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, 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 dross and a second molten liquid and a vortex of the first molten liquid is created, and the vortex is contacted with oxygen (O 2 ) to provide additional dross;
(c) separating the dross and the second molten liquid;
(d) cooling the second molten liquid to form first silicon crystals and a first mother liquid; and
(e) separating the first silicon crystals and the first mother liquid.
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), the first gas is formed by contacting the first molten liquid with a liquid, solid, or combination thereof to effectively evolve the first gas.
4. The method of claim 1 , wherein step (b) is carried out twice, with chlorine (Cl 2 ) and nitrogen (N 2 ); and oxygen (O 2 ) and argon (Ar), respectively.
5. The method of claim 1 , wherein in step (b), a rotary degasser creates the vortex, which mixes the dross in the first molten liquid.
6. The method of claim 1 , wherein the oxygen (O 2 ) is from the atmosphere.
7. The method of claim 1 , wherein in step (b), the dross forms on the surface of the second molten liquid.
8. The method of claim 1 , wherein after step (b) and before step (c), the second molten liquid is heated.
9. The method of claim 1 , wherein after step (b) and before step (c), the second molten liquid is heated above the liquidus temperature.
10. The method of claim 1 , wherein after step (b) and before step (c), the second molten liquid is heated to within about 20° C. above the liquidus temperature.
11. The method of claim 1 , wherein in step (c), the dross is removed from the surface of the second molten liquid.
12. The method of claim 1 , wherein in step (d), the second molten liquid is cooled to above the solidus temperature and below the liquidus temperature.
13. The method of claim 1 , wherein at least one of steps (a)-(e) is carried out multiple times.
14. The method of claim 1 , wherein each of steps (a)-(e) is carried out multiple times.
15. The method of claim 1 , wherein each of steps (a)-(e) is carried out multiple times, and the first mother liquid obtained in step (e) is employed as the solvent metal in subsequent step (a).
16. The method of claim 1 , further comprising, after step (e):
(f) heating the first silicon crystals to form a first molten bath.
17. The method of claim 16 , further comprising after step (f):
(g) directionally solidifying the first molten bath to form second silicon crystals and a second mother liquor.
18. The method of claim 17 , further comprising after step (g):
(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.
19. The method of claim 18 , further comprising after step (j):
(k) cooling the third molten bath to form silicon ingots.
20. The method of claim 18 , further comprising after step (j):
(l) contacting the third molten bath with water to form granulized silicon.
21. The method of claim 18 , further comprising after step (j):
(m) introducing the third molten bath into a mold and cooling to form a second silicon.
22. The method of claim 18 , further comprising after step (j):
(n) directionally solidifying the third 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.
23. A method for purifying silicon, 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 and dross;
(c) heating the second molten liquid;
(d) separating the dross and the second molten liquid;
(e) cooling the second molten liquid to form first silicon crystals and a first mother liquid;
(f) separating the first silicon crystals and the first mother liquid;
(g) heating the first silicon crystals to form a first molten bath;
(h) directionally solidifying the first molten bath to form second silicon crystals and a second mother liquor;
(i) heating the second silicon crystals to provide a second molten bath;
(j) contacting the second molten bath with a second gas to form a slag that forms on the surface of a third molten bath;
(k) separating the slag and the third molten bath;
and at least one of steps (l)-(o):
(l) cooling the second molten bath to form silicon ingots;
(m) contacting the second molten bath with water to form granulized silicon;
(n) introducing the third molten bath into a mold and cooling the third molten bath to form a second silicon; and
(o) directionally solidifying the third 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.