CO2 Sequestration at Sea by Gas-Lift System of Shallow Injection and Deep Releasing

• Published in: Environmental science & technology 2000-10, Vol.34 (19), p.4140-4145
• Main Authors: Saito, Takayuki, Kajishima, Takeo, Nagaosa, Ryuichi
• Format: Article
• Language: English
• Subjects: Air pollution caused by fuel industries; Applied sciences; Atmospheric pollution; Carbon dioxide; Combustion and energy production; Earth sciences; Earth, ocean, space; Energy; Energy. Thermal use of fuels; Engineering and environment geology. Geothermics; Exact sciences and technology; Fossil fuels; Global warming; Marine geology; Oceans; Pollution; Pollution reduction; Pollution, environment geology; Prevention and purification methods
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es990155a

To mitigate global warming, a system dissolving huge amounts of CO2 gas captured from fossil fuel fired power plants into the ocean with high acceptance by the ocean environment is indispensable. To this aim, we propose a sequestration system of CO2 in the deep ocean. The system is an inverse-J pipeline set in the ocean at a depth of 200−3000 m. In the system, a pumping effect by buoyancy of the dissolving CO2 bubbles is used to transport CO2-rich seawater to great depths. In the present paper, we discuss characteristics and performance of our proposal on the basis of experimental and numerical investigation. In a laboratory-scale experiment (pipe diameter of 25 mm and pipe height of 7.69 m), we observed over 98% dissolution of injected CO2 gas into tap water. The liquid-phase flow caused by gas-lift effect was strong enough to transport the CO2-rich water including nondissolved tiny bubbles into the deep ocean. Then a numerical simulation based on the experimentally derived models was applied to a system considering 10 MW class power plants. The results showed that our proposal is hopeful for an efficient method of CO2 disposal into the deep ocean.