Method for promoting purity of chlorine hydride recycled by reduction unit of polysilicon tail gas separating system

Abstract

The invention provides a method for promoting purity of chlorine hydride recycled by a reduction unit of a polysilicon tail gas separating system. Low-concentration chlorine hydride which is recycled by the reduction unit of the polysilicon tail gas separating system is directly sent to a hydrogenating unit of the system; technological parameters of the hydrogenating unit are optimized; the problem of low purity of the chlorine hydride recycled by the reduction unit of a polysilicon tail gas dry-method separating system is solved technically; in an absorption tower, the chlorine hydride gas in a gas mixture is completely absorbed by low-temperature chlorosilane liquid, thereby forming enriched liquid; and in a dissolving tower, the chlorine hydride gas in the chlorosilane can be completely dissolved from the enriched liquid, thereby efficiently promoting the purity of the recycled chlorine hydride. The purity of the chlorine hydride is increased to 85% from original 60%.

Description

technical field [0001] The invention relates to a method for improving the purity of hydrogen chloride recovered by a reduction unit of a polysilicon tail gas separation system. Background technique [0002] The existing polysilicon tail gas separation system reduction unit recovery process for hydrogen chloride is: 1. The tail gas produced from the polysilicon reduction workshop is directly transported to the polysilicon tail gas separation system reduction unit, and the reduction tail gas is first condensed by a four-stage condenser, and the tail gas 2. Separate the tail gas of chlorosilane, its main components are hydrogen and hydrogen chloride gas, these gases are pressurized from the original 0.45MPaG to 1.35MPaG by the compressor, and then After the hydrogen chloride gas in the gas is absorbed by the chlorosilane liquid in the absorption tower, the hydrogen is separated; 3. The separated hydrogen is sent to the adsorption column to purify the hydrogen, so that the puri...

AI Technical Summary

Problems solved by technology

[0002]The existing polysilicon tail gas separation system reduction unit recovery process of hydrogen chloride is: 1. The tail gas generated from the polysilicon reduction workshop is directly transported to the polysilicon tail gas separation system for reduction Unit, the reduction tail gas first condenses through the four-stage condenser to condense the chlorosilane in the tail gas, thereby separating the chlorosilane; 2. The tail gas of the chlorosilane is separated, and its main components are hydrogen and hydrogen chloride gas. These gases are compressed After the machine is pressurized from the original 0.45MPaG to 1.35MPaG, it is sent into the absorption tower to be absorbed by the chlorosilane liquid to absorb the hydrogen chloride gas in the gas, and then the hydrogen is separated; 3. The separated hydrogen is sent to the adsorption column to purify the hydrogen , so that the purity of hydrogen reaches 99%; 4. The chlorosilane liquid (called rich liquid) that has absorbed hydrogen chloride in the absorption tower is sent to the desorption tower through the pressure difference, and after the hydrogen chloride gas inside is decomposed by steam, the hydrogen chloride gas is regenerated After being cooled by refrigerant R507, it is sent to the synthetic trichlorosilane workshop for use. The purity of hydrogen chloride is low, which is not conducive to the synthesis of trichlorosilane; the chlorosilane liquid (called lean liquid) that decomposes hydrogen chloride gas is then passed through the cycle in turn. After the water and refrigerant R507 are cooled, they are sent to the absorption tower to continue absorbing hydrogen chloride gas;

[0003] The disadvantage of the above-mentioned existing method is that the purity of recovered hydrogen chloride is low after the tail gas produced from the polysilicon reduction workshop passes through the reduction unit process of the polysilicon tail gas separation system, On the one hand, it is not conducive to the synthesis and recycling of trichlorosilane; on the other hand, direct discharge will cause a lot of waste and increase production costs; at the same time, it will cause environmental pollution and increase the processing load of environmental protection workshops

Images