The present invention relates to a method for electrolytic production and refining of metals having a melting point above about 1000° C., particularly silicon, where there is provided a first electrolytic cell having an upper molten electrolyte layer of a first electrolyte, a lower molten alloy layer of an alloy of the metal to be refined and at least one metal more noble than the metal to be refined. The lower alloy layer is the cathode in the first cell and an anode is positioned in the upper molten electrolyte layer. A second electrolytic cell is also provided with an upper molten metal layer of the same metal as the metal to be refined, said layer constituting a cathode, a lower molten alloy layer, said lower layer constituting an anode, said alloy having a higher density than the metal to be refined, and an intermediate molten electrolyte layer having a density between the density of the upper and lower molten layers. Both electrolytes are oxide based electrolytes containing oxide of the metal to be refined, and the electrolyte is in molten state and has a melting point below the operating temperature of the process. Raw material comprising an oxide of the metal to be refined is added to the first cell and direct electric current is passed through the anode to the cathode such that the metal to be refined is moved from the anode and deposited in molten state at the cathode. The two cells can be operated in two separate steps. One to produce an alloy and the other to refine metal from the alloy.
Description
SHORT DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic view of the refining method according to the invention;
FIG. 2 shows a schematic view of the method for making the alloy and refining the metal according to the invention; and
FIG. 3 shows a schematic of a method for producing the alloy.
Claims
1. A method for producing and refining a metal in an electrolytic method characterized in that:
providing to a first electrolytic cell an upper molten electrolyte layer comprising a first oxide-based electrolyte containing an oxide of the metal to be refined, wherein the first electrolyte is in a molten state and has a melting point below the operating temperature of the process, an anode positioned in the upper molten electrolytic layer, and a lower molten alloy layer comprising an alloy of the metal to be refined and at least one metal more noble than the metal to be refined, said alloy constituting a cathode in the first electrolytic cell, said first electrolytic cell having a density less than the density of the alloy;adding a raw material to said upper molten electrolyte layer, the raw material comprising a metal oxide of the metal to be refined;passing a direct current through the anode to the cathode for reducing the metal oxide to produce an alloy having a higher concentration of the metal to be refined;transferring the alloy of the lower molten alloy layer of the first electrolytic cell to a second electrolytic cell so as to provide a lower molten alloy layer comprising the alloy to the second electrolytic cell, said alloy constituting an anode in the second electrolytic cell;providing to the second electrolytic cell an upper molten metal layer comprising a metal of the same metal as the metal to be refined, said upper molten metal layer constituting a cathode, and an intermediate molten electrolyte layer comprising a second oxide-based electrolyte containing an oxide of the metal to be refined, where the second electrolyte is in a molten state and has a melting point below the operating temperature of the process, said second electrolyte having a density between the density of the upper molten metal layer and lower molten alloy layer; andpassing a direct electric current through the anode to the cathode of the second electrolytic cell whereby the metal to be refined moves from anode alloy to the upper molten metal layer.
2. The method of claim 1 wherein the first cell and the second cell are separate vessels that are in fluid communication by a pipe.
3. The method of claim 1 wherein the first cell and the second cell are in the same vessel and are separated by a wall and are in fluid communication through a space under the wall.
4. The method of claim 1 wherein the metal to be refined is silicon, titanium or scandium.
5. The method of claim 1 wherein the first and second electrolyte are the same.
6. The method of claim 1 wherein the metal more noble than the metal to be refined is copper, iron or silver.
7. Method according to claim 1, characterized in that the lower molten alloy layer comprises an alloy of the metal to be refined and at least one metal more noble than the metal to be refined, has a melting point below the melting point of the metal to be refined.
8. Method according to claim 5, characterized in that the oxide-based electrolyte contains up to 20 wt. % of a halide.
9. Method according to claim 8, characterized in that the oxide-based electrolyte contains up to 7 wt. % of a halide.
10. Method according to claim 5 for refining of silicon, characterized in that the oxide-based electrolyte is the CaO—SiO2.
11. Method according to claim 10, characterized in that the oxide-based electrolytes contains 40-75 wt. % SiO2.
12. Method according to claim 1, characterized in that the oxide-based electrolyte is selected among CaO—Al2O3—SiO2 containing up to 50 wt % Al2O3, BaO—SiO2, BaO—TiO2—SiO2, CaO—TiO2—SiO2, MgO—TiO2—SiO2, Al2O3—CaO—MgO—SiO2, Al2O3—CaO—SiO2—TiO2 containing up to 40 wt % MgO and CaO—MgO—SiO2—TiO2.
13. Method according to claim 12, characterized in that the oxide-based electrolyte is BaO—SiO2 containing 25-60 wt % SiO2.
14. Method according to claim 12, characterized in that the oxide-based electrolyte contains about 10-50 wt % BaO, about 10-50 wt % TiO2 and about 10-50 wt % SiO2.
15. Method according to claim 12, characterized in that the oxide-based electrolyte contains about 10-50 wt % CaO, about 10-50% TiO2 and about 10-50% SiO2.
16. Method according to claim 12, characterized in that the oxide-based electrolyte contains about 10-50 wt % MgO, about 10-50 wt % TiO2 and about 10-50 wt % SiO2.
