Non-isothermal population balance model of the formation and dissociation of gas hydrates

Abstract

Data reduction processes based on laboratory-scale experiments related to hydrate formation and dissociation kinetics usually employ isothermal models where the hydrate particles and continuous phase are at the same constant temperature despite the large latent heat in this phase change phenomenon. In this study, we tested this hypothesis by developing a non-isothermal model of methane hydrate formation and dissociation in a three-phase agitated vessel with a cooling jacket. The hydrate particle mass and energy comprised the distribution variables in a bivariate population balance model, which included particle nucleation, growth, breakage, and aggregation. The mass and energy balances in the gas and liquid phases completed the model. The heat transfer between the liquid phase and the coolant in the jacket was also modeled. Under the conditions analyzed, the results showed that the particle temperatures were quite close to that of the liquid phase but large changes occurred during hydrate formation or dissociation due to the slow heat transfer to the cooling fluid. Therefore, hydrate formation or dissociation occur in a environment with a changing temperature, which must be considered to obtain meaningful kinetic data.