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

Abstract

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.

Determination of gas bubble fractionation rates in the deep ocean by laser Raman spectroscopy

“…T his m ay be d ue t o the fact that as the gas volume in th e cub e decreases an enriched liq uid layer i s confi ned in th e lower portion of the cube which sl ows the dissol ution rate over time. Saito et al (2000) have propo sed a method for CO 2 seq uestration th at employ s a gas-lift pum p (GLAD -Gas Lift Advanced Dissoluti on) system and would b e effective for low-purity CO 2 .…”

Bubble Motion and its Surrounding Liquid Motion through the Collision of a pair of Bubbles

“…The first one, interaction (1), is the interaction at the case (c) and (f); only horizontal velocity of bubble decreases after the collision. The second one, interaction (2), is the interaction at the case (d) and (g); both horizontal and vertical velocity decrease after the collision. Fig.8 shows the sketch of wake under a zigzagging bubble.…”

“…In addition, the bubbly flows are also applied to the field of environmental technology, such as GLAD system (e.g. Saito et al, 1999 (1) , 2000 (2) , 2001 (3) ). It is necessary for an optimal design and a control of those plants and systems to understand the structure and the mechanism of bubbly flows.…”

Pressure behaviour in riser tube of a short airlift pump

“…This fact combined with the low shear level encountered in the riser tube makes them attractive for applications in various types of reactors or bioreactors (Garnier et al 1990 or Isaacs andThomas 1992). To reduce CO 2 emissions in the atmosphere, airlift installations have been recently proposed for the injection of the exhaust gas from power plants into deep sea-water (Saito et al 2000).…”