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In this article, we studied the process of cold and hot mixing of sedimentary phosphates of Bouchane in order to optimize the energy requirements by reducing the organic matter and carbonates. The cold mixture is done at the ambient temperature whereas the hot mixture is made at the calcination temperature. The experimental process of the mixtures is performed under the atmospheric air using the same phosphate source and mixing in the same manner, in order to make possible the comparison between cold and hot. It appeared that the hot mixture using 33% of the same phosphate source can have an important impact on the energy saving while preserving the environment and responding to the quality requirements of the users.

A model taking into account the simultaneous influence of mechanical and hygrometric actions (Mrani and al., 1995a, 1995b) was applied to study of the dehydration of a cylinder of highly deformable biphase gel (agar gel) (Mrani and al., 1995b). Numerical solution of the water transport equation and the mechanical equilibrium equation provided access to the water content and stresses and strains in the cylinder. The numerical results were validated for water content and overall deformation of gel cylinders. The model clearly shows the inversion of the curve of the faces of the cylinder observed experimentally. Three deformation phases were observed. In the first phase, when the concaveness of the faces of the cylinder was turned inwards, tractive stress appeared at the surface of the sample. More uniform distribution of the water content became established in a second phase and the cylinder recovered its initial shape corresponding to the relaxation of the stress state. In the third phase, the con...

ABSTRACT A numerical model of isothermal drying of deformable substances is proposed. The model is applied in a uni-directional case to analysis of water transport in a sphere of agar ge. The simulation program makes it possible to calculate the water content fields and def rmations and stresses in the sphere during drying. Validation of the water content profile results is proposed by the experimental study of the dehydration of gel spheres in a sugar solution. The sensitivity of internal stresses to drying conditions is then analysed.