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During their operation or in the event of an accident, power transformer can release a certain amount of oil in the subjacent soil. In order to avoid a fire hazard or any contamination to the environment, it is critical to capture any oil that was accidentally spilled. For this reason, catchment basins are placed below each power transformer and each basin is connected through pipes to a gravitational oil–water separator, which allows the oil droplets carried by the water flow to rise toward the surface and coalesce near the free surface. By doing so, the oil phase is separated from the mixture and it can be properly disposed afterwards. Prior to 1995, gravitational separators at Hydro-Québec have not been designed according to the American Petroleum Institute (API) standards [1] but this does not necessarily imply that such separators do not comply with the environmental legislation in place. Thus, in order to evaluate if modifications to the existing gravitational separators are required, Hydro-Québec has launched in 2012 an R&D project aimed at performing separator efficiency studies through a Computational Fluid Dynamics (CFD). In this paper, a numerical simulation of a gravitational oil–water separator in service at Hydro-Québec using an inhomogeneous multiphase model is presented. Moreover, a new configuration of the existing separator is numerically tested and the results show that its performance is significantly improved.
CFD, inhomogeneous model, oil–water separator, two-phase flow
[1] Monographs on Refinery Environmental Control-Management of Water Discharges, Design and Operation of Oil-Water Separators. American Petroleum Institute Publication 421, 1990.
[2] Hansen, E.W.M., Heitmann, H., Lakså, B., Ellingsen, A., Østby, O., Morrow, T.B. & Dodge, F.T., Fluid flow modelling gravity separators. Proceedings of the 5th International Conference on Multi-Phase Production, Cannes, France, 1991.
[3] Hansen, E.W.M., Phenomenogical modelling and simulation of fluid flow and separation behaviour in offshore gravity separators. ASME Pressure Vessels and Piping Division, 431, pp. 23–29, 2001.
[4] Holdo, A.E. & Calay, R.K., Two-phase flow modelling for industrial applications. Fluid Mechanics Research Group, University of Hertfordshire, UK, 2006.
[5] Abdulkadir, M., Hernandez-Perez, V. & Hossain, M., Modelling of oil-water separator using computational fluid dynamics (CFD). Proceedings of the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Antalya, Turkey, 2010.
[6] Behin, J. & Aghajari, M., Influence of water level on oil-water separation by residence time distribution curves investigations. Separation and Purification Technology, 64, pp. 48–55, 2008. https://doi.org/10.1016/j.seppur.2008.08.009
[7] Das, S.K. & Biswas, M.N., Separation of oil water mixture in tank. Chemical Engineering Communications, 190, pp. 116–127, 2003. https://doi.org/10.1080/00986440302095
[8] Wilkinson, D., Waldie B., Nor, M.I.M. & Lee, H.Y., Baffle plate configurations to enhance separation in horizontal primary separators. Chemical Engineering, 77, pp. 221–226, 2000. https://doi.org/10.1016/s1385-8947(99)00170-9