Method and equipment for rapid collection and purification of polycrystalline silicon through directional solidification of tailing

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. According to the method, under the inert gas shielding environment, abluent silicon is heated to be fully melted so as to carry out directional solidification; ingot pulling is stopped when solidification is completed by 85-90%, a graphite bent pipe is stretched into surplus unset silicon at the upper layer, then the other end of the graphite bent pipe is vacuumed through a vacuum unit, so that the surplus unset silicon at the upper layer enters the graphite bent pipe under the action of pressure difference and enters a water cooling collection box through the guide of the graphite bent pipe; heating is stopped after all the surplus unset silicon at the upper layer enters the water cooling collection box, and cast ingot solidified in a crucible is silicon cast ingot of high purity. 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, and a tailing collection device can be used repeatedly, can collect more tailings, and is safe and reliable.

Description

technical field [0001] The invention belongs to the technical field of metallurgical purification, and in particular relates to a method and equipment for purifying polycrystalline silicon by tail material extraction type directional solidification. Background technique [0002] The purification of silicon raw materials is an important link in the solar photovoltaic industry chain, and the rapid development of the photovoltaic industry relies on high-efficiency and low-cost purification methods. Directional solidification technology has been widely used in many fields of metal purification, and achieved remarkable results. In the process of purifying silicon raw materials, metal impurities with a segregation coefficient much 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...

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%~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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