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Étude cinétique aux basses sursaturations et modèle thermodynamique de la précipitation oxalique de l’uranium IV

Abstract : Precipitation is widely used in many other industrial activities. Precipitation reactions are very sensitive to many operating parameters that play a major role in controlling the precipitate quality. In the nuclear industry, precipitation is a common operation, either in uranium extraction from uranium ore, nuclear fuel reprocessing or radioactive waste management. In this study we are interested in uranium IV oxalate precipitation. This study proposes a thermodynamic model and precipitation kinetics at low supersaturations on the basis of experimental acquisitions. New measures of uranium IV oxalate solubility at different acidities and oxalic excess led to the identification of the complexation constants and the solubility product. The supersaturation is calculated from free ions concentrations. The comparison with a constituent ions approach shows that the two concepts lead to equivalent supersaturation values. Regarding the identification of kinetics, many uranium IV oxalate precipitation continuous tests allowed the analysis of the influence of the operating parameters on efficiency and particle size distribution. Kinetic parameters are obtained by solving the population balance equation by the method of moments. Nucleation kinetics and agglomeration kernel are expressed from crystal growth kinetics. The nucleation mechanism corresponds to a secondary type and depends on the power dissipation and crystal concentration. As for the agglomeration kernel, it is identified of orthokinetic type
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Submitted on : Friday, March 4, 2022 - 8:59:09 AM
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Alexandra Gutiérrez Chavida. Étude cinétique aux basses sursaturations et modèle thermodynamique de la précipitation oxalique de l’uranium IV. Génie des procédés. Université de Lorraine, 2015. Français. ⟨NNT : 2015LORR0306⟩. ⟨tel-03596897⟩

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