Tail gas recovery method

Abstract

The invention discloses a tail gas recovery method. According to the tail gas recovery method, synthetic tail gas is fed into a buffer tank, and the pressure of the buffer tank is 0.3-0.8 Mpa; an adsorption system is formed by connecting two adsorption towers in parallel, one adsorption tower is in an adsorption state, the other adsorption tower is in a regeneration state, the two adsorption towers are respectively provided with an inlet control valve and an outlet control valve, and an adsorbent is active carbon; the synthetic tail gas enters the adsorption state adsorption tower, the pressure in the tower is 0.3-0.8 MPa, the temperature in the tower is 20-80 DEG C, and a large amount of chlorosilane is adsorbed by the adsorbent; the mixed gas of hydrogen and hydrogen chloride is discharged to an adsorption bag type filter, dust is removed, and the obtained gas enters a recovery gas buffer tank, one part is conveyed to a hydrogen chloride synthesis system, the other part is conveyed into the regeneration state adsorption tower, the temperature in the tower is 100-200 DEG C, and the pressure in the tower is 0.01-0.15 MPa; and the adsorbed chlorosilane is adsorbed at a high temperature so as to regenerate the adsorbent, filtering is performed with a regeneration bag type filter, dust is removed, and recovery is performed by a synthetic tail gas pressurization condensation system.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a tail gas recovery method. Background technique [0002] Trichlorosilane consumes a lot of chlorine and hydrogen in production. It is a good product for chlor-alkali enterprises to balance chlorine and improve economic benefits. It is also an important raw material for the production of monocrystalline silicon, polycrystalline silicon and other products. It is widely used in All fields of national defense, national economy and daily life. [0003] The main methods of trichlorosilane production are: [0004] Si+3HCl=SiHCl 3 +H 2 , the reaction temperature is about 300°C, after dedusting and pressurized condensation, there are still some non-condensable gases such as hydrogen, hydrogen chloride or a small amount of chlorosilane. Since the non-condensable gas contains hydrogen, it still contains about 10% trichlorosilane and silicon tetrachloride even if i...

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Problems solved by technology

[0006] Patent CN101279734A discloses a method for dry recovery of trichlorosilane synthesis tail gas, but the H2 in this method is incorporated into tail gas washing and venting, which not only causes waste of raw materials, but also increases the cost of trichlorosilane synthesis

[0007] Patent CN101125276 uses a hydrogen membrane separator to separate hydrogen, and the separated hydrogen is used as fuel or directly discharged into the atmosphere, causing waste of raw materials and increasing the production cost of trichlorosilane

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