Abstract:The kinetics on vacuum refining process of metallurgical grade silicon was studied using maximum evaporation rate, critical pressure and mean free path of phosphorus in the metallurgical grade silicon at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined in detail. The results show that the fractional vacuum distillation should be taken to obtain silicon with high purity. Impurity phosphorus volatilize with the maximum evaporation rate of 1.150×10⁵− 1.585×10⁶ g/(cm²·min) in the temperature range of 1 073−2 173 K and the pressure below 2.1 Pa. Because the value of w_{max, P} is at least 10⁸ times of w_{max, Si}, Si hardly evaporates and remains in the residual, which indicates that phosphorus can be removed from metallurgical grade silicon (MG-Si) completely.

Key words: metallurgical grade silicon; solar grade silicon; vacuum distillation; kinetics; phosphorus removal