Super Gravity Separation of Purified Si from Solvent Refining with the Al-Si Alloy System for Solar Grade Silicon

Abstract

The purification of metallurgical grade silicon (MG-Si) by using a combination of solvent refining and super gravity separation was studied. MG-Si was first alloyed with aluminum and then solidified at different cooling rates in order to precipitate dendritic primary Si from the Al-Si alloy. Primary Si dendrites were separated under super gravity, resulting in the ejection of Al-Si eutectics from the solid Si-eutectics melt mixture. The effect of the gravity coefficient on the separation efficiency and then influence of the cooling rate and proportion of Si in the Al-Si alloy on the removal efficiency of Al entrainment were investigated. The results demonstrate that super gravity is an effective tool for the separation of primary Si dendrites from Al-Si alloy, with an optimum gravity coefficient of 280. When the proportion of Si was held constant, varying the cooling rate had almost no effect on the entrainment of Al in the separated Si. However, increasing the proportion of Si in the Al-Si alloy had the effect of reducing Al entrainment.