Agglomeration Process and Recycling in Compacts of bauxite powders
Résumé
The bauxite is used in aluminium elaboration or directly as a raw material for calcium aluminates in technical cements. It is used, as a raw material, as block. Recently bauxite blocks are more and more rare and their handling can lead to wastes as dust that are not re-used. The objectives of this project are to recycle the fine mineral particles in compact shape to improve the use of natural mineral resource that are running out.
These products are compacted by direct compression. The bauxite is mixed with cement and water, and then the mixture is compacted. These compacts are then stored with controlled temperature and humidity to get a controlled cement hydratation. They must have specific properties in terms of density, porosity and mechanical resistance. X-Rays micro-tomography is used to describe the particle rearrangement and the density homogeneity. The porous distribution is then characterized by image analysis and compared with the mercury porosimetry results.
This study about the textural parameters evolution of the compacts leads to bring an understanding about the phenomenon during the compression stage. The optimization of the compression and mixture parameters, as amount of water or cement in the mixture or compression pressure, led us to get compacts with improving properties. The compression stage and the density of compacts will be improved by another stage including vertical vibrations of the granular bed. The vibrations stage will be optimized studying several vibrational parameters as the duration, the amplitude and the frequency of the vibrations. The optimization of this vibrational stage will follow to get compacts with even better properties than the ones produced with only the compaction stage.