Power plant chemistry ( External Water Treatment )

Power Plant Chemistry First
Module
Prepared By : -
Umar Farooq
Senior Chemist NOMAC
MSC ( Chemistry ) MBA ( Marketing )
SIWEP Shuaibah Jeddah
Saudi Arabia 1

Power Plant Chemistry
 Part 1
 Basic Chemistry
 Fundamental of Heat , Heat Transfer
 Water Chemistry , Type of Hardness
 External Water Treatment
 Water Softening , Demineralization
 Part 2
 Steam Water Cycle System
 Steam Generator ( Boiler )
 Parts of Boiler
 Boiler Ex auxiliaries
 Turbine & Generator

4
At the end of the respective training course, the participants will
be able to:
• Identify the chemical Hazards & how to handle chemical material safely.
• Now the foundations of Water Quality Control to avoid the scale
corrosion and biological growth in the Power plant system, and to
operate the mentioned at max performance.
• Understand the troubleshooting events to the plant chemistry system.
Vision
• Water Quality Control will lead all to understand the limitations and
international standards as well as increasing the plant availability.
• Occupational health will maintain within high standards, zero incident.
• Operational process will maintain highly performance due to plant chemistry
troubleshooting.
Umar Farooq Senior Chemist
NOMAC SIWEP Shuaibah Jeddah
Main Objective

Basic Chemistry
 Chemistry Branch of science which deals with properties
composition and structure of mater.
 Matter Any species having weight or mass and occupies space is
called matter. The mater exist in three state ,solids ,liquid & gases
 Substance Any matter which has uniform composition through
out.eg: gold , silver ,water is called substance.
 Atom The smallest particle of the element which can not exist in
free state but can take part in chemical reaction.
 Molecule Tow or more than two atoms that combine chemically
together to form a molecule.
 Element Pure substance in which all the atoms are same alike eg:
Iron , Cupper , Silver , Sodium . It cannot be decomposed by the
chemical action to a simpler substance.
NOMAC SIWEP Shuaibah Jeddah 5

Basic Chemistry
 Ion Charge particle are known as ions
 Cat ion Ions which move to cathode
 An ion Ions which move to anode
 Cathode Electrode having –ve Charge
 Anode Electrode having +ve Charge
 Electrolysis ( Lyses = Analysis ) Electrolysis is the motion of cat
ion and anion to words respective electrodes. It is accompanied by
all chemical changes under the influence of electrical field in
aqueous solution
 Hydrolysis Decomposition of water into H+ and OH- Ions

Basic Chemistry
 Mixture It is simply the combination of two or more than two
elements which retain their properties
 Compound Chemical combination of two or more elements
combine together chemical reaction takes place is called compound
 Valences The combining power of one element to another element
is called valences.
 Atomic weight Total number of proton and neutron in an atom is
called atomic weight
 Atomic Number The number of proton which are present in
nucleus of an atom is called atomic number.

Fundamental of Heat
 Heat It is common form of energy .Heat added to a body makes it
hotter removing heat cools it . Heat energy can be turned into
mechanical energy to do work.
 Temperature It describes the degree of hotness or coldness of
body .It has two units centigrade and Fahrenheit scale. Conversion
Formula C/5=F-32/9
 Calorie It is the amount of heat required to raise the temperature of
1 g of H2O through 1C*
 B.T.U It is the amount of heat required to raise the temperature of
1Lb of H2O through 1F*.
 C.H.U It is standard abbreviation of centigrade heat unit.
 Sensible Heat: The heat shown by the thermometer or the heat
which sense the temperature.

Fundamental of Heat
 Latent Heat: The heat added or taken into produce a change in
state with out any change in temperature.
 Latent heat of evaporation: The amount of heat which is added
for the evaporation of liquid is called latent heat of evaporation
 Latent heat of vaporization: The amount of heat required to
vaporize 1Lb of water to steam at 14.7psi at 212C* is termed as
latent heat of vaporization.
 Latent heat of fusion: It is the amount of heat required to melt 1g
of ice into water at 0C* or 32 F*.
 Latent heat of condensation: The amount of heat taken to
condense 1 Lb of steam into water at 14.7psi and 212 F*

Heat Transfer
 Heat always flows from a warm area to cool area .ie from hot body
to cold body This is accomplished in three ways.
 Conduction: In this method heat energy is conducted
through a substance or metal or transferred from one
place to another place or from molecule to molecule .
The amount of heat that will pass through a given
material depends on conductivity of material.
 Convection: In this method heat energy is transmitted
from hot to cold body by movement of conveying subs:
(medium).In side boiler ,furnace the conveying
substance is the gases of combustion . In this case the
hot body is flue gases the cold body is boiler tubes, air
pre heater or any things else having a lower temperature
in the flue gas path.

