Mix Bed Plant

A mixed bed exchange has both cation and anion resin mixed together in a single vessel. As water flows through the resin bed, the ion exchange process is repeated many times, “polishing” the water to a very high purity. During regeneration, the resin is separated into distinct cation and anion fractions. The resin is separated by back washing, with the lighter anion resin settling on top of the cation resin. Regenerate acid is introduced through the bottom distributor, and caustic is introduced through distributors above the resin bed. The regenerate streams meet at the boundary between the cation and anion resin and discharge through a collector located at the resin interface. Following regenerate introduction and displacement rinse, air and water are used to mix the resins. Then the resins are rinsed, and the unit is ready for service.

Counter flow and mixed bed systems produce a purer water than conventional cation-anion demineralizers, but require more sophisticated equipment and have a higher initial cost. The more complicated regeneration sequences require closer operator attention than standard systems. This is especially true for a mixed bed unit.

After the exchange, the quality of water is as follows:

•   Cation quality - less than 10 Micro siemens per centimeters

•   7.5 to 8.5 pH

•   Used as a polishing unit, the mixed bed has less than

1 micro siemens quality