Dissolved ionic material from water is removed by demineralization process. This process is followed to obtain pure water. Demineralization takes place in an ion exchange unit called as demineralizer or deionizer that consist of cation bed, an anion bed and a mixed bed in series. The mixed bed consist of both cation and anion resins and is called as polisher. The mixed bed provides the highest ion removal efficiency.
Positively charged ions like calcium, magnesium and sodium are removed by the cation bed whereas negatively charged ions like sulfate and chloride are removed by the anion beds. Depending on the composition of water to be purified, the resin bed is chosen. Using conductivity regeneration of the ion exchange unit is accomplished. Control over cation and anion beds are necessary and it is achieved by measuring the inlet and outlet conductivity to obtain a ratio. This process is called as "Across the Bed" monitoring. Conductivity within the bed and the outlet is measured to get the information that when the regeneration is necessary.
Water Demineralizer Plant
The demineralizer plant consist of both cations and anions vessel which are placed in series. Anion unit receives the effluent of the cation unit whereas the effluent from enters the top of the anion unit and the discharge from the anion unit goes to the treated water header or into a polishing unit.
It was only after the production of different types of resins demineralization on large scale began. The popular resin used for demineralization purpose are:
• Strong Acid Cation
• Weak Acid Cation
• Strong Base Anion
• Weak Base Anion