Separation kinetics of an oil-in-water emulsion under enhanced gravity

The breakup of crude oil emulsions to produce clean oil and water phases is an important task in crude oil processing. We have investigated the demulsification kinetics of a model oil-in-water emulsion in a centrifugal field to mimic the forces acting on emulsion droplets in oil/water separators such as hydrocyclones. The rate of growth of separated oil phase and the change in mean droplet diameter of the emulsion layer was measured as a function of surfactant concentration, centrifugal acceleration and time. Demulsification is enhanced with increasing centrifugal acceleration and time and decreasing surfactant concentration. A kinetic analysis was performed that allows to estimate the characteristic coalescence times between droplets in the emulsion and between a droplet and the separated oil interface. The experimental procedure presented in this work can serve as a simple, but useful test to predict the separation efficiency of emulsions in separators with swirling flow fields.

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► We present a simple method to assess the stability of emulsions in centrifugal flow fields.
► The change in drop size and growth of pure oil phase in an O/W emulsion was measured.
► A kinetic model is presented that allows calculation of characteristic coalescence times.
► The procedure may be of help for the petroleum industry in choosing a separator for a given produced fluid.