Electrolytic cell

Patent metadata

Field	Value
Publication number	US-9932681-B2
Application number	US-201314373170-A
Country	US
Kind code	B2
Filing date	Jan 18, 2013
Priority date	Jan 20, 2012
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

The present disclosure relates to an electrolytic cell for the production of aluminium by reducing alumina. The cell may comprise a sidewall including at least one side block. The side block may comprise an aluminous material having an apparent porosity of less than about 10% and a composition, as a weight percentage on the basis of the aluminous material and for a total of about 100%, such that: Al2O3>about 50%, beta-alumina being less than about 20% of the weight of the aluminous material, oxides that are less reducible than alumina at 1000° C.<about 50%, Na2O<about 3.9%, and other components<about 5%.

First claim

The invention claimed is:

1. An electrolytic cell for the production of aluminum by reduction of alumina, said cell containing an electrolyte bath and having a side wall that comprises at least one side block, said side block comprising an aluminous material having
an open porosity of less than 10%, and
a composition, as a weight percentage on the basis of the aluminous material and for a total of 100%, such that:
Al 2 O 3 >50%, beta-alumina representing less than 20% of the weight of the aluminous material,
oxides that are less reducible than alumina at 1000° C.: <46%,
Na 2 O <3.9%,
other constituents <2%,
said composition of the aluminous material being such that: Al 2 O 3 +MgO +CaO >95%.

2. The cell as claimed in claim 1 , the electrolyte bath comprising AlF 3 and at least one alkali metal fluoride NaF or KF at an (NaF+KF)/AlF 3 molar ratio of less than 3.

3. The cell as claimed in claim 1 , the electrolyte bath comprising a molar content of AlF 3 of greater than 30%.

4. The cell as claimed in claim 1 , the electrolyte bath comprising a molar content of AlF 3 of greater than 37%.

5. The cell as claimed in claim 1 , said side block having a minimum thickness of greater than 40 mm.

6. The cell as claimed in claim 1 , said side block having a total porosity of less than 5%.

7. The cell as claimed in claim 1 , a content of oxides that are less reducible than alumina at 1000° C. being less than 10%.

8. The cell as claimed in claim 1 , a content of oxides that are less reducible than alumina at 1000° C. being less than 5%.

9. The cell as claimed in claim 1 , said composition of the aluminous material being such that: SiO 2 <1.5%.

10. The cell as claimed in claim 1 , the aluminous material comprising at least a corundum and/or magnesium spinel crystalline phase and/or a hibonite (CaO.6Al 2 O 3 ) phase.

11. The cell as claimed in claim 1 , said composition of the aluminous material being such that: Al 2 O 3 >92%.

12. The cell as claimed in claim 1 , the composition of the aluminous material being such that: Na 2 O <3%.

13. The cell as claimed in claim 1 , said composition of the aluminous material being such that: Na 2 O <1%.

14. The cell as claimed in claim 13 , said composition of the aluminous material being such that: Na 2 O <0.1%.

15. The cell as claimed in claim 1 , a thermal conductivity of the aluminous material at 600° C. being less than 10 W/m·K.

16. The cell as claimed in claim 1 , an electrical resistivity of the aluminous material at 700° C. being greater than 2000 ohm·cm.

17. The cell as claimed in claim 1 , the electrolyte bath being a cryolite bath or a potassium bath.

18. The cell as claimed in claim 1 , a temperature of the electrolyte bath being below 950° C. and/or above 800° C.

19. The cell as claimed in claim 1 , a total content of other constituents being less than 4.5%.

20. The cell as claimed in claim 1 , said side block being obtained by a fusion process or by a sintering process comprising a compaction step and/or comprising a sintering step at a temperature above or equal to 1300° C.

21. The cell as claimed in claim 1 , said side block being in contact with the electrolyte bath.

22. The cell as claimed in claim 1 , comprising an insulating material placed so as to limit heat losses through said side block.

23. A process for producing aluminum by passing an electric current into the electrolyte bath of a cell as claimed in claim 1 .

