Direct oxidation refining purification method for industrial silicon melt

Abstract

The invention relates to a directly oxidizing refining and purifying method for industrial silicon melt, which comprises the following steps: adding melt state industrial silicon into a graphite crucible of a heating converting furnace through a pouring box, keeping the temperature of the silicon melt between 1450 and 1600 DEG C by adopting the intermediate sensing heating way, blowing the gas-solid mixture of compressed air and SiO2-CaO slag oxidant powder into the silicon melt to be oxidized and refined, removing most part of metallic impurity Al, Ca, Ti and the like and a small amount of impurity element B; and then closing the compressed air, blowing oxidized gas H2O steam, removing the residual metallic impurity and non-metallic impurity B; and finally, blowing H2 to remove the impurity element P in silicon. The invention achieves the purposes of reducing metallic impurity in the silicon to be less than 1.0 ppmw, reducing the non-metallic impurities B and P respectively to be less than 0.2 ppmw and 0.5 ppmw, and increasing the t electric resistivity to be larger than 2.5 Omega*cm.

Description

1. Technical field [0001] The invention relates to a method for directly oxidizing, refining and purifying industrial silicon melt, and belongs to the technical field of purifying industrial silicon materials by metallurgical methods. 2. Background technology [0002] Industrial silicon (MG-Si) mainly contains metal impurities such as Fe, Al, Ca and non-metallic impurities such as B, P, C, O, etc. The purity is generally above 98%, and the total content of impurities is usually higher than 10000ppm; solar-grade silicon The purity requirement of (SoG-Si) is 5N~7N. In order to ensure the required photoelectric conversion efficiency, the total impurity content in silicon should not exceed 50ppmw, usually Fe, Al, Ca and other metal impurities are below 5.0ppmw, B, P impurities are low At 1.0ppmw, C, O, etc. are below 5.0ppmw. In order for solar-grade silicon to be widely used, low-cost and high-volume production processes must be used. [0003] In 2007, global solar photovolta...

AI Technical Summary

Problems solved by technology

AlemanyC, a joint laboratory of France and Canada, published a paper "Refining of metallurgical-grade silicon by inductive plasma" (2002, 72(1-4): 41-48) on "Sol.Energy Mater.Sol.Cells", etc. using plasma flame Gas blowing refining, this method has a good removal efficiency for many impurities in silicon, especially the removal of Al, Ca, Fe, B and other elements is very obvious, but the removal effect of element P is poor, this is because P Easily form non-volatile Si with Si 2 P, SiP phase, when there is more Ca in the melt, it will also combine into a stable compound Ca 4 (PO 4 ) 2 (OH)