Refining agent for boron removal of slagging and refining industrial silicon melt

Abstract

The invention provides a refining agent for the boron removal of a slagging and refining industrial silicon melt. The refining agent comprises the following ingredients in mass percent: 1-99% of Li2O, 1-99% of SiO2 and 0-98% of basic oxides. A using method of the refining agent comprises the following steps: industrial silicon with the boron content of 1-500 ppmw is taken as a raw material and is mixed with the refining agent for the boron removal of the slagging and refining industrial silicon melt according to a mass ratio of 10:1 to 1:10, the slagging and refining is carried out at the temperature of 1450-1850 DEG C, then, the cooling is carried out, and finally, the slag-silicon separation is carried out, so that the impurity, i.e. boron is removed along with slag. The refining agent has a remarkable effect in boron removal, and the using method of the refining agent has the advantages that: the boron content of industrial silicon can be lowered to be less than 1 ppmw, the slag-silicon separation is easy, the process operation is simple, the requirements on equipment are low, the cost is low, the energy consumption is low, the pollution is little, no harmful gases are generated, the waste slag can be recycled and reutilized, and the method is environment-friendly.

Description

technical field [0001] The invention relates to a refining agent for removing boron impurities in industrial silicon melt, belonging to the technical field of metallurgical purification of industrial silicon. Background technique [0002] Due to the energy crisis and the pollution of the environment by traditional energy sources, polycrystalline silicon solar cells have become a hot spot of global concern. At present, the production of kilo-ton polysilicon mainly adopts the modified Siemens method, and the key technologies are still mastered by a few developed countries such as the United States, Germany, Japan and Norway, forming a technology blockade and market monopoly. To solve the situation that my country's solar cells and their materials are mainly dependent on imports, and to allow solar cells to enter the production and life of ordinary people, it is necessary to explore new methods and new ways of producing solar-grade silicon. [0003] Metallurgical preparation o...

AI Technical Summary

Problems solved by technology

[0004] Due to the special physical properties of some impurity elements, the purification effect of some metallurgical methods is very poor

For example, boron element shows that the impurity element boron has a relatively large separation coefficient of 0.9, which is much higher than that of metal impurities. Even after two directional solidification processes, the purity of boron element still cannot meet the requirements of solar-grade silicon; and 1823K , the saturated vapor pressure of boron is 6.78×10 -7 Pa, far less than the vapor pressure of silicon at this time 0.40Pa, so the method of vacuum smelting cannot effectively remove boron

However, the impurity boron element remains in the material and is easy to form defects, and the defects will recombine with minority carriers, which will reduce the conversion efficiency of the battery

Electron beam and plasma beam melting can effectively remove boron in silicon, but due to the high cost of refining equipment and high energy consumption in the refining process, the limitations of the industrial production of electron beam melting and plasma beam melting