Aluminium Pechiney

Gerard Pignol

Jean-Marc Rousseaux

Yves Magnan

A process for the production of alumina trihydrate by alkaline digestion of bauxite using the Bayer process in which aluminate liquor and insoluble residues are separated using a solid/liquid separation device (E; W; DC) characterised in that the said slurry (') is at least partially passed through a hydrocyclone (H; H; H; H) to improve and accelerate the separation of the sodium aluminate liquor from the insoluble residues in the slurry (&#x2032;) containing the said liquor and the said residues and that supplies or is derived from the said liquid-solid separation device. In a first embodiment, at least one hydrocyclone is used at the upstream side of the settler-thickener, as clarifier of the pregnant liquor. In a second embodiment, at least one hydrocyclone is used as a thickener of insoluble residue mud. In a third embodiment, a hydrocyclone is used in combination with the causticisation settler.

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Gardanne, France

Gerard Pignol