24. The process as claimed in claim 23 , wherein, under steady-state operation, the aluminous material is in contact with the electrolyte bath.

25. The process as claimed in claim 23 , wherein, under steady-state operation, the electrolyte bath is at a temperature below 950° C.

26. The process as claimed in claim 23 , wherein the electrolyte bath is passed through by an electric current having an intensity of greater than 100 kA.

27. A process for purifying aluminum by passing an electric current into an electrolyte bath by means of a cell as claimed in claim 1 .

28. An electrolytic cell for the production of aluminum by reduction of alumina, said cell containing an electrolyte bath and having a side wall that comprises at least one side block, said side block comprising an aluminous material having
an open porosity of less than 10%, and
a composition, as a weight percentage on the basis of the aluminous material and for a total of 100%, such that:
Al 2 O 3 >50%, beta alumina representing less than 20% of the weight of the aluminous material,
oxides that are less reducible than alumina at 1000° C.: <46%,
Na 2 O <3.9%,
other constituents <5%,

wherein MgO >28%.

29. The cell as claimed in claim 28 , said side block having a total porosity of less than 5%.

30. The cell as claimed in claim 28 , a content of oxides that are less reducible than alumina at 1000° C. being less than 10%.

31. The cell as claimed in claim 28 , a content of oxides that are less reducible than alumina at 1000° C. being less than 5%.

32. The cell as claimed in claim 28 , said composition of the aluminous material being such that: SiO 2 <1.5%.

33. The cell as claimed in claim 28 , the aluminous material comprising at least a corundum and/or magnesium spinel crystalline phase and/or a hibonite (CaO.6Al 2 O 3 ) phase.

34. The cell as claimed in claim 28 , the composition of the aluminous material being such that: Na 2 O <3%.

35. The cell as claimed in claim 28 , said composition of the aluminous material being such that: Na 2 O <1%.

36. The cell as claimed in claim 28 , said composition of the aluminous material being such that: Na 2 O <0.1%.

37. An electrolytic cell for the production of aluminum by reduction of alumina, said cell containing an electrolyte bath and having a side wall that comprises at least one side block, said side block comprising an aluminous material having
an open porosity of less than 10%, and
a composition, as a weight percentage on the basis of the aluminous material and for a total of 100%, such that:
Al 2 O 3 >50%, beta alumina representing less than 20% of the weight of the aluminous material,
oxides that are less reducible than alumina at 1000° C.: <46%,
Na 2 O <3.9%,
other constituents <5%,

wherein CaO >1%.

38. The cell as claimed in claim 37 , said side block having a total porosity of less than 5%.

39. The cell as claimed in claim 37 , a content of oxides that are less reducible than alumina at 1000° C. being less than 10%.

40. The cell as claimed in claim 37 , a content of oxides that are less reducible than alumina at 1000° C. being less than 5%.

41. The cell as claimed in claim 37 , said composition of the aluminous material being such that: SiO 2 <1.5%.

42. The cell as claimed in claim 37 , the aluminous material comprising at least a corundum and/or magnesium spinel crystalline phase and/or a hibonite (CaO.6Al 2 O 3 ) phase.

43. The cell as claimed in claim 37 , the composition of the aluminous material being such that: Na 2 O <3%.

44. The cell as claimed in claim 37 , said composition of the aluminous material being such that: Na 2 O <1%.

Assignees

• Saint Gobain Centre De Rech Et Detudes European
• Saint Gobain Ct Recherches

Inventors

• Jorge Eric
• Francy Olivier
• Panagiotis Olivier

Classifications

• C25C3/18

  Electrolytes · CPC title

• C04B2235/3293

  Tin oxides, stannates or oxide forming salts thereof, e.g. indium tin oxide [ITO] · CPC title

• C04B2235/3241

  Chromium oxides, chromates, or oxide-forming salts thereof · CPC title

• C04B35/63488

  Polyethers, e.g. alkylphenol polyglycolether, polyethylene glycol [PEG], polyethylene oxide [PEO] · CPC title

• C04B2235/3232

  Titanium oxides or titanates, e.g. rutile or anatase · CPC title