Study of the Dispersed Phase Behaviour in a Pulsed Column for Oxalate
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Study of the dispersed phase behaviour in a pulsed column for oxalate predipitation in emulsion A. Amokrane 1 , S. Charton 1 , F. Lamadie 1 , J. P. Klein 2 , F. Puel 2 1 CEA, DEN, F-30207, Bagnols-sur-Cèze, France; tel. +33 4 66796186, e-mail: abdenour.amok [email protected] 2 Université de Lyon F-69622, Lyon, France / Université Lyon 1, Villeurbanne, CNRS UMR5007, Laboratoire d’Automatique et de Génie des Procédés (LAGEP), CPE-Lyon, France Keywords: liquid-liquid dispersion, pulsed column, CFD, population balance modeling, nuclear fuel reprocessing An alternative to the current method of reprocessing spent nuclear fuel would be to co-extract the actinides and to co-precipitate them in a single step. In this scope, we are studying a new process based on continuous oxalic precipitation in emulsion using a pulsed column. The novelty of this process, which feasibility was already demonstrated [1] , lies in the containment of the reagents in drops of aqueous phase dispersed in an inert continuous organic phase (figure 1). The precipitation occurs in aqueous drops after they coalesce. The pulsed column is used as a liquid contactor. The process has therefore the double advantage of: i) implementing a well-known technology of the nuclear industry, and ii) ensuring the confinement of the sticky precipitates by the inert organic diluent (Tetrapropylene Hydrogen TPH). pulsation Feed 1 (oxalic acid) Feed 2 (catio n nitra te ) toward filtration Figure 1. Cerium oxalate precipitation in pulsed column. Sketch of the pulsed column –and photo of the solid phase enclosed in aqueous drops . A thorough understanding of the precipitation mechanisms and their interactions with the particular hydrodynamic conditions prevailing around the liquid drops in the apparatus is essential for the process optimization. In this context, modeling and numerical simulation are
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Transcript of Study of the Dispersed Phase Behaviour in a Pulsed Column for Oxalate
8/3/2019 Study of the Dispersed Phase Behaviour in a Pulsed Column for Oxalate
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8/3/2019 Study of the Dispersed Phase Behaviour in a Pulsed Column for Oxalate
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powerful tools complementary to the experiments in order to study both the dispersed liquid
phase behaviour within the pulsed column (and there from their residence times and collision
frequency) and the reagents mixing of the reactants within the drops.
The present study is focused on the behavior of the aqueous droplets inside the column. On
one hand, the residence time and velocity of the droplets were determined experimentally by
means of an optical approach consisting of a high speed camera combined with a backlightsystem. This Lagrangian experimental approach is completed by a Lagrangian simulation
approach under the commercial CFD software Fluent®, using the Discret Phase Model (figure
2).
On the other hand, an Eulerian modeling approach is developed to investigate the behavior of
the dispersed liquid phase. The Euler-Euler model in Fluent® has been used first. Available
dispersed phase models have been tested, assuming either fluid-fluid or a fluid-solid system,
thus revealing the importance of drops interactions. The population balance equation (PBE) is
then solved to account for the events affecting the droplets. Different PBE resolution
methods, coalescence and breakage kernels are tested. Both Euler-Euler and PBE-type
simulations are validated on mean hold–up experimental values and Sauter mean diameters
measurements. An example, based on the experimental results published by Jahya et al [2] isalso given.
Figure 2. (left) the experimental set-up; (middle) example experimental results : droplet
falling in the column;(right) example of simulation results : drop trajectories
References: [1] Borda, G.; Brackx, E.; Boisset, L.; Duhamet, J.; Ode D. Use of a pulsed column as a
continuous oxalate precipitator. Nuclear Engineering and Design. 2011, 241, 801-814
[2] Jahya, A. B.; Stevens, G. W.; Pratt, H. R. Pulsed disc-and-doughnut column
performance. Solvent Extraction and Ion Exchange. 27: 63-82, 2009.
