Power plant chemistry ( External Water Treatment )

Power Plant Chemistry First Module

Prepared By : -

Umar FarooqSenior Chemist NOMACMSC ( 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

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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.

Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah

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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


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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.


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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.Umar Farooq Senior Chemist

NOMAC SIWEP Shuaibah Jeddah 8

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*


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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.Umar Farooq Senior Chemist


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*.

Umar Farooq Senior Chemist


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.


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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 compoundBi 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.Umar Farooq Senior Chemist


Water ChemistryDissolve 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


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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.


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Marine Ecology Survey Conduct By WSP Auditor At Shuaibah Sea


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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*


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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


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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 SO42-

Iron Fe2+ (ferrous) Chloride Cl -

Aluminum AI3+ Nitrate NO3-

Potassium K+ Fluoride F-

Umar Farooq Senior Chemist


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 Umar Farooq Senior Chemist


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

Umar Farooq Senior Chemist 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 )


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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


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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.

Umar Farooq Senior Chemist 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 O2 nd pass

Feed pumpPermeate

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

25Umar Farooq Senior Chemist

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


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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


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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 + 2CaCl2The soluble CaSO4 and CaCl2 are produced and contribute “non

carbonated hardness” There must be removed to attain complete softening of water


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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 SolubleCaCO3 formed is precipitated as sludge the resulting NaSO4 and NaCl

are highly soluble non scale formingUse 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.


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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


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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.


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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+ 2NaCl2Material 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.


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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


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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 mediaUmar Farooq Senior Chemist


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


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37

DemineralizationDemineralization or Deionization is the process of removing mineral saltsfrom 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.


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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


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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


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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 )


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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 Senior Chemist


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. CO32- , 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


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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.


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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.


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Short Brake


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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.


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Condenser


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http://en.wikipedia.org/wiki/File:Surface_Condenser.png

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.


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Surface type condenserIn this type cooling water is inside the tube while

steam is outside the tubes. Contact type CondenserIn this type of condenser condensation takes place

by direct contact i.e. exhausted steam and cooling water are mixed together.

Condenser pumpsThese pumps takes condensed water from hot well

and give to the main condensate line.


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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.


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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.


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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.


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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.


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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


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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.Umar Farooq Senior Chemist


Steam Generator ( Boiler )

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 pressure1) Low pressure boiler under 20kg/cm2

2) Medium pressure boiler 20- 75 kg/cm2

3) High pressure boiler above 75 kg/cm2


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Steam Generator ( Boiler ) Water tube boiler


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o Used for high steam demand and

pressure requirements o Capacity range of 4,500 –

120,000 kg/houro Combustion efficiency enhanced

by induced draft provisionso 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.


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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.


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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.


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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 BoilerBoiler AuxiliariesBoiler EX- AuxiliariesBoiler Safety Boiler AuxiliariesSteam 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.


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Parts of BoilerSupper 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.


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Parts of BoilerGeneration 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.


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Parts of BoilerFurnace 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.

EconomizerThe economizer is a heat

exchanger where heat from flue gases can be used to heat the feed water economically. Umar Farooq Senior Chemist



Economizer.


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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 BoilerCyclone 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.


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Parts of BoilerStack 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.


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Boiler Ex auxiliariesAir 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.


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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.


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Boiler Ex auxiliariesInduced 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.


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Boiler Safety EquipmentInter 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 decreases3) On the failure of forced draft fan 4) When turbine trips boiler also tripsSafety 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.


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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


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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.


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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 Transformer20KV to 400KV

SYNCHRONOUSGENERATOR

UAT20Kv to 6.KV

Unit Auxiliary Transformer: This transformer is used to step down the produced voltage and use for Auxiliary purpose.

THANK

YOU


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Power plant chemistry ( External Water Treatment )

Technology

Transcript of Power plant chemistry ( External Water Treatment )