Research On Purifying Metallurgical Grade Silicon By Metallurgical Method

In 21st century, the shortage of energy and the deterioration of environment are becoming increasingly serious. In order to solve those problems, people become aware of the importance of developing and utilizing new energy. Photovoltaic (PV) energy has aroused great attention as a recyclable energy and has been rapidly developed, since it has a series of merits such as cleanness and environmental protection, convenience and safety. With the rapid development of PV industry, the supply of solar grade silicon (SOG-Si) has fallen short of demand, which has become the bottleneck of PV industry. Metallurgy method is specialized in providing feedstock for PV industry. Producing SOG-Si in metallurgy method has the merits of less environment pollution and lower cost, so it can meet the demand of PV industry's rapid development.In this paper, all the efforts were devoted to producing high purity multi-crystalline silicon. The research of purifying MG-Si was carried out by acid leaching, directional solidification, electron beam melting, slagging. Main metallic impurities had been removed by acid leaching, and the removal efficiency of main metallic impurities got to 88.9%. The multi-crystalline silicon ingot with coarse columnar crystal was made by directional solidification, and metallic impurities congregated at the top of the ingot. Electron beam melting had a good effect on the removal of elements with high vapor pressure, such as P and Ca. The contents of P and Ca got to the maximum at the top of the silicon pie, and had the minimum at the bottom. After slagging, boron and metallic impurities congregated in slag, and the content of B in MG-Si decreased from 15ppmw to 2ppmw.