Study On Purification Of Industrial

With the continuous depletion of fossil fuels, renewable energy sources will be the direction of energy development in future. Solar energy as a clean and high-efficiency renewable energy has been rapidly developed and extensively applied, but in the condition of inadequate supply of raw material polysilicon in the market of solar cell, where the demand exceeds the supply, there are still some disadvantages such as high energy consumption and high pollution in the purification process of solar-grade silicon raw materials. So that the development of photovoltaic industry has been severely constrained. As an effective method to reduce the production of solar-grade silicon, metallurgical method has been widely used, in conformity with the direction and needs of the photovoltaic industry.The experimental researches are made in the paper aiming at the difficulty in removing non-metallic impurity P from industrial silicon. The calcium-silicon alloy is proposed to use as a refining agent, combined with the hydrometallurgy process method to remove P in order to ultimately achieve a lower P content in silicon, which can meet the quality requirement of solar-grade silicon. The experimental studies in slovent refining method shows that CaSi2is generated from the reaction of Ca and Si after the calcium-silicon alloy is added to the MG-Si The CaSi2phase produced by impurity elements in MG-Si forms an enriched impurity region of CaSi2, which includes the phases AlFeSi, FeSi2, Al and other metal impurities as well. The effects of different ratios of calcium-silicon alloy on P removal after the treatment of wet process are compared and the optimum calcium-silicon alloy ratio of5.16wt%is obtained. Through the solvent refining experiments followed by the hydrometallurgy process, the optimum process conditions are:the particle size of0.106-0.150mm, acid species of HC1, acid concentration of5mol/L, leaching temperature of60℃, leaching time of3h, liquid-solid ratio of4:lv/m and the stirring rate of800r/min. With this optimal condition of calcium-silicon alloy solvent refining, the removal rate of P reaches more than90%, which can meet the production requirement of a low P MG-Si.