Electrodialysis of salts from heat-transfer medium solutions using ion-exchange membranes

Abstract

Recycling system that can recover the useful amount of glycol-based chemicals from the spent water-soluble heat-exchanging coolant liquids by electrodialysis (ED) is proposed in this paper. The majority of antifreeze liquids used is based on ethylene glycol (EG), but propylene glycol products are becoming more common. Glycol-based waste streams can originate from heat-exchanging liquids mediums, engine coolants or aircraft deicing fluids. Chemical additives as well as corrosion products and glycol degradation products were removed by ED with heterogeneous Ralex^® AMH-PES and CMH-PES membranes, and pure glycol in water solution was produced. Laboratory experiments with model NaCl and EG solution were carried out. Real heat-transfer fluid from central heating equipment in the civil buildings was also demineralised by laboratory ED unit P EDR-Z (MemBrain s.r.o.). An efficient depletion of NaCl was achieved by reaching 99% desalination degree for the model EG solution. Ninety-eight per cent removal of salt additives was achieved by ED for EG sample from civil buildings cooling system.

Keywords:

• Electrodialysis
• Heterogeneous ion-exchange membranes
• Transport properties of IEMs
• Glycol reuse

Acknowledgements

Work was supported by the Ministry of Education and Sports of the Czech Republic using the infrastructure of the Membrane Innovation Centre (No. CZ 1.05/2.1.00/03.0084).

Notes

Presented at the MELPRO 2014 conference Membrane and Electromembrane Processes, 18–21 May 2014, Prague, Czech Republic