Siberian Federal University

In the Metallurgical Grade Si (MG-Si), the B and P contents are in average above 30 ppm as the carbon reduction materials used in the arc furnace are either rich in B (coal) or in P (charcoal). A decrease of both impurities by a factor 3 by using purer raw materials would allow the direct production of the Upgraded Metallurgical Grade (UMG).This would significantly improve the efficiency of the resulting PV cells made with the refined Solar Grade Silicon (SoG-Si) or decrease massively the costs of Si purification by shortening the number of steps needed for reaching B and P contents below 1 ppm requested for the SoG-Si used for the PV cells. A composite C/SiO2 briquette fulfilling the purity targets for the direct production of UMG-Si in arc furnace was developed. The composite contains several carbon materials with different levels of reactivities and quartz sand. The raw materials aspects, the paste and briquette preparation, as well as the final carbonization step are commented. The finished briquettes are free of volatiles and are mechanically and thermally very stable, thus ensuring stable arc furnace charges with minimum losses of dust and SiO gas. Semi-industrial trials including the downstream purification steps for the production of SoG-Si by a metallurgical low cost route are contemplated