Laboratory Investigations in Support of Dioxide-Limestone Sequestration in the Ocean [electronic resource]
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Online Access |
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| Format: | Government Document Electronic eBook |
| Language: | English |
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Washington, D.C. : Oak Ridge, Tenn. :
United States. Department of Energy. ; distributed by the Office of Scientific and Technical Information, U.S. Department of Energy,
2008.
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| Abstract: | Research under this Project has proven that liquid carbon dioxide can be emulsified in water by using very fine particles as emulsion stabilizers. Hydrophilic particles stabilize a CO₂-in-H₂O (C/W) emulsion; hydrophobic particles stabilize a H₂O-in-CO₂ (W/C) emulsion. The C/W emulsion consists of tiny CO₂ droplets coated with hydrophilic particles dispersed in water. The W/C emulsion consists of tiny H₂O droplets coated with hydrophobic particles dispersed in liquid carbon dioxide. The coated droplets are called globules. The emulsions could be used for deep ocean sequestration of CO₂. Liquid CO₂ is sparsely soluble in water, and is less dense than seawater. If neat, liquid CO₂ were injected in the deep ocean, it is likely that the dispersed CO₂ droplets would buoy upward and flash into vapor before the droplets dissolve in seawater. The resulting vapor bubbles would re-emerge into the atmosphere. On the other hand, the emulsion is denser than seawater, hence the emulsion plume would sink toward greater depth from the injection point. For ocean sequestration a C/W emulsion appears to be most practical using limestone (CaCO₃) particles of a few to ten ?m diameter as stabilizing agents. A mix of one volume of liquid CO₂ with two volumes of H₂O, plus 0.5 weight of pulverized limestone per weight of liquid CO₂ forms a stable emulsion with density 1087 kg m⁻³. Ambient seawater at 500 m depth has a density of approximately 1026 kg m⁻³, so the emulsion plume would sink by gravity while entraining ambient seawater till density equilibrium is reached. Limestone is abundant world-wide, and is relatively cheap. Furthermore, upon disintegration of the emulsion the CaCO₃ particles would partially buffer the carbonic acid that forms when CO₂ dissolves in seawater, alleviating some of the concerns of discharging CO₂ in the deep ocean. Laboratory experiments showed that the CaCO₃ emulsion is slightly alkaline, not acidic. We tested the release of the CO₂-in-H₂O emulsion stabilized by pulverized limestone in the DOE National Energy Technology Laboratory High Pressure Water Tunnel Facility (HPWTF). Digital photographs showed the sinking globules in the HPWTF, confirming the concept of releasing the emulsion in the deep ocean. We modeled the release of an emulsion from the CO₂ output of a 1000 MW coal-fired power plant at 500 m depth. The emulsion would typically sink several hundred meters before density equilibration with ambient seawater. The CO₂ globules would rain out from the equilibrated plume toward the ocean bottom where they would disintegrate due to wave action and bottom friction. Conceptual release systems are described both for an open ocean release and a sloping seabed release of the emulsion. |
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| Item Description: | Published through SciTech Connect. 09/30/2008. Dan Golomb; Eugene Barry; David Ryan; Stephen Pennell; Peter Swett; Huishan Duan; Michael Woods; Carl Lawton; John Hannon; Devinder Arora; Tom Lawlor. |
| Type of Report and Period Covered Note: | Final; |