Cycle Single Stage Demineralization

COMBINED CYCLE SINGLE STAGE DEMINERALIZATION Mixed Bed H+/OH Cycle 

As the name implies, demineralization occurs through ideally simultaneous exchange of cations and anions across a uniform mixture of strong acid cation and strong base anion (Type 1) resins in the hydrogen and hydroxide forms respectively, all contained in a single vessel  

Ideally a 1 1 equivalent mixture of cation and anion exchange resins may be considered as an infinite multitude of uniformly distributed cation-anion pairs effecting demineralization in a single pass and the construction of such a unit is discussed briefly under Chapter 10. 

In this application a mixed bed is widely used to remove or polish the ion residuals remaining in demineralized water after prior stage-wise coflow or counterflow demineralization. The anion cation resin volume ratio often differs from 1 1 for polishing mixed beds depending upon the anticipated loading of cations (sodium) and anions ( silica ). Since no hardness cations are present, only sodium, precipitation reactions are absent and a well designed unit with clean resins 

This approach of stage-wise demineralization followed by mixed bed polishing represents the long established classical process philosophy for the production of high quality make-up demineralization water for high pressure steam generation and manufacturing process waters. 

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Mixed Beds (see Chapter 8, Combined Cycle Single Stage Demineralization )... 

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