Mathematical modeling of dispersed phase behavior of water-in-oil emulsions in electrostatic crude oil desalters

Abstract

The produced crude oil from reservoirs usually contains a considerable amount of water which is submitted to large shear rates through production process, and due to the existence of natural surface-active agents in crude oils, stable water-in-oil (W/O) emulsions are formed. Effectively purifying the emulsified crude oil through the electrostatic desalting process plays an important role in reducing its water and water-soluble salts contents, which otherwise exacerbate oil deterioration, equipment corrosion, and catalysts deactivation in subsequent units. The electrostatic desalting process has proved to be an efficient means of separation using electrodes subjected to a high voltage to enhance the coalescence of water droplets. In this study, a mathematical model was developed to simulate the W/O dispersed flow to study the evolution of droplet size distributions in crude oil desalters. The population balance approach was employed to describe the behavior of W/O emulsions in the continuous phase assuming that the process is controlled by two simultaneous physical phenomena; breakage and coalescence of droplets. Experimental results on the W/O system were utilized to validate the mathematical model and the employed numerical technique. The agreement between the developed model and experimental droplet volume size distributions was shown to be satisfactory, confirming the further applicability of the model. The present study can be helpful for optimizing crude oil desalting operating conditions, enhancing efficiency, and decreasing energy and chemical consumption.