Heat Transfer
 Radiation In this method heat energy is transfer from
one place to another place with out the help of any
medium. Heat is transferred directly by heater radiation
that require no intermedium.eg heat of sun rating to the
earth.
 Saturated ( wet ) Steam Steam containing maximum
water vapors that it can steam is said to be saturated.
When it temperature is the same as that of boiling water
at pressure eg. At 14.7psi water boiled at 212F* and the
saturated steam temperature is 212 F*.

Heat Transfer
 Super heated steam ( Dry Steam )
The steam having temperature higher than its
saturation temperature. The addition of heat to saturated
steam increase its temperature or sensible heat. The
increase in sensible heat above saturation temperature
is called super heated steam.
If saturated steam at 1500psi and 569.23F* is
heated to 950F* with pressure remaining constant the
amount of super heated is 950-596.23=353.77F*
Un like saturated steam a loss of heat from
superheated steam result is reaction in temperature.

Water Chemistry
 Water is an excellent solvent and dissolve to varying
degree. any thing it comes into contact with it.
Water born impurities
 Water contains some impurities which are
Dissolved inorganic compound
Bi Carbonate, Carbonates, Sulphate , nitrates , Chlorides of
calcium , magnesium ,sodium and potassium , inorganic
Suspended materials, like clay, silt ,sand , soil and metal
oxides, These can not be remove by filtration.

Water Chemistry
Dissolve Organic Compound
 Humic acid , fulvic acid , tannin
insoluble matter such as dead
bacteria and other biological
products
Dissolve gasses
 Such as oxygen , nitrogen ,
carbon dioxide , sulpher
dioxide , ammonia , and
hydrogen sulphide absorbed
from atmosphere and solid
surface
Micro Organism
 Such as bacteria algae and fungi

Marine Ecology Survey Conduct by WSP Auditor
The weather conditions in the morning for the
control site were characterized by an 8 km/h easterly
wind, with the air temperature recorded to be 26 ºC, and
seawater temperature to be 31 ºC at the
surface and 30 ºC at depth. The underwater visibility was
good, estimated to be 10-15 meters.
The plume of turbid and warm water from the
outfall seems to have contributed to coral death on the
reef, and therefore no live hard coral was observed.
The overall area supports some surgeonfishes
(Acanthuridae), which graze on the benthic algae.

Marine Ecology Survey Conduct By WSP Auditor
At Shuaibah Sea
Humbug Dascyllus
Pale Damselfish AmblyglyphidodonBlue green Chromes
Acanthuruse Sohal Surgeonfish and Turf Algea

Why Water is Unique
 Water is only substance that exist in form of solid , liquid
and steam
 Specific heat = 1calorie/gram
 It expand = 1600 time
 Three Isotopes = H , D2O , T2O
 Heat of fusion = 144Btu / Lbs
 Heat of vaporization = 980 Btu / Lbs
 Freezing Expand = 1/9
 Depending upon pressure ,its boil with in the
temperature = 35-704F*

Properties of Water
 It is chemical compound expressed by the formula H2O.
 It is formed by two item of hydrogen and one atom of
oxygen
 Due to different electro negativities of hydrogen and
oxygen.H20 Molecule is electrically charged .
 When the other molecule combine with it then will be
formed hydrogen bonding
 Water is the best solvent .
It dissolved different substance
In it and the process of dissolving
Is desolation
Model of hydrogen bonds
Between modules of water

Sea Water Impurities
 It is store house of impurities
 It contain 3.6% by weight of solids.
 Normally 75% impurities of sea water are Br, I , So4 ,
and Ca ,Mg , K , etc.
 Cat ion and Anion Salts in Sea water
Cations Anions
Calcium Ca++ Bicarbonate (HCO3
-),
Magnesium Mg+ + Carbonate (CO3
2-),
Sodium Na+ Sulfate SO4
2-
Iron Fe2+ (ferrous) Chloride Cl -
Aluminum AI3+ Nitrate NO3
-
Potassium K+ Fluoride F-

Types of Hardness
Temporary Hardness ( Alkaline Hardness )
 It is due to presence of bicarbonates of calcium
and magnesium in water , also called carbonate
hardness. It can be removed by boiling and
pretreatment process
Permanent Hardness(Non Alkaline Hardness )
 It is due to presence of chlorides , sulphate and
nitrate of calcium and magnesium , it can be
remove by ion exchange and desalination
process

