Method for producing high-purity concentrated hydrochloric acid by adopting hydrogen chloride gas containing chlorosilane

Abstract

The invention discloses a method for producing high-purity concentrated hydrochloric acid by adopting hydrogen chloride gas containing chlorosilane, which comprises the following steps: injecting hydrogen chloride gas containing chlorosilane into a hydrolyzer, carrying out hydrolyzation reaction with water in concentrated hydrochloric acid in the hydrolyzer, removing chlorosilane in the gas, adopting water circulation to absorb hydrogen chloride in the gas in falling film absorbers after the gas passes through at least two serial falling film absorbers in sequence to obtain concentrate hydrochloric acid, and discharging tail gases after the hydrogen chloride is absorbed. By utilizing the method, the high-purity concentrated hydrochloric acid is produced by adopting hydrogen chloride gas containing chlorosilane, thus the problem that pure hydrochloric acid can not be obtained in the traditional method that water is directly used for absorbing hydrochloric acid is solved; the production stability, the mutual independence and the flexible operability of a polysilicon production device are increased; and meanwhile, the high-purity hydrochloric acid can be also obtained, recycled and sold as a by-product.

Description

technical field [0001] The invention belongs to the field of fine chemical industry, and in particular relates to a method for recovering hydrogen chloride gas containing chlorosilane. Background technique [0002] The main units of the Siemens method polysilicon production process are: trichlorosilane preparation unit; trichlorosilane rectification unit; tail gas (HCl / H 2 ) recovery unit; silicon tetrachloride conversion unit and polysilicon finished product production unit. [0003] In the preparation of trichlorosilane, a part of the hydrogen chloride tail gas containing chlorosilane after condensation enters the vent washing system and is absorbed by alkali solution, causing great pressure on environmental protection. [0004] During the normal production of polysilicon, the hydrogen chloride from the tail gas recovery unit and silicon tetrachloride conversion unit returns to the trichlorosilane preparation unit to react with silicon powder to produce trichlorosilane, w...

AI Technical Summary

Problems solved by technology

[0003] In the preparation of trichlorosilane, a part of the hydrogen chloride tail gas containing chlorosilane after condensation enters the vent washing system and is absorbed by lye, causing great pressure on environmental protection

However, the hydrogen chloride absorption of chlorosilanes in the production of polysilicon is currently absorbed by the traditional method of water absorption, that is, three-stage water absorption. This hydrogen chloride absorption method will cause blockage of the absorption tower (commonly used as a packed tower) and pipelines, and in severe cases. It is difficult to clean up, and the hydrochloric acid produced by absorption has a lot of impurities such as silica gel, which cannot be used for analysis and recovery.

This is due to the silica gel produced by the reaction of chlorosilane in hydrogen chloride gas with water, which is easy to block the absorber, circulation pump and pipeline during absorption, and cannot operate for a long time

At the same time, the reaction is an exothermic reaction, and a large amount of HCl is evaporated by heat, which makes absorption difficult.

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