Poster De Conférence Année : 2018

Use of high velocity flows to determine the chemical kinetics constant during uranium(VI) extraction

Résumé

The development of advanced solvent extraction processes requires the knowledge of the mass transfer coefficients and the understanding of the implied phenomena in order to simulate the process in contactors with short residence time and for its upscaling to industrial contactors. Because classical methods to study solvent extraction kinetics as Single drop method or Lewis cells only allow to determine apparent mass transfer constants, the microfluidics fields appear as an interesting alternative to study kinetics at sub-millimetric scales and, try to reach the individual diffusion and/or chemical constants. In this context, our study considers the well-known solvent TBP 30% diluted in TPH used to reprocess spent nuclear fuels as a reference solvent to study mass transfer kinetics. Attempts to determine the chemical kinetics constant of uranium(VI) transfer from nitric acid to TBP 30% diluted in TPH are carried out by means of experiments in a dolomite Y-Y chip with a microchannel of 0.2 mm width and 12.5 mm length. The experimental set-up developed to study the extraction of uranium (VI) between the phases allows working with stratified flows at high velocities (from 0.28 m.s-1 to 0.96 m.s-1 for the aqueous phase) in order to accelerate interfacial mass transfer by decreasing the diffusion contribution to the global mass transfer as low as possible. The effects of the solute concentration and the residence times on the kinetics of uranium extraction have been studied. The results have been exploited to determine if diffusion still limits the extraction process in such conditions. The chemical mass transfer constant (ke) should be higher than 4.2 10-4 m.s-1 for the extraction of a 0.12 M U(VI) aqueous solution assuming equilibrated reactions at the interface with first order kinetic laws. The results hardly fit with a preliminary 2D COMSOL model even if increasing the supposed ke twice and the U(VI) molecular diffusion coefficient (DU) by a decade. Confronted with these extremely enhanced kinetics, the future work will focus on enhancing the chemicalmodel for example by examining the Hatta number and looking at the existence of interfacial convection in order to understand the transfer mechanism in the studied system.

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Dates et versions

cea-04756514 , version 1 (28-10-2024)

Identifiants

  • HAL Id : cea-04756514 , version 1

Citer

Florian Corne, Anne Lelias, Alastair Magnaldo, Christian Sorel, Nathalie Di Miceli Raimondi, et al.. Use of high velocity flows to determine the chemical kinetics constant during uranium(VI) extraction. IMRET 2018 (15th International Conference on Micro Reaction Technology), Oct 2018, Karlsruhe (Allemagne), Germany. ⟨cea-04756514⟩
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