Method for treating tail gas of thionyl chloride chlorination

Abstract

The present invention discloses a disposal method of a tail gas, which is produced from a thionyl chloride used in a chlorination reaction. The cost of the prior traditional tail gas disposal method is high because of large consumption of alkali, and a high environmental protection pressure is resulted from a plurality of finally produced waste water which contains heteroions. Firstly, the present invention uses water to absorb the hydrogenchloride of the tail gas by controlling the water consumption, and a first grade absorption obtains a concentrated hydrochloric acid, the a hydrogenchloride content of which is approximately saturated and little sulfur dioxide is contained; a second grade absorption is that water is used to process the tail gas after the first grad absorption for the second grade absorption, which is that the added water is not discharged to obtain a diluted hydrochloric acid which contains little hydrogenchloride and little sulfur dioxide, and the diluted hydrochloric acid is used as a liquid of raw material used for the first grade absorption; then the alkali or alkaline water is used to process the tail gas after the second grade absorption for a third grade absorption to absorb the sulfur dioxide in the tail gas and obtain a quite pure sodium sulfite aqueous solution. The disposal efficiency of the present invention is high, and the tail gas absorption is complete, which reduces the environmental protection pressure.

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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