Polycrystalline silicon centrifugal directional solidification purification method and device

Abstract

The invention discloses a polycrystalline silicon centrifugal directional solidification purification method and device. A rotary centrifugal directional solidification principle is adopted, that is, a cooling body with a circulating refrigerant introduced into a middle cavity is inserted into molten silicon liquid at a certain rotating speed, and due to the fact that a large temperature gradient exists between the cooling body and the molten silicon liquid, the silicon liquid can solidify a layer of crystals with high purity on the cooling body, and after a period of time, the cooling body and the crystals rise together and are separated by virtue of external force, so that the purpose of rapid and efficient purification is achieved. According to the method for preparing the polycrystalline silicon with the purity of 6-7 N grade by taking the 2-4 N grade industrial silicon as the raw material, the invention provides the directional solidification purification device and the directional solidification method for the metallurgical solar grade polycrystalline silicon, and the device has the characteristics of large single-furnace productivity, good impurity removal effect, continuous production, short process time and low operation energy consumption, and is suitable for large-scale production.

Description

technical field [0001] The invention belongs to the technical field of metallurgical solar-grade polysilicon production, specifically relates to a directional solidification technology for efficiently removing metal impurities in polysilicon, and provides a polysilicon centrifugal directional solidification purification method and device. Background technique [0002] Photovoltaic power generation, green and clean energy, as a way of solar energy utilization, has developed rapidly in recent years. Its main basic material is solar-grade polysilicon (purity ≥ 99.9999%, 6N), which is currently mainly prepared by chemical method-improved Siemens method to purify industrial silicon technology . Metallurgical polysilicon technology is also a method of preparing solar-grade polysilicon. Because of its potential advantages such as low project investment, short process flow, low energy consumption, and environmental friendliness, it has attracted widespread attention from the industr...

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Problems solved by technology

However, these existing methods more or less have the problems of high energy consumption and low efficiency. The DSS Bridgman method uses quantitative addition of raw materials in the same crucible for smelting, and then realizes directional solidification molding by controlling the temperature gradient to dissipate heat. , the crystal growth rate is slow at 0.8-1.0mm / min, the solid-liquid interface remains macroscopically static, the impurities discharged from the solid cannot be quickly and evenly diffused into the liquid, and the effect of removing impurities at one time is not good; EMCP electromagnetic continuous casting method combines cold crucible induction melting and Continuous casting technology can effectively improve the purification effect and shorten the production cycle, but the use of water-cooled copper crucible will inevitably consume a large amount of induction heat energy, which is not conducive to the reduction of energy consumption; although the FZ zone melting and refining method and the CZ crystal pulling method are not professionally used Polysilicon is purified, but it has the function of directional solidification. It has no forced refrigerant, and the solidified crystal is long cylindrical, with long growth cycle and high energy consumption (about 30Kwh / Kg). The ratio (V / S) is also small, which is not conducive to the effective discharge of impurities

Based on this, the conventional directional solidification method for polysilicon purification technology and equipment is difficult to balance energy consumption and purification efficiency, which restricts its large-scale production and application in the field of metallurgical solar-grade polysilicon production technology

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