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Indexed by:Journal Papers

Date of Publication:2019-12-01

Journal:INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER

Included Journals:EI、SCIE

Volume:144

ISSN No.:0017-9310

Key Words:Methane hydrate dissociation; Pore-scale; Mass-transfer-limitation; Depressurization

Abstract:A mathematical model has been proposed to predict and assess effects of mass-transfer-limitation on the methane hydrate decomposition inside the pore channels. A gradually thickened water layer accumulates near the hydrate surface during the decomposition. The hindrance of the water layer to the escape of gas molecules into the gas phase is considered to be the mass-transfer-limitation, which ultimately affects the driving force of hydrate decomposition. The reliability of proposed model has been validated by comparing with the experiment data and a good agreement has been obtained. And then the impacts of masstransfer-limitation on the methane hydrate decomposition were investigated with the consideration of micro-scale effects. The hydrate dissociation rate, hydrate volume fraction, distribution of water and methane, gradient of methane volume percentage concentration near the dissociation interface, cumulative methane generation, residual hydrate, and change in heat caused by hydrate dissociation were elucidated. Our findings showed that methane hydrate dissociation is severely affected by masstransfer-limitation effect. Specially, the movement of methane from the hydrate decomposition interface to the gas phase is hindered, and the generated methane cannot leave the hydrate decomposition interface in time. A concentration gradient of methane volume percentage is formed in a direction away from the hydrate surface. This series of phenomena eventually leads to a reduction in the driving force for hydrate decomposition, and the decomposition of hydrate is postponed. (C) 2019 Elsevier Ltd. All rights reserved.