THERMAL POWER PLANT - PowerPoint PPT Presentation


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THERMAL POWER PLANT Thermal Power Stations Coal Fired Turbo alternators driven by steam turbine Oil Fired Crude oil OR Residual oil Gas Fired Fastest growing primary ... – PowerPoint PPT presentation

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Thermal Power Stations
  • Coal Fired
  • Turbo alternators driven by steam turbine
  • Oil Fired
  • Crude oil OR Residual oil
  • Gas Fired
  • Fastest growing primary fuel, worldwide
  • Combined cycle
  • First stage - Gas turbine Second stage - Steam
  • Diesel Fired
  • IC Engine as prime mover
  • Standby power plants

Selection of site
  • Nearness to load center
  • Supply of water
  • Availability of coal
  • Land requirement
  • Type of land
  • Labour supplies
  • Ash disposal
  • Distance from populated area

thermodynamic cycle
  • a type of steam engine involving a continuous
    cycle of vaporization of liquid and condensation
    back to liquid in a sealed system

merits demerits
  • Merits
  • Fuel used is cheaper
  • Cheaper installation cost comparatively
  • Cheaper production cost in comparison with
    diesel power plant
  • Can be installed at ay place irrespective of the
    existence of fuels unlike HEPP
  • Can be located near to load center unlike HEPP
  • Able to respond rapidly changing loads without
  • Steam engines and turbine can work under under
    25 of over load continuously
  • Portion of steam raised can be used as process
    steam in various industries (paper mills,
    textile mills etc)

Merits Demerits
  • Demerits
  • High maintenance and operating cost
  • Pollution
  • Requirement of water in huge quantity
  • Handling of coal and ash is quite difficult
  • The plant cost increases with the increases in
    the operating temperature and pressure
  • Require long time for erection and put into
  • Efficiency fall rapidly below 75 of full load

Schematic diagram of Coal Fired Power Plant
  • 1. Cooling tower 6. L.P turbine
    11. H.P turbine 16.
    Coal pulverizer 21. Re-heater
  • 2. Cooling water pump 7. Condensate pump 12.
    De-aerator 17. Boiler steam drum
    22. Combustion
  • 3. Transmission line 8. Surface condenser
    13. Feed water heater 18. Bottom ash
    23. Economizer
  • 4. Transformer 9. I.P turbine
    14. Coal conveyor 19.
    Super-heater 24. Air pre-heater
  • 5. Generator 10. steam control
    valve 15. Coal hopper 20. Forced
    draught 25. Precipitator

Fuel Ash Handling
  • Coal delivery by trucks, wagons etc
  • Coal storage Dead Live storage
  • Crusher coal is crushed to increase the area
  • Magnetic separator removes impurities
  • Pulverizer device to transform coal into fine
  • Ash pit when fuel gets burnt, ash is collected
    in ash pit
  • Ash quenching Ash is hot dusty, hence needs to
    be quenched
  • Ash delivery Quenched ash is taken using
    conveyors to the site

  • A place where fuel is burnt
  • Encloses burning equipments
  • Types
  • Grate fired uses stationary or movable grates,
    suited for solid fuels.
  • Hand fired uses stationary grate, small size
    plants, discontinuous process
  • Stoker fired uses movable grate, medium large
    size plants, continuous process
  • . Over feed stoker the fuel air
    move are not in the same direction
  • . Under feed stoker the fuel air
    move in the same direction
  • Chamber fired suited for pulverized coal, liquid
    or gaseous fuels.

  • Water tube boiler DM water circulates through
    tubes hot flue gases flow over them.
  • Less liable to explosion, produce high pressure
    steam, high efficiency, heating surface is large
  • Fire tube boiler hot flue gases pass through the
    tubes which are surrounded by water.
  • Low cost, compact in size, heating surface is
    small, cannot produce high pressure steam, liable
    to explode, low efficiency

  • Water tube boiler
    Fire tube boiler

Methods to improve thermal efficiency
  • Air pre-heater
  • hot flue gases are used to pre-heat the air
  • pre-heats the air to be supplied to the furnace
  • Accelerates combustion
  • Economizer
  • hot flue gases are used to heat the feed water
  • Improves efficiency
  • Reduces heat losses of flue gas
  • Reduces fuel consumption
  • Super heater
  • Increases temperature of generated steam
  • High thermal efficiency
  • Avoids corrosion of turbine blades
  • Re-heaters
  • Exhaust Steam from hp turbine is expanded
  • High turbine efficiency as the stages increase

  • Types
  • Surface condenser
  • No direct contact between steam cooling water
  • Impure water can be used for cooling
  • Low running cost , high vacuum is obtained
  • Increased efficiency
  • Requires large space
  • High initial cost
  • Jet Condenser
  • Direct contact between steam cooling water
  • Low initial cost
  • Compact
  • Low efficiency

Impulse -H.P turbine And Reaction - L.P I.P
Cooling towers
  • To reduce thermal pollution which occurs in open
  • To cool water coming out of the condenser in a
    closed system
  • Water cooled, Air cooled cooling towers
  • Uses either natural draft or mechanical draft
  • Natural draft utilizes buoyancy large space,
    high cost, less efficient
  • Mechanical draft uses fan, requires less space,
    improves efficiency
  • Forced draft tower blower type fan is
    located at the base of the tower forces air
    into the tower
  • Induced draft tower fan is located at the
    top of the tower pulls air through the tower.
    The fan induces hot moist air out the

  • Different types of cooling towers
    Induced draft

  • Draught difference between absolute gas
    pressure the ambient atmosphere pressure.
  • If Patmlt Pg as draught is positive
    PatmgtPgas draught is negative
  • Types of Draught Natural Mechanical
  • Natural draft is subjected to outside air
    conditions and temperature of flue gases leaving
    the furnace, as well as the chimney height. All
    these factors make proper draft hard to attain
    and therefore make mechanical draft equipment
    much more economical.
  • Mechanical draft reduces chimney height,
    independent of weather condition, easy control
  • Induced draft This is obtained by simply using
    an induced draft fan (ID fan) which removes flue
    gases from the furnace and forces the exhaust gas
    up the stack. Almost all induced draft furnaces
    operate with a slightly negative pressure.
  • Forced draft Draft is obtained by forcing air
    into the furnace by means of a fan (FD fan) and
    ductwork. Forced draft furnaces usually have a
    positive pressure use under fed stoker firing.
  • Balanced draft Balanced draft is obtained
    through use of both induced and forced draft.
    This is more common with larger boilers . The
    induced draft fan works in conjunction with the
    forced draft fan allowing the furnace pressure to
    be maintained slightly below atmospheric.

Fuel and ash handling
Governing system
  • Functions
  • To maintain constant shaft speed at all loads
  • To maintain constant steam flow through turbine
  • To maintain constant pass out and inlet/outlet
    steam pressures at all flows
  • Methods of governing
  • Throttle governing
  • Nozzle control governing
  • By-pass governing
  • Fly ball speed governing etc

Governing system