Simulation of an Industrial Three Phase Boot Separator Using Computational Fluid Dynamics

Three-phase separators are used to separate immiscible phases in petroleum industries. Computational fluid dynamics (CFD) simulation of industrial separators are rather limited in the literature and most of them are based on Eulerian-Eulerian (E-E) or Eulerian-Lagrangian (E-L) approaches with poor agreement between simulation and industrial data. In this research a coupled E-E and E-L method, i.e., the combination of the volume of fluid (VOF) and dispersed phase model (DPM) was developed to simulate an industrial three phase boot separator. Noted that despite the wide usage of boot separators in petroleum industry, no research has been performed on it. In order to develop the coupled model, effects of different sub-models including virtual mass force, droplet break up and also discrete random walk (DRW) model which was ignored in most of the researches, were considered. Liquid droplet entrainment in the gas outlet taken from data of Borzoyeh Petrochemical Company in the south of Iran, was the criteria for evaluating the CFD model. It is concluded that the coupled model using three mentioned sub-models with the high importance of applying DRW, is a successful way in predicting the separator efficiency so that considering all sub-models decreases the simulation error from 40.81% to 12.9%. Using the validated model, effects of inlet droplet size and flow rate on the separation performance were considered. Results demonstrated that decreasing droplet size (by 20%) and increasing flow rate (from 5800-6475 kg/hr), decreased the efficiency, such that the liquid entrainment in the gas outlet increased by 29% and 38 % respectively.