RELATIVE SETTLING VELOCITIES OF SAND
and SILT PARTICLES IN STILL WATER
Particle Diameter, mm Order of Magnitude Time Required to Settle 1 Foot
10.0 Gravel 0.3 Seconds
1.0 Coarse Sand 3 Seconds
0.1 Fine Sand 38 Seconds
0.01 Silt 33 Minutes
0.001 Bacteria 35 Hours
0.0001 Clay Particles 230 Days
0.00001 Colloidal Particles 63 Years
SIWEP NOMAC 21

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 )

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

What is RO Desalination
 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 while the
membrane prevents the passage of the
dissolved minerals leaving them in the
concentrated brine.
SIWEP NOMAC 24

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
25
SIWEP NOMAC

What is MSF Desalination
 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 Umar Farooq Senior Chemist

MSF Desalination Process

 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
Water Softening

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

 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.

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

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.

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 polyacryllates.

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

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

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

37
Demineralization
Demineralization or Deionization is the process of removing mineral salts
from water by using the ion exchange process.
Resin is composed of high-molecular-weight polyelectrolyte's that can
exchange their mobile ions for ions of similar charge from the surrounding
medium.
Cation exchange resins will release Hydrogen (H+) ions.
Anion exchange resins will release hydroxyl (OH-) ions.

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, aldehydes,
styrene's and vinyl derivatives. They differ in
properties due to difference polar group.

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

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

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 )

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

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 prepaired in deionized water is passed
through the filter almost 70 minute

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.

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.

Short Brake
NOMAC SIWEP Shuaibah Jeddah

Steam Water Cycle System
 The Circulation of water from condenser to boiler is
called water cycle from boiler to turbine and then again
in condenser is called steam cycle collectively it is called
steam water cycle . All the equipment of this system are
explained below.
 Condenser:
It is a large hollow box rows of small tubes
are installed in Cold water passes through these tubes ,
steam condense outside these tubes and collected in hot
well which is at the bottom of condenser.

Condenser

Condenser
 While converting steam into water a
vacuum is also created in the condenser
which make the turbine operation more
efficient because pressure of exhaust
steam is reduced by condensation than
reason flow of steam will increase the
cover this pressure and this process help
to move the turbine more fast.

 Surface type condenser
In this type cooling water is inside the tube while
steam is outside the tubes.
 Contact type Condenser
In this type of condenser condensation takes place
by direct contact i.e. exhausted steam and
cooling water are mixed together.
 Condenser pumps
These pumps takes condensed water from hot well
and give to the main condensate line.

Steam jet air Ejector
 Since condenser operates under vacuum , small
quantity air comes from joint of the condenser ,
exhausted steam also contains non
condensable gases which are coming from
turbine sealing drains into condenser , this air
will cause the condenser to become air bond.
Air in the condenser will cause a
loss of vacuum and decrease the cooling of
exhaust steam . To eliminate this problem.
There is an instrument which is attached to the
condenser to remove air and ensure vacuum .
This instrument are called steam jet air ejector.

Steam jet air Ejector
 Vacuum of condenser may drop due to
following reason.
1) By increasing the temperature of cooling water
2) By decreasing the flow of cooling water .
3) An increasing in level of S.J.A.E.
4) Reducing pressure of ejector operating steam.
5) By increasing level of condenser from it normal stage
6) Leakage of diaphragm .
7) Over loading of condenser.

Dearator and Feed Tank
 There are two type of dearator
1) Spray Type
2) Tray Type.
The working principle of both dearator are same , but
there is difference of design. The spray type dearator are
only used in marine ship.
In power plant house after last heater condensate
water is taken spray type dearator .which removed
dissolved gases like O2,CO2,N2,NH3 from condensate
water. Umar Farooq Senior Chemist

Dearator and Feed Tank
 Water temperature ( 145 C* ) Comes downward
init a no: of perforated plates and steam
temperature ( 150 C* ) goes to the up ward
direction. So it contact with the water , which is
in form of droplets. Steam heated due to high
temperature gases expands and the solubility
decrease. This mixture is removed from the top
of the dearator which is filled at the bottom of the
Dearator called feed tank.

Steam Generator ( Boiler )
 Boiler are built in verity of sizes
shapes and form to fulfill the
conditions of different kinds of
plants.
Generally boilers are
classified into two groups.
Fire tube Boiler
 Fire tube boiler are those in
which hot combustion products
pass through the tube heat is
transferred to water which
surrounding the tubes.

