Purification of metallurgical silicon using iron as an impurity getter part I: Growth and separation of Si

Purification of metallurgical grade silicon (MG–Si) by a combination of solvent refining and physical separation has been studied. MG–Si was alloyed with iron and solidified under different cooling rates to grow pure Si dendrites from the alloy. The Si dendrites were then separated using a gravity–based method. The separation method relies on significantly different densities of Si and FeSi2, and uses a heavy liquid with specific gravity between the two phases to float the light Si particles to the surface of the liquid, while the heavy iron silicide sinks. The effect of particle size and cooling rate on the yield and separation efficiency of the Si phase was investigated by quantifying the fraction of Si in the sinks and floats. The results show that the crushing size of the particles prior to separation should be about the same as the width of the dendrites in order to maximize the separation efficiency and at the same time lower the grinding cost.The authors would like to thank ARISE Technologies Co. and NSERC for their financial support of this research