Effects of inhibitors on the morphology and kinetics of hydrate growth on surface of bubble

Abstract

This study provided direct evidences for the evolution of the growth modes, morphology, lateral growth rate and the mass transfer channels during the thickening growth of hydrates on gas (CH4 – C3H8) bubble suspended in water with inhibitors. Uniform and dense hydrate film was observed on the bubble and at the gas-liquid planar interface during thickening growth in absence of inhibitor (Growth Mode 1), but the film was heterogeneous when low concentration kinetic inhibitor was added (Growth Mode 2) and even not able to form when high concentration thermodynamic inhibitor was added (Growth Mode 3). In the Growth Mode 2, the adsorption of inhibitor on the frontier of the hydrate film destroyed the continuity of the hydrate growth and decreased the lateral growth rate of the hydrate film on the bubble. Moreover, the heterogeneousness resulted in numerous cross-shaped or circular craters on the film, which served a new mass transfer channel and accelerated the initial thickening growth of the hydrate. In the Growth Mode 3, the evolution of the hydrate morphology was correlated to the viscosity of the hydrate formed in the reaction systems and the spreading ability of the aqueous solution on the reactor wall. To the best of our knowledge, this was the first study on the microscopic effects of inhibitors on the kinetics of the hydrate growth on gas bubbles, which is of added value for better understanding the hydrate evolution process in the hydrate inhibition scenarios with gas bubbles.