Reuse of residuals
Energy-efficient salt recovery with Eutectic Freeze Crystallization
Geert-Jan Witkamp, professor at Delft University of Technology, collaborates with KWR on Eutectic Freeze Crystallization for Evides Industriewater.
“When you use water, you want to produce as little waste as possible. You try to transform the used water into clean water and residual products. We’re working on a technique that in theory transforms 100% of the water.” These are the words of Geert-Jan Witkamp, professor at TU Delft and a specialist in “green” processes like Eutectic Freeze Crystallization. “With Eutectic Freeze Crystallization (EFC) you can transform membrane concentrate (a desalinisation residual stream) from seawater and industrial water into salt and ice crystals. You can easily separate the salt from the water and reuse the salt,” says Witkamp. In collaboration with KWR, he’s working on the implementation of the technique at Evides Industriewater. The other partners in the project are Hatenboer Water and EFCseparations, a TU Delft spin-off. The project is partly financed by the Top consortium Knowledge and Innovation (TKI) Water Technology programme.
“From an economic perspective, the application of Eutectic Freeze Crystallization is of interest in the case of water that contains a lot of salt. It is not a substitute for membrane technology,” says Witkamp. “The focus of EFC is the salt crystallization process, not the water production; even though both techniques could be perfectly combined.” EFC is more sustainable, for example, than evaporation crystallization, which is currently still often applied. “The evaporation temperature for water is high. The freezing of water requires less energy,” says Witkamp.
Evides uses ion exchangers to soften its water. They function as a pre-treatment step, after which the water is purified by filters. The ion exchangers have to be periodically regenerated with salt. KWR is working with Witkamp on the construction of an installation to help separate the released salt solution into pure water and salt. EFC is to be used in combination with techniques such as nanofiltration and reverse osmosis. The salt can be reused. The installation will be ready in the autumn of 2014 and installed at Evides.
© 2017 KWR Watercycle Research Institute
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Manager Water Systems and Technology