ZHAO Li-xin, WANG Zhi, GUO Zhan-cheng, LI Cheng-yi

(1. National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China; 

2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China; 

3. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China; 

4. School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083, China)

Abstract：

The removal of B and P consumes most of heat energy in Si metallurgical purification process for solar-grade Si. Metal-liquating purification of metallurgical grade silicon (MG-Si), also called Si-recrystallization from metal liquid, was a potential energy-saving method for the removal of B and P efficiently, since Si could be melted at lower temperature by alloying with metal. The selection criteria of metal-liquating system was elaborated, and Al, Sn and In were selected out as the optimum metallic mediums. For Sn-Si system, the segregation coefficient of B decreased to 0.038 at 1 500 K, which was much less than 0.8 at the melting point of Si. The mass fraction of B was diminished from 15×10í 6 to 0.1×10í 6 as MG-Si was purified by twice, while that of most metallic elements could be decreased to 0.1×10í 6 by purifying just once. During the metal-liquating process, the formation of compounds between impurity elements and Si was also an important route of impurity removal. Finally, one low-temperature metallurgical process based on metal-liquating method was proposed.

Key Words：

metal liquating method; metallurgical purification process; tin-silicon system; solar grade silicon