1. THERMAL POWER PLANT

2. 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 Turbine
Diesel Fired
IC Engine as prime mover
Standby power plants

3. 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

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

5. 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 difficulty
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)

6. 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 action
Efficiency fall rapidly below 75% of full load

7. Schematic diagram of Coal Fired Power Plant

8. Components
1. Cooling tower L.P turbine H.P turbine Coal pulverizer Re-heater
2. Cooling water pump 7. Condensate pump De-aerator Boiler steam drum Combustion
3. Transmission line Surface condenser Feed water heater Bottom ash Economizer
4. Transformer I.P turbine Coal conveyor Super-heater Air pre-heater
5. Generator steam control valve 15. Coal hopper Forced draught Precipitator
26. Induced draught
27. Flue gas stack

9. 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 powder
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

10. Furnace 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.

11. Boiler
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

12. 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

13. CONDENSER Types Surface condenser Jet 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

14. Impulse -H.P turbine And Reaction - L.P & I.P turbine

15. TYPES OF TURBINE

16. Cooling towers To reduce thermal pollution which occurs in open system
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

17. Contd..
Different types of cooling towers Induced draft

18. Draught
Draught : difference between absolute gas pressure & the ambient atmosphere pressure.
If Patm< Pg as draught is positive & Patm>Pgas 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.

19. ELECTROSTATIC PRECIPITATOR

20. Fuel and ash handling

21. 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

22. Governing system