Mass transfer and structure of bubbly flows in a system of CO 2 disposal into the ocean by a gas-lift column

Abstract

A new method for ocean sequestration of low-purity CO 2 gas emitted from fired power plant is developed. This is a gas-lift pump system, named progressive gas lift advanced dissolution (P-GLAD) system, to dissolve only CO 2 gas of combustion gas in seawater at shallow waters and to transport CO 2-rich seawater to great depths. The system is an inverse-J pipeline set at the ocean at a depth between 200 and 3000 m and a releasing system of indissoluble gas. To improve the efficiency of the P-GLAD, one should elucidate bubbly flows accompanying gas phase dissolution formed in the gas-lift column of the system. In the present paper, first, the authors discuss mass transfer in bubbly flows of pure CO 2 gas and filtrated tap water along the pipe axis in laboratory-scale P-GLAD of 25 mm in diameter and 7.69 m in height. Second, mass transfer in bubbly flows of mixed gas (95% volume of CO 2 and 5% volume of pure air) and filtrated tap water in the same setup is discussed. The mass transfer coefficient of CO 2 in the later system has the values of 3.1×10 −4–8.5×10 −5. It is shown that the mass transfer coefficient is a function of the distance from the gas injection. Finally, the performance of the system is elucidated on the basis of the experimental and numerical investigations. The laboratory-scale P-GLAD dissolved over 98.5% of CO 2 injected in the liquid phase.