Purification of metallurgical grade Si combining Si-Sn solvent refining with slag treatment

In order to develop a low-cost metallurgical route for solar grade silicon (SOG-Si) production, a novel process sequence of slag treatment and solidification refining using Si-Sn solvents under induction heating, followed by acid leaching was investigated. Slag and metal phases can be fully separated due to their density difference. Refined Si crystals were agglomerated in the metal by combining the electromagnetic stirring effect with controlled cooling. The purification efficiency showed high removal of impurities, especially B content decreasing to 0.3 ppmw, satisfying its allowable content in usage of solar cell. This route allows more effective removal of B with much less usage of slag volume which has the great potential for practical application and an overall low-cost process for producing SOG-Si using Si-Sn solvent was proposed.