Steam Power Plants

SELECTION OF SITE FOR STEAM POWER PLANTAvailability of landAvailability of sufficient amount of good boiler feed

water and cooling water Availability of fuel.Necessity for future expansion.Availability of other power other power servicesAway from urban areasInitial cost of plantMagnitude and nature of load to be handled

LAY OUT OF STEAM POWER PLANT

GENRAL LAYOUT

Fuel handling unit Ash handling unitBoiler unitFeed water unitCooling water unitGenerator unitTurbine unit

MAIN FLOW CIRCUITS

Fuel and ash circuit

Air and gas circuit

Feed water and steam circuit

Cooling water circuit

FUEL AND ASH CIRCUIT

Fuel stored is fed to boiler through conveyer belt.

Coal – particular size for complete burning.

Coal is passed through crushers , sizers and magnetic

separators before feeding to boiler.

As a result of combustion, ash is produced from coal

fuel which is removed from boiler through ash

handling equipments.

AIR AND GAS CIRCUITAir is required for complete combustion of the

fuel – supplied through Forced draught(FD) and Induced draught(ID) fans.

Air which is fed to the boiler, is passed through preheater – to extract energy of flue gases from boiler.

Flue gas consist of several gases and ash – passed through precipitator and finally go to atmosphere via chimney .

FEED WATER AND STEAM CIRCUITMost power plants are condensing type – steam is

converted to water by condenser.For safety of turbine water is demineralized – better

economic operationAdding make up water in feed water system

compensate leakages.The boiler feed pump (BFP) feeds water to boiler

drum – heated to form steam.Wet steam heated in super heater passed to turbine

and runs it

FEED WATER AND STEAM CIRCUIT

Stages of prime mover depending on size of power plant

1. High Pressure Turbine HP2. Intermediate Pressure Turbine IP3. Low Pressure turbine LP

FEED WATER AND STEAM CIRCUIT

COOLING WATER CIRCUIT

To condensate the steam in condenser and maintaining low pressure in it, large quantity of cooling water is required.

After passing it through condenser, it is fed back to river or pondage.

Cooling tower or cooling ponds are used in case of shortage.

Drawback- Excessive water loss

PARTS OF STEAM POWER PLANTBoiler- Water tube boilerCoal Mills Boiler feed pump- high capacity IMAir preheater- extract heat from flue

gasesDraught system- supply air to the furnace

and to take the flue gases from the boilerEconomizers- extract heat from flue

gases

PARTS OF STEAM POWER PLANTSuperheaters and ReheatersTurbinesCondenserCooling towerAlternators- high speed synchronous

generators

COOLING OF ALTERNATOR

Important due to damage of insulation at high temperature.

Closed circuit cooling widely used in modern alternators (Hydrogen as cooling medium).

ADVANTAGES OF HYDROGEN COOLINGMore heat transfer and thermal conductivity is

7 times more than air.Low ventilation lossesLife of insulation is more as no oxidation of

insulating material .Fire hazards minimizedLess noiseSize of frame reduced

DISADVANTAGES OF HYDROGEN COOLINGChances of formation of explosive

mixture.Expensive than airSpecial oil seals required Problem of ensuring complete tightness

of hydrogen