Covestro is planning to build its own chlorine production plant in Tarragona (Spain) and will use oxygen-depolarized cathode technology, which consumes around a quarter less energy than the conventional method.
Tarragona/Spain — Covestro is currently investing around $ 231,7 million at Tarragona to increase the site’s competitiveness. The new chlorine production plant is a key component of that. About one third of the production costs for chlorine are usually spend on energy. Thus, the selected technology makes an important economic contribution. According to Chief Technology Officer Dr. Klaus Schäfer, sustainability and energy efficiency played a vital role in choosing the process.
Chlorine is needed to make around two-thirds of all polymers, yet it does not occur naturally in its pure form. Instead, it is only found in chemical compounds — such as in rock salt, from which chlorine can be obtained using electrolysis. However, the process uses a significant amount of energy. Covestro and Thyssenkrupp Uhde Chlorine Engineers have therefore developed an innovative technology that consumes around 25 % less energy than conventional electrolysis through the use of an oxygen-depolarized cathode (ODC).
ODC technology is based on the conventional membrane process, in which chlorine, caustic soda and hydrogen are usually produced from rock salt and water. The crucial difference: The hydrogen-generating electrode normally used is replaced by an oxygen-depolarized cathode. Only chlorine and caustic soda are produced. As a result, a voltage of just around two instead of three volts is required.
Initial invention and development work for this technology began in Covestro's lab back in 1992. Then the companies developed it further and were able to start up the first demonstration plant on an industrial scale in Krefeld-Uerdingen in 2011.
Construction of the new plant in Tarragona is scheduled to begin in the first half of 2019. Chlorine is mainly needed at Tarragona to make MDI. MDI is a precursor for rigid foam, which is an excellent insulation material and is used, for example, in buildings and refrigerators to reduce their power consumption. Compared with the conventional method, it cuts CO2 emissions by around 22,000 metric tons per year.