increased by releasing in areas of downwelling or by forming solid CO 2-hydrates, which can sink to the ocean floor.