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Numerical study of Liquid-Liquid Emulsions in a Taylor-Couette Contactor

Abstract : In the field of R&D studies for liquid-liquid extraction (LLE) processes, scale-reduction is a strong issue, especially in the nuclear industry. However, reduction of the diameter of a LLE column is often associated with a decrease of its efficiency, due to enhanced wall effects, for instance in pulsed columns with internal diameter (ID) below 15 mm ID. A miniaturized liquid-liquid extraction column based on Taylor-Couette flow has been designed and tested [1]. It is able to operate with the same separation performances as an industrial pulsed flow column (operated at some m3 /h) but with a flow-rate as low as some 100 mL/h, thus involving minimal amounts of solvent and of radioactive material. The device consists in two concentric cylinders. The inner cylinder (OD 17 mm) is rotating while the outer one (ID 20 mm) is fixed. The column is operated at counter-current and the emulsion of the two immiscible liquid phases is provided by the shear-stress prevailing within the Taylor-vortex flow. Taylor-Couette flow appears at a critical speed. Above this speed, it is known to evolve through a sequence of flow instabilities until a turbulent state is reached. When the shear stress is high enough, for instance in turbulent regime, emulsification happens, and droplets of one phase are dispersed in the other phase. Although a comprehensive study of the mixing properties has already been conducted in one-phase flow [2], few studies are dedicated to the behaviour of liquid-liquid systems in this particular setup [3, 4]. The main objective of this study is to show the ability of numerical simulation to predict the effect of various parameters on the emulsification process and the achieved configuration (whether the organic phase or the aqueous phase is continuous), by comparison with experimental observations on our device. The effect of the wall wettability (i.e. contact angle) and relevant liquids properties (i.e. surface tension, viscosity) is investigated. The numerical study is carried out on Fluent 14.5 using a Volume of Fluid (VOF) multiphase model. Following [3], and contrary to [4], the domain’s height is limited in order to decrease the simulation cost, and axially periodic conditions are considered (closed domain, no settler).
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Submitted on : Monday, March 16, 2020 - 3:10:30 PM
Last modification on : Tuesday, April 28, 2020 - 11:28:18 AM

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  • HAL Id : cea-02509154, version 1

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N. Verdin, H. Roussel, S. Charton. Numerical study of Liquid-Liquid Emulsions in a Taylor-Couette Contactor. 10th International Congress of Chemical and Process Engineering (ECCE10), Sep 2015, Nice, France. ⟨cea-02509154⟩

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