Umar Farooq prepared a document on ion exchange processes used in power plant chemistry. It provides an overview of various water treatment methods including reverse osmosis desalination, multi-stage flash distillation, lime soda softening, zeolite softening, and demineralization using various ion exchange resins. The document describes the chemical processes involved and advantages and disadvantages of each method. It also discusses common issues with ion exchange like excessive regeneration frequency and solutions to improve treated water quality and production.

1. Power Plant Chemistry
Ion Exchange Process
Prepared By : -
Umar Farooq
Chemist “A” Chemical Section
MSC ( Chemistry ) MBA ( Marketing )
umar7325@yahoo.com
107301@se.com.sa
SEC Shoaiba Jeddah
Saudi Arabia 1

2. Power Plant Chemistry
 Table of Content
 External Water Treatment
 RO Desalination
 MSF Desalination
 Lime Soda Softening
 Zeolite Softening
 Demineralization
 Weak Cation Resin
 Strong Cation Resin
 Weak Anion Resin
 Strong Anion Resin
 Mix Bed

4. External Water Treatment
 It is the removal of impurities from water
out side the ( Condenser ) in power plant
because raw water taken from the river or
sea contain a large number of impurities
with respect to surrounding ,so it is very
necessary to make cleaned and purify the
water before it entrance to wards
( Condenser boiler )
Umar Farooq Chemist
“A” Shoaiba Jeddah 4

5. External Water Treatment
 Practically all surface water contain small
amount of mud, clay ,silt ,decayed, vegetation,
Micro Organisms etc.
To obtain required quantity of water
various techniques are applied Such as
Clarification ,Filtration ,Evaporation ,Softening,
Desalination (MSF & RO ) , Ion Exchange , De
Aeration , Aeration
Note: External water treatment for Pretreatment System and RO
System already discussed in earlier training module
Umar Farooq Chemist
“A” Shoaiba Jeddah 5

6. What is RO Desalination
Umar Farooq Chemist
“A” Shoaiba Jeddah 6
Reverse osmosis is a membrane process where salty source
water is supplied under pressure to a semi- permeable
membrane resulting in the passage of fresh water through the
membrane prevents the passage of the dissolved minerals
leaving them in the concentrated brine

7. Seawater supply Pump
D M F
Cartridge
filter
H P Pump
Booster Pump
1st pass R O
E R D
2 nd pass R O
2 nd pass
Feed pump
Permeate
Transfer pump
Potabilisation
Backwash water
Tank
Out fall
To SWCC Shuaibah II
Storage Tank
S MBS
Anti scalant
Anti Scalant
Caustic sodaAcid
Coagulant
Polymer
Back wash
7Umar Farooq Chemist
“A” Shoaiba Jeddah

8. What is MSF Desalination
Umar Farooq Chemist
“A” Shoaiba Jeddah 8
Multi-stage flash distillation (MSF) is a water desalination
process that distill sea water by flashing a portion of the water
into steam in multiple stages of what are essentially counter
current heat exchangers .Multi-stage flash distillation plants
produce 85% of all desalinated water in the world

9. Umar Farooq Chemist
“A” Shoaiba Jeddah
9
CEP
Sea Water Inlet
Starting Ejector
Brine Heater 1 2 3 4 10 19 20 21 D / A
Duty Ejector
2nd stage Ejectors
I P Steam
After Condenser Inter Condenser Pre Condenser
B V P
1st stage Ejectors
Quick filling
Sea Water Discharge
Make Up
Sea Water Outlet
L P Steam
BRP 1
Cond. Rtn
DP
BRP2
Prodn.
BBDP
Cooling water to
vacuum condensers

10.  The process by which Ca ++ and Mg ++ ion
removed from water is known as water
softening. There are two method is used
 Lime soda softening or precipitation
method
 Ion exchange method
Umar Farooq Chemist
“A” Shoaiba Jeddah 10
Water Softening

11. Lime soda softening
 It is the process by which calcium and magnesium salt that cause
hardness in H2O are chemically precipitated and removed by
treatment with lime and soda ash .
Mg(HCO3)2 + 2Ca ( OH) Mg(OH )2 + 2CaCO3+2H2O
Ca(HCO3)2 + Ca(OH) 2CaCO3 + 2H2O
Soluble Insoluble
 Most of CaCO3 and Mg(OH)2 from a sludge can be removed by
settling and filtration. So lime can be used for removal of temporary
hardness
MgSO4 + 2Ca ( OH) Mg(OH )2 + 2CaSO4
MgCl2 + 2Ca ( OH) Mg(OH )2 + 2CaCl2
The soluble CaSO4 and CaCl2 are produced and contribute “non
carbonated hardness” There must be removed to attain complete
softening of water
Umar Farooq Chemist
“A” Shoaiba Jeddah 11

