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Thermal regulation of methane hydrate dissociation: Implications for gas production models

Energy and Fuels

By:
, ,
DOI: 10.1021/ef0500437

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Abstract

Thermal self-regulation of methane hydrate dissociation at pressure, temperature conditions along phase boundaries, illustrated by experiment in this report, is a significant effect with potential relevance to gas production from gas hydrate. In surroundings maintained at temperatures above the ice melting point, the temperature in the vicinity of dissociating methane hydrate will decrease because heat flow is insufficient to balance the heat absorbed by the endothermic reaction: CH4??nH2O (s) = CH4 (g) + nH2O (l). Temperature decreases until either all of the hydrate dissociates or a phase boundary is reached. At pressures above the quadruple point, the temperature-limiting phase boundary is that of the dissociation reaction itself. At lower pressures, the minimum temperature is limited by the H2O solid/liquid boundary. This change in the temperature-limiting phase boundary constrains the pressure, temperature conditions of the quadruple point for the CH4-H2O system to 2.55 ?? 0.02 MPa and 272.85 ?? 0.03 K. At pressures below the quadruple point, hydrate dissociation proceeds as the liquid H2O produced by dissociation freezes. In the laboratory experiments, dissociation is not impeded by the formation of ice byproduct per se; instead rates are proportional to the heat flow from the surroundings. This is in contrast to the extremely slow dissociation rates observed when surrounding temperatures are below the H2O solid/liquid boundary, where no liquid water is present. This "anomalous" or "self" preservation behavior, most pronounced near 268 K, cannot be accessed when surrounding temperatures are above the H2O solid/liquid boundary. ?? 2005 American Chemical Society.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Thermal regulation of methane hydrate dissociation: Implications for gas production models
Series title:
Energy and Fuels
DOI:
10.1021/ef0500437
Volume
19
Issue:
6
Year Published:
2005
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Energy and Fuels
First page:
2357
Last page:
2363
Number of Pages:
7