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Recovery of Methane from a Variable-Volume Bed of Silica Sand/Hydrate by Depressurization

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journal contribution
posted on 16.12.2015, 16:52 by Cef Haligva, Praveen Linga, John A. Ripmeester, Peter Englezos
Methane hydrate was formed in water occupying the interstitial spaces of a cylindrical bed of silica sand particles. The sand particles have an average diameter equal to 329 μm. The amount of methane consumed during the experiment (methane gas uptake) was determined through pressure and temperature measurements and mass balance calculations. Three different sized beds of silica sand particles were used. Water conversion to hydrates in the range of 73−84% was achieved for all of the formation experiments. Hydrate formation was followed by decomposition at 4.0 °C driven by depressurization at 3.1 MPa (nine experiments) and 2.3 MPa (one experiment). Methane recovery measurement curves were determined for each experiment. The initial rate of recovery was found to be strongly dependent on the silica sand bed size. The rate of recovery was found to depend weakly on the size during the second stage, and after 1.25 h, it was constant. During decomposition at 2.3 MPa, the temperature in some locations inside the bed dropped below the freezing point of water and the gas recovery rate was enhanced. This is in agreement with recently reported conclusions by Tsypkin [Fluid Dynamics 2005, 40 (1), 117−125] and Zhou et al. [Ind. Eng. Chem. Res. 2009, 48 (6), 3142−3149]. Finally, the gas recovery data was correlated with an empirical model with one parameter that was found to depend linearly on the bed size.