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Etude expérimentale et modélisation d’un procédé semi-continu de neutralisation d’une solution d’acide sulfurique par une suspension de calcite conduisant à la formation de gypse par conversion et par précipitation

Abstract : The present study deals with the formation of gypsum resulting from the neutralization of sulfuric acid solution by addition of a calcite suspension in a half batch reactor. Phenomenology and impact of operating parameters are observed by sampling of solid and solution and analyzed off online. Samples are used to assess deviations from equilibrium generated at various stages of mixing and the geometric characteristics of the gypsum precipitate. The solubility of gypsum is evaluated as a function of temperature and sulphate concentration via a speciation model.Depending on operating conditions used, gypsum is formed mostly on the calcite surface by partial conversion or in solution by precipitation. Process modelling is two-staged. Conversion is simulated on the basis of a model of grain with shrinking core, suited to represent calcite dissolution together with the growth of a gypsum porous layer. The precipitation in solution is simulated through population balance and solved by a method of characteristics. Parameters of nucleation and growth kinetic laws are evaluated by an optimization algorithm. The conversion model reflects the process sensitivity to solution’s acidity and calcite particle size. The precipitation model provides supersaturation profiles and PSD consistent with experiments. The possibilities for process control lay mainly on adjusting the acid concentration, which largely determines the rate of calcite dissolution and the proportion of gypsum formed by replacement.
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  • HAL Id : tel-00716458, version 1

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Frédéric Bard. Etude expérimentale et modélisation d’un procédé semi-continu de neutralisation d’une solution d’acide sulfurique par une suspension de calcite conduisant à la formation de gypse par conversion et par précipitation. Autre. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2011. Français. ⟨NNT : 2011EMSE0624⟩. ⟨tel-00716458⟩

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