PRESENTATION BY

ASHISH MISHRA

THERMAL POWER PLANT

A Thermal Power Plant converts the heat energy of coal into electrical energy. Coal is burnt in a boiler which converts water into steam. The expansion of steam in turbine produces mechanical power which drives the alternator coupled to the turbine.Thermal Power Plants contribute maximum to the generation of Power for any country

Thermal Power Plants constitute 75.43% of the total installed captive and non-captive power generation in India

In thermal generating stations coal, oil, natural gas etc. are employed as primary sources of energy.

Introduction

General layoutthermal power plant

Coal handling plant Pulverizing plant Draft fans Boiler Ash handling plant Turbine Condenser Cooling towers and ponds Feed water heater Economizer Superheated and Reheated Air preheated

Main and Auxiliary e q u i p m e n t s

Raw Coal Wagon- Coal is brought to the site through a Wagon as per requirement.

Wagon tippler-The coal is unloaded from the Wagon and is transported to crushers and for storage place through conveyor.

Junction tower- JT’s are used where the conveyor has any angular deviation.

Primary Crusher-The Raw coal is crushed into fine pieces to 45mm grit).

Primary crusher is also called Rotary Breaker since the coal is crushed by a rotating plate.

Rejected- The stones and

unwanted coal is rejected

Coal Handling Plant

Stacker & Reclaimer- It is used to store the powdered coal for emergency purpose

Two way conveyor

Atmospheric air (Through FD fan)

Junction Tower

Mill Bunker-The 25mm grit coal is crushed into very fine powder for feeding the boiler.

We will have a spare Bunker for each Boiler.

BOILER

Secondary Crusher-The fine pieces of coal is crushed to powder (to 25mm grit)

In modern thermal power plant , coal is pulverized i.e. ground to dust like size and carried to the furnace in a stream of hot air. Pulverizing is a means of exposing a large surface area to the action of oxygen and consequently helping combustion.

Pulverizing mills are further classified as:

1. Contact mill2. Ball mill3. Impact mill

Pulverizing plant

The circulation of air is caused by a difference in pressure, known as Draft.

Draft is a differential pressure b/w atmosphere and inside the boiler.

It is necessary to cause the flow of gases through boiler setting

It may be –1.Natural draft2.Mechanical draft

Draft system

Boiler

Air

Air

Fuel HFO,LDO & Coal

Boiler

Fuel HFO,LDO & Coal

Dryer

Air compressor

FD Fan

Atmospheric Air

The boiler is fed with HFO and LDO initially to ignite the coal in the Boiler. Types of boilers:1. Water tube Boiler: A boiler in which water circulates in tubes heated externally by the

fire.2. Fire tube Boiler: Water is present in the drum inside the boiler and Hot air is

circulated around maintain the temperature.

• The fuel and air are feed from 2 directions to increase the efficiency

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

In a Thermal Power Plant generally 3 turbines are used to increase the efficiency.

High Pressure Turbine(HPT): The superheated steam is directly fed to this turbine to rotate it.

Intermediate Pressure Turbine(IPT): The out put from the HPT is reheated in a reheated(RH) and used to rotate IPT .

Low Pressure Turbine(LPT): The Exhausted steam from the IPT is directly fed to rotate the shaft of LPT.

Turbine

Condenser

HPT IPT LPT

RH

Steam

Super Heater

Generator

Steam

Shaft

*All the turbines are connected to a single shaft which is connected to the Generator.

Steam after rotating steam turbine comes to condenser. Condenser refers here to the shell and tube heat exchanger (or surface condenser) installed at the outlet of every steam turbine in Thermal power stations of utility companies generally.

CONDENSER

o A condenser needs huge quantity of water to condense the steam .

o Typically a 2000MW plant needs about 1500MGallon of water.

o Most plants use a closed cooling system where warm water coming from condenser is cooled and reused

o Small plants use spray ponds and medium and large plants use cooling towers.

o Cooling tower is a steel or concrete hyperbolic structure having a reservoir at the base for storage of cooled water

o Height of the cooling tower may be 150 m or so and diameter at the

Cooling towers and ponds

Advantages of heating water before feeding back to the boiler:-

a) Feed water heating improves overall plant efficiency.b) The dissolved oxygen and carbon dioxide which would

otherwise cause boiler corrosion are removed in feed water heater

c) Thermal stresses due to cold water entering the boiler drum are avoided.

d) Quantity of steam produced by the boiler is increased.e) Some other impurities carried by the steam and

condensate, due to corrosion of boiler and condenser are precipitated outside the boiler

Feed water heater

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

Economizer

Super heater :

Super heater is a component of a steam-generating unit in which steam, after it has left the boiler drum, is heated above its saturation temperature

Reheater : Some of the heat of superheated steam is used to rotate the turbine where it loses some of its energy

Super heater and Reheaters

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

Air preheaters

Water in a Power Plant is used for1. Production of Steam- for rotating turbine.2. Cooling Purpose- For cooling of various equipment .

Water is recycled and used for various purpose:

Water Handling Plant(WHP)

3% of water is wasted during this process. Appx 4 cubic mt water is lost /day/MW

Raw Water

Purified DM water

For cooling purpos

e

Steam

Condenser

Reservoir

Water Clarification

DM Plant(Demineralized Plant)

Chlorification &

Filtration

Various Equipment Cooling Water

Cooling Tower

CT

Auxiliary cooling Water (ACW)

DMCWP

DMCW Demineralized cooling Water

CWPCT CWP CWP

Steam to Water

Cool water from CWP

Condenser

Boiler

Steam

water

Cool water

Hot water

Hot WellDearator

25D 35D

25D 20D

PHE

Various Equipment

D-DegreesCWP-cooling water PumpPHE-Pre heat Exchange

Water Cycle

The coal is brought and crushed to powder. This is feed to Boiler for producing heat

In Boiler the water is converted to steam. In Super heater the moisture content is removed from the steam and that

steam is called super heated steam The superheated steam rotates the shaft of the High pressure turbine The Exhausted steam is sent to preheater and the steam then rotates the

Intermediate pressure(IP) Turbine The steam from the IP turbine is then feed to low pressure turbine. The turbine shaft is connected to the Generator, which produces Electric

Power. The power generated is then Transmitted.

Operation Mechanism

The Synchronous Generator is used to Generate power by connecting the shaft of the Turbine to the shaft of the generator which cuts the magnetic flux producing Emf.

The Generated Voltage will generally 11KV to 20 KV max. The Generated Voltage is stepped up by connecting Step up

transformer and is transmitted and is also used for Auxiliary purposes .

Generator

Bus Duct

Generator Transformer20KV to 400KV

SYNCHRONOUSGENERATOR

UAT20Kv to 6.KV

Unit Auxiliary Transformer: This transformer is used to step down the produced voltage and use for Auxiliary purpose.