Method for removing boron impurity from industrial silicon

Abstract

The invention discloses a method for removing boron impurity from industrial silicon, which comprises the following steps of: performing crushing, magnetic separation, acid washing and drying on the industrial silicon, then adding SiO2 and alkali metal compound into the silicon powder, mixing the powdery materials, and stirring the mixed powder uniformly; adding a puffing accelerant into the stirred mixed powder to puff the mixed powder, and putting the puffed mixed powder into an intermediate frequency furnace, a high frequency furnace, a solar furnace, a novel solar furnace or a laser or light-gathering LED to perform high-temperature smelting; or performing high-pressure formation on the puffed mixed powder, and putting the formed blocks into an intermediate frequency furnace, a solar furnace, a novel solar furnace or a laser or light-gathering LED to perform high-temperature smelting; and cooling and separating silicon and slag after smelting, smashing and acid-washing the silicon material so as to efficiently remove the boron element in the industrial silicon.

Description

technical field [0001] The invention relates to a method for purifying silicon materials, especially a method for removing boron impurities contained in industrial silicon. Background technique [0002] At present, there are two types of silicon purification methods, namely chemical purification and physical purification. Chemical purification, such as Siemens method, modified Siemens method and silane method, can achieve higher purity, including electronic grade purity. However, the cost of purification by chemical methods is high, power consumption is large, and it poses threats to the environment (tail gas emissions containing gases such as silicon tetrachloride). The purity that can be achieved by physical purification is lower than that of chemical methods. Due to the difficulty of removing boron impurities in industrial silicon, it can only achieve a purity close to the solar level. However, the cost and power consumption of this method are generally lower than chemic...

AI Technical Summary

Problems solved by technology

However, no matter what method is used, due to the large surface tension of the silicon melt, the silicon melt and the slag melt are not easy to get close to each other, so the effects of the above three methods of increasing the contact area of ​​the silicon and slag melt are still limited. limit

Another way is to add a flux, such as CaF 2 , to increase the fluidity of the slag agent and thus increase the effective contact area; but the co-solvent actually reduces the temperature of the eutectic of silicon and slag agent, which reduces the removal efficiency of boron