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Method for treating tail gas of acyl chlorination

A technology of acid chlorination and tail gas, applied in chemical instruments and methods, separation methods, chlorine/hydrogen chloride, etc., can solve the problems of ineffective recovery of by-products, etc., and achieve the effects of easy control, pollution reduction, and process safety

Active Publication Date: 2009-01-14
JIANGSU YANGNONG CHEM +2
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  • Description
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Problems solved by technology

Now the usual treatment method of production enterprises is to directly absorb the tail gas with liquid caustic soda to obtain high-salt wastewater, which is diluted with a large amount of clean water and then undergoes biochemical treatment. This not only cannot effectively recover the by-products of the acyl chloride process, but also produces a large amount of waste water. waste water

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  • Method for treating tail gas of acyl chlorination

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Experimental program
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Effect test

Embodiment 1

[0017] The absorption separation of embodiment 1 hydrogen chloride gas

[0018] The permethrin acid chloride tail gas continuously enters the tail gas cooling system, the system temperature is controlled at -25°C, the tail gas is detected, the sulfur dioxide is 1.3%, the hydrogen chloride is 98.7%, and the liquid sulfur dioxide content is greater than 99%. Hydrogen chloride gas enters the first-stage falling film absorption system, and the absorption temperature is 20-23°C. The sulfur dioxide content in the primary absorption liquid increases gradually. When the sulfur dioxide content reaches 5%, sulfur dioxide gas begins to appear in the overflow tail gas, and the primary absorption liquid starts to be extracted, and water is added according to the output. The detection result of the sulfur dioxide content in the overflowing exhaust gas was 0. Hydrogen chloride gas enters the secondary absorption, the absorption temperature is 20-22°C, and 30-35% hydrochloric acid is obtaine...

Embodiment 2

[0019] The absorption separation of embodiment 2 hydrogen chloride gas

[0020] The tail gas of permethrin acid chloride enters the tail gas cooling system continuously, the system temperature is controlled at -30°C, and the tail gas of non-condensable gas is detected, the sulfur dioxide is 0.8%, the hydrogen chloride is 99.2%, and the liquid sulfur dioxide content is greater than 99%. Hydrogen chloride gas enters the first-stage falling film absorption system, and the absorption temperature is 20-23°C. The sulfur dioxide content in the primary absorption liquid increases gradually, and when the sulfur dioxide rises to 4%, the primary absorption liquid starts to be produced, and water is added according to the production amount. The detection result of the sulfur dioxide content in the overflowing exhaust gas was 0. Hydrogen chloride gas enters the secondary absorption, the absorption temperature is 20-22°C, and 30-35% hydrochloric acid is obtained.

Embodiment 3

[0021] Embodiment 3 sodium sulfite preparation

[0022] The temperature of liquid sulfur dioxide is raised to 0°C, and gas is gradually released, and the gas is passed into 30% sodium hydroxide solution, and the flow is continued until the pH value of the system is 6-7, and the obtained sodium sulfite aqueous solution enters the crystallization system, and the temperature is lowered to 2°C , keep warm for 30 minutes, centrifuge, dry in an oven until the water content is less than 0.2%, and the analysis content is 97.9%

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Abstract

The invention relates to a processing method of thionyl chloride acyl-chlorinated tail gas. Mixed tail gas produced by a acyl chlorinating process contains hydrogen chloride and sulfur dioxide; the sulfur dioxide is liquefied under a certain temperature condition; the incondensable hydrogen chloride and a little sulfur dioxide are absorbed in two stages by water; the absorbed tail gas in a first stage is pure hydrogen chloride gas; after being absorbed in a second stage, the qualified chlorhydric acid is obtained; first-stage falling film absorption liquid is resolved by heating; then the tail gas is sent to a liquefying process again; the liquid sulfur dioxide can be canned as a product; or after being vaporized, the liquid sulfur dioxide is absorbed by 30 percent of sodium hydroxide solution to obtain sodium sulfite aqueous solution which is further dried after low temperature crystallization or distillation to obtain 97 percent of sodium sulfite solid. With the method, the hydrogen chloride, the sulfur dioxide and a little thionyl chloride produced by an acyl chlorination synthetic process can be separated out to obtain the chlorhydric acid and the pure sodium sulfite solid. The processing method of the thionyl chloride acyl-chlorinated tail gas of the invention is capable of effectively recovering the thionyl chloride acyl-chlorinated tail gas, which has the advantages of safety process and easy control.

Description

technical field [0001] The invention relates to a method for treating tail gas of acid chlorination of thionyl chloride, by which hydrogen chloride, sulfur dioxide and a small amount of thionyl chloride produced in the synthesis process of acid chlorination can be separated to obtain hydrochloric acid and pure sodium sulfite solid. Background technique [0002] Acyl chlorides are important intermediates for the production of pyrethroids. The preparation process is obtained by the reaction of thionyl chloride and chrysanthemic acid. The reaction process produces a mixed tail gas of hydrogen chloride and sulfur dioxide. Now the usual treatment method of production enterprises is to directly absorb the tail gas with liquid caustic soda to obtain high-salt wastewater, which is diluted with a large amount of clean water and then undergoes biochemical treatment. This not only cannot effectively recover the by-products of the acyl chloride process, but also produces a large amount o...

Claims

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Application Information

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IPC IPC(8): B01D53/14B01D53/50F25J3/08C01B7/07C01B17/62
Inventor 戚明珠姜友法朱建荣孙迎东
Owner JIANGSU YANGNONG CHEM
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