The MIEX® Resin is designed specifically to be used in a continuous ion exchange process that utilizes the high surface area of the resin beads to provide ion exchange in mixed or fluidized bed reactors at very low resin concentrations and short detention times. The magnetic properties of the resin beads result in the beads forming agglomerates that will settle rapidly or fluidize at high hydraulic loading rates, thus allowing small unit process footprints. There are two reactor configurations in which the MIEX® Resin can be applied. A description of the reactor configurations and regeneration process is as follows:
High Rate Configuration
Raw water fed to the base of the reactor vessel is mixed with the MIEX® Resin and the ion exchange process occurs in a fluidized bed (Figure 1). In the fluidized bed the magnetic particles are attracted to each other to form large agglomerates that form a stable resin suspension at hydraulic loading rates of up to 12 gpm/ft2. An agitator operating at slow speeds keeps the resin/water suspension uniformly mixed. A small stream of resin is withdrawn from the reactor vessel, regenerated with a 12% NaCl solution and returned to maintain the ion exchange capacity of the process.
A series of plates (or tube settlers) at the top of the reactor vessel separate the resin from the water and treated effluent overflows into collection launders to downstream treatment processes.
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Figure 1: High Rate MIEX® Process Flow Diagram
Dual Stage Configuration
Ion exchange occurs in a flow-through mixed tank (contactor) where the resin particles are dispersed to provide a high surface area for ion exchange to occur (Figure 2). The magnetic resin particles then agglomerate and settle rapidly in a gravity separator designed for a hydraulic loading rate of 6 gpm/ft2. In the separator, the resin is recovered and most is recycled back to the contactor while a small side-stream is regenerated with a 12% NaCl solution and then returned to the contactor to maintain the ion exchange capacity of the process. Treated water overflows the resin separator to downstream treatment processes.
Figure 2: Dual Stage MIEX® Process Flow Diagram
Resin Regeneration Process
A small volume of resin is continuously removed from the reactor vessel to the regeneration system. Fresh regenerated resin is returned to the reactor to maintain a consistent ion exchange capacity. The continuous withdrawal of loaded resin and return of regenerated resin ensures a consistent treated water quality and prevents the chromatographic peaking that can occur with conventional ion exchange columns. Brine solutions typically consist of NaCl but other salts such as KCl, MgCl2, NaSO4, or NaHCO3 can also be used if sodium or chloride is not desired in the waste discharge.