HCl ODC Yantai Juli
In 2009 thyssenkrupp Uhde Chlorine Engineers was awarded an engineering and procurement contract for the construction of a hydrochloric acid electrolysis plant by Yantai Juli Isocyanate Co. Ltd., a Chinese manufacturer of polyurethane.
The plant, with a production capacity of 100,000 tpa hydrochloric acid, was constructed in Laiyang, Shandong Province, China, approximately 100 km north of Qingdao. Since successful commissioning in 2011, the plant has been operating as planned.
thyssenkrupp Uhde Chlorine Engineers’ scope of supply included the process license, major components of the engineering package, the supply of the electrolyzers, and assistance with the construction and commissioning of the plant.
The new membrane electrolysis plant is used to convert the by-product hydrochloric acid obtained from an isocyanate production line of Yantai Juli. The hydrochloric acid is converted into high-purity chlorine by oxygen-depolarized cathode (ODC) technology. The ODC principle is based on oxygen reacting with hydrogen ions at the cathode side of the cell. This cathode reaction takes place at a notably lower cell voltage than that needed in conventional diaphragm electrolysis, allowing energy savings of up to 25 per cent. The anode reaction remains the same.
ODC-based membrane electrolysis provides a wide operating window and maximum process flexibility and is consequently a key factor in optimizing site conditions.
The recycling of hydrochloric acid using electrolysis is gaining in importance and making a critical contribution to improving plant efficiencies, meeting environmental requirements and making the isocyanates business independent of the vinyl production chain. This innovative technology was developed by thyssenkrupp Uhde Chlorine Engineers and is sold worldwide.