Method for recycling byproduct during production of polycrystalline silicon

Abstract

The invention discloses a method for recycling a byproduct during production of polycrystalline silicon. The method comprises the following steps of: preparing a series of phase change energy storage materials from a polycrystalline silicon byproduct serving as a raw material by using different energy storage substances; performing hydrolysis reaction on the gasified byproduct and water in aqueous solution of polyethylene glycol at normal temperature; performing sol-gel reaction to generate hydrogen chloride and silicon dioxide gel with a three-dimensional grid structure; drying the silicon dioxide gel wrapped by a phase change energy storage material by using a cyclone dryer to prepare a product made of the phase change energy storage material; concentrating and resolving the hydrogen chloride through solution of hydrochloric acid and calcium chloride and removing water by using a silicon tetrachloride leaching tower to prepare hydrogen chloride with water content of less than 0.05 percent; and directly introducing into a polycrystalline silicon production system for preparing trichlorosilane, and matching with silicon tetrachloride hydrogenation technology for use to form a fully closed cycle for producing a material from the polycrystalline silicon and fully recycle the byproduct, so that approximate zero emission of solid waste and waste gas which are generated during the production of the polycrystalline silicon and pollution-free production are realized.

Description

technical field [0001] The invention relates to a polysilicon production process, in particular to a method for reusing by-products in the polysilicon production process. Background technique [0002] Polysilicon is the most important basic functional material for electronic information industry, solar photovoltaic industry and semiconductor power devices. With the increasing shortage of global fossil energy, the new energy industry based on solar energy has obtained good development opportunities. In 2005, 2006, 2007 and 2008, the growth rate was 50%, 41%, 36% and 99% respectively. In 2010, due to the impact of the financial crisis, the growth of the photovoltaic industry will slow down and is expected to maintain a growth rate of 30%. [0003] More than 80% of the world's polysilicon is produced by the modified Siemens process, and the polysilicon projects that have been built and are under construction in my country all use the modified Siemens process. During the produ...

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Problems solved by technology

[0004] At present, there are three methods for treating polysilicon by-products: one is to convert high-purity silicon tetrachloride into trichlorosilane by thermal hydrogenation or cold hydrogenation for recycling, and this process can recover most of silicon tetrachloride; The second is that chlorosilane rich in impurities must be discharged. About 2-3 kilograms of such silicon tetrachloride should be discharged for every kilogram of polysilicon produced. At present, domestic polysilicon manufacturers use the method of leaching, which will produce a large amount Waste slag, not only the cost of treatment is high, but also pollutes the environment

The third is to use silicon tetrachloride to produce other chemical products, such as white carbon black, ethyl silicate and organic silicon products, but due to market and cost problems, it is impossible to digest such a huge amount of silicon tetrachloride

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