Demin Brochure

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


M3per

ANION Min. Min. cycle From m3/cycle Hr GPM TO

Displace 60 60 50 Cation 50 50 220 Treated Tank


Settle 30 120 0 - 0 0 0 -



Fast Rinse 60 240 35 Polish 35 35 154 Waste sump

Total HRS 4

Total Polish 135 33.75Total Waste 100 25


M3per

Mixbed Min. Min. cycle From m3/cycle M3/Hr GPM TO

Displace 15 15 25 Polish 25 100 440


Settle 15 45 0 - 0 0 0 -



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.

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