17. Method according to claim 1, characterized in that the anode alloy is a Cu—Si alloy.
18. Method according to claim 1, characterized in that the anode alloy is a ferrosilicon alloy.
19. Method according to claim 1, characterized in that the anode alloy is a Cu—Fe—Si alloy.
20. A method for electrolytic refining of metals having a melting point above about 1000° C., particularly silicon, characterized in that providing an upper molten metal layer comprising a metal of the same metal as the metal to be refined, said upper molten metal layer constituting a cathode, a lower molten alloy layer comprising an alloy of the metal to be refined and at least one metal more noble than the metal to be refined, said lower molten alloy layer constituting an anode, said alloy having a higher density than the metal to be refined, and an intermediate molten electrolyte layer comprising a second oxide-based electrolyte containing an oxide of the metal to be refined, where the first electrolyte is in molten state and has a melting point below the operating temperature of the process, said second electrolyte having a density between the density of the upper molten metal layer and lower molten alloy layer; and passing a direct electric current from the anode through the electrolyte to the cathode whereby the metal to be refined is moved from the anode and deposited in molten state at the cathode.
21. Method according to claim 20, characterized in that the metal to be refined is silicon, titanium or scandium.
22. Method according to claim 20, characterized in that the lower molten alloy layer comprises an alloy of an alloy of the metal to be refined and at least one metal more noble than the metal to be refined, has a melting point below the melting point of the metal to be refined.
23. Method according to claim 20, characterized in that the oxide-based electrolyte contains up to 20 wt % of a halide.
24. Method according to claim 23, characterized in that the oxide-based electrolyte contains up to 7 wt % of a halide.
25. Method according to claim 20, characterized in that the oxide-based electrolyte is the CaO—SiO2.
26. Method according to claim 25, characterized in that the first oxide-based electrolyte contains 40-75 wt % SiO2.
27. Method according to claim 20 for refining of silicon, characterized in that the oxide-based electrolyte is selected among CaO—Al2O3—SiO2 containing up to 50 wt % Al2O3, BaO—SiO2, BaO—TiO2—SiO2, CaO—TiO2—SiO2, MgO—TiO2—SiO2, Al2O3—CaO—MgO—SiO2, Al2O3—CaO—SiO2—TiO2 containing up to 40 wt % MgO and CaO—MgO—SiO2—TiO2.
28. Method according to claim 27, characterized in that the oxide-based electrolyte is BaO—SiO2 containing 25-60 wt % SiO2.
29. Method according to claim 27, characterized in that the oxide-based electrolyte contains about 10-50 wt % BaO, about 10-50 wt % TiO2 and about 10-50 wt % SiO2.
30. Method according to claim 27, characterized in that the oxide-based electrolyte contains about 10-50 wt % CaO, about 10-50% TiO2 and about 10-50% SiO2.
31. Method according to claim 27, characterized in that the oxide-based electrolyte contains about 10-50 wt % MgO, about 10-50 wt % TiO2 and about 10-50 wt % SiO2.
32. Method according to claim 20, characterized in that the anode alloy is a Cu—Si alloy.
33. Method according to claim 20, characterized in that the anode alloy is a ferrosilicon alloy.
34. Method according to claim 20, characterized in that the anode alloy is a Cu—Fe—Si alloy.
35. A method to electrolytically produce an alloy comprising a first and second metal characterized in that:
providing to a first electrolytic cell, an upper molten electrolyte layer comprising a first oxide-based electrolyte containing an oxide of the first metal wherein the first electrolyte is in a molten state and has a melting point below the operating temperature of the process, an anode positioned in the upper molten electrolytic layer, and a lower molten alloy layer comprising an alloy of the first metal and the second metal wherein the second metal is more noble than the metal to be refined, said alloy constituting a cathode in the first electrolytic cell, said first electrolyte having a density less than the density of the alloy;adding a raw material to said upper molten electrolyte layer, the raw material comprising a metal oxide of the first metal; andpassing a direct current from the anode to the cathode alloy to in the first electrolytic cell to produce an alloy having a higher concentration of the first metal.
36. Method according to claim 35, characterized in that the metal to be refined is silicon, titanium or scandium.
37. Method according to claim 35, characterized in that the lower molten alloy layer comprises an alloy of an alloy of the metal to be refined and at least one metal more noble than the metal to be refined, has a melting point below the melting point of the metal to be refined.
38. Method according to claim 35, characterized in that the oxide-based electrolyte contains up to 20 wt % of a halide.
39. Method according to claim 38, characterized in that the oxide-based electrolyte contains up to 7 wt % of a halide.
40. Method according to claim 35, characterized in that the oxide-based electrolyte is the CaO—SiO2.
41. Method according to claim 40, characterized in that the first oxide-based electrolyte contains 40-75 wt % SiO2.
42. Method according to claim 35 for refining of silicon, characterized in that the oxide-based electrolyte is selected among CaO-Al2O3-SiO2 containing up to 50 wt % Al2O3, BaO—SiO2, BaO—TiO2—SiO2, CaO—TiO2—SiO2, MgO—TiO2—SiO2, Al2O3—CaO—MgO—SiO2, Al2O3—CaO—SiO2—TiO2 containing up to 40 wt % MgO and CaO—MgO—SiO2—TiO2.
43. Method according to claim 35 characterized in that the alloy is a Cu—Si alloy.
44. Method according to claim 35 characterized in that the alloy is a ferrosilicon alloy.
Patent Application
20070215483
