Layout of steam power plant

CLASSIFICATION OF POWER PLANTS

reasons:

1.     Steam can be raised quickly from water

2.     It does not react much with materials.

3.     It is stable at temperatures required in the plant

LAYOUT OF STEAM POWER PLANT:

The layout of steam power plant has the following circuits:

1.     Fuel (Coal) and ash circuit

2.     Air and flue gas circuit

3.     Feed water and steam flow circuit

4.     Cooling water flow circuit.

1 COAL AND ASH CIRCUIT:

Layout of Steam power Plant

Coal and Ash Circuit:

•         Coal from mines is delivered by ships, rails or trucks to the power station.

•         Coal received at coal yard.

•                      

•         Coal is sized by crushers, breakers etc.,

•         The sized coal is stored in coal storage.

•         From stock yard, the coal is transferred to the boiler furnace by means of conveyors, elevators etc.,

•           The coal is burnt in the boiler and ash is formed.

•         Ash coming out of the furnace will be too hot, dusty and accompanied by poisonous gases.

•           The ash is transferred to the ash storage.

•         Generally the ash will be quenched to reduce the temperature and the dust content.

2 AIR AND FLUE GAS CIRCUIT:

•         Air is taken from the atmosphere by the action of FD fan.

•           It is passed through an air pre heater

•           The air is preheated by the flue gases in the pre heater.

•           This preheated air is supplied to the furnace to aid the combustion of fuel.

•         Due to the combustion of fuel the flue gases are formed.

•           The flue gases from the furnace pass over the boiler tubes and super heater tubes.

•           Then the flue gases pass through economiser to heat the feed water.

•           After that it passes through a dust collector.

It is then exhausted to atmosphere through chimney

3 WATER AND STEAM  CIRCUIT

La yout of Steam Power Plant

Water and Steam Circuit:

•           The water is preheated by the flue gases in the economiser.

•           This preheated water is then supplied to the boiler drum.

•           Heat is transferred to the water by the burning of the coal.

•    Due to this, water is con verted into the steam.

•           The steam raised in boil er is passed through a super heater.

•         It is superheated by the flue gases.

•           The turbine drives generator to produce electric power.

•           The expanded steam is t hen passed through the condenser.

•         In the condenser, steam i s condensed into water there circulated.

4 COOLING WATER CIRCUIT:

•         The exhaust steam from t he turbine is condensed in the condenser.

•           In the condenser, the cold water is circulated to condense the steam into water.

•   The steam is condensed b y losing its latent heat to the circulating the col d water.

•         Hence the cold water get s heated.

•           This hot water is then ta ken to a cooling tower.

•           In cooling tower the water is sprayed in the form of droplets through nozzzles.

•           The atmospheric air ente rs the cooling tower from the openings provided at the bottom of the tower.

•           This cold water is again circulated through the pump, condenser and the cooling

•         Some amount of water may be lost during circulation.

•           Hence make up water is added to the pond by means of a pump

Layout of Steam ( Thermal) Power Plant

Energy Conversion Process:  

Chemical Energy (Fuel/Coal)  -- >

Heat Energy(Boiler)  -- >

Mechanical Energy(Turbine)  -- >

Electrical Energy(Generator)

Advantages of Steam Power Plant (Thermal plant)

•         Life of plant is more (25-30 years ) compared to Diesel plant (2-5 years)

•       Repair and maintenance cost is low when compared to diesel plant. Initial cost is less compared to nuclear plant.

•           Suitable for varying load conditions.

•           No radioactive harmful wastes are produced

•           Unskilled operators can operate the plant.

•           The power generation does not depend on the water storage.

•           There are no transmission losses, as they are located near load centres.

Disadvantages of thermal power plant:

•         Less efficient than diesel plants.

•           Starting up and bringing into service takes more time.

•         Cooling water required is more.

•           Space required is more.

•           Storage required for the fuel is more.

•           Ash handling is a big problem

•           Not economical in areas which are remote from coal fields.

•           Manpower required is more.

•           For large units, the capital cost is more.