Three domestic methods for producing HCl gas

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Currently, there are mainly three methods for producing hydrogen chloride both domestically and internationally: the synthesis method, the hydrochloric acid desorption method, and the by-product hydrochloric acid method. In China, the synthetic method is predominantly used; that is, chlorine and hydrogen are combined to produce hydrogen chloride, which is then cooled by air and water before being sent directly to the vinyl chloride synthesis system. This method features a simple process flow and is mature and stable, but the purity of the hydrogen chloride gas produced is relatively low, at around 90%-96%, which poses many disadvantages for the synthesis of vinyl chloride. Abroad, the hydrochloric acid desorption method is primarily used; hydrogen chloride produced by this method has a high purity (greater than 99%) with minimal fluctuations in purity, which is beneficial for the subsequent synthesis of vinyl chloride. The by-product hydrochloric acid method is mainly suitable for small polyvinyl chloride production plants, allowing for the comprehensive utilization of by-products chloride derived from organic chlorides to produce high-purity chlorides for use in vinyl chloride production facilities; the purity of the chlorides obtained by this method can also reach 99.9%. Since the 1980s, as requirements for the purity of hydrogen chloride increased, China has also gradually shifted from the synthesis method to the hydrochloric acid desorption method. Hydrogen chloride is an important raw material for producing hydrochloric acid and PVC via the calcium carbide process. Polyvinyl chloride (PVC) is one of the main general-purpose plastics; its production volume ranks third in the world among the five major plastics, behind polyethylene (PE) and polypropylene (PP). At present, the calcium carbide method is predominantly used in China for PVC production. As one of the raw materials in this process, hydrogen chloride’s production volume and quality thus become key factors that directly influence the development of PVC production. Developing new synthesis processes, utilizing advanced equipment, and comprehensively utilizing energy are the development trends for hydrogen chloride synthesis.