Steam Power Plants

STEAM POWER PLANTS

SELECTION OF SITE FOR STEAM POWER PLANT

Availability of land

Availability of sufficient amount of good boiler feed water and cooling water

Availability of fuel.

Necessity for future expansion.

Availability of other power other power services

Away from urban areas

Initial cost of plant

Magnitude and nature of load to be handled

LAY OUT OF STEAM POWER PLANT

GENRAL LAYOUT

Fuel handling unit

Ash handling unit

Boiler unit

Feed water unit

Cooling water unit

Generator unit

Turbine 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 CIRCUIT

Air 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 CIRCUIT Most power plants are condensing type – steam is

converted to water by condenser.

For safety of turbine water is demineralized – better economic operation

Adding 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 HP

2. Intermediate Pressure Turbine IP

3. 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 PLANT

Boiler- 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 boiler

Economizers- extract heat from flue gases

PARTS OF STEAM POWER PLANT

Superheaters 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 COOLING More heat transfer and thermal

conductivity is 7 times more than air. Low ventilation losses Life of insulation is more as no

oxidation of insulating material . Fire hazards minimized Less noise Size of frame reduced

DISADVANTAGES OF HYDROGEN COOLING

Chances of formation of explosive mixture.

Expensive than airSpecial oil seals required Problem of ensuring complete

tightness of hydrogen