TM 5-810-15
(2) Sodium zeolite (NaZ) softeners are
(dealkalizer) may be used in conjunction with NaZ
used to remove calcium (Ca) and magnesium (Mg)
softener to remove carbonate, bicarbonate and
from the feedwater. NaZ softeners do not remove
CO2. Used in this manner, the dealkalizer takes the
silica, bicarbonate, or carbonate, and should be
place of a hydrogen cycle softener and degasifier in
used alone when these constituents are not a
the split stream system. A dealkalizer application is
problem in the boiler feedwater. A typical NaZ
shown in figure 7-7. This particular type system
softener is shown in figure 7-5.
will not reduce TDS.
(3) A split stream softener with degasifier
(5) A weak cation exchanger, regenerated
should be used when it is necessary to remove
with acid, followed by a strong acid cation ex-
hardness (Ca, Mg) and carbon dioxide (CO2)
changer, salt regenerated, can be used in conjunc-
formed from bicarbonate and carbonates. A typical
tion with a degasifier. The weak acid exchanger
split stream system is shown in figure 7-6. The use
will remove the alkalinity and the hardness associ-
of split stream versus other options will be decided
ated with alkalinity, and the salt regenerated strong
by means of a LCCA and an evaluation of applica-
acid cation exchanger will remove the balance of
ble safety restrictions. This particular type system
the hardness. This balance will depend on. the
will result in a reduction of total dissolved solids
hardness to alkalinity ratio of the raw water. The
(TDS).
degasifier will be used to strip the CO2 formed in
(4) Chloride
anion
exchangers
the weak acid exchange process.
7-7
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