Separation and recovery of hydrogen chloride and sulfur dioxide mixed gas

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When chlorination reactions are carried out using sulfuryl chloride or thionyl chloride as chlorinating agents, a large amount of mixed exhaust gas consisting of sulfur dioxide and hydrogen chloride is generated; this exhaust gas also contains a certain amount of organic vapor along with vapor of the chlorinating agents. Currently, the treatment method used in most factories involves multi-stage water absorption followed by alkaline absorption, with the aim of converting acidic exhaust gases into by-product salts, acids, and sodium sulfite. However, this process cannot separate hydrogen chloride from sulfur dioxide satisfactorily; as a result, the large amounts of by-product salts, acids, and sodium sulfite produced cannot be utilized effectively due to purity issues, and they ultimately have to be neutralized before being treated as wastewater. The pressure swing distillation process can effectively address the separation challenges associated with such exhaust gases, enabling the production of high-purity hydrogen chloride and sulfur dioxide, while also allowing for the recovery and reuse of most of the chlorinating agents and some of the organic compounds. By recovering hydrogen chloride, sulfur dioxide, and chlorinating agents from the exhaust gases, not only are valuable products obtained, but liquid alkali required in the original treatment method is also eliminated; furthermore, waste liquid generation is reduced, resulting in significant economic and social benefits. The unit consists of several components such as pretreatment, pressure swing distillation, reactor liquid recovery, hydrogen chloride charging, sulfur dioxide charging, and an emergency absorption system. For the pretreatment stage, a suitable approach must be selected based on factors such as the composition, temperature, and pressure of the exhaust gas; this step is essential in most operating conditions ； The pressure swing distillation process is the core of this unit ； The other parts can be configured as needed based on existing conditions. This process is now a mature one, with existing plants in operation; students interested in it can contact me.