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Thermal Power Plants

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Thermal Power Plants Presentation Transcript

  • 1. A presentation on Steam Generator
  • 2. Coal to Electricity ….. Basics Coal Chemical Energy Super Heated Steam Pollutants Thermal Energy Turbine Torque Heat Loss In Condenser Kinetic Energy Electrical Energy Alternating current in Stator Mech. Energy Loss ASH Heat Loss Elet. Energy Loss
  • 3. Major Energy Sources of India
  • 4. Why Coal? Share of Coal in Power Generation
    • Advantages of Coal Fuel
    • Abundantly available in India
    • Low cost
    • Technology for Power Generation well developed.
    • Easy to handle, transport, store and use
    • Shortcomings of Coal
    • Low Calorific Value
    • Large quantity to be Handled
    • Produces pollutants, ash
    • Disposal of ash is Problematic
    • Reserves depleting fast
    • India’s Coal Reserves are estimated to be 206 billion tonnes. Present consumption is about 450 million tonnes.
    • Cost of coal for producing 1 unit of electricity (Cost of coal Rs 1000/MT)is Rs 0.75.
    • Cost of Gas for producing 1 unit of electricity (Cost of Gas Rs 6/SMC)is Rs 1.20.
  • 5. Knowing more about Coal
    • Coal production
    • Surface Mining
    • Underground Mining
    • Coal Transportation
    • Rail
    • Truck
    • Conveyor
    • Ship
    • Coal Properties
    • Calorific Value
    • Grade of Coal (UHV)
    • Proximate Analysis
    • Ultimate Analysis
    • Ash and Minerals
    • Grindability
    • Rank
    • Physical Characteristics
    • Coal Beneficiation
    • Why?
    • Processes
    • Effectiveness
    • Coal production
    • Surface Mining
    • Underground Mining
    Useful Heat Value (UHV) UHV= 8900-138(A+M)
  • 6. Boiler/ steam generator
    • Steam generating device for a specific purpose.
    • Capable to meet variation in load demand
    • Capable of generating steam in a range of operating pressure and temperature
    • For utility purpose, it should generate steam uninterruptedly at operating pressure and temperature for running steam turbines.
  • 7. Boiler/ steam generator
    • Raw materials for design of boilers
    • Coal from mines
    • Ambient air
    • Water from natural resources (river, ponds)
    • Generating heat energy
    • Air for combustion
    • Working fluid for steam generation, possessing heat energy
    • A 500MW steam generator consumes about 8000 tonnes of coal every day
    • It will be considered if it requires about 200 cubic meter of DM water in a day
    • It will produce about 9500 tonnes of Carbon di Oxide every day
  • 8. Coal analysis
    • Typical composition (Proximate analysis)
    • 1. Fixed carbon
    • 2. Fuel ash
    • 3. Volatile material
    • 4. Total Moisture
    • 5. Sulfur
    • High calorific value/ Lower calorific value (Kcal/kg)
    • Hardgrove Index (HGI)
  • 9. Combustion of coal
    • Carbon, hydrogen, sulfur are sources of heat on combustion
    • Surface moisture removed on heating during pulverization.
    • Inherent moisture and volatiles are released at higher temperature, making coal porous and leading to char/ coke formation. (Thermal preparation stage)
  • 10. Fuel Oil
    • Three liquid fuels used in power plants
      • 1. Heavy Fuel Oil (HFO)
      • 2. LSHS (Low Sulfur Heavy stock)
      • 3. High speed Diesel (HSD)
      • Oil firing is preceded by
      • Lowering viscosity and increasing flowability on heating for better combustion in given turn down ratio.(125 o C)
      • Droplet formation on atomization (by steam/ compressed air/ mechanical pressurization)
      • Combustion initiation by High energy spark ignition
  • 11. Combustion of reactants
    • Reaction rate depends on concentration of one of the reactants
    • Concentration varies on partial pressure of the reactants.
    • Partial pressure is a function of gas temperature.
    • Therefore, reaction rate depends on temperature and substance that enter the reaction.
