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7/28/2019 Demin Brochure
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5946 Ridgedale Drive, Houst on, Texas 77039, USA; Tel: (281) 227-9577, Fax: (281) 227-9578E-mail: [email protected], www.spec-pro.com
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DEMINERALIZING SYSTEMS
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Demineralizers
Demineralizers can produce high-purity water for nearly every use. Deminerlaized water is widely used for h
pressure boiler feed water and for many process waters. The quality of water produced in comparable to dist
water, usually at a fraction of the cost. Demineralizers come in a wide variety of sizes. Systems range from labora
columns that produce only a few gallons per hour to systems that produce thousands of gallons per minute.
Like other ion exchange systems, demineralizers require filtered water in order to function efficiently. Resin foul
and degrading agents, such as iron and chlorine should be avoided or removed prior to demineralization. Anion re
are very susceptible to fouling and attack from the organic materials present in many surface water supplies
demineralizer does not remove some forms of silica, known as colloidal, or non-reactive. Hot, alkaline boiler w
dissolves the colloidal material, forming simple silicates that are similar to those that enter the boiler in a soluble fo
As such, they can form deposits on tube surfaces and volatilize into the steam.
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REGENERATION CYCLE SAMPLE
Regeneration Step ElapsedM3per Effluent
M3per
Cation Min. Min. cycle From m3/cycle M3/Hr GPM TO
Displace 60 60 50 Polish 50 50 220 Anion unit
Backwash 30 90 35 Polish 35 70 308 Waste sump
Settle 30 120 0 - 0 0 0 -
Acid Injection 30 150 10 Polish 10 20 88 Waste sump
Slow Rinse 30 180 10 Polish 10 20 88 Waste sump
Fast Rinse 60 240 35 Polish 35 35 154 Waste sump
Total HRS 4
Total Polish 135 33.75
Total Waste 100 25
Regeneration Step ElapsedM3per Effluent
M3per
ANION Min. Min. cycle From m3/cycle Hr GPM TO
Displace 60 60 50 Cation 50 50 220 Treated Tank
Backwash 30 90 70 Polish 70 70 308 Waste sump
Settle 30 120 0 - 0 0 0 -
Acid Injection 30 150 20 Polish 20 20 88 Waste sump
Slow Rinse 30 180 20 Polish 20 20 88 Waste sump
Fast Rinse 60 240 35 Polish 35 35 154 Waste sump
Total HRS 4
Total Polish 135 33.75Total Waste 100 25
Regeneration Step ElapsedM3per Effluent
M3per
Mixbed Min. Min. cycle From m3/cycle M3/Hr GPM TO
Displace 15 15 25 Polish 25 100 440
Backwash 15 30 20 Polish 20 80 352 Waste sump
Settle 15 45 0 - 0 0 0 -
Acid Injection 30 75 20 Polish 20 40 176 Waste sump
Slow Rinse 15 100 20 Polish 20 80 352 Waste sump
Fast Rinse 20 120 35 Polish 35 462 396.26 Waste sump
Total HRS 2
Total Polish 195 97.5
Total Waste 50 25
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MIXED BED / SEPARATE BED 18" Dia. 36" Dia. 72" Dia. 96" DiaModel SP-18DM SP-36DM SP-72DM SP-96DM
ANION/CATION/CAUSTIC
StrongBase II
StrongBase I
StrongBase II
StrongBase I
StrongBase II
StrongBase I
StrongBase II
StrongBase I
SERVICE FLOW RATES (GPM)
Minimum 5 5 23 23 79 79 168 158
Normal 15 15 65 60 210 200 450 420
Maximum 30 23 125 120 350 350 800 800
ION EXCHANGE DATACation resin/ft3 3 3 14 12 47 40 101 84
Anion Resin /ft3 4 4 17 18 58 60 123 126
Nominal total capacity (KGR) 64 48 272 214 928 714 1968 1500
REGENERANT CHEMICALS
Cation Resin, lbs 100% HCL 18 18 84 72 282 240 606 504
Approximate Gal. 30% HCL 6 6 28 24 94 80 202 168
Anioin Resin, lbs 100% NaOH 32 32 130 144 464 480 984 1008
Approximate Gal. 50% NaOH 5 5 21.4 22.6 729 75.4 154.6 158.4
DIMENSIONS
Column Diameter 18 18 36 36 66 66 96 96
Straight Side 90 90 96 96 96 96 96 96
Overall Height 106 106 120 120 130 130 146 146Overall Width 35 35 59 59 89 89 124 124
Overall Depth 37 37 55 55 86 86 129 129
CONNECTIONS/ ACCESS SIZES (IN.)
