ORGANIC IMPURITY REMOVAL PROCESS FOR BAYER LIQUORS

摘要

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 (10), such as a spent Bayer liquor, is fed to a wet oxidation process (12) to produce a first processed liquor which is depleted in organic compounds, but enriched in sodium carbonate and/or sodium oxalate. The wet-oxidised processed liquor is directed to a leach tank (18) immediately following a dry oxidation process. The dry oxidation process is typically a liquor burner (16). A substantial component of the sodium compounds in a feed slurry to the liquor burner (16) is reacted to produce a processed discharge product. The liquor burner discharge product is directed into the leach tank (18), where it dissolves in the processed liquor from the wet oxidation process (12). The resultant increase in the leach tank solutions ionic strength causes the sodium carbonate and sodium oxalate to become supersaturated, so that they precipitate from the leach tank liquor. The precipitated sodium carbonate and/or sodium oxalate are separated (20) from the leach tank liquor and recycled in a mix tank (14) providing the feed slurry to the liquor burner (16). When the wet and dry oxidation processes are combined in this way, the combined system is capable of destroying and fully causticising twice the amount of TOC as the liquor burner alone.