Précipitation continue de produits minéraux : étude de l'influence des conditions de mélange à la précipitation sur les caractéristiques d'oxydes mixtes de cérium et de zirconium

Abstract : An automated experimental set-up with rapid mixers is used to study the influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides. The intensity of mixing is controlled by the inlet flowrates of the reacting solutions. An engulfment model is used to estimate a mixing time from the measurement of a segregation index by the Villermaux-Dushman reaction system. Three geometries of Hartridge Roughton mixers are compared. Mixing performance is better when a separate mixing chamber upstream of a narrower outlet pipe is present. A better mixing decreases the maximal reducibility temperature of the material and increases the crystal strains of the particles calcined at 1100 °C. This is probably due to a better homogenization of the particles content. The important incorporation of nitrates in the particle at the outlet of the mixers shows precipitation occurs while the mixing process is not finished. This experimental result was confirmed by numerical simulation and an estimation of sursaturations during the mixing process.
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Nicolas Di Patrizio. Précipitation continue de produits minéraux : étude de l'influence des conditions de mélange à la précipitation sur les caractéristiques d'oxydes mixtes de cérium et de zirconium. Génie chimique. Ecole Nationale Supérieure des Mines de Paris, 2015. Français. ⟨NNT : 2015ENMP0001⟩. ⟨tel-01139348⟩

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