Method for treating polysilicon reduction tail gas

Abstract

The invention discloses a method for treating polysilicon reduction tail gas. The method comprises: (1) performing a first condensation treatment on the polysilicon reduction tail gas; (2) using a membrane separator to separate the polysilicon reduction tail gas after the first condensation treatment , so as to obtain hydrogen and mixed gas respectively; (3) supply hydrogen to reduction furnace and carry out reduction reaction with trichlorosilane; (4) carry out second condensation treatment to mixed gas, obtain chlorosilane condensate and noncondensable gas; ( 5) Adsorbing the non-condensable gas to obtain hydrogen and an adsorbent for adsorbing chlorosilane and hydrogen chloride, and supplying a part of the hydrogen to the reduction furnace; (6) using another part of the hydrogen in step (5) to absorb chlorosilane and hydrogen chloride The hydrogen chloride adsorbent is desorbed to obtain a mixture containing chlorosilane and hydrogen chloride; and (7) hydrogenating the mixture with silicon tetrachloride. This method can significantly reduce energy consumption and equipment investment costs.

Description

technical field [0001] The invention belongs to the technical field of polysilicon production, in particular, the invention relates to a method for treating polysilicon reduction tail gas. Background technique [0002] In the process of producing high-purity polysilicon by modified Siemens vapor deposition, the molar ratio of 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 of silicon tetrachloride, hydrogen chloride, dichlorodihydrosilane, etc., wherein 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, ...

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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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