Method for recovering hydrogen gas from trichlorosilane tail gas

Abstract

The invention relates to the adsorption and the separation of gas, in particular to a method for recovering hydrogen gas from trichlorosilane tail gas. The trichlorosilane tail gas is subjected to dust removal, chlorosilane recovery and hydrogen chloride recovery, contains 85 percent of hydrogen gas and 15 percent of nitrogen gas, is subjected to the pressurization and the heating and then enters an adsorption system. The method comprises the following steps of: adsorbing the hydrogen gas by an adsorbent in a packed tower; after the adsorption is finished, exhausting from the tower top by using a vacuum pump; meanwhile, exhausting the unabsorbed mixed gas stayed in the packed tower out of the packed tower by using a mode of introducing the purified hydrogen gas from the bottom of the packed tower; after finishing discharging impurities, desorbing the hydrogen gas absorbed in the packed tower and pumping to a hydrogen chloride synthesis furnace for recycling; and recovering the nitrogen gas from the tower top, leaching and introducing the leached nitrogen gas into a cloth bag dust filter for recycling. The method has the advantages of less investment, lower operation expense, simple process, high recovery rate of hydrogen gas and high purity of the recovered hydrogen gas.

Description

technical field [0001] The invention relates to the adsorption and separation of gases, in particular to a method for recovering hydrogen from the tail gas of trichlorosilane production. Background technique [0002] Trichlorosilane, also known as trichlorosilane and silicon chloroform, is a volatile and deliquescent colorless liquid. It is also a widely used organosilicon monomer. It is widely used in organosilane, alkyl, aryl and The synthesis of organofunctional chlorosilane is the most basic monomer in organosilane coupling agent and the main raw material for polysilicon production. [0003] In the prior art, the common method for synthesizing trichlorosilane is as follows: [0004] 1. Synthesis of hydrogen chloride: H 2 +Cl 2 = 2HCl, [0005] 2. Synthesis of trichlorosilane [0006] Si+3HCl=SiHCl 3 +H 2 (main reaction) [0007] Si+4HCl→SiCl 4 +2H 2 (side effects) [0008] During the synthesis of trichlorosilane, the conversion rate of hydrogen chloride is gen...

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Problems solved by technology

The advantage of the adsorption treatment method is that the process route is mature, but the disadvantage is that the separation is not complete, the purity of the recovered gas is low, and the recovery of hydrogen into the hydrogen chloride synthesis furnace will not only affect the yield of hydrogen chloride, but also bring hidden dangers to safe production

[0013] In order to improve the purity of the recovered hydrogen, the pressure swing adsorption system discharges the miscellaneous gas in the dead space of the adsorption tower through the pressure equalization drop, but the process of equalizing the pressure drop cannot make the miscellaneous gas in the dead space in the tower rise in a higher proportion. It is effectively discharged, which reduces the purity of the recovered hydrogen, and the utilization rate of the packed tower and the adsorbent is low; in addition, in the process of equalizing pressure drop, the hydrogen adsorbed by the adsorbent will decrease with the pressure inside the tower However, the escape from the adsorbent is discharged out of the adsorption tower together, which reduces the working efficiency. In order to improve the purity of the recovered hydrogen, multiple equal pressure drops can be used. In this way, the working efficiency of the adsorption system will be lower, and increase Operating costs of the adsorption system

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