Method for purifying silicon
View Patent ↗The present invention provides for methods of purifying silicon, methods for obtaining purified silicon, as well as methods for obtaining purified silicon crystals, purified granulized silicon and/or purified silicon ingots.
1. A method for purifying silicon to solar-grade purity, the method comprising:
(a) forming a first molten liquid from silicon and a solvent metal selected from the group of copper, tin, zinc, antimony, silver, bismuth, aluminum, cadmium, gallium, indium, magnesium, lead, an alloy thereof, and combinations thereof;
(b) contacting the first molten liquid with a first gas, to provide a second molten liquid;
(c) cooling the second molten liquid to form first silicon crystals and a first mother liquid;
(d) separating the first silicon crystals and the first mother liquid;
(e) heating the first silicon crystals to form a first molten bath;
(f) directionally solidifying the first molten bath to form second silicon crystals and a second mother liquor;
(g) separating the second silicon crystals and the second mother liquor;
(h) heating the second silicon crystals to provide a second molten bath;
(i) directionally solidifying the second molten bath below the melting point, thereby forming a third silicon crystals, and separating the upper portion and the lower portion; wherein the upper portion comprises a third mother liquor and the lower portion comprises a third silicon.
2. The method of claim 1 , wherein in step (a), the first molten liquid is formed by heating above the liquidus temperature.
3. The method of claim 1 , wherein in step (b), a rotary degasser creates a vortex.
4. The method of claim 1 , wherein at least one of steps (a)-(d) is carried out multiple times.
5. The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out step (e).
6. The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(i), and the first mother liquid obtained in step (d) comprises the solvent metal in step (a) of a prior sequence of steps (a)-(d).
7. The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(i), and the first silicon crystals obtained in step (d) comprise the silicon in step (a) of a subsequent sequence of steps (a)-(d).
8. A method of manufacturing solar cells, the method comprising making solar cells that comprise the third silicon of claim 1 .
9. A method for purifying silicon to solar-grade purity, the method comprising:
(a) forming a first molten liquid from silicon and a solvent metal selected from the group of copper, tin, zinc, antimony, silver, bismuth, aluminum, cadmium, gallium, indium, magnesium, lead, an alloy thereof, and combinations thereof;
(b) contacting the first molten liquid with a first gas, to provide a second molten liquid;
(c) cooling the second molten liquid to form first silicon crystals and a first mother liquid;
(d) separating the first silicon crystals and the first mother liquid;
(e) heating the first silicon crystals to form a first molten bath;
(f) directionally solidifying the first molten bath to form second silicon crystals and a second mother liquor;
(g) separating the second silicon crystals and the second mother liquor;
(h) heating the second silicon crystals to provide a second molten bath;
(i) contacting the second molten bath with a second gas to provide a slag that forms on the surface of a third molten bath; and,
(j) separating the slag and the third molten bath.
10. The method of claim 9 , wherein in step (a), the first molten liquid is formed by heating above the liquidus temperature.
11. The method of claim 9 , after steps (a)-(j) further comprising:
(k) heating the second silicon crystals to provide a second molten bath;
(l) contacting the second molten bath with a second gas to provide a slag that forms on the surface of a third molten bath; and,
(m) separating the slag and the third molten bath.
12. The method of claim 11 , after step (m) further comprising:
(n) cooling the third molten bath to form silicon ingots.
13. The method of claim 11 , after step (m) further comprising:
(n) contacting the third molten bath with water to form granulized silicon.
14. The method of claim 11 , after step (m) further comprising:
(n) introducing the third molten bath into a mold and cooling the third molten bath to form a second silicon.
15. The method of claim 11 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(j), and the first mother liquid obtained in step (d) comprises the solvent metal in step (a) of a prior sequence of steps (a)-(d).
16. The method of claim 11 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(j), and the first silicon crystals obtained in step (d) comprise the silicon in step (a) of a subsequent sequence of steps (a)-(d).
17. The method of claim 9 , wherein in step (b), a vortex is created.
18. The method of claim 9 , wherein at least one of steps (a)-(d) is carried out multiple times.
19. The method of claim 9 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out step (e).
20. A method of manufacturing solar cells, the method comprising making solar cells that comprise the third silicon of claim 9 .