Sustainability is also a top priority at Covestro's site in Krefeld-Uerdingen – for instance, in chlorine production. Chlorine, for example, is used in around two-thirds of all chemical products, including plastics. Unfortunately, chlorine is not found in nature and has to be produced through an energy-intensive process. Covestro and its partners are helping to change that: the company has developed a process that reduces the required amount of electricity by up to 25 percent. The oxygen depolarized cathode (ODC) method has been used successfully in a pilot plant at the Krefeld-Uerdingen site since 2011.
That innovation was based on the commonly used membrane process in chlor-alkali electrolysis, which has become a standard method for manufacturing chlorine. In this process, chlorine, sodium hydroxide and hydrogen are derived from table salt (NaCl) and water. However, things are about to change. Krefeld-Uerdingen will now no longer use customary hydrogen-producing electrodes but rather an oxygen depolarized cathode. Supplying the cathode with oxygen prevents the formation of hydrogen, leading only to the production of chlorine and sodium hydroxide.
As a result, the process now requires only two volts instead of three volts of electricity. This might sound small, but in reality it has a huge impact: If this innovative technology were used across Germany, it would reduce the energy consumption of the entire country by one percent. This corresponds to the total annual energy needs of a major city like Cologne.
In addition, the Covestro site succeeded in reusing the salty industrial wastewater that is produced through polycarbonate manufacture in an industrial pilot plant for the first time. This will save up to 30,000 tons of salt and 400,000 tons of fully desalinated water per year. Since the recycled waste water can be reused in chlorine production, this process also saves valuable drinking water resources.
The roll out of the technology to other Covestro sites is also ongoing. Currently, researchers continue to work intensively on multiple projects and procedures or using wastewater containing salt and increasing the quantity of recycled materials.