Advantages of fire tube boilers are
as follows
1)Low cost
2)Fluctuations of steam demand can be met easily
3)It is compact in size.
Water tube boilers are classified as
1. Horizontal straight tube boilers
(a) Longitudinal drum (b) Cross-drum.
2. Bent tube boilers
(a) Two drum (b) Three drum
(c) Low head three drum (d) Four drum.
3. Cyclone fired boilers

Advantages of fire tube boilers are
as follows
According to position of furnace.
(i) Internally fired (ii) Externally fired
 In internally fired boilers the grate combustion chamber
are enclosed within the boiler shell
 whereas in case of extremely fired boilers and furnace
and grate are separated from the boiler shell.
According to the position of principle axis.
(i) Vertical (ii) Horizontal (iii) Inclined.

Water tube boiler
 Water tubes boiler are those in which
products of combustion pass ( through )
around the tubes containing water.
Classification of Boilers
Based on boiler pressure
1) Low pressure boiler under 20kg/cm2
2) Medium pressure boiler 20- 75 kg/cm2
3) High pressure boiler above 75 kg/cm2

Water tube boiler
o Used for high steam demand and
pressure requirements
o Capacity range of 4,500 –
120,000 kg/hour
o Combustion efficiency enhanced
by induced draft provisions
o Lower tolerance for water quality
and needs water treatment plant
(Your Dictionary.com)

Merits of water tube boilers over
fire tube boilers
 Generation of steam is much quicker due to small ratio
of water
content to steam content. This also helps in reaching
the steaming temperature in short time.
 Its evaporative capacity is considerably larger and the
steam pressure range is also high-200 bar.
 Heating surfaces are more effective as the hot gases
travel at right angles to the direction of water flow.
 The combustion efficiency is higher because complete
combustion of fuel is possible as the combustion space
is much larger.

Merits of water tube boilers over
fire tube boilers
 The boiler can be easily transported and erected as its
different parts can be separated.
 The thermal stresses in the boiler parts are less as
different parts of the boiler remain at uniform
temperature due to quick circulation of water.
 Damage due to the bursting of water tube is less
serious. Therefore, water tube boilers are sometimes
called safety boilers.
 All parts of the water tube boilers are easily accessible
for cleaning, inspecting and repairing.
 The water tube boiler's furnace area can be easily
altered to meet the fuel requirements.

Demerits
 It is less suitable for impure and sedimentary water, as
a small deposit of scale may cause the overheating and
bursting of tube. Therefore, use of pure feed water is
essential.
 They require careful attention. The maintenance costs
are higher.
 Failure in feed water supply even for short period is
liable to make the boiler over-heated.

Comparison between Fire-tube & water-tube boilers
S no. Particulars Fire tube boilers Water tube boilers
1. Mode of firing Internally fired Externally fired
2. Rate of steam
production
lower Higher
3. construction Difficult Simple
4. transportation Difficult Simple
5. Treatment of water Not so necessary More necessary
6. Operating pressure Limited to 16 bar Under high pressure as
100 bar
7. Floor area More floor area Less floor area
8. Shell diameter Large for same power Small same power
9. explosion Less More
10. Risk of bursting lesser More risk

Parts of Boiler
Boiler Auxiliaries
Boiler EX- Auxiliaries
Boiler Safety
Boiler Auxiliaries
Steam Drum
 Steam drum is made up of steal and is that part
of boiler , where steam is separated and all the
impurities of the system are collected here and
expelled out by blow down.

Parts of Boiler
Supper Heater
An equipment or device in which heat
could be added to steam after its leave the boiler drum is
known as super heater .super heater tubes are made up
of special alloy steel placed in the flue gas path and the
wet steam is heated there to produce dry steam called
as super heated steam .
It has two advantage over wet steam.
1) It increase the efficiency.
2) By the use of super heated steam condensation of
steam is the turbine is minimized to a point where it is
harm less.

Parts of Boiler
Generation tubes ( Up risers )
These tubes are directly placed in the
path of hot flue gases. These tubes received
water from drum and contain mixture of water
and steam when heated by flue gases.
Down Comers
The tubes in which water flow down
ward with respect to up risers. These tubes not
only protect the furnace wall but also become an
important part of the furnace heating surface.

Parts of Boiler
Furnace
The most important
device where actual burning
of the fuel tubes place energy
produced in furnace is used
to heat water and change it in
to steam.
Economizer
The economizer is a heat
exchanger where heat from
flue gases can be used to
heat the feed water
economically.

