Miscellaneous Mechanical ComponentsDOE-HDBK-1018/2-93DEMINERALIZERSSummaryThe important information in this chapter is summarized below.Demineralizers SummaryDemineralization of water is one of the most practical and commonmethods used to remove dissolved contaminates. Dissolved impuritiesin power plant fluid systems can generate corrosion problems anddecrease efficiency due to fouled heat transfer surfaces. Demineralizers(also called ion-exchangers) are used to hold ion exchange resins andtransport water through them. Ion exchangers are generally classifiedinto two groups: single-bed ion exchangers and mixed-bed ionexchangers.A demineralizer is basically a cylindrical tank with connections at thetop for water inlet and resin addition, and connections at the bottom forthe water outlet. The resin can usually be changed out through aconnection at the bottom of the tank. The resin beads are kept in thedemineralizer by upper and lower retention elements, which are strainerswith a mesh size smaller then the resin beads.The water to be purified enters the top at a set flow rate, flows downthrough the resin beads where the flow path causes a physical filtereffect as well as a chemical ion exchange. The chemistry of the resinexchange is explained in detail in the Chemistry FundamentalsHandbook. There are two types of demineralizers, single-bed and mixed-bed. Single-bed demineralizers have resin of either cation or anion exchangesites. Mixed-bed demineralizers contain both anion and cation resin.All demineralizers will eventually be exhausted from use. To regenerate the resin and increase the demineralizer's efficiency, thedemineralizers are regenerated. The regeneration process is slightlydifferent for a mixed-bed demineralizer compared to the single-beddemineralizer. Both methods were explained in this chapter.Rev. 0ME-05Page 29
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