Numerical study of non-uniform electric field effect on water droplet coalescence in crude oil

One of the most important stages in extraction of petroleum is to separate emulsified water from crude oil, which is a way to speed up separation process, forcing droplets to coalesce and form larger droplets by using an electric field. In this article, the process of coalescing two droplets of water in an oil medium numerically was studied under uniform and non-uniform electric field conditions. The continuity and momentum (Navier-Stokes) equations was used for simulating two fluid phases and their interface was tracked by using phase field and volume of fluid (VOF) method. Effects of field’s waveform, frequency and field intensity on the coalescing process was investigated in the non-uniform field situation. The results showed a good agreement with the experimental results in the uniform field mode. In part (a) of the geometry, square, half-wave and sine wave shapes had the best performances, whilst in part (b), the sine wave performed better than the half-wave. According to the results, increasing field intensity speeds up the coalescence but increasing the frequency has no effect on the composition speed.

Keywords:

Electro coalescence , Crude oil-water separation , Emulsion , Desalting