Inlet Flange 15 1.5 2.5 2.5 4 4 6 6
Outlet Flange 1.5 1.5 2.5 2.5 4 4 6 6
Drain Flange 1 1 2 2 4 4 6 6
Top Access 18 Flg 18 Flg12 x16
12 x16 12 x 16 12 x 16 12x 16 12 x 16
Media Removal 14 14 2 NPT 2 NPT 2 NPT 2 NPT 2 NPT 2 NPT
WEIGHTS (LBS)
Dry without Resin 770 770 1705 1705 4230 4230 12375 12375
Operating 1860 1860 6410 6410 21450 21450 48900 48900
STANDARD VESSEL SIZES
CAUSTIC VESSEL ACID VESSEL
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APPLICATION
ndividual Bed Ion Exchangers consist of in line vessels containing cation and anion
resins. These units reduce the ionic impurities exchanging positively charged ions for
hydrogen ions in the cation vessel, and negatively charged ions for hydroxyl ions in
the anion vessel. The released hydrogen and hydroxyl ions combine to form purewater. Individual bed exchangers are typically capable of producing water quality
between 20,000 and 500,000 Ohm-cm, depending on feedwater quality and resin
selection. Each resin vessel has a finite capacity for removing positively or
negatively charged ions. After each processed batch, the cation vessel of the separate
bed exchanger is regenerated using an acid solution, while the anion vessel is
regenerated using a caustic solution.
APPLICATION
A mixed bed exchanger has both cation and anion resin mixed together in a single
vessel. As water flows through the resin bed, the ion exchange process is repeated
many times, polishing the water to a very high purity. During regeneration, the
resin is separated into distinct cation and anion fractions. The resin is separated by
backwashing, with the lighter anion resin settling on top of the cation resin.
Regenerate acid is introduced through the bottom distributor, and caustic is
ntroduced through distributors above the resin bed. The regenerate streams meet
at the boundary between the cation and anion resin and discharge through a
collector located at the resin interface. Following regenerant introduction and
displacement rinse, air and water are used to mix the resins. Then the resins are
rinsed, and the unit is ready for service.
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Demineralization
Softening alone is insufficient for most high-pressure boiler
eed waters and for many process streams, especially those
used in the manufacture of electronics equipment. In
addition to the removal of hardness, these processes require
emoval of all dissolved solids, such as sodium, silica,
alkalinity, and the mineral anions (C1-, SO42-and NO3
-).
Demineralization of water is the removal of essentially all
norganic salts by ion exchange. In this process, strong acid
cation resin in the hydrogen form converts dissolved salts
nto their corresponding acids, and strong base anion resin in
he hydroxide form removes these acids. Demineralization
produces water similar in quality to distillation at a lower
cost for most fresh waters.
Principles of Demineralization
A demineralizer system consists of one or more ion exchange resin columns, which include a strong acid cation, u
and a strong base anion unit. The cation resin exchanges hydrogen for the raw water cations. A measure of the
concentration of the strong acids in the cation effluent is the free mineral acidity (FMA). In a typical service run
FMA content is stable most of the time
cation exchange were 100% efficient,
FMA from the exchanger would be equ
the theoretical mineral acidity (TMA) of
water. The FMA is usually slightly lo
than the TMA because a small amoun
sodium leaks through the cation exchan
The amount of sodium leakage dependthe regenerant level, the flow rate, and
proportion of sodium to the other cation
the raw water. In general, sodium lea
increases as the ratio of sodium to t
cations increases.
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Effluent silica and conductivity are
mportant parameters to monitor during a
demineralizer service run. Both silica and
conductivity are low at the end of the fast
inse. When silica breakthrough occurs at
he end of a service run, the treated water
silica level increases sharply. Often, theconductivity of the water decreases
momentarily then rises rapidly. This
emporary drop in conductivity is easily
explained. During the normal service run,
most of the effluent conductivity is
attributed to the small level of sodium
hydroxide produced in the anion
exchanger. When silica breakthrough
occurs, the hydroxide is no longer
available, and the sodium from the cation exchanger is converted to sodium silicate, which is much less conduc
han sodium hydroxide.
When the end of a demineralizer run is detected, the unit must be removed from service immediately. If
demineralizer is allowed to remain in service past the breakpoint, the level of silica in the treated water can rise ab
hat of the influent water, due to the concentrating of silica that takes place in the anion resin during the service
Strong base anion exchangers are regenerated with a 4% sodium hydroxide solution. As with cation regeneration
elatively high concentration of hydroxide drives the regeneration reaction. To improve the removal of silica from
resin bed, the regenerate causti
usually heated to 120 F or to
temperature specified by the r
manufacturer. Silica removal is
enhanced by a resin bed preheat
before the introduction of w
caustic.
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As a cation exchange unit nears
exhaustion, FMA in the effluent
drops sharply, indicating that the
exchanger should be removed from
service. At the time the resin should
be regenerated with an acid solution,
which returns the exchange sites tohe hydrogen form. Sulfuric acid is
normally used due to its affordable
cost and its availability. However,
mproper use of sulfuric acid can
cause irreversible fouling of the resin
with calcium sulfate. To prevent the
occurrence, the sulfuric acid is
usually applied at a high flow rate (1
gpm per square foot of resin) and an
nitial concentration of 2% or less.
Some installations use hydrochloric acid for regeneration. This necessitates the use of special materials of construc
n the regenerant system. As with sodium zeolite unit, an excess of regenerant (sulfuric or hydrochloric acid
equired up to three times the theoretical dose. To complete the demineralization process, water from the cation
s passed through a strong base anion exchange resin in the hydroxide form. The resin exchanges hydrogen ions
both highly ionized mineral ions and the more weakly ionized carbonic and silicic acids.