Economizer
.
Flue gases coming out of
the boiler carry lot of
heat. An economizer
extracts a part of this heat
from flue gases and uses
it for heating feed water.
This use of economizer
results in saving fuel
consumption and higher
boiler efficiency

Parts of Boiler
Cyclone separator.
It is a device which use the centrifugal
action for separation of material of different
densities. These are placed in boiler drum and
are made up of steel.
Burners
These are adjusted in
the wall of furnace.
Fuel starts to burn here.

Parts of Boiler
Stack Chimney
These portion from where
the flue gases are expelled out
from furnace to the atmosphere.
Re Heater
Re heaters heat the steam after it passes
through high pressure turbine. They are just
after super heaters in the path of flue gases.
In re heaters temperature of steam
rise to increases the efficiency of turbine.

Boiler Ex auxiliaries
Air pre heaters
The air pre heater in steam
generating unit reclaim some heat from flue
gases and adds the heat to the air required for
the combustion of fuel rise of pre heated air will
speed up the combustion al all loads improve
combustion allow load and increases efficiency .
Air pre heater are generally of two type.
1) Tubular air pre heater
2) Rotary air pre heater.

Air pre heater
 There are three types
of air pre heater:
1. Tubular type
2. Plate type
3. Storage type
 This picture shows that a
tubular type air pre heater.

Boiler Ex auxiliaries
Induced draft fan
Induced draft fan are used to remove the flue gases from
furnace to chimney
Forced draft fan
It takes the air from atmosphere and after heating
by pre heater suppress air to two places by force.
Air supplied for combustion in of two types.
1) Primary air ( used for burning with gases fuel )
2) Secondary air ( use for adjusting the flame )
Recirculation fan
 Recirculation fan are used to keep the temperature constant in furnace
chamber . It also used for extra heating to air coming from atmosphere.

Boiler Safety Equipment
Inter lock system.
Inter lock system is used in the boiler to prevent
it from ( boiler ) damage .
Boiler is tripped in the following condition
1) When gas air ratio disturbed
2) When level of water decreases
3) On the failure of forced draft fan
4) When turbine trips boiler also trips
Safety valve
It is set up for safety of boiler and adjusted above the
required pressure and when pressure rises from limiting
factor. Then the extra pressure of boiler is maintain with
in the limit. Umar Farooq Senior Chemist

Turbine & it types
 Turbine is a device which converts heat
energy into mechanical energy .
There is number of
blades on the wheels at same axle ( rotor )
and between there are also wheels which
don't move called stationary blades. By
these blades steam gets pressure again
and act upon next blades through nozzles
with high speed and soon.
It is necessary to extract
steam from its out let other wise pressure
will become same at out let and inlet and
turbine is stopped and it may damage any
part . steam is extract from turbine and
used for different purposes.
A large amount of steam
is condensed in condenser to use it again
for turbine rotation.

Turbine & it types
Turbine is
classified into three types
based on blades of
turbine.
1) Impulse type turbine
2) Reaction type turbine
3) Velocity compound type
turbine

In a Thermal Power Plant generally 3 turbines are used to increase the efficiency.
 High Pressure Turbine(HPT): The superheated steam is directly fed to this
turbine to rotate it.
 Intermediate Pressure Turbine(IPT): The out put from the HPT is reheated in a
reheated(RH) and used to rotate IPT .
 Low Pressure Turbine(LPT): The Exhausted steam from the IPT is directly fed
to rotate the shaft of LPT.
Turbine
Condenser
HPT IPT LPT
RH
Steam
Super
Heater
Generator
Steam
Shaft
*All the turbines are connected to a single shaft which is connected
to the Generator.

Generator
It is final and main part
of power plant house where electricity
is produced. An electrical generator or
is a device where mechanical energy
converted into electrical energy .
In generator a magnet
moves with the movement of turbine
shaft . Electrical field is produced in the
winding of stator. The winding will heat
up due to current pressure with may
resist in the flow of current . So it is
necessary to keep it cool. There fore
demineralization water and hydrogen
gas are used for this purpose.

The Synchronous Generator is used to Generate power by connecting the
shaft of the Turbine to the shaft of the generator which cuts the
magnetic flux producing EMF.
 The Generated Voltage will generally 11KV to 20 KV max.
 The Generated Voltage is stepped up by connecting Step up
transformer and is transmitted and is also used for Auxiliary purposes.
Generator
Bus Duct
Generator Transformer
20KV to 400KV
SYNCHRONOUS
GENERATOR
UAT
20Kv to 6.KV
Unit Auxiliary Transformer: This transformer is used to step down the
produced voltage and use for Auxiliary purpose.

Power plant chemistry ( External Water Treatment )

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