Analytical and numerical models of chemical leaching with gypsum precipitation in porous media

Résumé : In the present thesis we develop the optimized phenomenological model of in-situ chemical leaching (ISL) of uranium by the injection of sulfuric acid, with special account for the precipitation of non-soluble species as gypsum, which reduces the uranium recovery. The suggested model describes the mass transport with heterogeneous chemical reactions between liquid and solid rocks, leading to dissolve uranium oxides and recover uranium in liquid form. It includes both useful reactions, describing the dissolution of various kinds of uranium oxides, and detrimental reactions, leading to the precipitation of solid sediments (gypsum), whose flakes cover the surface of porous channels and reduce the efficiency of useful reactions. Among the qualitative results we revealed the existence of a critical rate of gypsum sedimentation, below which the ultimate uranium recovery is complete. In contrast, it tends to a limit value lower than 100% when the sedimentation rate is higher than the critical value. This limit recovery depends on various parameters of the process. The theory and the methodology developed in this work can be easily extended and applied on other type of ores that are recovered by in-situ leaching method and other types of solvents
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Alibek Kuljabekov. Analytical and numerical models of chemical leaching with gypsum precipitation in porous media. Engineering Sciences [physics]. Université de Lorraine; Al-Farabi Kazakh National University (Almaty, Kazakhstan), 2014. English. ⟨NNT : 2014LORR0369⟩. ⟨tel-02075294⟩

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