Demineralization completely removes the cations and anions from the water. In reality, because ion exchange react
are equilibrium reactions, some leak
occurs. Most leakage from cation uni
sodium. This sodium leakage is conve
to sodium hydroxide in the anion u
Therefore, the effluent pH of a two
cation-anion demineralizer system
slightly alkaline. The caustic produce
the anions causes a small amount of
leakage. Demineralization using st
anion resins removes silica as well as o
dissolved solids. Effluent silica as we
other dissolved solids.
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Operational Problems
Changes in raw water quality have a significant
mpact on both the run length and the effluent
quality produced by an ion exchange unit.
Although most well waters have a consistent
quality, most surface water compositions vary
widely over time. A 10% increase in the hardness
of the water to a sodium zeolite softener causes a
10% decrease in the service run length. An
ncrease in the ratio of sodium to total cations
causes increased sodium leakage from a
demineralizer system. Regular chemical analysis
of the influent water to ion exchangers should be
performed to reveal such variations.
Other causes of ion exchange operational problems include:
Improper regenerations, caused by incorrect regenerant flows, times, or concentrations. Manufactu
recommendations should be followed when regenerating ion exchange resins.
Channeling, resulting from either high or low flow rates, increased suspended solids loading or p
backwashing. This causes premature exhaustion even when much of the bed is in a regenerated state.
Resin fouling or degradation, caused by poor-quality regenerant.
Failure to remove silica from the resin, which can result from low regenerant caustic temperature. This can
to increased silica leakage and short service runs. Excess contaminants in the resin, due to previous opera
past exhaustion loads. Because the resin becomes loaded with more contaminants than a normal regeneratio
designed to remove, a double regeneration is required following an extended service run.
Leaking valves, which cause poor quality effluent and prolonged rinses.
Broken or clogged distributor, which leads to channeling.
Resin loss, due to excessive backwashing or failure in the under drain screening or support media.
Cation resin in the anion unit, causing extended rinse times and sodium leakage into the demineralized water Instrumentation problems, such as faulty totalizers or conductivity meters, which may indicate a problem w
none exists, or may introduce poor quality water to service. Instrumentation in the demineralizer area shoul
checked regularly.
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Equipment and Operation
The equipment used for cation-
anion demineralization is similar to
hat used in zeolite softening. The
primary difference is that the
vessels, valves, and piping must be
made of (or limed with) corrosion-
esistant materials. Rubber and
polyvinyl chloride (PVC) are
commonly used for ion exchange
vessel linings. The controls and
egenerant systems for
demineralizer are more complex, to
allow for such enhancements as
stepwise acid and warm caustic
egenerations.
The water used for each step
anion resin regeneration should
free from hardness, to preprecipitation of hardness alts I
alkaline anion resin bed. Continu
conductivity instruments and s
analyzers are commonly used
monitor anion effluent water qu
and detect the need for regenera
In some instances, conduct
probes are placed in the resin
above the under drain collector
detect resin exhaustion before s
breakthrough into the treated w
occurs.
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QUALITY BY DESIGN
Separate Bed Ion Exchanger is designed to
provide reliable service and long operation life.
During the development of this product, strict
attention is paid to ease of use and serviceability.Our successful integration of these design
philosophies enablesSPECto offer a product serieswith excellent value, while helping our customers to
reduce installation, commissioning and operating
costs. Hydrostatic and factory testing of each unit
prior to shipment permits quality performance when
placed in operation. Units are delivered pre-
assembled and ready for resin loading.
VESSELS
Vessels are constructed of carbon steel and are rated for 100 psig. Each is designed with structural steel channel
and bolt-down footpads. These rugged construction features assure long product life and makeSPEC Ion Exchansuitable for Seismic Zone IV applications. To simplify installation all vessels in the series are designed with lif
ugs. Units are supplied with full size flanged and gasketed top manways to allow complete access to vessel inte
for the purpose of applying and inspecting internal coatings. Vessels come standard with a media removal por
simplify resin replacement and a sight glass to permit checking resin level and condition. Both vessels are mounted
a rugged unitized base.
PLC CONTROLLED PROCESS
Ion Exchangers are controlled with
programmable logic control panels. Process is
monitored through a HMI (Human Machine Interface)
unit. Errors and alarms are displayed on the control
panel to alert the operator.
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Selection of material is the most important step in the construction of a demineralizing system. SPECs stand
material of consruction exceed the requirements of most major engineering firms and we provide them
competitive prices. Look carefully at our above-standard specifications:
All stainless steel external piping, welded contruction.
All stainless steel NEMA 4X electrical enclosures.
All stainless steel conteruction of internal piping systems.
All stainless steel construction of small skid and supprt bra
structural members.
All stainless steel instrument tubing and tubing support tray
ASME code, rubber-lined ion exchange vessels.
All carbon steel surfaces coated with premium-grade phen
epoxy.
Equipment size based on resin capacities derated
compensate for anticipated capacity loss 20 25%.
Corrosion-free, structurally sound equipment designed
reduce downtime and maintenance cost.