Predicting the Induction Time of Hydrate Formation on a Water Droplet

Abstract

Despite the importance of the induction time in hydrate formation studies, the scientists have not yet developed a generalized model due to its stochastic property. In this work, the induction time of hydrate formation of multicomponent gas mixtures on a water droplet has been modeled. Mass transfer through the droplet surface was modeled based on a diffusion equation where the rate of reaction was expressed based on the nucleation theory. Driving force for the hydrate formation was calculated based on the change in the Gibbs free energies of the gas, water and the hydrate. The model was validated by comparison of the predicted results with the experimental data from the literature. The induction time was calculated for hydrate formation from a mixture of 89.4% methane + 10.6% ethane on 1.5-7 mm in diameter of water droplets at 273.85 K and 3.6-5.1 MPa. It was found that, induction time is highly sensitive to the value of the driving force. Moreover, the induction times were not dependent on the size of the droplets and the induction time for the water droplets with hydrate memory was shorter than the droplets without hydrate memory.