Method for treating polycrystalline silicon reduction tail gas

Abstract

The invention discloses a method for treating polycrystalline silicon reduction tail gas. The method comprises the steps that (1), primary condensing is carried out on the polycrystalline silicon reduction tail gas, (2), a membrane separator is adopted for separating the polycrystalline silicon reduction tail gas treated through primary condensing, so that hydrogen and mixed gas are respectively obtained; (3), the hydrogen is supplied to a reducing furnace to be subjected to reduction reaction with trichlorosilane; (4), secondary condensing is carried out on the mixed gas to obtain chlorosilane condensate and non-condensable gas; (5), adsorbing is carried out on the non-condensable gas to obtain the hydrogen and adsorbing agents for adsorbing chlorosilane and hydrogen chloride, and a part of the hydrogen is supplied to the reducing furnace; (6), the other part of the hydrogen in the step (5) is adopted for carrying out desorption on the adsorbing agents for adsorbing the chlorosilane and the hydrogen chloride to obtain a mixture containing the chlorosilane and the hydrogen chloride; (7), the mixture and silicon tetrachloride are subjected to hydrogenation reaction. The method can remarkably reduce energy consumption and the equipment investment cost.

Description

Technical field [0001] The invention belongs to the technical field of polysilicon production. Specifically, the invention relates to a method for processing polysilicon reduction tail gas. Background technique [0002] In the process of producing high-purity polysilicon by modified Simon process, the molar ratio of feed trichlorosilane to hydrogen is about 1:3 to 1:8, and the reaction conversion rate of trichlorosilane to elemental silicon is about 10% Therefore, the reduction tail gas contains a large amount of unreacted hydrogen, trichlorosilane, and reaction by-products such as silicon tetrachloride, hydrogen chloride, and dichlorosilane, among which the molar ratio of hydrogen accounts for more than 75%. The currently commonly used dry recovery process consists of three parts: "condensation recovery of chlorosilane-absorption and desorption of hydrogen chloride-adsorption purification". However, with the continuous expansion of polysilicon production scale, the requirements...

AI Technical Summary

Problems solved by technology

However, with the continuous expansion of polysilicon production scale, the requirements for the large-scale reduction tail gas dry recovery system are getting higher and higher, and the investment in equipment and pipelines and the instability of operation are increasing.

At the same time, since the hydrogen in the reduction tail gas participates in the state changes such as condensation and pressurization throughout the process, the power consumption of the refrigeration and compression processes is relatively large

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