System and process for recovering pure hydrogen and liquid HCl through polysilicon tail gas treatment

Abstract

The invention discloses a system for recovering pure hydrogen and liquid HCl through polysilicon tail gas treatment, and the system mainly comprises a tail gas circulated condensing and washing tower, a chlorosilane stripper and a HCl rectifying tower, wherein the tail gas circulated condensing and washing tower is equipped with a polysilicon tail gas inflow pipe, a first chlorosilane solution outflow pipe and a first hydrogen outflow pipe, and the first chlorosilane solution outflow pipe is connected with the chlorosilane stripper; the chlorosilane stripper is equipped with a reboiler, a second chlorosilane solution outflow pipe, a first HCl outflow pipe and a stripping backflow pipe, and the first HCl outflow pipe and the stripping backflow pipe are connected with the HCl rectifying tower; and the HCl rectifying tower is equipped with a condenser, a separator and a second HCl outflow pipe which are connected in turn, and the separator is equipped with a non-condensable gas outflow pipe. The invention also discloses a process for recovering pure hydrogen and liquid HCl through polysilicon tail gas treatment. Through the system and process disclosed by the invention, the polysilicon tail gas is turned into things of value, the resources are saved, and simultaneously the energy consumption during the treatment process is reduced.

Description

technical field [0001] The invention relates to polysilicon tail gas recovery and treatment technology, which belongs to the field of gas separation, and specifically refers to a polysilicon tail gas treatment system and a process for recovering pure hydrogen and liquid HCL. Background technique [0002] In the production of polysilicon, a large amount of tail gas will be produced in the synthesis process and reduction process of trichlorosilane. It is estimated that for every 1 kg of polysilicon product produced, 40 kg of tail gas will be produced. The main components are: hydrogen (H2), hydrogen chloride (HCL), Dichlorodihydrosilane (SiH2CL2), trichlorosilane (SiHCL3), and silicon tetrachloride (SiCL4), where SiH2CL2, SiHCL3, and SiCL4 are collectively referred to as chlorosilanes. [0003] Polycrystalline silicon tail gas is not only an effective raw material gas or an intermediate product, but also a substance that is extremely harmful to the environment. If it is only d...

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Problems solved by technology

At present, the rectification operation of chlorosilane solution is carried out in a tower, and its operating pressure is 0.6~1.5Mpag. The temperature of the condenser at the top of the tower needs to drop to -40°C to condense HCL into liquid, and the bottom of the tower needs to be heated to 126°C The chlorosilane liquid can only be partially vaporized to provide heat to the tower, so the temperature difference in the axial direction of the rectification tower is very large. The huge temperature difference between the upper and lower sides is a major hidden danger for the safe operation of the equipment. At the same time, changing the operating pressure cannot take into account the condensation temperature and reboiling temperature. , resulting in a large energy consumption

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