REPORT ON“GENERATION OF THERMAL POWER”ATNTPC DADRI

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About NTPC

• NTPC, the largest power Company in India, was setup in 1975 to accelerate power development in the country.

• NTPC has installed capacity of 29,394 MW.• It has 15 coal based power stations (23,395 MW)• 7 gas based power stations (3,955 MW)• 4 power stations in Joint Ventures (1,794 MW). • The company has power generating facilities in

all major regions of the country. • It plans to be a 75,000 MW company by 2017.

Generation of Electricity

• Prime mover coupled to Alternator

• Prime mover is driven by energy obtained from various sources such as

• burning of fuel• pressure of water• Force of wind etc.

Fig. Fundamental of generation of Electricity

Thermal Power Plant• A generating station which converts heat energy of coal combustion

into electrical energy is known as a steam power station.• Steam is produced in the boiler by utilizing the heat of coal

combustion. The steam is then expanded in the steam turbine and is condensed in a condenser to be fed into the boiler again. The steam turbine drives the alternator which converts mechanical energy of the turbine into electrical energy.

WORKING OF STEAM POWER PLANT

• Coal is burnt in a boiler ,which converts water into steam.• The steam is expanded in a turbine used to drive alternator.• The steam expanded is condensed in a condenser to be feed into the

boiler again.• The entire arrangement of steam power plant can be divided into :

a. fuel and ash plant.b. air and fuel gas plant.c. feed water and steam plant.d. cooling water plant.

The most important constituents of a steam power station are:

a. Steam generating equipmentb. Condenserc. Prime moverd. Cooling towers e. Electrical equipment

Steam generating equipment includes:

• Boiler• Boiler furnace • Superheater• Economiser• Air Pre-heater

BoilerA boiler is closed vessel in which water is converted into steam by utilising the heat of coal combustion. Steam boilers are broadly classified into following two types:(a) Water tube boilers (b) Fire tube boilers

In a water tube boiler, water flows through the tubes and the hot gases of combustion flow over these tubes. Water-tube boilers are used for high-pressure boilers

In a fire tube boiler, the hot products of combustion pass through the tubes surrounded by water.

• The heated water then rises into the steam drum. Here, saturated steam is drawn off the top of the drum. The steam will reenter the furnace in through a superheater in order to become superheated. Superheated steam is used in driving turbines. Since water droplets can severely damage turbine blades, steam is superheated to 730°F (390°C) or higher in order to ensure that there is no water entrained in the steam.

Super heater

• A device which removes last traces of moisture.

• It helps in reduction in requirement of steam quantity.

• steam being dry reduces the mechanical resistance of turbine.

• No corrosion at the turbine blades.

Economiser and Air Pre-heater

• They are such devices which recover the heat from the flue gases on their way to chimney and raise the temperature of feed water.

• Economiser raises boiler efficiency.• Air Pre-heaters recover the heat from the

flue gases leaving the economiser and heat the incoming air required for combustion

Condenser

• Which condenses the steam at the exhaust of turbine.

• It creates a very low pressure at the exhaust of turbine, this helps in converting heat energy of steam into mechanical energy in the prime mover.

• The condensed steam can be used as feed water to the boiler.

Prime Mover (i.e. Turbine)A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into mechanical energy.About 86% of all electric generation in the world is by use of steam turbines.It has almost completely replaced the reciprocating piston steam engine.

BOILER GENERATOR

STEAM TURBINE

Cooling Towers

• Remove heat from the water discharged from the condenser so that the water can be discharged to the river or re circulated and reused.

• Air can be circulated in the cooling towers through natural draft and mechanical draft.

Electrical EquipmentsAlternatorAn alternator is coupled to a steam turbine and converts mechanical energy of the turbine into electrical energy.It may be hydrogen or air cooled.The necessary excitation is provided by means of main and pilot exciters directly coupled to the alternator shaft.Transformers(a) main step-transformers, which steps-up generated voltage transmission of power(b) station transformers, general purpose(c) auxiliary transformers, which supply to individual unit-auxiliaries.Switchgearwhich locates fault on the system and isolate faulty part from healthy section.It contains circuit breakers, relays, switches and other control devices.

Coal Handling Plant Details

• Source of coal = Piparwar Mines North Karanpur (Jharkhand)

• Location = Near Ranchi

• Distance = 1200 Kms.

• Type of coal = F-grade (Washed)• E grade (Raw)

• Coal requirement = 13,000 MT/Day• ( 04 rakes )

Ash Handling Technique

• A natural result from the burning of fossil fuels, particularly coal, is the emission of flyash. Ash is mineral matter present in the fuel. For a pulverized coal unit, 60-80% of ash leaves with the flue gas.

• Two emission control devices for flyash are the fabric filters and electrostatic precipitators.

• Electrostatic precipitators have collection efficiency of 99%, but do not work well for flyash with a high electrical resistivity (as commonly results from combustion of low-sulfur coal). In addition, the designer must avoid allowing unburned gas to enter the electrostatic precipitator since the gas could be ignited.

Top View of ESP Schematic Diagram

• The fluegas laden with flyash is sent through pipes having negatively charged plates which give the particles a negative charge. The particles are then routed past positively charged plates, or grounded plates, which attract the now negatively-charged ash particles.

• The particles stick to the positive plates until they are collected. The air that leaves the plates is then clean from harmful pollutants.

Side view of ESP Schematic Diagram

Coal Ash can be used in:

• Construction of embankments and fills• Construction of road in sub-base• Manufacture of cement• Manufacture of bricks/blocks• Filling as flowable fill material• Agriculture as soil amendment/source of

essential plant nutrients