Method and system for deep purification of polysilicon reduction tail gas

Abstract

The invention provides a deep purification method for polysilicon reduction tail gas. Cool the reduction tail gas; in the two-stage hydrogen chloride absorption tower, use the top-down chlorosilane lean liquid in the tower to absorb the hydrogen chloride in the mixed gas whose cooling capacity has been used; The chlorosilane-rich liquid output from the bottom of the absorption tower is analyzed and treated, and the lean liquid of chlorosilane is output from the bottom of the tower, and the light component is output from the top of the tower; The chlorosilane poor liquid output from the analysis column kettle is cooled. Accordingly, a deep purification system is provided. The invention makes the quality of recovered hydrogen meet the corresponding requirement of electronic-grade polysilicon, and at the same time reduces the consumption of additional refrigeration and lightens the load of the absorption tower.

Description

technical field [0001] The invention relates to the technical field of polysilicon production, in particular to a polysilicon reduction tail gas deep purification method and a polysilicon reduction tail gas deep purification system. Background technique [0002] In the current era of increasing shortage of fossil energy, the rise of new energy has become an inevitable trend. As a key raw material for integrated circuits and photovoltaic power generation, polysilicon is the basic material for the country's new energy development. However, as the basic material of new energy, the production of polysilicon is a production process with high energy consumption, and the quality requirements for polysilicon are becoming higher and higher. With the formulation of polysilicon grading standards, the quality requirements of polysilicon pose greater challenges. [0003] At present, polysilicon is mainly produced by the improved Siemens method (that is, the reduction method of trichlor...

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Problems solved by technology

[0009] Combining the analysis of the consumption degree of cooling capacity and the influencing factors of the recovered hydrogen quality, it can be seen that in the process of low-pressure condensation, Freon is usually used to deeply condense the reduction tail gas, which requires a large amount of cooling capacity and directly enters the absorption tower. There is more hydrogen chloride gas in the mixed gas, which increases the load of the absorption tower;

[0010] Moreover, since the absorption tower needs a low-temperature and high-pressure environment to remove a large amount of hydrogen chloride gas in the mixed gas, but the temperature in the northern quarter changes greatly, making the temperature in the absorption tower unstable, resulting in fluctuations in the quality of hydrogen output from the top of the tower Larger, which further leads to an increase in the delay time of the adsorption column;

[0011] In addition, carbon molecules will be entrained in the pure hydrogen gas output from the top of the tower after being adsorbed by activated carbon. When polysilicon is produced using this hydrogen gas entrained with carbon molecules, it will affect the carbon concentration of polysilicon, so that the quality of polysilicon cannot be effectively improved, resulting in production The polysilicon cannot meet the corresponding requirements of electronic grade polysilicon (hydrogen chloride content <50ppm, carbon content <3ppm)

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