Recovery system and recovery method

Abstract

The invention provides a recycling system and a recycling method. The recovery system includes: a condensation unit, the reduction tail gas passes through the condensation unit to obtain non-condensable gas and condensed liquid, and the outlet of the condensation unit is connected with a non-condensable gas output pipeline and a condensed liquid output pipeline; The gas output pipeline is connected, and the adsorption and desorption unit is used to separate the hydrogen in the non-condensable gas. The non-condensable gas is absorbed and desorbed by the adsorption and desorption unit to obtain the desorbed gas, and the outlet of the adsorption and desorption unit is connected with hydrogen. An output pipeline and a desorption gas output pipeline, and the hydrogen output pipeline is connected to the inlet of the polysilicon reduction system, and the desorption gas output pipeline is connected to the inlet of the silicon tetrachloride hydrogenation system. Using the above recovery system avoids frequent heating and cooling of liquid chlorosilane materials, reduces the consumption of cold and heat in the dry recovery system, avoids the waste of cold energy returned to the condensation unit of the recovery system, and also avoids the enrichment of impurities .

Description

technical field [0001] The invention relates to the technical field of polysilicon preparation, in particular to a recovery system and recovery method. Background technique [0002] The improved Siemens process of hydrogen reduction of trichlorosilane to produce polysilicon, the reaction conversion rate is about 10%, unreacted hydrogen, trichlorosilane and reaction by-products of silicon tetrachloride, hydrogen chloride, dichlorodihydrogen silicon together form the reduction tail gas , into the dry recovery system for separation and recovery. The traditional dry recovery system consists of three parts: "condensation and separation of chlorosilane - absorption and desorption separation of hydrogen chloride - absorption and purification and recovery of hydrogen". The specific process is that the reduction tail gas is compressed and condensed to recover liquid chlorosilane, and then separated and recovered most of the hydrogen chloride in the non-condensable gas by low-tempera...

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Problems solved by technology

[0003] However, in the actual production of polysilicon, a large amount of hydrogen chloride in the reduction tail gas is easily dissolved in the low-temperature condensed chlorosilane condensate, so the amount of hydrogen chloride recovered by the dry recovery system is very small, and it also causes frequent liquid chlorosilane materials. Cooling and heating, resulting in large cooling and heat consumption

At the same time, in addition to chlorosilane and hydrogen chloride, the desorption gas of the desorption adsorption column also contains trace impurities such as boron, phosphorus, nitrogen, oxygen, carbon, etc. After desorption, the gas returns to the dry system, and the impurities are always in the hydrogen Circular enrichment, which also affects the quality of high-purity polysilicon products

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