Steam Power Plant and Components

The Ash from the boiler is collected in two forms:

1. Bottom Ash(Slurry):It’s a waste which is dumped into a Ash Pond

2. Fly ash: Fly ash is separated from Flue Gases in ESP(Electro static Precipitator).

Ash Handling Plant

Fly Ash & Flue Gases

Economizer ESP

Bottom ash(wet ash)

Ash Pond

Boiler

Cylo

Cement Factory

Economizer : Reduces the temperature

Chimney

Fly ash

Flue Gases

Flue Gases

Economizer

• Flue gases coming out of the boiler carry lot of heat. An economizer extracts a part of this heat from flue gases and uses it for heating feed water. This use of economizer results in saving coal consumption and higher boiler efficiency

Air preheaters• After flue gases leave

economizer, some further heat can be extracted from them and used to heat incoming heat. Cooling of flue gases by 20 degree centigrade increases the plant efficiency by 1%.

• Air preheaters may be of three types

Plate type Tubular type Regenerative type

Boiler is a closed vessel in which water under pressure is transferred into steam by the application of heat.

In the furnace, the chemical energy in the fuel is converted into heat. It is the function of the boiler to transfer this heat to the water in the most efficient manner.

A boiler should be designed to absorb the maximum amount of heat released in the process of combustion.

Boiler

CLASSIFICATION OF BOILERS

• According to what flows in the TUBE

1. Water tube.2. Fire tube.

FIRE-TUBE BOILER

A fire-tube boiler is a type of boiler in which hot gases from a fire pass through one or more tubes running through a sealed container of water. The heat energy from the gases passes through the sides of the tubes by thermal conduction, heating the water and ultimately creating steam.

Boiler Types and Classifications

• Fire Tubes submerged in waterApplication

• Used for small steam capacities ( upto 25T/hr and 17.5kg/cm2

Merits• Low Capital Cost and fuel

Efficient (82%)• Accepts wide & load

fluctuations• Packaged Boiler

Fire Tube Boiler

Fire – tube Boilers

WATER-TUBE BOILER

A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Water tube boilers are used for high-pressure boilers. Fuel is burned inside the furnace, creating hot gases which heats water in the steam-generating tubes.

Boiler Types and ClassificationsWater Tube Boiler• Water flow through tubes

• Water Tubes surrounded by hot gasApplication

• Used for Power Plants• Steam capacities range from

4.5- 120 T/hrCharacteristics

• High Capital Cost• Used for high pressure high

capacity steam boiler• Demands more controls • Calls for very stringent water

quality

Water tube boilers

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•

A steam turbine is a thermo-mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion.

Steam turbine

SteamSteam is vaporized water. It is a transparent gas. At standard temperature and pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the volume of an equal mass of liquid water.

Saturated steam is steam at equilibrium with liquid water at the same pressure and temperature.

Superheated steam is steam at a temperature higher than its boiling point at a given pressure

Impulse & Reaction turbines An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage.

Reaction turbineIn the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine also makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.

Working of steam turbine based power plant

Working

•Steam is generated in steam generator and supplied to steam turbine at high pressure. (Usually sub critical pressure)

•This steam enters the high pressure rotor and expands , to produce work.

•Low pressure turbine stage is provided to extract more amount of work from the steam leaving into the condenser.