CFD BASED MICROSCALE NUMERICAL STUDIES OF OIL SEPARATION FROM SAND PARTICLES

Abstract

This work is devoted to CFD-based numerical studies of oil separation from sand particles under the influence of water flow velocity. A single micro-scale (diameter of 100nm) particle is covered by a thin oil film which is immersed in a uniform flow. The oil-particle separation has been modeled at different contact angles of 0o, 90o, 170o and different Reynolds numbers of 1, 3, 5, 7, 10, 20, 100, 150, 200. Differ- ent Reynolds number (Re) indicates different inlet velocities, meanwhile, different contact angles indicate different hydrophobicities. The desired status is when the oil completely moves away from the particle. A commercial computational fluid dynamics (CFD) software called ANSYS Fluent 14.5 [1] is used to perform all mod- eling works. Applied to the micro-scale modeling, Volume of Fluid (VOF) serves as the major method. This work is unique at the time, because, for the first time, a 2D numerical modeling has been done for Newtonian laminar flow on a micro- scale particle. The bounce-back phenomenon due to the sudden pressure drop is first-ever investigated and described. There is a critical Reynolds number (Recrit) to be found at different contact angles. The definition of Recrit is a Reynolds num- ber of the particle when the complete oil separation happens. Additionally, the oil separation from a porous particle is first-time modeled by introducing an artificial roughness of 17%. As a result, oil stays in the pore at Re of 5 with contact angle of 170o and Re of 200 with contact angles of 0o, 90o, 170o. The influence of the model dimension (2D and 3D), model parameters (interfacial tension, volume of oil, diameter of particle, fluids’ properties), and computational grids are investigated. The models have been validated against experimental data in Mehrabian et al. [2]. Good agreement between numerical predictions and experimental data is observed. A typical experiment is repeated numerically using CFD-based numerical simulation, but with a different submodel. One valuable finding from the validation case is that while retaining the same situation, the separation occurs easily when a higher water viscosity than the oil. Different from Mehrabian et al. [2], this work is renovated and performed under normal water phase conditions, specifically the assumption of that the viscosity of water phase is the same with it is in the oil phase (1mPa s).