Water, even if it is occurring in nature, consists of
lot of minerals which is harmful for both humans and animals. The
consumption of these harmful minerals can be avoided by using
demineralizer. The minerals present in water are normally calcium,
magnesium, sodium, alkalinity, chlorides, sulfates, nitrates, and silica
which can also harm industrial pipes, boilers etc by causing corrosion,
scale building, spotting on finished surfaces, precipitation in chemical
products and other related problems. The demineralizer is designed to
sort out these problems.
Ion Exchange Resins Ion-exchange
resins are available in the form of granules, beads, or sheets.
They are light weight porous solids that swells when immersed in
solution. For specific ion exchange resins of suitable chemical
and physical properties can be synthesized.
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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.
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
External Source
Demineralization
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