Power plant chemistry ( External Water Treatment )

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Power plant chemistry ( External Water Treatment )

  1. 1. Power Plant Chemistry First Module Prepared By : - Umar Farooq Senior Chemist NOMAC MSC ( Chemistry ) MBA ( Marketing ) SIWEP Shuaibah Jeddah Saudi Arabia 1
  2. 2. 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
  3. 3. 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
  4. 4. 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 Jeddah 5
  5. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 6
  6. 6. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 7
  7. 7. 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
  8. 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* Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 9
  9. 9. 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 NOMAC SIWEP Shuaibah Jeddah 10
  10. 10. 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 NOMAC SIWEP Shuaibah Jeddah 11
  11. 11. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 12
  12. 12. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 13
  13. 13. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 14
  14. 14. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 15
  15. 15. Marine Ecology Survey Conduct By WSP Auditor At Shuaibah Sea Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 16 Humbug Dascyllus Pale Damselfish AmblyglyphidodonBlue green Chromes Acanthuruse Sohal Surgeonfish and Turf Algea
  16. 16. 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* Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 17
  17. 17. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 18
  18. 18. 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- Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 19
  19. 19. 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 NOMAC SIWEP Shuaibah Jeddah 20
  20. 20. 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
  21. 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 ) Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 22
  22. 22. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 23
  23. 23. 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
  24. 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 Umar Farooq Senior Chemist SIWEP NOMAC
  25. 25. 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 NOMAC SIWEP Shuaibah Jeddah 26
  26. 26. MSF Desalination Process Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 27
  27. 27.  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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 28 Water Softening
  28. 28. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 29
  29. 29.  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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 30
  30. 30. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 31
  31. 31. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 32
  32. 32. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 33
  33. 33. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 34
  34. 34. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 35
  35. 35. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 36
  36. 36. 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.
  37. 37. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 38
  38. 38. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 39
  39. 39. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 40
  40. 40. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 41
  41. 41. 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 NOMAC SIWEP Shuaibah Jeddah 42
  42. 42. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 43
  43. 43. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 44
  44. 44. 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 Senior Chemist NOMAC SIWEP Shuaibah Jeddah 45
  45. 45. Short Brake Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah
  46. 46. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 47
  47. 47. Condenser Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 48
  48. 48. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 49
  49. 49.  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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 50
  50. 50. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 51
  51. 51. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 52
  52. 52. 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 NOMAC SIWEP Shuaibah Jeddah 53
  53. 53. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 54
  54. 54. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 55
  55. 55. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 56
  56. 56. 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 NOMAC SIWEP Shuaibah Jeddah 57
  57. 57. 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 pressure 1) Low pressure boiler under 20kg/cm2 2) Medium pressure boiler 20- 75 kg/cm2 3) High pressure boiler above 75 kg/cm2 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 58
  58. 58. Steam Generator ( Boiler ) Water tube boiler Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 59 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)
  59. 59. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 60
  60. 60. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 61
  61. 61. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 62
  62. 62. 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
  63. 63. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 64
  64. 64. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 65
  65. 65. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 66
  66. 66. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 67
  67. 67. Economizer . Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 68 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
  68. 68. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 69
  69. 69. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 70
  70. 70. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 71
  71. 71. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 72
  72. 72. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 73
  73. 73. 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 NOMAC SIWEP Shuaibah Jeddah 74
  74. 74. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 75
  75. 75. 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 Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 76
  76. 76. 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.
  77. 77. 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. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 78
  78. 78. 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.
  79. 79. Umar Farooq Senior Chemist NOMAC SIWEP Shuaibah Jeddah 80

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