Studies on the normal-to-abnormal emulsion inversion of waxy crude oil-in-water emulsion induced by continuous stirring

In this paper, the normal-to-abnormal emulsion inversion induced by continuous stirring in a waxy crude oil, water and Triton X-100 emulsion was investigated. The emulsion inversion from the preferred O/W to W/O occurs through the formation of a w/O/W multiple emulsion, in which water from the external phase is continuously included as droplets in the dispersed oil phase drops until a critical dispersed phase value is reached and the inversion takes place. The inversion time, tinv, is an appropriate parameter to describe the emulsion inversion difficulty. And tinv increases with increasing emulsifier or NaCl concentrations while decreases with increasing stirring rate, meaning that the emulsion inversion becomes difficult with increasing emulsifier or NaCl concentrations while becomes easy with increasing stirring rate. The influence of φo on tinv is complicate due to the increase of emulsion viscosity with increasing φo. In general, increasing φo favors the emulsion inversion thus decreasing tinv. However, the increased emulsion viscosity is adverse for the emulsion inversion thus increasing tinv. At high stirring rates (≥ 1500 rpm), the emulsion viscosity has little influence on the emulsion inversion and then tinv decreases with increasing φo; at low stirring rates (≤ 750 rpm), the stirring intensity is too low to trigger the emulsion inversion at every value of φo; at intermediate stirring rates, the value of tinv is influenced not only by φo but also by the emulsion viscosity.

► We studed the normal-to-abnormal emulsion inversion induced by continuous stirring.
► The inversion occurs through the formation of a w/O/W multiple emulsion.
► The effcts of φo, emulsifer and NaCl concentrations on the inversion were studied.