Thermodynamic evaluation of phosphorus removal within metallurgical grade silicon by fractional melting process

In the current study, a new method for the purification of metallurgical grade silicon (MG-Si), fractional melting process, was proposed and discussed. The proposed method combines the phosphorus segregation behavior between solid silicon and Al-Si melt to removal phosphorus. The segregation coefficient of phosphorus between solid silicon and Al-Si melt decreases with the drop of temperature, which demonstrate the thermodynamic feasibility of silicon purification within Al-Si system. By alloying MG-Si with Al, phosphorus could segregate into the Al-Si eutectics from MG-Si, and form a specific Al-Si-Ca-P impurity phase. Content of phosphorus in the impurity phase was relatively stable. After three times refining, the content of phosphorus is reduced to 0.68×10^-6 with the removal fraction of 94.89%. The recovery of refined silicon is increased with the Si proportion increased.