  • 12. Combustion Reactions (Carbon)
    • Main reactions
    • 2C + O 2 = 2CO + 3950 BTU/lb (Deficit air)
    • C + O 2 = CO2 +14093 BTU/lb
    • Secondary reactions
    • 2CO + O 2 = 2CO 2 + 4347BTU/lb C + CO 2 = 2CO -7.25MJ/kg
  • 13. Combustion Reactions (Carbon)
    • Carbon reaction
    • 2C + O 2 =2CO [Eco =60kJ/mol]
    • C + O 2 =CO 2 [Eco 2 =140kJ/mol]
    • reaction at 1200 o C
    • 4C + 3O 2 =2CO + 2CO 2 (Ratio 1:1)
    • Reaction at 1700 o C
    • 3C + 2O 2 = 2CO +CO 2 (Ratio 2:1)
    • It is desirable to supply combustion air at lower temperature regime in furnace
  • 14. Combustion Reaction (H 2 , S)
    • Hydrogen reaction
    • 2H 2 + O 2 = 2H 2 O +61095 BTU/lb
    • Sulfur reaction
    • S + O 2 = SO 2 + 3980 BTU/lb (undesirable)
  • 15. Coal for combustion
    • Anthracite
    • Semi-anthracite
    • Bituminous
    • Semi-Bituminous
    • Lignite
    • Peat
    • High CV, low VM
    • High CV, low VM
    • Medium CV, medium VM
    • Medium CV, medium VM
    • Low CV, high VM, high TM
    • Very low CV, high VM & TM
  • 16. Heat Generation in furnace
    • Heat input in the furnace
    • Efficiency of thermal power plants is 37%-45% for different types of cycle
    • For typical conventional P.F. boilers, coal flow rate is
    • 290-350 T/hr For 500 MW units
    • 120-145 T/hr For 200 MW units
  • 17.  
  • 18.  
  • 19. Tangential Firing System
  • 20.  
  • 21.  
  • 22.  
  • 23. MAIN EQUIPMENTS OF FUEL & FIRING SYSTEM
    • MILLS OR PULVERISERS
    • FEDDERS
    • BURNERS
    • TYPES OF FEEDERS
    • VOLUMETRIC FEEDRES
    • GRAVIMETRIC FEEDERS
  • 24. PULVERIZERS
    • OBJECTIVES
    • TO CRUSHED THE COAL
    • REDCED TO A FINENESS SUCH THAT 70-80% PASSES THROUGH A
    • 200MESH SIEVE
    ADVANTAGES OF PULVERISED COAL FIRING
    • EFFICIENT UTILISATION OF CHEAPER GRADE OF COALS
    • FLEXIBILITY IN FIRING WITH ABILITY TO MEET FLUCTUATING LOADS
    • BETTER COAL COMBUSTION INCREASING THE BOILER EFFICIENCY
    • HIGH AVAILIBILITY
  • 25.  
  • 26. BOWL MILL Model no. Base capacity(T/Hr) 623XRP 18.4 703XRP 26.4 763XRP 33.8 803XRP 36.5 883XRP 51.1 903XRP 54.1 1003XRP 68.1 1043XRP 72.0 BASE CAPACITY(T/HR) AT HGI -55 Total Moisture-10% Fineness-70% THRU 200 MESH
  • 27. BALL& RACE MILL(E MILL) Model no. Base capacity(T/Hr) 7E9 25 8.5E10 35 8.5E9 40 10E10 55 10.9E11 61 10.9E10 70 10.9E8 80
  • 28. TUBE MILL Model no. Base capacity(T/Hr) BBD4760 83 BBD4772 90
  • 29. AIR AND DRAFT SYSTEM
    • OBJECTIVES
    • THE AIR WE NEED FOR COMBUSTION IN THE FURNACE AND FLUE GAS THAT WE MUST EVACUATE
    • TRANSPORT AND DRY THE PULVERISED COAL
    • SEALING OF BEARINGS FROM COAL/DUST
    DRAFT SYSTEM
    • DRAFT MEANS THE DIFFRENCE BETWEEN THE ATMOSPHERIC PRESSRE AND PRESSURE EXISTING IN THE FURNACE
    • NATURAL DRAFT- OBTAINED BY TALL CHIMNEY
    • INDUCED DRAFT- BY ID FANS
    • FORCED DRAFT- BY FD FANS
    • BALANCE DRAFT - BY ID AND FD FANS
    • GENERALLY IN POWER PLANT BALANCE DRAFT SYSTEM IS USED.
  • 30. FANS IN POWER PLANT
    • FORCED DRAFT FAN
    • INDUCED DRAFT FAN
    • PRIMARY AIR FAN
    • SEAL AIR FAN
    • SCANNER AIR FAN
    • THE BASIC INFORMATION NEEDED TO SELECT A FAN ARE
    • AIR OR GAS FLOW-KG/HR
    • DENSITY(FUNCTION OF TEMPERATURE AND PRESSURE)
    • SYSTEM RESISTANCE(LOSSES)
  • 31. AIR PRE HEATERS
    • OBJECTIVES
    • TO RAISE THE TEMPERATURES OF PRIMARY AND SECONDARY AIR
    • BY UTILISING HEAT FROM FLUE GAS AT LOW TEMPERATURE
    ADVANTAGES OF AIR PREHEATERS
    • INCREASE THE BOILER EFFICIENCY
    • STABILITY OF COMBUSTION IMPROVED BY USE OF HOT AIR
    • PERMITTING TO BURN POOR QUALITY COAL
  • 32.  
