Numerical simulation for dissolution of liquid CO2 droplets covered with clathrate film in intermediate depth of ocean

Abstract

Dissolution of liquid CO 2 droplets at intermediate depth of ocean is strongly effected by the release methods of liquid CO 2 and hydrate formation. The present paper presents numerical simulations for the dissolution behavior of C02 droplets released from (1) pipeline outlet which is a fixed point at intermediate ocean depth and (2) pipe of moving ship. Clathrate-hydrate formation on the CO 2 droplet surface was fully included for both cases (1) and (2). External flow conditions around the CO 2 droplets are different between (1) and (2). A rising plume water flow is formed for case (1) and a free stream turbulence induced by the wake behind the pipe is for case (2). It was indicated that, for case (1) the released droplet diameter is required to be controlled to be less than 0.8cm to obtain the complete dissolution for the travel distance less than 1000m. The large travel distance is caused by the rising motion of plume water flow. Even if the CO 2 is released from 16 separated branches, the travel distance is reduced to 30%. In addition, increase of ambient CO 2 concentration drastically decreases the dissolution. On the other hand, for case (2), it was demonstrated that easier released droplet size condition to obtain complete dissolution is acceptable when liquid C02 is released from a pipe of moving ship, which also possesses a high potential that the ambient CO 2 concentration would not increase.