Film-Growth Rates of Methane Hydrate on Ice Surfaces

Abstract In this paper, the film growth of methane hydrate on ice is observed by optical scanning microscopy at 0.50, 0.75, and 1.00 MPa of super pressure at the equilibrium temperature, which is between 260.3 K and 274.0 K. Methane hydrate crystals grew along the gas–ice interface for all experimental conditions. The growth rates increased with a rise in the equilibrium temperature, and the super pressure up to 0.75 MPa. Since the state at the growing site can be assumed to be in equilibrium, it is likely that, at high equilibrium temperatures, the increased mobility of water molecules accelerates the growth of methane hydrate. The results suggest that a mass transfer of methane and water molecules is dominant, constituting a rate-limiting process for growth. Indeed, the super pressure and the equilibrium temperature are vital factors for the film growth of methane hydrate on ice.