Recycling waste water for plastic production

A new, environmentally-friendly process for recycling saline waste water for the production of plastics, provides an outstanding example of how a closed cyclic approach can be applied in practice by industry. It also has a number of significant ecological benefits.

Materials manufacturer Covestro (formally Bayer Material Science) tested an innovative and environmentally-friendly process for recycling saline waste water used in the production of plastics. A processing pilot plant for this was recently opened in Krefeld-Ürdingen in Germany.

This new technology can lower the salt content in water, such as in the river Rhine. The water is used in the production of polycarbonate, a high performance plastic used in many sectors, including the automotive industry, electronics and medical technologies. This latest process will contribute towards saving raw materials and protecting the environment. It forms another step in the development of sustainable technologies and products.

Electrolysis

This is the first time in Germany that industrial saline waste water has been recycled on an industrial scale in a pilot plant. Saline water is usually discharged into waterways adjacent to factory sites, such as the Rhine in this case. Thanks to this new pilot plant, some of this waste water can now be used in an electrolytic process to produce chlorine. Chlorine is one of the raw materials used in the production of polycarbonates and other plastics.

This new process contributes towards an annual saving of 30,000 tons of salt and 400,000 tons of completely desalinated water used in chlor-alkali electrolysis. This is equivalent to preventing an annual emission of 6,200 tons of CO2. The process prevents the discharge of 70 m3 of saline waste water into the Rhine every hour, thereby protecting an equal volume of drinking water.

The chlor-alkali electrolysis process had already been improved by applying various energy-saving initiatives. This included oxygen depolarised cathode technology developed in collaboration with Covestro, which reduced energy consumption by a further 30 per cent in comparison with the standard process. If all chlorine production in Germany applied this proven industrial process, the total national energy consumption could be reduced by 1 per cent. This is approximately equivalent to the annual consumption of a large German city such as Cologne.

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