Modeling of Kinetics of Water Droplets Coalescence in Crude Oil Emulsion Subjected to an Electrical Field

Water is used in petroleum desalting units to dilute and remove the salted water droplets that the crude oil contains. The basic processes promote the coalescence of small droplets of conducting water dispersed in a crude oil emulsion. In order to make separation easier, the emulsion is distributed horizontally between two electrodes and subjected to an electrical field, which generates an attractive force among the droplets, promoting coalescence phenomena and further sedimentation. The main purpose of this study is to reduce the demand of fresh water and the liquid effluent generation in refineries. This paper presents a new model developed in order to calculate the droplets velocity by using the balance of the acting forces. The model is able to determine the droplets trajectory in order to define if they can be separated from the continuous phase. Besides the deterministic approaches based on traditional equations, the model uses also the concept of cellular automata. Thus it is possible to solve the problem in a stochastic way and to show visually the sequence of droplets collisions and coalescence phenomena. This methodology enables to calculate the amount of water that can be separated of the emulsion for a number of different operating conditions and then to optimize the process. Comparisons between the obtained results by the developed model and the operational performance of a real desalting unit are carried out. A good accuracy is observed, which shows that the real process is very well represented by the developed model.