- 23 August 2006 -

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Novel technology: Fresh approach to countercurrent ion exchange

By reversing a commonly-used way of distributing fluids to ion-exchange cells, Belgian separations technology company PuriTech has developed a liquid adsorption separation technology, which could improve liquid-resin contact efficiency, while reducing plant operating costs and CAPEX, explains Filip Rochette.

Where can ion exchange be used?

The applications for ion exchange have many forms, and these will undoubtedly increase as awareness of the technology continues to grow. As scientists and engineers create an ever-increasing variety of polymers and other materials, the potential for producing new, useful ion exchange resins will also expand.

Ion exchange is mostly used in the treatment of water for drinking, for commercial and industrial use, and wastewater treatment. Ion exchangers can soften and deionise water, and they can even be used in desalination. And the process is also used in the industrial sectors where pure water is crucial to both product development and yield - for example in the manufacture of semiconductors.

A growing focus on clean water is creating enormous opportunities for the water treatment business worldwide, particularly in regions such as Asia and Africa . The order flow for ion exchange systems and resins has been growing steadily, and long-term growth prospects appear to be bright. And recent developments and refinements in resin technologies make ion exchange one of the best and most complete forms of wastewater treatment available today.

Ion exchange can also help in the preparation of various acids, bases, salts and solutions, and the recovery of valuable metals is also possible using resins.

The use of ion exchange and adsorbent technology for the processing of food streams within the nutrition market place is well established, with a history stretching back decades. The food industry uses the process in a variety of ways, ranging from wine-making to sugar manufacture.

Changing the ion exchange approach

Against this background of strengthening markets and the growing potential of ion exchange, PuriTech has developed IONEX - a liquid adsorption separation technology - with an aim to build on and improve existing systems (particularly the continuous countercurrent process) and broaden the technology's application base.

Existing technologies include fixed-bed and continuous and continuous countercurrent ion exchange systems. Based on a batch-style operation, fixed-bed units are used in around 90% of the projects, but compared with continuous countercurrent systems their performance is relatively weak. Furthermore, they waste 2%-4% of the treated fluid flow in water treatment applications.

Continuous ion exchange, which makes use of an array of automated valves for each resin cell, offers an improved approach and some advantages, but relies on a lot of piping and complex controls. Two major companies have developed continuous countercurrent ion exchange units that use a turntable, or carousel, to rotate the resin cells around a central valve. This also requires complex controllers, and the use of flexible hoses between the valve and resin chambers.

With its IONEX system, PuriTech has reversed a tried and tested approach to distributing fluids to ion exchange cells or chambers, by creating a system that can improve liquid resin contact efficiency and lead to a reduction in plant operating costs and capital expenditure.

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