12.  This is done by treating soluble salt of Ca SO4 and CaCl2 with soda
ash ( Na2Co3).when these salt are precipitated as insoluble
carbonate.
CaSO4+Na2CO3 CaCO3+ NaSO4
CaCl2+Na2CO3 CaCO3+ NaCl
Insoluble Soluble
CaCO3 formed is precipitated as sludge the resulting NaSO4 and NaCl
are highly soluble non scale forming
Use of Coagulant in lime soda process
 Coagulant serve to agglomerate the particles in softening process
 They speed up settling of sludge
 Sodium Aluminates has a special advantage as a coagulant in lime
soda softening .practically in reducing magnesium .
 Effective use of coagulant to remove silica in the softening process.
Umar Farooq Chemist
“A” Shoaiba Jeddah 12

13. Advantage of Lime soda Softening
 Main advantage is reduction of hardness alkalinity TDS
and Silica
 Prior Clarification of water in not usually necessary
 Reduction of TDS can decrease the conductivity of feed
water, there by decreasing blow down and conserving
heat.
 Energy can be saved because of solid reduction in hot
process
 With hot process lime soda softening removal of oxygen
and CO2 can be achieved up to same extent
Umar Farooq Chemist
“A” Shoaiba Jeddah 13

14. Disadvantage of Lime soda Softening
 The main disadvantage is that while
hardness is remove it is not completely
finished.
 Since this process involves adjusting the
amount of lime and soda ash being feed
there fore wide variation in water
composition and flow rate also make
control of this method difficult.
Umar Farooq Chemist
“A” Shoaiba Jeddah 14

15. Ion Exchange Zeolite Softening
(Na2Al2Sio2O8.XH2O)
 Zeolite softening consist of passing water through a bed of material
that possess the property of removing calcium and magnesium from
water and replacing these ion with sodium or potassium. The
exchange takes place rapidly, so that hard water is passing through
Zeolite bed can be almost completely softened ,regardless of
variation in solution, bicarbonates, sulfate , chlorides etc.
 Considering only chloride as an example ,for the sake of simplicity
the softening reaction are.
Na2Z+CaCl2 CaZ+ 2NaCl2
Na2Z+MgCl2 MgZ+ 2NaCl2
Material usually applied for this purpose can be naturally occurring
Zeolite I.e. green sand , sulfonated coal or alumina silicate or
synthetic resin based on poly styrene or poly acryllates.
Umar Farooq Chemist
“A” Shoaiba Jeddah 15

16. Advantage of Na2Z Softening
 Softened water has low scaling
tendency
 Operation is simple and
reliable
 Regeneration is easy to handle
 Waste disposal is not a
problem
 Softener's are easily available
and efficient
 Variation in water flow rate up
to large extent have not effect
on treated water quality
Umar Farooq Chemist
“A” Shoaiba Jeddah 16

17. Disadvantage of Na2Z Softening
 Softening process has no effect upon alkalinity.
 Turbidity and the presence of iron and aluminum
can be deter mental for the ion exchanger.
 Strong oxidizing agent like chlorine present in
the water will attack the resin.
 At higher pressure and temperature the
exchange capacity of resin is effected.
 Zeolite material is unstable in high acidic and
alkaline media
Umar Farooq Chemist
“A” Shoaiba Jeddah 17

18. Demineralization
 Removal of all kind of ion from water by ion
exchange is called demineralization. Any
salt dissolved in water consist of two types
of ions, +Ve ion called cat ion and -Ve
ion's called anion . In demineralization
process cat ion and anion present in water
are removed one after other by organic ion
exchange resin
The organic resin's are of four
types
 Weak Cat ion resin
R-COOH Carboxylic group
 Strong Cat ion resin
R-HSO3 Sulphonic group
 Weak anion resin
R-NH2OH Phenolic hydroxyl group
 Strong anion resin
R-NH3OH Amino group
Umar Farooq Chemist
“A” Shoaiba Jeddah 18

19. Ion exchange material
 Ion exchange material are either natural or
synthetic. The natural ion exchangers are
termed as Zeolite e.g. green sand aluminous
silicate and sulphonated coal. These can be
regenerated by NaCl solution and are used for
the removal of hardness from water.
 Synthetic resins are polymer and co-polymers of
organic compounds like phenol, al dehydes,
styrene's and vinyl derivatives. They differ in
properties due to difference polar group.
Umar Farooq Chemist
“A” Shoaiba Jeddah 19

20. Cat ion Exchangers
Weak Cat ion
 This filter bed removers cat ion of salt of weak
acids from water in the following manner e.g.
 2RCOO.H + CaSiO3 (RCOO)2 Ca+H2SiO3
 2RCOO.H + Ca(HCO3)2 (RCOO)2 Ca+2H2CO3
 2RCOO.H + CaCO3 (RCOO)2 Ca+H2CO3
 2RCOO.H + Mg(HCO3)2 (RCOO)2 Mg+2H2CO3
 2RCOO.H + MgCO3 (RCOO)2 Mg+H2CO3
 2RCOO.H + NaHCO3 (RCOO)2 Na+H2CO3
 2RCOO.H + NaCO3 (RCOO)2 Na+H2CO3
The water at the outlet of weak cat ion exchanger contain weak acids
Umar Farooq Chemist
“A” Shoaiba Jeddah 20

