Modeling Gas Hydrate Formation from Ice Powders Based on Diffusion Theory

Resumo

Based on the diffusion theory, a gas–solid reaction model for gas hydrate formation from monosize ice powders was constructed and an effective diffusion coefficient through the gas hydrate shell was obtained by solving the diffusion equation. This model can be applied for a gas–solid reaction process with gas pressure drop during hydrate formation. Two cases termed as M₁ and M₂ were discussed and compared with each other. In the M₁ case, the spherical particle geometry was assumed to be squeezed by adjacent particles. In the M₂ case, the effect of adjacent particles on the object particle geometry was neglected. The results showed that the gas effective diffusion coefficient was a critical parameter for accurately simulating the reaction process, and it was found to vary during hydrate formation. In this model, the time-dependent gas effective diffusion coefficient was calculated by means of the measured gas pressure during hydrate formation, and the degrees of hydrate formation were obtained. In addition, the geometrical changes of the hydrate shell and ice powders were obtained during hydrate formation.