Method for treating tail gas of thionyl chloride chlorination

Abstract

The invention discloses a method for treating tail gas generated in chlorination reaction by using thionyl chloride. The existing traditional tail gas treatment method is costly due to a large amount of alkali consumption, and the pressure on environmental protection is high due to the final generation of a large amount of waste water containing heteroions. In the present invention, by controlling the amount of water, the hydrogen chloride in the tail gas is subjected to two-stage absorption with water, and the concentrated hydrochloric acid with a hydrogen chloride content close to saturation and a small amount of sulfur dioxide is obtained through the first-stage absorption; the second-stage absorption: after the first-stage absorption, the The exhaust gas is subjected to the second-stage absorption, and the added water is not discharged to obtain dilute hydrochloric acid containing a small amount of hydrogen chloride and a small amount of sulfur dioxide. The dilute hydrochloric acid is used as the raw material water for the first-stage absorption; after the above-mentioned secondary absorption treatment, it is then treated with alkali or alkali The third level of water absorption is used to absorb sulfur dioxide in the tail gas to obtain a relatively pure aqueous solution of sodium sulfite. The invention has high treatment efficiency, complete tail gas absorption, and reduces the pressure on environmental protection.

Description

technical field [0001] The invention relates to tail gas treatment of chemical reactions, in particular to a method for treating tail gas produced in chlorination reactions with thionyl chloride. Background technique [0002] Thionyl chloride (also known as sulfur oxychloride; thionyl chloride; thionyl chloride), molecular formula SOCl 2 , molecular weight 118.97, relative density 1.676 (4°C), melting point -104.5°C, boiling point 78.8°C, vapor density 4.1, vapor pressure 14.66kPa (110mmHg26°C), colorless to light yellow or light red smoking liquid, suffocating Odor, miscible with benzene, chloroform, and carbon tetrachloride, corrosive and irritating, decomposes into hydrogen chloride and sulfur dioxide when exposed to water, decomposes into chlorine gas, sulfur dioxide, and disulfur dichloride when heated above 140°C. As a basic chemical raw material, thionyl chloride is widely used in chlorination reactions, such as the chlorination of alcohol hydroxyl groups into chlori...

AI Technical Summary

Problems solved by technology

[0006] Whether it participates in the chlorination reaction normally or is decomposed by water after the reaction, a large amount of hydrogen chloride and sulfur dioxide gas will be produced; if it is not treated, it will inevitably cause serious environmental pollution

[0007] The existing commonly used treatment method is hierarchical absorption: first absorb most of the mixed gas with water to obtain a mixture of hydrochloric acid and sulfur dioxide or sulfurous acid; then absorb the gas that has not been absorbed before with alkaline water to obtain alkali and chloride salts and sulfite mixed waste lye, the mixed waste lye obtained in this way can only be treated as wastewater, and the treatment cost is high; and the mixed acid obtained by the first stage absorption cannot be used, and generally only alkali can be used Treat as wastewater after neutralization

In a social environment where environmental protection requirements are increasing, the above-mentioned traditional tail gas treatment methods are costly due to a large amount of alkali consumption, and the pressure on environmental protection is high due to the final generation of a large amount of waste water containing heteroions.

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