Patent ID: 7820126

Claim:
A method of purifying silicon, comprising: (a) inputting an impure solid silicon feedstock and purified recycled silicon-bearing vapors into a first fluidized bed reactor, wherein the first fluidized bed reactor is maintained at a temperature between 1200° C. and 1350° C., and wherein the purified recycled vapors include SiI 4 and I 2 vapors; (b) reacting the impure solid silicon feedstock and the purified recycled silicon-bearing vapors to form a mixture of vapors, wherein the mixture of vapors includes SiI 2 , SiI 4 , I 2 , I and iodine-bearing vapors of impurities from said impure solid silicon feedstock; (c) outputting, from said first fluidized bed reactor, an output including excess impure solid silicon and the mixture of vapors; (d) transferring said output into a solid-gas separator; (e) separating said output into separated solids and a separated vapor; (f) removing a fines portion of said separated solids from the solid-gas separator and returning a coarse part of said separated solids to said first fluidized bed reactor; (g) transferring said separated vapor to a second fluidized bed reactor, the second fluidized bed reactor maintained at a temperature between 800° C. and 1000° C.; (h) initially providing said second fluidized bed reactor with pure silicon seed particles; (i) forming pure silicon granules from the separated vapor; and (j) outputting pure silicon granules from the second fluidized bed reactor.