Critical distribution state of droplets dispersed in oil subjected to electric and centrifugal fields

Oil-water emulsions are extensively produced in industry, which may affect subsequent work or bring about environmental problems. Hence, it is necessary to demulsify and dewater it first. A coupling unit based on high-voltage electric and swirl centrifugal fields is adopted to satisfy emulsion demulsification and dewatering. The droplet size dis-tribution is closely related to the separation performance of the coupling unit, while the droplet size distribution changes dynamically due to coalescence and breakage of the droplets. Droplets possess corresponding distribution under different coupling conditions, and the droplets size distribution may have a specific critical distribution state, in which the separation efficiency of the coupling unit reaches the optimal. Therefore, a numerical model is established to study the critical distribution state under double-field coupling in this study. The influence of coupling conditions on the droplet size distribution is studied to obtain the critical state of droplet size distribution, and the relationship between the critical state and the inlet droplet diameter is investigated. The results show that the critical state exists, and its distribution is as follows: there is a stable region with the maximum diameter gradient within 15 mu m from the tail of the large cone section to the front of the small cone section (z = 700-760 mm) of the coupling unit; in the cross sections of the small cone section Z = 660-690 mm, the distribution of droplets volume fraction are almost identical, and the droplet diameter with the largest volume fraction is close to the median diameter. Moreover, the above critical state also exists for different inlet droplet diameters.(c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.