Bayer process

Patent metadata

Field	Value
Publication number	US-12006225-B2
Application number	US-201916971379-A
Country	US
Kind code	B2
Filing date	Feb 22, 2019
Priority date	Feb 23, 2018
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

A Bayer process increases oxalate removal in the red side of the Bayer process and at least substantially minimises, for example by at least substantially suppressing, precipitation of oxalates in the white side of the Bayer process.

First claim

The invention claimed is:

1. A Bayer process for dissolving alumina contained in bauxite comprising controlling the concentration of oxalates in solution in Bayer liquor in a red side of the process to be as high as possible to drive oxalate removal from Bayer liquor in the red side of the process without resulting in oxalate precipitation in a precipitation step in a white side of the process, the process including: adding a reagent that has oxalate modifying properties to Bayer liquor to minimize oxalate precipitation in the precipitation step, controlling a bauxite reactive silica concentration in Bayer liquor to facilitate removal of oxalates from solution in Bayer liquor in the red side of the process in accordance with a relationship that the concentration of oxalate in solution in Bayer liquor decreases as the bauxite reactive silica concentration increases, and adding Bayer liquor to bauxite on the red side of the process to increase the oxalate concentration in solution in Bayer liquor resulting from digestion of bauxite in the red side of the process, with the increased oxalate in solution driving removal of oxalate as a desilication product (DSP) on the red side of the process.

2. The process defined in claim 1 including heating a slurry produced in the process and causing chemical dissolution of alumina contained in bauxite, thereby causing formation of additional oxalate by decomposition of organic material in bauxite.

3. The process defined in claim 2 further including holding the slurry at a temperature and for a time and forming the DSP that incorporates at least as much oxalate as the increased oxalate.

4. The process defined in claim 3 further including cooling the resultant slurry to a temperature at which solid/liquid separation can be conducted and separating solids and liquor.

5. The process defined in claim 4 further including washing separated solids and disposing of the oxalate-containing desilication product with the solids.

6. The process defined in claim 1 including controlling the concentration of oxalates in solution in Bayer liquor on the white side to be super-saturated.

7. The process defined in claim 1 wherein the reagent is a carboxylic acid.

8. The process defined in claim 1 wherein the reagent is a quaternary ammonium compound.

9. The process defined in claim 1 wherein the reagent is a crystal growth modifier.

10. The process defined in claim 1 including removing oxalates from solution in Bayer liquor in the red side of the process by absorbing oxalates onto bauxite residues produced in the red side of the process and separated from Bayer liquor in the red side of the process.

11. The process defined in claim 1 including controlling the bauxite reactive silica concentration in Bayer liquor to be below a maximum concentration.

12. The process defined in claim 1 including increasing oxalate concentration in Bayer liquor by stopping altogether oxalate precipitation in the precipitation step of the process.

13. The process defined in claim 1 including increasing oxalate concentration in solution in Bayer liquor by stopping altogether oxalate removal in the white side of the process.

14. The process defined in claim 1 including adding additional silica to Bayer liquor to further facilitate removal of oxalate as the desilication product (DSP), on the red side of the process.

15. A Bayer process for dissolving alumina contained in bauxite comprising controlling the concentration of oxalates in solution in Bayer liquor in a red side of the process to be as high as possible to drive oxalate removal from Bayer liquor in the red side of the process without resulting in oxalate precipitation in a precipitation step in a white side of the process, the process including: adding a reagent to Bayer liquor to minimize oxalate precipitation in the precipitation step in the white side of the process, controlling a bauxite reactive silica concentration in Bayer liquor to facilitate removal of oxalates from solution in Bayer liquor in the red side of the process, controlling and removing oxalates from solution in Bayer liquor in the red side of the process by absorbing oxalates into bauxite residues produced in the red side of the process and separated from Bayer liquor in the red side of the process.

Assignees

• Rio Tinto Alcan Int Ltd

Inventors

• Hofstee Neil
• Gillespie Alistair
• Mach Tomas
• Staker Warren

Classifications

• B01J20/16

  Alumino-silicates (B01J20/12 takes precedence) · CPC title

• C01F7/473 Primary

  Removal of organic compounds, e.g. sodium oxalate · CPC title

• C01F7/147

  Apparatus for precipitation · CPC title

• C01F7/145 Primary

  characterised by the use of a crystal growth modifying agent other than aluminium hydroxide seed · CPC title

• B01J2220/4887

  Residues, wastes, e.g. garbage, municipal or industrial sludges, compost, animal manure; fly-ashes · CPC title