Etude et modélisation des fours tournants de défluoration et réduction du difluorure d'uranyle

Abstract : This work is concerned with the study and modelling of rotary kJns for uranium oxides preparation. The first chapter deals with the study of the movement of solid in rotary kJns equipped with lifters. A method was developed to calculate the average distribution of powder in a transverse section of the kJn. It is based on geometrical considerations and on experiments (unloading law of the lifters and velocity of the falling swarms of powder). Measurements of Residence Time Distribution allowed to determine the mean residence time and the axial dispersion in the industrial kJns, making it possible to choose a model to calculate the bed depth profJe. The second chapter is concerned with mechanisms and kinetic laws, established experimentally in the operating conditions of the industrial kJns in terms of temperature and gas composition. On this base, a kinetic model was set up, which allows to calculate the conversion of solid as a function of the powder transverse distribution by using the law of additive reaction times. The third chapter describes thermal aspects of rotary kJns. The thermal balances are established on the solid, the gas and the inner equipments. The thermal conductivities of powders and the emissivities of walls and powders were experimentally measured. The heat transfer coefficients were obtained by means of measurements in a laboratory kJn or from correlations from the literature. The complete model of kJns, discribed in the fourth chapter, is based on the measurements presented in the previous chapters, and on dynamic, kinetic and thermal models developed concurrently. At the present time, the model represente satisfactorJy how industrial kJns work, and allows to suggest ways to improve the process
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Marie Debacq. Etude et modélisation des fours tournants de défluoration et réduction du difluorure d'uranyle. Autre. Institut National Polytechnique de Lorraine, 2001. Français. ⟨NNT : 2001INPL003N⟩. ⟨tel-01752272⟩



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