Method and apparatus for purifying polycrystalline silicon through rotation and blow induced inversion solidification

Abstract

The invention belongs to the technical field of metallurgical purification, and especially relates to a method and an apparatus of induced inversion solidification. The method comprises the following steps of: in the vacuum environment, heating the cleaned silicon material until the silicon material is completely melted and directionally solidified; when 80-90% of solidification is completed, rotating the crucible so that the silicon melt of the upper layer is gathered towards the sidewalls of the crucible under the action of the centrifugal force, and simultaneously blowing an inert gas to the center of the top of the left silicon melt of the upper layer so that the left silicon melt of the upper layer is gathered towards the sidewalls from the center of the crucible under the action of the gas flow and quickly solidified inversely, and is completely solidified at the sidewalls of the crucible; after the whole silicon ingot is cooled, removing the cast ingot of the upper layer obtained through solidification on the sidewalls of the crucible, so as to obtain the left cast ingot as the high-purity silicon cast ingot. The apparatus provided by the invention is added with the functions of crucible rotation and blowing on the basis of the previous solidification apparatus. The method and the apparatus provided by the invention have the advantages that back-diffusion of impurities is reduced, the yield of the cast ingot is improved, the process links are reduced and the energy consumption is reduced; the equipment is convenient to reform and mount; the impurities enriched at the tail part of the cast ingot are effectively removed; and the production cycle and the production cost are saved.

Description

technical field [0001] The invention belongs to the technical field of metallurgical purification, in particular to a method for inducing reverse solidification to purify polysilicon, and also to its equipment. Background technique [0002] The development of the solar photovoltaic industry relies on the purification of silicon raw materials. In the process of purifying silicon raw materials, the directional solidification method is very important for removing metal impurities with very small segregation coefficients in silicon raw materials. One of the most effective methods, moreover, the directional solidification technique is widely used in metallurgical purification. Directional solidification is the use of forced means to form a temperature gradient in a specific direction in the melt, so that the melt at the low temperature part crystallizes and nucleates, and becomes the starting point for the solidification of the melt. Solidify in the opposite direction to obt...

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Problems solved by technology

[0003] However, at the end of the solidification of the ingot, impurities are enriched in the melt at the top of the crucible. During the final slow solidification process, the parts with high impurity content will diffuse to the parts with low impurity content, so that the purity of silicon will gradually increase with the prolongation of the holding time. Reduced, which affects the purification effect, and in this case, the tail waste removed is as high as 25%~35%, that is, the yield is only 65-75%, and the

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