地球環境と混相流 CO₂海洋貯留と混相流

抄録

CO₂sequestration in ocean posseses a characteristic of multi-phase flow where CO₂ clathrate-hydrate is formed at the interface between liquid CO₂ and seawater in high pressure condition in ocean. The present report describes following three items of multi-phase flow in CO₂ sequestration in ocean which are dissolution of liquid CO₂ droplets at intermediate sea depth and formation of liquid CO₂ pool at a seabed deeper than 3000m. The first one is an experiment of liquid CO₂ dynamic behavior affected by hydrate-clathrate, which are CO₂ injection from a nozzle, formation of CO₂ pool and propagation of hydrate-clathrate film induced by the nucleation. The second one is measurement of liquid CO₂ droplet dissolution rate in the pressurized water flow with clathrate on the surface, which is important in dissolution of liquid CO₂ droplets at intermediate sea depth. Effects of flow velocity, temperature and pressure on the dissolution rate were clarified. Further, the dissolution behavior of liquid CO₂ droplets dispersed in the sea water has been numerically simulated, where the effects of released droplet size and ambient CO₂ concentration have large effect on the dissolution behavior due to the CO₂ clathrate-hydrate. The last one is an experiment of dissolution of liquid CO₂ pool which simulates liquid CO₂ stored at a seabed and dissolves into an undercurrent flow. The measured surface concentration was applied to the estimation of time-scale for dissolution, where the mass transfer coefficient was obtained from the actual conditions of deep ocean data.