Boron removal from metallurgical silicon using CaO-SiO2-CaF2 slags

The removal of boron from metallurgical silicon in slag system of CaO-SiO2–10%CaF2 was investigated. The partition coefficient of boron (LB) between slag and silicon phase was studied under different conditions of slag basicity (CaO/SiO2 ratio), temperature, mass ratio of slag to silicon and gas blowing. The results show that LB has a maximum value of 4.61 when the CaO/SiO2 mass ratio is around 2 at 1 873 K. The logarithm of LB is linear to the reciprocal of temperatures in the range of 1 773-1 973 K. LB increases with the increase of mass ratio of slag to silicon, but it does not increase markedly when the ratio excesses 3. Gas blowing can significantly increase the removal of boron, and LB increases with the increase of water vapor content.