Water containing a variety of ions percolate through a bed of ion exchange resin and the undesirable ions are removed. When the resin is exhausted, regeneration is done to remove the undesirable ions from the resin.
Mixed beds were introduced in the 1950’s, condensate polishers, powdered resins and countercurrent technology in the in the 1960’s. Since then, there have been a number of engineering advances to refine these processes.
In recent years there has been interest in packed bed technology. The resin is “packed” into the vessel with a small layer of inert material to protect the upper distribution system from resin fines and suspended solids and to aid in chemical distribution during regeneration. The resin is regenerated in a direction opposite to the water flow. A reverse flow packed bed system offers a number of advantages over conventional ion exchange:
Higher product water quality
Lower chemical costs – higher chemical efficiency
Less waste water.