Numerical investigation of droplet coalescence of saltwater in the crude oil by external electric field

Abstract

The existence of saltwater in extracted crude oil causes major problems such as corrosion and low quality of the extracted crude oil. Therefore, droplet coalescence of saltwater and desalination have been paid much attention by researchers about refining crude oil. In this study, movement and coalescence of dual droplets in a channel exposed by external electric field have been investigated. An electro hydrodynamic and an electrostatic model was designed based on computational fluid dynamic. Phase field method in hydrodynamic model that is able to locate circular flows inside and outside of droplets and the effect of surface tension is carried out by COMSOL Multi-physics software. The effect of the electrostatic field intensity, inlet velocity and surface tension between two phases has been investigated. The related results were compared with the existent experimental data. The results show that raising velocity causes decreasing in the time of the droplets coalescence. Also, by changing the properties of saltwater and lowering surface tension, coalescence time increases. Studying the electrostatic field intensity, showed that increasing electrostatic field intensity causes decreasing the time of coalescence and raising coalescence efficiency of droplets. In velocity 100 mm/s, by increasing the electrostatic field from 0 to 3 the droplets coalescence time decreases 47%. Also In Surface tension 0.4, by increasing the electrostatic field from 0 to 3 the droplets coalescence time decreases 31%.