Influence des conditions d'agglomération sur la morphologie de la gibbsite et les propriétés d'usage de l'alumine

Abstract : The improvement of the solidity of alumina which is produced for aluminium refinery and the reduction of fine particles generation which result of shocks during calcination and transport are essential points for the Bayer producers. The aim of this study is to link the gibbsite precipitation conditions to the morphology of the crystals and to verity their impact on alumina solidity. Analysis on industrial and lab-made products was done. We have focused our attention on the role of the agglomeration step. The experimental procedure was chosen to be as close as possible to the industrial process. Gibbsite morphology was quantified by using three visualization methods (optical microscopy with different immersion liquids, scanning electron microscopy on free powder and on polished section) and a setof different shape parameters. Five shape parameters quantify the two-dimensional shape of the crystals from the point of view of their roughness, elongation and concavity. Principal component analysis have enabled an information simplification for a better precision of the results and a better interpretation. The scanning electron microscope on free powder enables the tacet network visualization. Pseudo three dimensional parameters were calculated to describe the tacet network. On polished section, the crystal frames are weil defined and enable the sizing of the crystal sides related to the tacet sides. Alumina solidity was evaluated with a standardized fluidized bed and two indices. The attrition index quantifies the proportion of particles of size less than 45 1-1m which have been created du ring the test. The breakage index quantifies the evolution of the size distribution after the test
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http://docnum.univ-lorraine.fr/prive/INPL_T_2003_PLAGNIEUX_V.pdf
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Submitted on : Thursday, March 29, 2018 - 1:38:43 PM
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Virginie Plagnieux. Influence des conditions d'agglomération sur la morphologie de la gibbsite et les propriétés d'usage de l'alumine. Autre. Institut National Polytechnique de Lorraine, 2003. Français. ⟨NNT : 2003INPL088N⟩. ⟨tel-01752217⟩

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