Method and device for preparing polysilicon by electromagnetically separating aluminum-silicon alloy solution

Abstract

The invention belongs to the technical field of polysilicon, and relates to a method and device for preparing polysilicon by electromagnetically separating an aluminum-silicon alloy solution. The invention is characterized in that after the temperature of molten Al-Si alloy on a liquid line is kept for 20 minutes, the molten Al-Si alloy is cast into a preheated crucible, a pulling device is used to pull the crucible quickly into a magnetic field generator, and a cast ingot enriched with a large amount of primary silicon at the periphery is obtained through a magnetic field separation technology; and the primary silicon at the periphery of the Al-Si alloy cast ingot is collected through a machining method, and the intermediate Al-Si alloy is reserved as the raw material which is further molten together with silicon for purification. When the Al-Si alloy is subjected to melting and temperature-keeping operations, the operations can be performed under atmospheric pressure; and when the specific gravity of Si is higher than 34%, the operations are appropriately performed under vacuum conditions. A crystalline silicon shell with a diameter of 120 millimeters and a height of 300 millimeters can be prepared in only 25 minutes. After being subjected to acid washing, the separated primary silicon can achieve a higher purity, thereby having wide application prospects.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and new material preparation, and in particular relates to the efficient preparation of solar-grade polysilicon by metallurgy. Background technique [0002] With the gradual depletion of traditional energy such as coal, oil, and natural gas, and the aggravation of environmental pollution caused by energy consumption, countries around the world have increased the development and utilization of clean and renewable energy, and the utilization of solar energy has become the focus of research. , while more than 90% of solar cells are made of high-purity silicon. The preparation of high-purity silicon materials mainly includes chemical methods and metallurgical methods. At present, the improved Siemens method is mainly used in industrial production, but this process is more complicated and the investment cost is higher, but the purification of polysilicon by metallurgical method is simpler than the ...

AI Technical Summary

Problems solved by technology

In 1977, U.S. patents (US4124410, US4193974, US4193975, US4195067) proposed alloying directional solidification of low-cost polysilicon earlier, and proposed adding slagging agent Na in alloying smelting 2 O-SiO 2 , BaO-SiO 2 etc., but it is inevitable to increase the smelting temperature of the alloy while adding the slagging agent. The longer smelting time not only results in energy consumption but also low production efficiency.

Japanese scholar Kazuki Morita made a detailed introduction to the segregation of silicon-aluminum alloy melts, and proposed directional solidification under the action of an electromagnetic field and adding Ti to the alloy melt to remove B. Reference: Refining of silicon during its solidification from a Si–Al melt, Takeshi Yoshikawa. Kazuki Morita. Journal of Crystal Growth 311(2009)776–779; Boron removal by titanium addition in solidification refining of silicon with Si-Al. T. Yoshikawa, K. Arimura, K. Morita, Metall.Mater.Trans.B36B (2005)837, under the action of electromagnetic force, the first solidified primary silicon from the aluminum-silicon alloy melt gathers at the bottom of the ingot, and collects the enriched crystalline silicon at the bottom of the ingot for acid washing purification , but the casting speed of this alloy directional solidification is 0.02mm / min~0.08mm / min, the solidification speed is slow, and the production efficiency is low

Chinese patents CN200810121943, CN201010040050.4, and 201010040053.8 propose a method of cooling aluminum-silicon melt to precipitate solid silicon, coating aluminum film to purify polysilicon, and melting aluminum film coated with silicon powder to obtain silicon with a purity of 4-5N. However, in Al-Si alloy During the segregation process, the separation of silicon and alloy elements is a difficult problem in industrial production. Even if alloy directional solidification is used, the ingot must be kept at a very slow casting speed, and the production efficiency is low, which does not meet the value orientation of industrial production.

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