Formation of CO2 Hydrate in Pure and Sea Waters.

Ohgaki, Kazunari; Makihara, Yoshihiro; Takano, Kiyoteru

doi:10.1252/jcej.26.558

Cited by 156 publications

(95 citation statements)

References 12 publications

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“…The enthalpy change of reaction (i.e., the difference between the overall enthalpy change and the heat of dissolution) is ϳ50 kJ mol Ϫ1 (Ohgaki et al 1993). Aya et al (1997) measured a temperature increase of ⌬T ഠ 2.2 K associated with hydrate formation during their experiments at 30 MPa using a simulation facility for a 3,000-m-deep ocean.…”

Section: Discussionmentioning

confidence: 99%

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Dissolution from a liquid CO² lake disposed in the deep ocean

Fer

Haugan

2003

Limnology & Oceanography

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The dissolution from a liquid CO 2 lake source located at a flat ocean bottom at 3,000 m depth is investigated. Using the unsteady, two-dimensional advection-diffusion equation, temporal and spatial distribution of CO 2 dissolved from the source of 500 m length and of unit span is sought in a domain of 20 km horizontal and 200 m vertical extent. Different cases were run with uniform longitudinal speed and constant horizontal and vertical diffusion coefficients and with vertical profiles of velocity and diffusivity derived from turbulent boundary layer theory. Each case was run with and without a hydrate film at the interface between the seawater and the liquid CO 2 . The properties of the hydrate film are modeled using a capillary permeation model. The computations show that the presence of a hydrate layer retards the dissolution rate by a factor of 2.7 when the density effects due to the increase of CO 2 concentration as a result of the dissolution are neglected. However, the strong, stable stratification above the hydrate layer, as a consequence of the increase in density of seawater enriched by CO 2 , suppresses the vertical mixing considerably and reduces the sensitivity to hydrate. The dissolution rate is found to be 0.1 m yr Ϫ1for realistic vertical profiles of longitudinal velocity (order of 5 cm s Ϫ1 ) and diffusivity. However, during conditions of a benthic storm (20 cm s Ϫ1 ), the dissolution rate reaches 1.6 m yr Ϫ1.Enhanced emission of greenhouse gases, particularly carbon dioxide (CO 2 ), to the atmosphere is widely accepted to affect the global climate system (Houghton et al. 1995). The atmospheric CO 2 content at present is about 25% higher than preindustrial levels. Over the past two decades, multidisciplinary research has been intensified with a focus to stabilize the CO 2 level in the atmosphere. One of the potential options to mitigate atmospheric levels is to capture it from fossil fuel combustors and purposefully dispose of and sequester it elsewhere (e.g., in ocean, deep saline aquifers, depleted gas and oil wells, coal beds, etc.). The ocean appears to be a preferable option because it is the largest potential sink for anthropogenic CO 2 . Marchetti (1977) was the first to propose ocean disposal to accelerate the natural ocean uptake of atmospheric CO 2 . He suggested that efficient long-term sequestration could be achieved through the Gibraltar Strait, where the outflow of dense water cascades to ϳ1,000 m depth and, in consequence, spreads out in the North Atlantic.The research on ocean disposal options has mostly focused on predicting the behavior and the dissolution time scale of the released CO 2 and on quantifying the environmental impacts to marine systems (see, e.g., Handa and Ohsumi 1995). Different scenarios of CO 2 disposal in the ocean have been proposed at various depths and in different forms in relation to the phase properties of CO 2 . The phase diagram for the CO 2 -water system shows that when pressure is greater than ϳ4.5 MPa and the temperature is less than 9.85Њ...

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Section: Discussionmentioning

confidence: 99%

“…The rough limit for hydrate formation in pure water is represented by the hatched area using the data given by King (1969). The phase boundary for hydrate formation in seawater is depicted by circles (Mitsubishi 1990) and crosses (Ohgaki et al 1993). The inset shows solubility in the pressure range 0.1-5 MPa for clarity.…”

Section: Symbolmentioning

confidence: 99%

Dissolution from a liquid CO² lake disposed in the deep ocean

Fer

Haugan

2003

Limnology & Oceanography

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“…Small-scale laboratory experiments have been carried out in Japan (Aya et al, 1992;Kimuro et al, 1993;Ohgaki et al, 1993;Ozaki et al, 1993;Saito et al, 1995;Kobayashi et al, 1995), and in the US (Masutani et al, 1993) to investigate this problem. Nakashiki et al (1991) conducted the first field experiment using solid CO 2 (dry ice) and measured its descending velocity.…”

Section: A Backgroundmentioning

confidence: 99%

Deep ocean experiments with fossil fuel carbon dioxide: Creation and sensing of a controlled plume at 4 km depth

Brewer¹,

Peltzer²,

Walz³

et al. 2005

J Mar Res

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The rapidly rising levels of atmospheric and oceanic CO 2 from the burning of fossil fuels has lead to well-established international concerns over dangerous anthropogenic interference with climate. Disposal of captured fossil fuel CO 2 either underground, or in the deep ocean, has been suggested as one means of ameliorating this problem. While the basic thermodynamic properties of both CO 2 and seawater are well known, the problem of interaction of the two fluids in motion to create a plume of high CO 2 /low pH seawater has been modeled, but not tested. We describe here a novel experiment designed to initiate study of this problem. We constructed a small flume, which was deployed on the sea floor at 4 km depth by a remotely operated vehicle, and filled with liquid CO 2 . Seawater flow was forced across the surface by means of a controllable thruster. Obtaining quantitative data on the plume created proved to be challenging. We observed and sensed the interface and boundary layers, the formation of a solid hydrate, and the low pH/high CO 2 plume created, with both pH and conductivity sensors placed downstream. Local disequilibrium in the CO 2 system components was observed due to the finite hydration reaction rate, so that the pH sensors closest to the source only detected a fraction of the CO 2 emitted. The free CO 2 molecules were detected through the decrease in conductivity observed, and the disequilibrium was confirmed through trapping a sample in a flow cell and observing an unusually rapid drop in pH to an equilibrium value.

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“…After hydrates had formed, the temperature was increased to 287 K at the rate of 0.3 K/hr. The rate of 0.3 K/hr has been used in previous literature where CO 2 hydrate was formed (Ohgaki et. al, 1993).…”

Section: Formation Of Hydratementioning

confidence: 99%

University/Netl Student Partnership Program

Holder¹

2003

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Formation of CO2 Hydrate in Pure and Sea Waters.

Cited by 156 publications

References 12 publications

Dissolution from a liquid CO² lake disposed in the deep ocean

Dissolution from a liquid CO² lake disposed in the deep ocean

Deep ocean experiments with fossil fuel carbon dioxide: Creation and sensing of a controlled plume at 4 km depth

University/Netl Student Partnership Program

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Formation of CO2 Hydrate in Pure and Sea Waters.

Cited by 156 publications

References 12 publications

Dissolution from a liquid CO2 lake disposed in the deep ocean

Dissolution from a liquid CO2 lake disposed in the deep ocean

Deep ocean experiments with fossil fuel carbon dioxide: Creation and sensing of a controlled plume at 4 km depth

University/Netl Student Partnership Program

Contact Info

Product

Resources

About

Dissolution from a liquid CO² lake disposed in the deep ocean

Dissolution from a liquid CO² lake disposed in the deep ocean