Better reuse of salt and water from waste flows

Converting salty waste flows from ion exchangers regenerate into new products and saving energy at the same time is possible by using Eutectic Freeze Crystallisation (EFC): a technique for recovering salt from water by freezing. Evides Industriewater, Hatenboer-Water, KWR and EFC Separations have conducted a pilot study within TKI Water Technology which shows that EFC works. Now it’s time for developing the technique further to see how end users can use it.

EFC: an attractive alternative

Salty waste flows are created by the decolouration or softening of drinking water or industrial water for example. The need for processing this regenerate efficiently, cost-effectively and sustainably is growing. In a joint TKI project it was demonstrated using a mobile semi-industrial pilot plant that EFC is a promising technique for processing regenerate flows from ion exchange (in this case cation exchange, for softening water). It even appears to be an attractive alternative for ‘state of the art’ processes, such as evaporation and crystallisation. EFC is technically and economically feasible and produces a high-quality end product.

Pure salt

The salt produced by EFC is of a sufficiently pure quality for reuse. Although the investment and depreciation costs of EFC are slightly higher than current techniques, savings can be made on operational costs. In net terms, this means that the costs for scenarios with or without EFC are approximately the same. Even for the recovery of table salt (a salt with a relatively low economic value) the use of EFC is competitive with current techniques. When (higher value) salts other than the relatively inexpensive table salt can be recovered and reused, then there is added (economic) value for EFC. In addition, there is technical and economic potential for EFC because the technology is still at a relatively early stage of the learning curve.

Circular economy

Increasing interest in the environmentally-friendly processing of residual flows offers good opportunities for the use of EFC in the circular economy. There are already various initiatives for and discussions about using the technique for treating industrial waste flows containing high levels of salt, such as those from the steel industry and cheese processing sector.

Further development and cost saving

A number of the TKI partners are currently studying other process flows and the next stages for further developing the EFC technology: under pilot and practical conditions, with further scaling up and in a continuous process. EFC Separations is also researching and developing how costs can be further reduced through process improvements and integration with filtration techniques. EFC Separations recently purchased the first industrial-scale system for treating ‘acid mine drainage’, with the aim of recovering sulphate salts and reusing the clean water.

EFC pilot.