The liquid/liquid sedimentation process: From droplet coalescence to technologically enhanced water/oil emulsion gravity separators: A review

Crude oil is nearly always produced along with water in the form of water/crude oil emulsions. Gravity settlers are the most common technology to separate these dispersions. A short description is given of the coalescence mechanism (droplet collision, film drainage, film rupture). Three micromechanical sedimentation models (Hartland, Lobo, Henschke) and one set of design rules (Polderman) are described. IFP experimental data are presented that confirm the difference between sedimentation-based and coalescence-based models. Technological enhancements used in order to accelerate and/or increase the separation (heating, chemical demulsifiers, mechanical barriers, electrocoalescence, ultrasound, microwaves) are presented.