Electrocoalescence of water droplet trains in sunflower oil under the coupling of Non-uniform electric and Laminar flow fields

Abstract

Electrocoalescence is an energy-efficient and environmentally-friendly process for demulsifying water-in-oil emulsions, which has been extensively used in the oil and petroleum industries. In the present study, the electrocoalescence process of water droplet trains in sunflower oil under the coupling effect of non-uniform electric and laminar flow fields was experimentally investigated. The results showed that at high Ca (=a∊m∊0E2/γ) and Re (=4ρwVw/πμwdi), the water train presented complex dynamic behaviors under the coupling of non-uniform electric and flow fields, and excessive large droplets were formed. In the presence of SDS, a long pearling water chain were easily formed and difficult to return to a spherical shape due to low surface tension. The electrocoalescence efficiency decreased with increasing particle concentrations ranging from 0 wt% to 1.5 wt%., and no short-circuiting occurred at a particle concentration of 2.0 wt%. The coupling of non-uniform electric and flow fields could be a promising method to facilitate phase separation. The rank order of the electrode performance is: the second group of the double mesh electrode > the first group of the double mesh electrode > mesh electrode > grid electrode. In addition, a large Re, i.e. large droplet velocity, gave rise to higher coalescence efficiency. The outcome of this work is potentially useful in the design of compact and efficient oil–water electro-dehydration devices.