Diffusion model of gas hydrate dissociation into ice and gas that takes into account the ice microstructure

A diffusion model of gas hydrate dissociation into ice and gas is presented, which allows us to simulate the self-preservation effect of gas hydrates. This model takes into account that the forming ice layer has a porous structure that changes during the process of gas hydrate dissociation. Three problems of gas hydrate dissociation into ice and gas were considered separately: the dissociation of a spherical gas hydrate particle, the dissociation of a cylindrical gas hydrate, and the dissociation of a flat gas hydrate layer. For each problem, a solution in the framework of a quasi-stationary approximation is obtained. From the comparison of the calculated data with the available experimental data on the kinetics of dissociation of a powdery methane hydrate into ice and methane, the molecular diffusion coefficient of methane in ice and the diffusion coefficient of methane through the system of pores in the forming ice layer were estimated. Based on this estimation, an explanation of the anomalous preservation thermal regime of methane hydrate is provided. (C) 2019 Elsevier Ltd. All rights reserved.