Effect of electric field on separation characteristics of oil–water–solid three phases separating device

Abstract

Lubricating oil can decay as a result of the mixing of water with solid impurities in the working process, and this process can adversely affect the performance of the machinery. Therefore, desolidification and dewatering are key steps in overall oil purification. In general, a basic swirl device cannot sustain efficient dewatering and desolidification. Thus, a three-phase separating device enhanced by an electric field has been proposed. To study the performance of the oil-water-solid separation process, a numerical model of the device was conceived based on combining the governing equations of the flow field and the electric field with the particle-tracking equation giving due consideration to the population balance model. The tangential velocity and the distribution of solid particles at various voltage amplitudes were analyzed, and the effect of the electric field on the oil, water and particle separation process was studied. The results show that at 3 kV, the tangential velocity increased by 5.06%, compared with that at 12 kV. Application of an electric field to the device was found to accelerate more solid particles which assembled near the wall of the device, and where the number of the particles near the axial plane decreased. The maximum particle concentration near the wall at the z = 630 mm plane is 20.24%. Moreover, the average residence time of the solid particles initially exhibited an increasing and then a decreasing trend. Additionally, the increase in the droplet size and enhancement of the oil-water separation process are promoted through the action of the electric field. The rate for desolidification, deoiling and dewatering at 3 kV are 93.60%, 93.30% and 95.59%, respectively.