Production of high purity alumina and/or smelter-grade alumina
AssigneeAndromeda Technologies Holdings Pty Ltd
InventorBryn HARRIS
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Abstract
A method for the recovery of high-grade alumina products (HPA and/or SGA) from an aluminous material feedstock, such as from kaolinite or halloysite. The process includes leaching the calcined material in recycled 18% hydrochloric acid, removal of anionic impurities such as iron and zinc via ion exchange, a novel removal step for magnesium and calcium, pyrohydrolysing the resultant solution, and washing followed by calcining of the crude alumina solids. Optionally, a final purification step is introduced via caustic leaching of the washed solids, followed by hydrolysis to gibbsite.
Claims20
A process for producing alumina from an aluminous material feedstock, the process comprising:
- i. producing an AlCl3 liquor,
- ii. reducing the content of impurities in the AlCl3 liquor by ion exchange or solvent extraction to produce a semi-purified AlCl3 liquor,
- iii. pyrohydrolysing the semi-purified AlCl3 liquor to produce crude alumina solids,
- iv. washing the crude alumina solids to remove non-hydrolysable chlorides and/or residual alkaline earth oxides and bicarbonates and produce washed solids, and
- v. drying and calcining the washed solids to produce alumina.
Dependencies are inferred from the claim text.