On mechanisms of the hydrate shell growth on the surface of supernatant gas bubbles

A theoretical model of the methane bubble migration under conditions of the hydrate development in an upward flow of water in a vertical pipe is proposed and constructed. We consider two limiting mechanisms that determine the hydrate development kinetics in the process of gas bubble floating-up. If the hydrate development intensity is determined by the heat removal from the bubble surface by a liquid, the height at which the hydrate formation process terminates amounts to fractions of meters; in the case where the process is limited by gas diffusion through the hydrated peel, tens of meters.
The critical mass flow rates of gas and water needed to complete the process of hydrate formation have been obtained. It is found that the migration of gas bubbles in the reactor is accompanied by two possible modes of the hydrate development depending on the initial mass flow rate of water: gas bubbles go over into the hydrated state either completely as separate inclusions or partially with the formation of bubbles with a hydrate shell. The influence of the initial mass flow of water on the dynamics of the hydrate formation process is analyzed at different values of hydrostatic pressure (or gas source operation depths).