PROCESS AND APPARATUS FOR PURIFYING LOW-GRADE SILICON MATERIAL

摘要

A process and apparatus for purifying low-purity silicon material and obtaining a higher-purity silicon material is provided. The process includes providing a melting apparatus equipped with an oxy-fuel burner, and melting the low-purity silicon material in the melting apparatus to obtain a melt of higher-purity silicon material. The melting apparatus may include a rotary drum furnace and the melting of the low-purity silicon material may be carried out at a temperature in the range from 1410° C. to 1700° C. under an oxidizing or reducing atmosphere. A synthetic slag may be added to the molten material during melting. The melt of higher-purity silicon material may be separated from a slag by outpouring into a mould having an open top and insulated bottom and side walls. Once in the mould, the melt of higher-purity silicon material can undergo controlled unidirectional solidification to obtain a solid polycrystalline silicon of an even higher purity.