The invention discloses a method for preparing solar-grade
silicon through purification of industrial
silicon (2N). The method comprises that: the industrial
silicon is subjected to primary pulverization pretreatment and is put into a high-temperature
solid-
phase reaction furnace; the industrial silicon and active gas are subjected to gas-
solid reaction at high temperature to achieve the aim of removing
metal impurities; then
crystalline silicon is cleaned; the purity of the
crystalline silicon reaches as high as 99.999 percent (5N), and is further subjected to vacuum melting of
electron beams and oriented condensation treatment; finally, active
atmosphere plasma is adopted to further purify the
crystalline silicon, and volatile elements which have
high activity and are easily oxidized to generate high saturated
vapor pressure are removed; and polysilicon is cast in an integrated furnace for
casting plasma polysilicon and is directly used for manufacturing a
cell chip. The method combines high-temperature gas-
solid reaction to remove the
metal impurities, the
electron beams to remove the volatile elements and a
plasma purification and
casting integrated furnace technology, improves the purity of the polysilicon to 99.99999 percent (7N) and, fully meets requirement of a
solar cell industry on the solar-grade silicon.