US 6,555,077 B1Granted

Organic impurity removal process for bayer liquors

AssigneeWorsley Alumina Pty. Ltd.

InventorsSteven Philip Rosenberg, Wayne Tichbon, Steven James Healy

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Abstract

A process for the removal of organic impurities in a Bayer process liquor in which wet and dry oxidation processes are linked together in a complementary way, such that the weaknesses of each individual organic removal process become a strength of the combined process. An organics-rich liquor stream is fed to a wet oxidation process to produce a first processed liquor which is depleted in organic compounds, but enriched in sodium carbonate and/or sodium oxalate. A feed slurry is fed to the dry oxidation process, typically including a liquor burner, where sodium compounds react to produce a discharge product. The first processed liquor and discharge product are directed into a leach tank, resulting in the formation of precipitated products including sodium carbonate and/or sodium oxalate. The precipitated products are separated from the leach tank and recycled in a mix tank providing the feed slurry to the liquor burner.

Claims10

Dependent claims

A process for the removal of organic impurities from a Bayer process liquor, comprising:

feeding a first liquor stream including organic impurities to a wet oxidation process to produce a first processed liquor which is depleted in organic compounds, but enriched with sodium carbonate and/or sodium oxalate;
reacting sodium compounds with at least one of an aluminum oxide, an aluminum hydroxide, an iron oxide and an iron hydroxide in a feed slurry fed to a dry oxidation process, wherein at least part of the sodium compounds react in the dry oxidation process to produce a processed discharge product;
feeding at least a first portion of the first processed liquor to a leach tank to which is added the processed discharge product from the dry oxidation process, wherein the sodium carbonate and/or sodium oxalate precipitate in the leach tank to form precipitated products;
and
separating the precipitated products from the leach tank and recycling the precipitated products to form at least part of the feed slurry fed to the dry oxidation process;
wherein organic impurities in the first liquor stream and residual organic impurities remaining in the first processed liquor or in the recycled precipitated products are causticised to sodium aluminate or sodium ferrate in the dry oxidation process.

3 more elements

Dependencies are inferred from the claim text.