Method and equipment for directional solidification and purification of polycrystalline silicon through taking tailing by quartz tube

Abstract

The invention belongs to the technical field of metallurgy purification, and particularly relates to a method and equipment for directional solidification and purification of polycrystalline silicon through taking tailing by a quartz tube. According to the method, under inert gas environment, silicon is melt and then is cooled to pull ingot; when solidification is completed by 85-90%, the quartz tube is stretched into the surplus melt silicon, vacuumizing is stopped, inert gas is led in, the surplus melt silicon enters the quartz tube under the action of pressure difference, ingot pulling is continuously carried out, after the upper end of a crucible leaves a heating area, a tailing collection box is stretched below the quartz tube with a point; the power is cut off so as to stop heating, melt silicon in the quartz tube expands, then the quartz tube cracks and falls into the tailing collection box, and cast ingot of high purity in the crucible is obtained. Due to the method, back-diffusion of impurity is prevented, technology processes are reduced, and the yield of cast ingot is improved. The equipment is convenient to improve and install, is simple to operate, can effectively remove impurities accumulated at the tail of the cast ingot, save production period and cost, and is applicable to industrial production.

Description

technical field [0001] The invention belongs to the technical field of metallurgical purification, and in particular relates to a method and equipment for directional solidification and purification of polysilicon by tailing material extraction. Background technique [0002] The purification of silicon raw materials is an important link in the solar photovoltaic industry chain. The rapid development of the photovoltaic industry depends on high-efficiency and low-cost purification methods. Directional solidification technology has been widely used in many fields of metal purification, and has achieved remarkable results. In the process of purifying silicon raw materials, metal impurities whose segregation coefficient is far less than 1 will be enriched in the liquid phase during the directional solidification process and finally removed. This method is one of the key links in the current metallurgical preparation of solar-grade polysilicon, and is the most effective method f...

AI Technical Summary

Problems solved by technology

In the subsequent slow cooling process, the impurities in the high-concentration area will diffuse to the low-concentration area, so that the purity of silicon will gradually decrease with the prolongation of the holding time, which affects the purification effect, and in this case, the tail that needs to be removed The waste is as high as 25% to 35%, and the finished product rate is only 65-75%

At the same time, due to the relatively high hardness of silicon, high-power cutting equipment is needed to separate the purified silicon ingot from the ingot tailings with high impurity content at the tail. At present, wire cutting and diamond saw band cutting are generally used for cutting, but cutting The high cost of equipment and the large consumption of saw bands are not conducive to the reduction of industrial production costs. At present, there are few effective methods in China to facilitate the removal of tailings

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