  • 33. Ljungstrom type Bisector
  • 34. TWO PASS BOILER ARRANGEMENT
  • 35. Electro Static Precipitator
    • To remove fly ash from the flue gases electrostatic precipitators are used.
    • They have collection efficiency over 99.5%
    • The efficiency depends on various parameters such as velocity of flow, quantity of gas, resistivity of ash, voltage of fields, temperature etc
  • 36. Principle of Operation The fluegas laden with flyash is sent through ducts having negatively charged plates which give the particles a negative charge. The particles are then routed past positively charged plates, or grounded plates, which attract the now negatively-charged ash particles. The particles stick to the positive plates until they are collected by periodically rapping.
  • 37.  
  • 38.  
  • 39.
    • SELECTION OF BOILER
    • TYPE OF BOILER
    • Based on steam parameter- Subcritical/ Supercritacal
    • Based on steam/ water circuit-Once throuh/ drum type
    • Based on air/ flue gas path- Tower/Two path/ T-type
    • Type of fuel- Coal fired/ oil fired
    • Type of draft system-
    • Type of burner arrangement- Tangential/Front/ opposed
    • Selection of Firing system- Type of mills
    • Single reheat/ double reheat
    • Type of water wall tube- Plain, rifled
    • Type of tubing arrangement- Spiral/ straight
  • 40.
        • Tube leakages from boiler pressure parts.
        • Erosion of tubes due to high ash content and velocities
        • Over heating of tubes
        • Passing from valves causing difficulty in maintaining the parameters
        • Failure or incorrectness of measured parameters
        • Overloading of boiler due to very poor quality of coal
        • Deposition of ash (clinkers) on furnace walls.
        • Difficulties in removal of ash from the boiler
        • Reduced effectiveness of heat transfer leading to loss of efficiency.
        • Improper combustion of coal in the boiler.
    Typical Boiler Problems
  • 41.
        • Air ingress from the nose arch, penthouse and boiler second pass and quantification thereof
        • Difference between on line reading and the actual oxygen in the flue gas duct
        • Difference between actual and 'on line' temperature
        • measurement of air heater air / gas outlet temperatures
        • Fouling and Slagging
        • High unburnt Carbon in flyash or bottomash
        • High air heater leakage
        • Boiler operation at high excess air
    Typical Boiler Problems contd..
  • 42. A Few words on Super Critical Boiler
    • Definition
    • “ CRITICAL ” is a thermodynamic expression describing the state of a substance beyond which there is no clear distinction between the liquid and gaseous phase.
    • The critical pressure & temperature for water are
    • Pressure = 225.56 Kg / cm2
    • Temperature = 374.15 C
  • 43. SUPERCRITICALTHERMAL CYCLE ADVANTAGES (1)
    • Improvements in plant efficiency by more than 2 %
    • Decrease in Coal Consumption
    • Reduction in Green House gases .
    • Overall reduction in Auxiliary Power consumption .
    • Reduction in requirement of Ash dyke Land & Consumptive water.
  • 44. SUPERCRITICAL – ADVANTAGES (2)
    • Sliding pressure operation because of Once through system .
    • Even distribution of heat due to spiral wall arrangement leading to less Boiler tube failure, thereby improving system continuity and availability of the station.
    • Low thermal stress in Turbine .
    • The startup time is less for boiler.
  • 45. SUPERCRITICAL – DISADVANTAGES
    • Higher power consumption of BFP
    • Higher feed water quality required.
    • More complex supporting and framing in Boiler due to Spiral Wall tubes.
    • Slight higher capital cost.
  • 46. COMPARISION OF 660 MW Vs 500 MW BOILER 255.2 291.4 0 C FEED WATER TEMP 46.1 51.17 KG/CM 2 RH STEAM PRESS INLET 540 568 0 C RH STEAM TEMP OUTLET 338.5 303.7 0 C RH STEAM TEMP INLET 1397.4 1742 T/HR RH STEAM FLOW 540 540 0 C SH STEAM TEMP 179 256 KG/CM 2 SH STEAM PR 1625 2225 T/HR S/H STEAM FLOW 500 660 unit Description
  • 47. 500 MW 660 MW DESCRIPTION 0.63 Cr 0.6Cr Cost of TG Per MW 6 634.31 Cr 1204.72 Cr Cost of TG for entire stage 5 1.02 Cr 1.07 Cr Boiler cost Per MW 4 1020.54 Cr 2124.00 Cr Total cost of Boiler + ESP 3 Included above 153.00 Cr Cost of ESP 2 1020.54 Cr 1970.73 Cr Cost of Boiler alone
    • 1
    COST COMPARISON FOR 660 MW vs. 500 MW