Exhaust gas treatment method and system in polysilicon production process

Abstract

The invention discloses an exhaust gas treatment method and system in the polysilicon production process. The exhaust gas treatment method comprises the following steps: (1) exhaust gas is subjected to cooling liquefaction separation through an exhaust gas cooling tower, tower bottom liquid of the exhaust gas cooling tower is obtained in a tower bottom of the exhaust gas cooling tower, and a primary mixture comprises the tower bottom liquid of the exhaust gas cooling tower; and (2) the primary mixture is introduced into a separation tower to be fed for distillation purification, overhead gas is collected at the tower top of the separation tower and comprises hydrogen and hydrogen chloride, beside collection liquid is collected on the lateral line or the upper part of the tower top of the separation tower and comprises trichlorosilane and dichlorosilane, and tower bottom liquid of the separation tower is collected and comprises silicon tetrachloride. Hydrogen, hydrogen chloride, dichlorosilane, trichlorosilane and silicon tetrachloride in the tower bottom liquid of the exhaust gas cooling tower are separated, the separated components are not homologous compounds, the obtained mixtures have different proportioning requirements, and the downstream process requirements can be met.

Description

technical field [0001] The invention belongs to the technical field of polysilicon production, and in particular relates to a tail gas treatment method and system in the polysilicon production process. Background technique [0002] In the process of producing polysilicon by the improved Siemens method, the main function of the tail gas recovery process in the polysilicon production process is to recover the hydrogen, hydrogen chloride, dichlorodihydrosilane, trichlorosilane and silicon tetrachloride in the tail gas in the polysilicon production process. The principle of separation is as follows: firstly, according to the different boiling points of each component, the temperature of the tail gas is lowered several times. Chlorosilane has a high boiling point and is easy to be condensed. Under certain temperature conditions, chlorosilane is first condensed into liquid, while hydrogen and atmospheric Part of hydrogen chloride still exists in the gas phase, which realizes the p...

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Problems solved by technology

[0004] 1. High energy consumption and high cost: At present, the condensation part of the tail gas recovery process requires a large amount of cooling capacity to condense the high-temperature tail gas, and a large amount of heat is required to heat and analyze hydrogen chloride in the absorption and analysis part

The heat and cold here consume a lot of steam and electricity. A 10,000-ton polysilicon tail gas recovery process requires hundreds of thousands of yuan in steam and electricity costs every day, resulting in high production costs for polysilicon.

[0005] 2. Low efficiency and high investment: the existing tail gas recovery process can satisfy the separation and purification of hydrogen and hydrogen chloride, but trichlorosilane, silicon tetrachloride, and dichlorodihydrosilane are basically not separated and are still sent to To the purification process, separation and purification are carried out again in the rectification tower, and the separation efficiency of the tail gas recovery process is low

The re-separation of chlorosilanes in the purification process not only increases the separation steps and energy consumption, but also increases the equipment investment

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