21. Weak Cat ion Regeneration
Normally 2% HCl is passed
through bed for half hour .All cat ions
that had bed absorbed by resins during
normal service operation are replaced
by H + ion of acid and soluble chlorides
produced in the process of regeneration
are drained to waste
(RCOO)2 Ca + HCl 2RCOOH+CaCl2
Exhausted Resin Regenerated Resin
Umar Farooq Chemist
“A” Shoaiba Jeddah 21

22. Cat ion Exchangers
Strong Cat ion
 A regenerated strong cat ion resins has
sulphonic functional group (-HSO3) and
removes cat ion of both weak and strong
salts of acids from water as given below.
 2RSO3.H + CaSO4 (RSO3)2 Ca+H2SO4
 2RSO3.H + CaCl2 (RSO3)2 Ca+2HCl Strong Acid
 2RSO3.H + Ca(NO3)2 (RSO3)2 Ca+2HNO3
 2RSO3.H + Ca(HCO3)2 (RSO3)2 Ca+2H2CO3 Weak Acid
 The water at the outlet of strong cat ion exchanger cat
ion strong acids ( HCl , H2SO4 , & HNO3 )
Umar Farooq Chemist
“A” Shoaiba Jeddah 22

23. Cause of Strong Cat ion Exhaust
When strong cat ion filter bed exhausted . It has no H + ion to
exchange with the cat ion (Ca++,Mg+ +,Na+) These cat ion escape in
outlet water. In absence of H + ion . The conductivity of effluent water
decreases and pH is increases , Because H + ion are lightest of all
NaCl escape unchanged form 2nd stage to 3rd stage filter and are
release as NaOH in water
RNH2OH+NaCl RNH2Cl+NaOH
When weak anion filter is exhausted the conductivity
of effluent water increases stately but when strong cat ion resin gets
exhausted. The conductivity of effluent water of weak anion filter
more repaid. It is due to the formation of NaOH is 3rd stage filter by
leaking of Na+ from strong cat ion filter.
Acid Treatment
 Fresh 7% HCl solution prepared in deionized water is passed
through the filter almost 40 minute
Umar Farooq Chemist
“A” Shoaiba Jeddah 23

24. Anion Exchanger
Weak anion
 A regenerated weak anion resin which has amino (-NH2) functional
group will remove all the anions of strong acid from water.
 RNH2.OH + HCl RNH2Cl +H2O
 RNH2.OH + H2SO4 (RNH2)2SO4 +H2O
 RNH2.OH + HNO3 RNH2NO3 +H2O
 The water at the outlet of weak anion exchanger will contain only
anion of weak acid . If any e.g. CO3
2- , SiO3
2- in the form of H2CO3
and H2SiO3
Alkali Treatment
 Fresh 3% NaOH solution prepared in deionized water is passed
through the filter almost 70 minute
Umar Farooq Chemist
“A” Shoaiba Jeddah 24

25. Anion Exchanger
Strong anion
 This filter remove anion of both weak acids and strong acids.
 2RNH3.OH + H2CO3 (RNH3)2CO3 +2H2O
 2RNH3.OH + H2SiO3 (RNH3)2SiO3 +2H2O
 2RNH3.OH + HCl RNH3Cl +H2O
 2RNH3.OH + H2SO4 (RNH3)2SO4 +2H2O
 Alkali Treatment
 4% NaOH is used pass the alkali through the filter for one hour. This
filter is stopped for regeneration when SiO2 content increasing trend.
Umar Farooq Chemist
“A” Shoaiba Jeddah 25

26. Mix Bed Filter
 The filter bed contain strong cat ion
The cat ion and anion resin are so
intimately mixed that water following
through the bed may be considered to
have comes across a large number of
small strong cat ion and strong anion
beds. The water at the outlet of mix
bed is of higher quality purity and its
conductivity may be low as 0.5 µs/cm.
Increase in silica content
of effluent water of the mixed bed is a
signal of exhaustion of strong anion
resin and increase of conductivity
means exhaustion of cat ion resin.
Umar Farooq Chemist
“A” Shoaiba Jeddah 26

27. Ion Exchange Problems
 Excessive
Regeneration
Frequency.
 Higher Operating
Costs.
 Poor Treated water
Quality.
 Insufficient Volume of
Treated Water
Umar Farooq Chemist
“A” Shoaiba Jeddah 27

28. Common Causes of Ion Exchange
System Problem
Umar Farooq Chemist
“A” Shoaiba Jeddah 28
 Desalination Water Chemistry Variation
 Mechanical Malfunction
 Resin Fouling and Degradation
 Variation and operating and Regeneration Procedure
 Variation in Flow Demand

29. Umar Farooq Chemist
“A” Shoaiba Jeddah 29
Demineralizers are used to provide
highly purified water to high
pressure boilers as feed water make-
up. This highly purified water is also
used in a vast number of other
processes; such as wash water for
microchip manufacturing.
Uses of
Demineraliz
ation water

30. Umar Farooq Chemist
“A” Shoaiba Jeddah 30