Analysis of Consolidation Method of CO₂ Clathrate for CO₂ Disposal in Deep Ocean

Abstract

A system of CO₂ disposal, in the form of CO₂ clathrate, in the deep ocean has been proposed in order to prevent the green house effect caused by increase of CO₂ in the atmosphere. A process consisting of both the production of CO₂ clathrate and its in-situ consolidation is proposed for applying to the above CO₂ disposal system as an efficient process to obtain faster sedimentation of CO₂ clathrate blocks in the ocean and to prevent adverse environmental effects in the deep ocean. The process is experimentally analyzed and evaluated. It was confirmed that the CO₂ clathrate block is formed in the in-situ consolidation vessel through Compressing the CO₂ clathrate powders produced in the reaction vessel. Furthermore, it was confirmed that the clathrate block settled smoothly in artificial sea water under deep ocean conditions and that the process is one suitable method for application to the system. In addition, analysis of the consolidation mechanism was performed for the CO₂ clathrate. And it was found that consolidation proceeds via two step, i. e., the first one at low pressure shows the decrease in the spacing volume between the colonies consisting of CO₂ clathrate powders with pressurizing, and the second one at high pressure shows the breaking down step of the colonies. The boundary pressure between the first and second steps is ca. 2.3 MPa. Also, the dissolution rate of CO₂ clathrate block was measured CO₂-free artificial sea water and the rate was ca. 1.9 m/s at maximum.