Development of a New Method of Liquid CO₂ Injection Into the Seawaters for the Ocean Sequestration

A new type of injection method of liquid CO₂ into the seawaters via a Kenics-type static mixer for the ocean sequestration of CO₂ has been developed. Flows of liquid CO₂ and water will form a two-phase flow in a pipeline, and introduced to a static mixer, where the two-phase flow is mixed by the agitation effects of the mixing elements equipped in the mixer, and converted into various flow patterns. The following flow patterns were observed depending on the flow velocities; dispersed flow of liquid CO₂ drops, flow of CO₂ hydrate agglomerates, and flow of CO₂ hydrate particles. The results indicate that several options for CO₂ injection concerning the form of CO₂, size distribution of liquid CO₂ drops, could be realized by using the present method. The choice of such options is essential to control the fate of the disposed CO₂ and the consequent environmental impact. In this study, application of the present method to the disposal of liquid CO₂ at the intermediate depths (500 ∼ 1500 m) is assumed. The formation of the liquid CO₂ drops by the static mixer was studied experimentally, and the effect of the static mixer on the size distribution of the liquid CO₂ drops was investigated. The mean size of the liquid CO₂ drops were significantly reduced by using the static mixer, compared with the case without the mixer for a given flow velocity, and a sharper distribution of the drop size was obtained. Based on the experimental results, the ascending-dissolving fate of the liquid CO₂ drops disposed of in the ocean at the intermediate depth was numerically simulated. The shaper distribution and smaller mean diameter of the liquid CO₂ drops produced by the static mixer would results in the reduction of both the traveling distances and its dispersion of the disposed CO₂ drops.