A three-dimensional steady-state mathematical model of a rotary calcining kiln for the petroleum coke is presented. The model takes into account all the physical phenomena of interest, from gas flow, heat transfer, volatile matter and coke dust evolution and combustion, to the granular bed motion and the thermal effects of the refractories. The model is built in modular form with several submodels coupled together. This methodology facilitates the construction of the model and its use. This article gives a detailed mathematical description of the model. A complete simulation is presented, and the results are discuss,d. Data coming from an industrial kiln in operation are used for validation, and the results show that the model can be a useful tool for solving problems of kiln operation or design.

Une bonne performance des équipements de séparation solide-liquide est nécessaire pour l'exploitation économique du procédé Bayer. Un modèle de mécanique numérique des fl uides simulant l'écoulement transitoire dans le dernier épaississeur du circuit de lavage de boue d'une grande usine d'alumine canadienne est présenté. Une étude paramétrique, résultant de ce modèle et prenant en compte quatre paramètres géométriques et de procédé, conclut que le diamètre des particules de boue rouge fl oculée, le débit d'alimentation et le rayon du puits d'alimentation sont des paramètres critiques quant à la performance de l'épaississeur.A good performance of the solid-liquid unit operation is required for the economical exploitation of the Bayer process. A computational fl uid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of fl occulated red mud particles, the feed fl ow rate and the radius of the feed well are critical parameters for the operation of the thickener.

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