Simulation of the coalescence and breakup of water-in-oil emulsion in a separation device strengthened by coupling electric and swirling centrifugal fields

Demulsification and dewatering play significant roles in the petroleum chemical industry. Effectively purifying emulsified oil by using a single method or mean is evidently difficult. In this investigation, a swirling centrifugation separation device strengthened by an electric field is proposed. The device utilizes an electric field to coalesce droplets, meanwhile a swirling centrifugal field is used to realize the rapid separation of water from oil. The coalescence and breakup of droplets in emulsified oil, which are dynamic and complicated processes, directly influence the separation effect of the device. In this study, a coalescence and breakup model of emulsion droplets under coupling electric and swirling fields is constructed using a population balance model (PBM), and the coalescence and breakup of emulsion droplets in the device are simulated. Results show that the coalescence and breakup model can reasonably simulate the coalescence and breakup of droplets in the device and predict droplet size distribution and separation efficiency. The electric field exerts a significant influence on the coalescence of droplets, especially improves the ability of the device to process minute droplets. At 11 kV, the Sauter mean diameter (SMD) and separation efficiency reach the maximum, and increase by 69.1% and 43.8%, respectively, compared with the case of 0 kV. Although these results are advantageous for the coalescence of droplets at a low inlet velocity, backflow strength is weakened, and the oil-water separation effect is reduced. When the optimal inlet flow rate is 10 m/s, the separation efficiency reaches up to 90.8%.