Method and equipment for purifying polycrystalline silicon by directional solidification and filter slag melting

Abstract

The invention belongs to the technical field of purifying polycrystalline silicon by physical metallurgy technology. A method for purifying polycrystalline silicon by directional solidification and filter slag melting comprises the following steps: heating slag former in a melting crucible, keeping the slag former in a liquid state, simultaneously, melting polycrystalline silicon material with high boron and high metal in the other small crucible; introducing and dispersing polycrystalline silicon melt into the liquid slag former, conducting melting reaction to remove impurity boron, and when the melting crucible is fully filled with liquid, stopping adding polycrystalline melt, heating so as to lead the mixture in the melting crucible to be in a liquid state, conducting directional solidification on the mixture after melting, cutting polycrystalline silicon and waste residue with higher impurity content at the top of a silicon ingot, thus obtaining the polycrystalline silicon ingot with a lower boron and metal impurity content. The impurity boron and metal in the polycrystalline silicon are removed by filter slag melting and directional solidification, therefore, the purity of the polycrystalline silicon is improved effectively, the using requirement of solar silicon is achieved, the purifying effect is good, the technique is stable, the process is simple, the energy is saved, the cost is low and the production efficiency is high.

Description

technical field [0001] The invention belongs to the technical field of purifying polysilicon by physical metallurgy technology, and particularly relates to a method for removing boron and metal impurities in polysilicon; in addition, the invention also relates to its equipment. Background technique [0002] Solar-grade polysilicon material is an important raw material for solar cells. Solar cells can convert solar energy into electrical energy. In today's shortage of conventional energy sources, solar energy has great application value. At present, the preparation of polysilicon materials for solar cells has formed a large-scale production worldwide, and the current main technical routes are as follows: [0003] (1) Improved Siemens method: The Siemens method uses hydrochloric acid (or hydrogen, chlorine gas) and metallurgical grade industrial silicon as raw materials to perform hydrogen reduction from trichlorosilane. Now the relatively mature technology in foreign countri...

AI Technical Summary

Problems solved by technology

However, the improved Siemens method and silane method require large equipment investment, high cost, serious pollution, and complicated processes, which are not conducive to the popular application of solar cells. In comparison, the metallurgical method has the characteristics of short production cycle, low pollution, and low cost. The focus of R&D in various countries

Known application number is 201010215098.4 The method for preparing solar-grade polysilicon by metallurgical method and the invention patent of polysilicon prepared by this method, use induction heating to melt polysilicon, add slag agent to it and melt to remove impurities. In this method, the slag agent is not melted in advance Adding to the polysilicon melt will reduce the reaction temperature and the effect of impurity removal is not good

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