Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93DEMINERALIZERSFigure 13 illustrates a single-bed demineralizer. When in use, water flows in through the inletto a distributor at the top of the tank. The water flows down through the resin bed and exits outthrough the outlet. A support screen at the bottom prevents the resin from being forced out ofthe demineralizer tank.Single-BedRegenerationFigure 13 Single-Bed DemineralizerThe regeneration of a single-bed ion exchanger is a three-step process. The first step is abackwash, in which water is pumped into the bottom of the ion exchanger and up through theresin. This fluffs the resin and washes out any entrained particles. The backwash water goesout through the normal inlet distributor piping at the top of the tank, but the valves are set todirect the stream to a drain so that the backwashed particles can be pumped to a container forwaste disposal.The second step is the actual regeneration step, which uses an acid solution for cation units andcaustic solution for anion units. The concentrated acid or caustic is diluted to approximately10% with water by opening the dilution water valve, and is then introduced through adistribution system immediately above the resin bed. The regenerating solution flows throughthe resin and out the bottom of the tank to the waste drain.The final step is a rinsing process, which removes any excess regenerating solution. Water ispumped into the top of the tank, flows down through the resin bed and out at the bottom drain.Rev. 0ME-05Page 25
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