Innovative ODC technology cuts energy consumption and CO2 emissions in chlorine production

Innovative engineering achievements

Oxygen-depolarized cathode (ODC) technology is based on the common membrane process by which chlorine, caustic soda, and hydrogen are formed from rock salt (NaCl), water, and electricity – with one decisive difference. The oxygen-depolarized cathodes developed by Covestro were integrated into thyssenkrupp Uhde Chlorine Engineers’ NaCl electrolysis cells (single-element technology). By introducing oxygen into the cathode, the often-unwanted formation of hydrogen is suppressed and nothing but chlorine and caustic soda are produced. What makes this ODC process so interesting is that it cuts the energy required to produce chlorine by up to 25%. With CO2 emissions also cut by up to a quarter, this chlorine production process is much more resource- and environment-friendly. What’s more, thyssenkrupp engineers succeeded in raising the current density of the electrolyzer by 50% from 4 to 6 kA/m² so electrolyzers with the same size have now 50% more product output. Plant operators will profit from this smaller footprint, the lower maintenance costs, and the generally high efficiency of the NaCl-ODC electrolysis process.

Our energy-saving ODC technology can make a key contribution to the competitiveness of our customers in the chemical industry.

Denis Krude, CEO, thyssenkrupp Uhde Chlorine Engineers

Significant environmental benefits

Annual global production of chlorine is around 80 million metric tons, with output steadily rising. If all this chlorine were produced using ODC technology, around 35 million metric tons of CO2 emissions could be saved each year. And as energy accounts for around a third of a chlorine plant’s operating costs, ODC technology will prove an attractive proposition for plant operators, especially since the new technology can be easily integrated into existing facilities as cell size and brine circulation are 100% compatible.

Proven in practice

Covestro is already operating the ODC technology since 2011 at its plant in Krefeld-Uerdingen, Germany, and currently building the first world-scale chlorine plant based on ODC technology at its site in Tarragona, Spain. Annual CO2 emissions from the Tarragona plant will be around 22,000 metric tons lower than with production based on conventional single-element electrolysis. This is roughly the amount of CO2 emitted by 15,000 cars over the course of a year. Covestro also sees significant potential for the technology in applications beyond chlorine production, e.g. stationery energy storage systems, enhanced power generation from hydrogen, or decentralized water treatment. In other words, this innovative ODC technology will not only bring climate-related benefits to production of a key base chemical but can also help to power a more sustainable economy.

The bottom line: A groundbreaking collaboration between thyssenkrupp and Covestro resulted in an innovative technology for producing the vital base chemical chlorine in a much more environment- and resource-friendly way. ODC technology reduces by up to a quarter the energy required to produce chlorine and the carbon dioxide emissions generated by the conventional process. What’s more, ODC technology can be easily integrated into existing chlorine plants.