Destabilisation of water-in-oil emulsions under the influence of an AC electric field: Experimental assessment of performance

The destabilisation of water-in-oil emulsions is an important industrial process and is often the rate-determining step in the dewatering and desalting of crude oils. In this study the influence of a 50Hz sinusoidal electric field on flowing water-in-oil emulsions is reported. A horizontal rectangular duct was used, with emulsion flowing through at flow rates up to 100 litre/min, giving Reynolds numbers (Re) in the range 1000 to 12,000. Electrocoalescer performance was assessed by measuring water droplet growth, using a specially developed technique with a laser diffraction particle sizer. Under conditions of high water-cut, electrocoalescence can be so efficient that free-water drop-out may occur, even in conditions of turbulent now. This can lead to the formation of a layer of water co-flowing with the depleted emulsion in the duct. Study of the electrocoalescer behaviour under these conditions has been carried out by image analysis using a Hamamatsu Image Processor.