RE-Salt initiative: Recycling of industrial salty process water
In many industrial processes, large amounts of waste water, containing highly diluted common table salt (5-10%) are released into rivers, being a burden to the ecosystem, especially in terms of drinking water production. Salt is also a crucial raw material for the production of chlorine, key raw material for the manufacture of polycarbonate and other high performance plastics. After several years of research, now a pilot plant has been constructed and gone into operation within Covestro’s project Cycles (funded by German Federal Ministry of Environment BMUB), to demonstrate the reuse of low-concentrated salt- containing wastewater streams. The plant is operating with a throughput of 30m³/h of wastewater. After cleaning the brine, new salt is added to reach the needed concentration for chlorine production thus closing the loop from waste water to a valuable resource. Within another, currently ongoing, project RE-Salt (funded by the German Ministry for Education and Research BMBF), research is being conducted for the purification of saline waste water streams by adapted adsorptive and electrochemical processes.
- The current reduction of 30m³/ waste water per hour allows already reducing the amount of salt used in chlor-alkali electrolysis by 20 000 tons per year;
- The amount of fully desalinated water used will be cut by approximately 220 000 tons per year;
- This saves 1000 tons per year of CO2 emissions thanks to increased resource efficiency; it is aimed to increase the flow rate up to 50m³/h;
- The plant is still in test mode to ensure no negative long time effects occur;
- After successful evaluation, the implementation will be extended to other Covestro sites: the implementation in the production of polycarbonate has an exemplary character. It is known that nowadays 60-70% of all chemically manufactured products come into contact with NaCl.