Device and method for reducing content of light component impurities in polycrystalline silicon dry recovery process HCl absorption liquid

Abstract

The invention discloses a device and method for reducing the content of light component impurities in polycrystalline silicon dry recovery process HCl absorption liquid. The device comprises an absorption tower and a desorption tower, the bottom of the absorption tower is communicated with a tube pass inlet of a heat exchanger, and a tube pass outlet is connected to a feed inlet of the desorptiontower; a bottom outlet of the desorption tower is connected to a shell pass inlet of the heat exchanger through a delivery pump, and a shell pass outlet is connected to an absorption liquid inlet at the upper part of the absorption tower; a first branch pipeline is disposed between the delivery pump and the heat exchanger, and the end of the first branch pipeline is a high purity silicon tetrachloride inlet. A pure STC pipeline is added to an HCl absorption tower inlet pipeline for entering the HCl absorption tower together with the absorption liquid. Under the circumstances of constant circulation volume and desorption tower liquid level, STC is added, and HCl absorbent liquid can be discharged from the bottom of the HCl desorption tower uninterruptedly, and repeatedly, the effects of diluting the absorption liquid impurities and purifying HCl absorption liquid can be achieved, and then the influence of impurities on hydrogen can be reduced.

Description

technical field [0001] The invention relates to the technical field of polysilicon production, in particular to a device and method for reducing the content of light-component impurities in HCl absorption liquid in a polysilicon dry recovery process. Background technique [0002] In polysilicon production technology, most tail gas recovery adopts dry recovery process. The tail gas from the reduction furnace mixed with hydrogen, hydrogen chloride, dichlorodihydrosilane, trichlorosilane, and silicon tetrachloride undergoes multiple heat exchanges, most of the chlorosilanes are condensed and separated, and the uncondensed gas is pressurized by the compressor Enter the absorption tower, where the hydrogen chloride is sprayed and absorbed by the relatively pure chlorosilane absorption liquid at the top of the absorption tower, the unabsorbed hydrogen enters the adsorption tower for impurity removal and purification, and the chlorosilane liquid that absorbs impurities such as hydr...

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Problems solved by technology

[0003] In the polysilicon dry recovery process, although most of the chlorosilanes have been removed after condensation, a small amount of chlorosilanes will still enter the HCl absorption tower and be absorbed by the absorption liquid, and at the same time discharge the absorption liquid from the bottom of the HCl desorption tower The frequency and flow rate are very small, and as time accumulates, the absorption liquid will be enriched with impurities (mainly light component impurities) brought from the front-end chlorosilane, and these impurities will enter the reduction together with hydrogen in the HCl absorption tower furnace, thereby increasing the polysilicon impurity content and reducing the quality of polysilicon

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