Abstract: Settlement separation is widely used in Chinese petroleum industry, but theoretical research on it obviously lags behind the structural design and application research. Based on CFD-DEM coupled model, this paper took the discrete phase oil droplets in the settling tank as the research object. It constructed the mathematical model of the settlement separation of oil droplets in the gravity field. By using the method of theoretical analysis and numerical simulation, the paper analyzed the motion characteristics of oil droplets in the process of settling, obtained the motion trajectory of oil droplets in the settling and separation process and grasped the changes of velocity and force in the process of oil droplets separation. By improving the inclination and the equivalent spacing of the inclined plate, it was determined that the inclination of the inclined plate with the best oil phase separation effect was 60° and the equivalent spacing of the inclined plate was 150 mm. With the above parameters, the oil removal efficiency can be increased from 64% to 82%. The results of this study can provide theoretical basis and data reference for revealing the mechanism of settlement separation and guiding the design of new high-efficiency settlement device.

Key words: settlement separation, discrete element model, oil droplet, separation mechanism, motion characteristics