Claims
- 1. A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising the steps of:(a) providing a molten salt electrolyte consisting essentially of fluoride salts at a temperature of less than 900° C. having alumina dissolved therein in an electrolytic cell, said electrolyte having a surface, said cell having a liner for containing said electrolyte, said liner having a bottom and walls extending upwardly from said bottom; (b) providing a plurality of anode plates and cathode plates having planar surfaces disposed in a vertical orientation in said electrolyte, said anode plates and cathode plates arranged in alternating relationship to provide anode planar surfaces disposed opposite cathode planar surfaces to define a region therebetween, the cathode plates comprised of material substantially inert to molten aluminum the anode plates comprised of carbon; and (c) passing electrical current through said anode plates and through said electrolyte to said cathode plates, depositing aluminum at said cathode plates and forming a carbon-containing gas at said anode plates, said cell having a decomposition voltage for alumina in the range of 1.63 to 1.73 volts.
- 2. The method in accordance with claim 1 including maintaining said electrolyte in a temperature range of about 660° to 800° C.
- 3. The method in accordance with claim 1 wherein said electrolyte has a melting point in the range of 715° to 800° C.
- 4. The method in accordance with claim 1 including passing an electric current through said cell at a current density in the range of 0.1 to 1.5 A/cm2.
- 5. The method in accordance with claim 1 wherein said cathode plates are selected from the group consisting of titanium diboride, zirconium diboride, titanium carbide, zirconium carbide, molybdenum, and titanium and tungsten alloys.
- 6. The method in accordance with claim 1 including adding alumina to said cell on a substantially continuous basis.
- 7. The method in accordance with claim 1 wherein said electrolyte is comprised of one or more alkali metal fluorides.
- 8. The method in accordance with claim 1 wherein said electrolyte is comprised of one or more alkali metal fluorides and aluminum fluoride.
- 9. The method in accordance with claim 1 including maintaining alumina in said electrolyte in a range of 3.5 to 5.0 wt. %.
- 10. The method in accordance with claim 1 including operating said cell without a frozen crust.
- 11. The method in accordance with claim 1 including thermally insulating said cell sufficiently to avoid formation of frozen electrolyte on cell walls or formation of frozen electrolyte on said surface.
- 12. A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte, the method comprising the steps of:(a) providing a molten salt electrolyte at a temperature in the range of 660° to 800° C. having alumina dissolved therein in an electrolytic cell, said electrolyte having a surface, said cell having a liner for containing said electrolyte, said liner having a bottom and walls extending upwardly from said bottom, said cell having a decomposition value for alumina of less than 2 volts; (b) providing a plurality of anode plates and cathode plates having planar surfaces disposed in a vertical orientation in said electrolyte, said anodes and cathodes arranged in alternating relationship to provide anode planar surfaces disposed opposite cathode planar surfaces to define a region therebetween, the anodes comprised of carbon and having apertures through said anode planar surfaces to promote flow of alumina-enriched electrolyte to said region between said anode and cathode planar surfaces; and (c) passing electrical current through said anodes and through said electrolyte to said cathodes, depositing aluminum at said cathodes and forming a carbon-containing gas at said anodes at a current density in the range of 0.1 to 1.5 A/cm2, said cell having a decomposition voltage for alumina in the range of 1.63 to 1.73 volts.
- 13. The method in accordance with claim 12 wherein said electrolyte has a melting point in the range of 715° to 800° C.
- 14. The method in accordance with claim 12 wherein said cathodes are selected from the group consisting of titanium diboride, zirconium diboride, titanium carbide, zirconium carbide, molybdenum, and titanium and tungsten alloys.
- 15. The method in accordance with claim 12 including adding alumina to said cell on a substantially continuous basis.
- 16. The method in accordance with claim 12 wherein said electrolyte is comprised of one or more alkali metal fluorides.
- 17. The method in accordance with claim 12 wherein said electrolyte is comprised of one or more alkali metal fluorides and aluminum fluoride.
- 18. The method in accordance with claim 12 including operating said cell without a frozen crust.
- 19. The method in accordance with claim 12 including thermally insulating said cell sufficiently to avoid formation of frozen electrolyte on cell walls or formation of frozen electrolyte on said surface.
- 20. In a method of producing aluminum in an electrolytic cell containing alumina dissolved in a fluoride salt electrolyte wherein the cell is free of a frozen electrolyte crust, the electrolyte having alumina dissolved therein, and alumina add to the electrolyte on a continuous basis to provide alumina-enriched electrolyte, and wherein a plurality of anode plates and cathode plates are disposed in a vertical direction and in alternating relationship in said electrolyte, said cathodes having a flat surface, the method comprising:(a) providing carbon anodes having a planar surface disposed opposite the flat surface of the cathode to define a region between the cathode flat surface and the planar surface of the anode, said anodes having apertures through said anode planar surfaces to promote flow of alumina-enriched electrolyte to said region between said anode and cathode planar surfaces and; (b) passing electrical current through said anodes and through said electrolyte to said cathodes, depositing aluminum at said cathodes and producing carbon-containing gas at said anodes, said cell having a decomposition voltage for alumina in the range of 1.63 to 1.73 volts.
- 21. The method in accordance with claim 20 wherein said electrolyte is comprised of one or more alkali metal fluorides.
- 22. The method in accordance with claim 20 wherein said electrolyte is comprised of one or more alkali metal fluorides and aluminum fluoride.
- 23. The method in accordance with claim 20 including maintaining said electrolyte in a temperature range of about 660° to 800° C.
- 24. The method in accordance with claim 20 wherein said electrolyte has a melting point in the range of 715° to 800° C.
- 25. The method in accordance with claim 20 including passing an electric current through said cell at a current density in the range of 0.1 to 1.5 A/cm2.
- 26. The method in accordance with claim 20 wherein said cathodes are comprised of a material selected from the group consisting of titanium diboride, zirconium diboride, titanium carbide, zirconium carbide, molybdenum, and titanium and tungsten alloys.
Government Interests
The government has rights in this invention pursuant to Contract No. DE-FC07-98ID13662 awarded by the Department of Energy.
US Referenced Citations (14)