【Insights from Other Regions】Liu Hongbin’s team at Gansu Jinchuan Hengxin overcomes the challenge of recycling acidic wastewater containing chlorinated polymers

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Recently, the list of winners of the 2024 Gansu Province Science and Technology Progress Awards was announced, and the project titled “Industrialization of the Production Process Technology for the Resource Recovery of Acidic Wastewater Containing Chlorinated Polymers”, in which Liu Hongbin was involved, won the third prize. This project represents a landmark achievement, as it is the first time that a private enterprise in Jinchang has taken the lead in carrying out such a project and won a provincial-level science and technology award. It signifies an important breakthrough by Jinchang in the field of technological innovation within the chlor-alkali chemical circular economy industry. In 2020, Jinchuan Hengxin’s chlorinated polymer production line was faced with a dilemma. On the one hand, the companies’ production capacity accounts for a small share within the industry; they are located far from the end markets, their products are vulnerable to market fluctuations, and their profit levels are low ； On the other hand, the large amount of hydrogen chloride-containing wastewater generated during production results in high treatment costs and resource waste. “At that time, the circular economy industry in chlor-alkali chemicals in Jinchang was in a critical phase of transformation and upgrading. Leveraging the resource advantages of Jinchuan Group in terms of chlorine and hydrogen chloride, it was an inevitable trend to develop fine chemical products that require chlorine. ”Liu Hongbin said that finding a solution to the wastewater problem has become key for enterprises to break through development bottlenecks. Against this backdrop, the project \"Industrialization of the Production Process Technology for the Resource Recovery and Recycling of Acidic Wastewater Containing Chlorinated Polymers\" came into being. During the progress of the project, the biggest technical challenge faced by Liu Hongbin and his team was that in the acidic wastewater containing chlorinated polymers, hydrogen chloride forms an azeotrope with water, and conventional separation methods are ineffective; as a result, the chlorine utilization rate is low and wastewater treatment becomes difficult. “During that time, the laboratory became our second home. ”Liu Hongbin recalled that in order to find a solution, the team pursued efforts from three different directions at the same time. They first selected CaCl₂ as the anti-foaming agent, and repeatedly measured the gas-liquid equilibrium data for the HCl-H₂O-CaCl₂ system at different mass fractions of CaCl₂. By combining these measurements with extraction distillation experiments, they were able to determine the influence of the amount of anti-foaming agent on the purity of hydrogen chloride, the concentration of acidic solution after separation, and the separation temperature, thereby providing a solid theoretical basis for advanced separation processes. With the theory in place, practice follows soon after. Liu Hongbin led his team to establish a pilot-scale plant, and based on the data from this pilot plant, they developed process data models to systematically study the impact of key parameters such as the concentration and amount of anti-foaming agents, temperature, number of theoretical plates, and feed location on the separation efficiency. “The determination of each parameter involved hundreds of tests. ”Liu Hongbin said that team members took turns staying by the pilot plant, recording data and analyzing results, often working through the whole night. Ultimately, they successfully developed a salt-added distillation recovery process that enables the deep separation of hydrogen chloride through distillation at low temperatures and pressures, resulting in a purity of the recovered hydrogen chloride of ≥99.99 wt.%; this hydrogen chloride can be used directly in production or converted into industrial hydrochloric acid. The utilization rate of chloride ions increased from 50% to over 95%, and the wastewater generated after separation meets the standards for reuse, achieving virtually zero emissions in theory. Today, upon entering the Jinchuan Hengxin project site, facilities such as production workshops, hydrochloric acid separation units, and environmental protection exhaust gas treatment areas are arranged in an orderly manner. This 120,000 tons per year demonstration production line for the resource recovery of chlorinated polymer wastewater is constantly processing wastewater day and night. “Through resource recovery, 28,000 tons of hydrogen chloride can be obtained each year for the synthesis of polyvinyl chloride, as well as 89,000 tons of dilute acid water that can be used as raw material water for industrial hydrochloric acid production. ”Liu Hongbin explained. Beyond economic benefits, environmental benefits are also significant. “The hydrogen chloride recovery rate in acidic wastewater containing chlorinated polymers is ≥96%; the chloride content in the wastewater after treatment