【企画講演】ゼロエミッション社会構築にむけたCCS/CCUS技術開発［9/14(木) PM 第1会場］

[3101-11-05] レイリーベナール対流による物質輸送

○末包 哲也¹、Sin Sotheavuth¹ (1. 東京工業大学)

司会者：江﨑 丈裕 （九州大学）

キーワード：二酸化炭素地下貯留

In geological storage of carbon dioxide (CO2), CO2 captured from significant emission sources, such as thermal power plants, is injected into the brine-saturated reservoir under a supercritical condition with a density of 600-700 kg/m3. One of the primary concerns in geological storage is the leakage of CO2 due to buoyancy force. The dissolution of CO2 into formation brine improves CO2 storage security. Because natural convection between CO2-saturated and CO2-free brines governs the dissolution processes, many works have been reported on the onset of natural convection and its mass transfer using Rayleigh-Bénard convection. In this work, we report a three-dimensional (3D) experimental investigation on the onset of Rayleigh-Bénard convection in a porous medium and its mass transfer. A packed bed with plastic particles saturated with water was used as a 3D porous medium. In contrast, alkaline acid soap containing sodium iodide (NaI) was used for the top boundary to model the dissolution from a rigid solid surface. Dissolving alkaline acid soap into water forms an unstable density profile, triggering Rayleigh-Bénard instability in a porous medium. The fingering structures of Rayleigh-Bénard convection were visualized using the X-Ray micro-computed tomography scanner (X-Ray CT). Because the critical wavelength decreases with an increase in Ra, the finer fingers appear on the top boundary for the higher Ra. The fingers merged into the large fingers, which extended vertically downward with time. The onset time of convection reduces with Ra, and the mass transfer increases. These results are compared with the previous numerical works. Finally, we discuss the appropriate modeling of natural convection in geological storage.