PuriTech saw an opportunity in the competitive and growing international ion exchange market place for a liquid adsorption separation technology that not only reduced plant operating costs and capital expenditure, compared with existing systems, but also offered enhancements in both functionality and performance.
In developing IONEX, PuriTech`s main objective was to improve on existing system design, in particular continuous countercurrent processes, and broaden and extend the technology`s application base.
Traditional Design
Standard, existing technologies include fixed-bed and continuous countercurrent ion exchange systems. Based on a batch-style operation, fixed-bed units are used in around 90% of projects, but compared with continuous countercurrent systems their performance is relatively weak. Furthermore, they are prone to wasting 2–4% of the treated fluid-flow in water treatment applications.
Advanced fixed bed systems make use of an array of automated valves for each resin cell, offer an improved approach and some advantages, but rely on a lot of piping and complex controls.
Other continuous countercurrent ion exchange systems use a carousel to rotate the resin cells around a central valve. This approach again offers some advantages, but also needs complex controllers to operate, and requires the use of flexible hoses between the valve and resin chambers.
Elegant Solution
Realising the growing market potential of ion exchange, PuriTech has taken continuous countercurrent ion exchange system design to a new level. It sought solutions to problems that have restricted the development and broader use of current systems.
The company has effectively reversed a tried and tested approach to distributing fluids to ion exchange cells, or chambers, used by competitor companies, to create a cleverly conceived system. The elegant solution not only improves liquid-resin contact efficiency, but also reduces plant operating costs and requires a smaller investment in capital equipment.
Multi-Port Distribution Valve
IONEX uses a single, multi-port distribution valve, creating a process system for continuous, countercurrent ion exchange. The patented valve distributes different flow streams to several resin cells and determines whether the resin is in an adsorption, a regeneration or a rinsing cycle.
The technology is markedly different from other continuous, countercurrent ion exchange systems that are available in the market place. Instead of using a carousel to move the cells around a central valve, the process disc within the IONEX valve rotates around a central axis and distributes the different flow streams to the cells containing ion exchange resin or other adsorption materials. During a full rotation each cell is subjected to an entire sorption cycle.
Resin Usage and Regeneration
Adsorptive and ion exchange separation generally comprises a two- phase mass-transfer - an adsorption cycle and desorption cycle - separated by washing or rinsing of the solid phase between these mass transfer steps. The use of shorter and smaller resin beds allow for maximum resin usage.
The mass-transfer zone in a standard ion exchange plant is typically a small section of the actual operating bed length. This small production section, where mass transfer takes place, passes as a transfer zone through the bed - from a saturated resin to an unsaturated resin.
To avoid frequent bed regeneration, the content of a vessel is saturated before regeneration takes place. Each regeneration follows a batch sequence. Countercurrent contacting on a continuous basis does not suffer these limitations, because it is not a batch process.
Valve Configurations
Various valve configurations and materials are available for specific applications.
For instance, for a non-corrosive processing environment, PuriTech offers a standard stainless steel valve head with a polytetrafluoroethylene (PTFE) process disc. For applications that involve corrosive streams the company has developed a polyvinyl chloride (PVC) valve head and an adapted process disc. It also offers valve heads made from Hasteloy or Inconel and discs fabricated from polyvinylidenefluoride (PVDF) for specialist applications.
Benefits and Advantages
In short, the innovative features of PuriTech`s IONEX system make it suitable for separation and processing duties in a diverse range of applications. Many of these features, including those listed here, make the technology highly desirable, and will ensure its continued adoption in numerous sectors and industries worldwide. Essentially, IONEX systems:
- do not require the use of a turntable, or carousel
- do not rely on the use of hoses
- are easy to operate and need little maintenance
- are designed for high resin utilization
- produce lower waste volumes
- consume lower volumes of chemicals and water
- cost less to operate, compared with standard, existing technologies
- offers a high degree of flexibility - to deal with changing flows and concentrations in the feed stream
