Effects of droplet dynamic characteristics on the separation performance of a demulsification and dewatering device coupling electric and centrifugal fields

Efficient oil-water separation is difficult to achieve through a single process in oil exploitation and waste oil recycling. Therefore, a demulsification and dewatering device coupled with high-voltage electric and swirling centrifugal fields was proposed. It is inevitable for droplet breakup due to swirling shear during separation which will influence separation performance. The oil-water separation model which coupled droplet coalescence and breakage kernels was established. In this study, the separation performance of the coupling device is studied via numerical and experimental methods. The results indicate that the numerical results obtained by computational fluid dynamic coupling with population balance model (CFD-PBM approach) are in good accordance with experiments. Therefore, the effects of droplet dynamic characteristics cannot be ignored in oil-water separation process. In addition, when the voltage increases from 0 to 11 kV, the dewatering and deoiling rates increase by 15.3% and 12.4%, respectively. And with voltage continuing to increase, more droplet breakage occurs which leads to a slight decrease in separation efficiency. An appropriate inlet flow rate can produce minimum droplet breakage and strong back flow for separating water from emulsions. With the increase of inlet flow rate from 6 to 8 m/s, the separation efficiency has a significant promotion. The dewatering and deoiling rates increase by 9.5% and 6.9%, respectively, but decrease with the flow rate increasing further.

Automated summary

This study investigated the separation performance of a demulsification and dewatering device coupled with high-voltage electric and swirling centrifugal fields. The research showed that voltage and inlet flow rate play significant roles in separation efficiency and droplet breakage, highlighting the importance of dynamic characteristics of droplets in the oil-water separation process.