Method for preparing solar-grade silicon by refining industrial silicon



The invention discloses a method for preparing solar-grade silicon by refining industrial silicon. The problems of longer routes, more complicated equipment, higher cost, poorer process controllability and the like of existing processes for preparing solar-grade polycrystalline silicon by adopting a metallurgic method are mainly solved. The method includes the following steps that (1) metallurgical-grade silicon are molten in a furnace to obtain a silicon melt, protective gas and refinery gas are led to the furnace to perform slagging and refining, the slagging and refining operation includes a low-temperature slagging stage, a middle-temperature slagging stage and a high-temperature slagging stage; (2) vacuum refining is performed after slagging and refining; (3) the silicon melt is segregated and refined after vacuum refining is completed, and a finished product is obtained through directional solidification after segregation and refining. The method has the advantages of being low in investment, convenient to operate, capable of saving energy, suitable for large-scale production and the like.




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