Method for recycling hydrogen chloride in tail gas of polysilicon production

Abstract

The invention discloses a method for recycling hydrogen chloride in tail gas of polysilicon production. In the method, tail gas is cooled and condensed, so that most of chlorosilane is liquefied; compressed gas enters a hydrogen chloride absorption tower and absorbed by chlorosilane solution, and hydrogen gas is exhausted from the hydrogen chloride absorption tower and collected; liquid hydrogen-chloride-rich chlorosilane discharged from the bottom of the hydrogen chloride absorption tower is introduced into a hydrogen chloride distillation tower, and chlorosilane solution is discharged form the bottom of the hydrogen chloride distillation tower; and hydrogen chloride containing trace hydrogen gas is exhausted from the top of the hydrogen chloride distillation tower and enters a full condenser on the top of the distillation tower, condensate of the full condenser on the top of the distillation tower enters a return tank of the distillation tower, the trace hydrogen is exhausted from the top of the return tank of the distillation tower and collected, a part of the condensate of the return tank of the distillation tower is introduced into the hydrogen chloride distillation tower and used as return liquid, and the other part of the condensate enters a liquid hydrogen chloride reservoir for storage. The method improves the purity of recycled hydrogen chloride and the storage amount of hydrogen chloride and saves the investment of equipment.

Description

technical field [0001] The invention relates to the field of polysilicon production, in particular to a method for recovering hydrogen chloride. Background technique [0002] In the production of polysilicon, the composition of the tail gas produced in the reduction furnace and / or hydrogenation furnace is as follows: dichlorodihydrogensilane SiH 2 Cl 2 (referred to as DCS), trichlorosilane SiHCl 3 (TCS for short), silicon tetrachloride SiCl 4 (abbreviated as TET), hydrogen and hydrogen chloride. Tail gas recovery technology is to recover the above components separately from the mixed gas. The recovered hydrogen is returned to the reduction furnace and / or hydrogenation furnace as a reducing agent, and reacts with trichlorosilane in the reduction furnace to produce the final product polysilicon; the recovered hydrogen chloride is returned to the trichlorosilane synthesis section as a synthetic raw material. [0003] If the hydrogen content in the recovered hydrogen chlori...

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Problems solved by technology

[0013] The purpose of the present invention is to overcome the shortcomings of the high hydrogen concentration in the recovered hydrogen chloride and the difficulty in storing gaseous hydrogen chloride existing in the prior art, and provide a method for recovering hydrogen chloride in the tail gas produced by polysilicon

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