CO₂ Hydrate Composite for Ocean Carbon Sequestration

Abstract

Rapid CO2 hydrate formation was investigated with the objective of producing a negatively buoyant CO2-seawater mixture under high-pressure and low-temperature conditions, simulating direct CO2 injection at intermediate ocean depths of 1.0-1.3 km. A coflow reactor was developed to maximize CO2 hydrate production by injecting water droplets (e.g., approximately 267 microm average diameter) from a capillary tube into liquid CO2. The droplets were injected in the mixing zone of the reactor where CO2 hydrate formed at the surface of the water droplets. The water-encased hydrate particles aggregated in the liquid CO2, producing a paste-like composite containing CO2 hydrate, liquid CO2, and water phases. This composite was extruded into ambient water from the coflow reactor as a coherent cylindrical mass, approximately 6 mm in diameter, which broke into pieces 5-10 cm long. Both modeling and experiments demonstrated that conversion from liquid CO2 to CO2 hydrate increased with water flow rate, ambient pressure, and residence time and decreased with CO2 flow rate. Increased mixing intensity, as expressed by the Reynolds number, enhanced the mass transfer and increased the conversion of liquid CO2 into CO2 hydrate. Using a plume model, we show that hydrate composite particles (for a CO2 loading of 1000 kg/s and 0.25 hydrate conversion) will dissolve and sink through a total depth of 350 m. This suggests significantly better CO2 dispersal and potentially reduced environmental impacts than would be possible by simply discharging positively buoyant liquid CO2 droplets. Further studies are needed to address hydrate conversion efficiency, scale-up criteria, sequestration longevity, and impact on the ocean biota before in-situ production of sinking CO2 hydrate composite can be applied to oceanic CO2 storage and sequestration.

A new apparatus to enhance the rate of gas hydrate formation: Application to capture of carbon dioxide

“…During the past 15 years the emphasis has been on natural gas storage and transportation (Gudmundsson et al, 2000;Matsuda et al, 2006;Thomas and Dawe, 2003) and on carbon dioxide capture from flue and fuel gases (Aaron and Tsouris, 2005;Kang and Lee, 2000;Klara and Srivastava, 2002;Linga et al, 2007a;Seo et al, 2005). Hydrate formation is also a factor when considering injection of CO 2 into the ocean (Lee et al, 2003;Tsouris et al, 2004Tsouris et al, , 2007. If hydrate is to be formed from liquid water then the efficient contacting of the gas with water plays a key role in the above applications.…”

Capture of carbon dioxide from flue or fuel gas mixtures by clathrate crystallization in a silica gel column

“…For example, other arrangements such as bubbles dispersed in water or water droplets injected into a gas atmosphere have been proposed (Gudmundsson et al, 2000;McCallum et al, 2007;Ohmura et al, 2002;Tsuji et al, 2004). Tsouris and co-workers have presented novel and efficient crystallizers in the context of CO 2 sequestration work (Lee et al, 2003;Tsouris et al, 2004Tsouris et al, , 2007West et al, 2001). In addition, it has also been reported that when hydrate is formed from ice, temperature ramping enhances the conversion (Susilo et al, 2007b;Wang et al, 2002).…”

Quick Assessment of Potential Hydrate Promoters for Rapid Formation

“…Hydrate technology has advanced to greater proportions: implementing the high latent heats as refrigerant [1], safe carbon capture as carbon sequestration [2] in hydrates, purifying rare gases [3] in hydrates, and safe efficient transport of energy [4] using rapid hydrate formation. These account for only a small amount of the fundamental understanding of gas hydrates and the use of such a novel technology.…”