Claims
- 1. A method for purifying silicon comprising heating molten silicon in a container and providing controllable amounts of oxygen gas and hydrogen gas to the molten silicon.
- 2. The method of claim 1, further comprising introducing an additional inert gas into the molten silicon.
- 3. The method of claim 1, wherein the providing is performed with a gas lance submerged in the molten silicon.
- 4. The method of claim 1, wherein the providing is performed with a gas lance over the molten silicon.
- 5. The method of claim 1, further comprising introducing water vapor into the molten silicon.
- 6. The method of claim 1, further comprising introducing silica powder into the molten silicon.
- 7. The method of claim 6, further comprising introducing inert gas and water vapor into the molten silicon, wherein the purification of the silicon in the molten state is achieved at least in part by chemical reactions with the silica powder and water vapor so that the resultant products are vaporized or trapped in a slag.
- 8. The method of claim 1, wherein the oxygen and hydrogen are provided by a gas lance without a flame.
- 9. The method of claim 1, further comprising directionally solidifying the molten silicon in the container.
- 10. A method for purifying silicon comprising heating molten silicon in a container and using an oxygen-hydrogen torch positioned over the silicon to provide separately controllable amounts of oxygen gas and hydrogen gas.
- 11. The method of claim 10, further comprising introducing inert gas into the molten silicon with the torch.
- 12. The method of claim 11, further comprising introducing water vapor into the molten silicon with the torch.
- 13. The method of claim 10, further comprising introducing a silica powder into the molten silicon.
- 14. The method of claim 13, further comprising introducing inert gas and water vapor into the molten silicon, wherein the purification of the silicon in the molten state is achieved by chemical reactions with the silica powder and water vapor so that the resultant products are vaporized and trapped in a slag.
- 15. The method of claim 13, further comprising introducing an additive with the silica, the additive for making a slag in the molten silicon more basic.
- 16. The method of claim 15, further comprising introducing alumina with the silica and the additive.
- 17. The method of claim 16, wherein a sufficient amount of alumina is introduced to reduce the melting point of the slag with the silica, additive, and alumina to a point that is lower than the melting point of the silicon.
- 18. The method of claim 16, wherein a sufficient amount of alumina is introduced to cause the slag with the silica, additive, and alumina to sink in the molten silicon.
- 19. The method of claim 16, wherein the amount of alumina introduced is such that the slag with the silica, additive, and alumina floats on the molten silicon.
- 20. The method of claim 10, wherein the torch provides oxygen and hydrogen separately without a flame.
- 21. The method of claim 10, further comprising directionally solidifying the molten silicon in the container.
- 22. The method of claims 10, wherein the torch has two passages, one for oxygen gas and one for hydrogen gas.
- 23. A method for purifying molten silicon, the method comprising:maintaining silicon in a molten state; introducing into the molten silicon, a combination including (i) silica, (ii) an additive to make slags move basic, and (iii) alumina.
- 24. The method of claim 23, wherein the additive to make the slag more basic is selected from the group consisting of CaO, BaO, and CaF2.
- 25. The method of claim 23, wherein the additive mixture is provided into the molten silicon to control the acidity, melting point, and density of the slag.
- 26. The method of claim 23, wherein the combination additive mixture is provided into the molten silicon so that the melting point of the slag is less than that of the molten silicon.
- 27. A method for purifying molten silicon, the method comprising maintaining silicon in a molten state, and introducing into the molten silicon an inert gas with a gas lance without an electron beam gun and without creating a plasma jet.
- 28. The method of claim 27, wherein the introducing includes introducing hydrogen.
- 29. The method of claim 27, wherein the introducing includes introducing argon.
- 30. The method of claim 27, wherein the inert gas is introduced without a flame.
- 31. The method of claim 27, wherein the gas lance is submerged in the molten silicon.
- 32. The method of claim 27, wherein the gas lance is over the molten silicon.
- 33. A method for purifying molten silicon, the method comprising:maintaining at least one metric ton of silicon in a molten state; purifying the molten silicon by a combination of stirring, slagging, reaction with moisture, oxidation, evacuation, and reduction; and directionally solidifying the molten silicon.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of PCT/US98/17750, filed Aug. 27, 1998, which is a continuation-in-part of Ser. No. 08/919,898, filed Aug. 28, 1997, now U.S. Pat. No. 5,972,107. These documents are incorporated by reference for all purposes.
US Referenced Citations (10)
Non-Patent Literature Citations (1)
Entry |
Khattak, C. P. et al, Production of Solar-Grade Silicon by Refining of Liquid Metallurgical-Grade Silicon,, Reprint of NREL NCPV AIP Con Proc. 462, pp. 731-736 (1998). |
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
PCT/US98/17750 |
Aug 1998 |
US |
Child |
09/512947 |
|
US |
Parent |
08/919898 |
Aug 1997 |
US |
Child |
PCT/US98/17750 |
|
US |