Study of hydrate formation in water-in-waxy oil emulsions considering heat transfer and mass transfer.

Abstract Natural gas + water-in-diesel emulsion + AA systems with and without wax were used to investigate the influence of wax crystals and their heat- and mass-transfer effect on hydrate formation from macroscopic and microscopic aspect in a flow system. Hydrate nucleation and initial growth were found to be a partially occurred phenomenon. Wax was found to prolong the hydrate induction time through two significant effects: one was the macroscopic heat-transfer effect produced by wax deposition with insulating effect, and the other was the microscopic mass-transfer resistance originating from the wax crystals that were adsorbed at or adjacent to the oil-water interface. Hydrate induction time shortened and became less scattered with the increasing initial pressure. Based on the heat-transfer theory of a flow system and the hydrate nucleation theory, an improved model for hydrate induction time prediction was developed by coupling calculation of hydraulics and heat-transfer and by introducing mass-transfer effect of adsorption of wax crystals. The findings of this work are meaningful for providing essential information and supports for the ongoing deep-sea oil and gas production and the application of hydrate-management strategies in the presence of wax crystals in a flow system. [ABSTRACT FROM AUTHOR]