VOCATIONAL TRAINING PROJECT REPORT

ON

“COAL FIRED STEAM POWER PLANT”

NTPC SIPAT

Duration of training:- 02/06/2014- 28/06/2014

Under the Guidance of:- Mr. Praveen Patel (Manager Training Deptt.)

Submitted by:- JINENDRA NINAMA

VI SEM. (Mechanical Engg.)

M.A.N.I.T , BHOPAL

DECLARATION BY STUDENT

I hereby declare that work submitted entitled “VOCATIONAL TRAINING PROJECT

REPORT”, submitted towards completion of third year of B.E (MECHENICAL) at

M.A.N.I.T, BHOPAL comprises of my original work under the supervision of guided

at NTPC SIPAT. The result embodied in this report have not been submitted to any

other institution or University for fulfillment of any other curriculum.

JINENDRA NINAMA

VI SEMESTER

MECHENICAL ENGG.

M.A.N.I.T , BHOPAL

ACKNOWLEDGEMENT

I AM TRULY THANKFUL TO ALL THE FACULTIES/GUIDES WHO IMPARTED THE

LECTURES O0N VARIOUS SUBJECTS AND TOOK ME TO THE PLANT ON GUIDED

SYUDY VISIT ALONG DETAILED EXPLANATION ABOUT PLANT AND MACHINARY

DATE:-

NAME:- JINENDRA NINAMA

COLLAGE:- M.A.N.I.T, BHOPAL

BRANCH:- MECHANICAL

YEAR/SEM:- III YEAR/VI SEM

Sipat Thermal Power Plant

The newly setup NTPC's 2980 MW Super Thermal Power Plant at Sipat, which was

dedicated to the nation by Prime Minster Dr Manmohan Singh on Thursday, was

rechristened as Rajiv Gandhi Super Thermal Power Station (RGSTPS). The Prime Minister

also remotely laid the foundation stone of the Stage-I Lara Super Thermal Power Project, at

Lara village, Raigarh District.

Set up at a cost of Rs 13000 crores, RGSTPS is the second plant of the NTPC that has been

named after former Prime Minister Rajiv Gandhi.

It is located at Sipat in Bilaspur district in state of Chhattisgarh. The power plant is one of

the coal based power plants of NTPC.[2]

The coal for the power plant is sourced from Dipika Mines

of South Eastern Coalfields Limited.

The project has an installed capacity of 2980 MW consisting of two stages, stage one which got

commissioned late was of 3 units of 660 MW each invojving super-critical boilers technology and

stage two consisted of 2 units of 500 MW each.PM Manmohan Singh inaugurated the Sipat Thermal

Power Plant on September 20,2013.

Stage Unit Number Installed Capacity (MW) Date of Comisioning Status

1st 1 660 2011 June Running

1st 2 660 2011 December Running

1st 3 660 2012 June [4]

Running

2nd 4 500 2007 May Running

2nd 5 500 2008 August Running

Total Five 2980

Simplified Diagram

1.Cooling tower

A cooling tower is a heat rejection device which extracts waste heat to the atmosphere through the

cooling of a water stream to a lower temperature. Cooling towers may either use the evaporation of

water to remove process heat and cool the working fluid to near the wet-bulb air temperature or, in

the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near

the dry-bulb air temperature.

Common applications include cooling the circulating water used in oil refineries, petrochemical and

other chemical plants, thermal power stations and HVAC systems for cooling buildings. The

classification is based on the type of air induction into the tower: the main types of cooling towers

are natural draft and induced draft cooling towers.

Cooling towers vary in size from small roof-top units to very large hyperboloid structures (as in the

adjacent image) that can be up to 200 metres (660 ft) tall and 100 metres (330 ft) in diameter, or

rectangular structures that can be over 40 metres (130 ft) tall and 80 metres (260 ft) long. The

hyperboloid cooling towers are often associated with nuclear power plants,[1]

although they are also

used to some extent in some large chemical and other industrial plants. Although these large towers

are very prominent, the vast majority of cooling towers are much smaller, including many units

installed on or near buildings to discharge heat from air conditioning.

2.Three phase transmission line & step-up transformer

Three-phase electric power is a common method of alternating-current electric

power generation, transmission, and distribution.[1]

It is a type of polyphase system and is the most

common method used by electrical grids worldwide to transfer power. It is also used to power

large motors and other heavy loads. A three-phase system is usually more economical than an

equivalent single-phase or two-phasesystem at the same voltage because it uses less conductor

material to transmit electrical power.

In a three-phase power supply system, three conductors each carry an alternating current (of the

same frequency) but the phase of the voltage on each conductor is displaced from each of the other

conductors by 120 degrees. (One third of a 360 degree "cycle".) Hence, the voltage on any

conductor reaches its peak at one third of a cycle after one of the other conductors and one third of a

cycle before the third conductor. Using the voltage on one conductor as the reference, the peak

voltage on the other two conductors is delayed by one third and two thirds of one cycle respectively.

This phase delay gives constant power transfer over each cycle. It also makes it possible to produce

a rotating magnetic field in an electric motor.

With a three phase supply, at any instant, the potential of any phase is exactly equal to and the

opposite of the combination (sum) of the other two phases. This means that - if the load on the three

phases is "balanced" - the return path for the current in any phase conductor is the other two phase

conductors.

Hence, the sum of the currents in the three conductors is always zero and the current in each

conductor is equal to and in the opposite direction as the sum of the currents in the other two. Thus,

each conductor acts as the return path for the currents from the other two.

While a single phase AC power supply requires two conductors (Go and Return), a three phase

supply can transmit three times the power by using only one extra conductor. This means that a 50%

increase in transmission cost yields a 200% increase in the power transmitted.

3. Electric generator

an electric generator is a device that converts mechanical energy to electrical energy. A generator

forces electric current to flow through an external circuit. The source of mechanical energy may be a

reciprocating or turbine steam engine, water falling through a turbine or waterwheel, aninternal

combustion engine, a wind turbine,[1]

a hand crank, compressed air, or any other source of

mechanical energy. Generators provide nearly all of the power for electric power grids.

The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and

motors and generators have many similarities. Many motors can be mechanically driven to generate

electricity and frequently make acceptable generators.

4.Steam turbine

A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to

do mechanical work on a rotating output shaft. Its modern manifestation was invented by Sir Charles

Parsons in 1884.[1]

Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical

generator – about 90% of all electricity generation in the United States (1996) is by use of steam

turbines.[2]

The steam turbine is a form of heat engine that derives much of its improvement

in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which

results in a closer approach to the ideal reversible expansion process

.

Steam condenser- The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be

pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and

efficiency of the cycle increases. The surface condenser is a shell and tube heat exchanger in which

cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine

enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as

shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-

driven exhausters for continuous removal of air and gases from the steam side to maintainvacuum.

5.Boiler feedwater pump A boiler feedwater pump is a specific type of pump used to pump feedwater into a steam boiler. The water may be freshly supplied or returning condensate produced as a result of the condensation of the steam produced by the boiler. These pumps are normally high pressure units that take suction from a condensate return system and can be of the centrifugal pump type or positive displacement type. Feedwater pumps range in size up to many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. Large industrialcondensate pumps may also serve as the feedwater pump. In either case, to force the water into the boiler, the pump must generate sufficient pressure to overcome the steam pressure developed by the boiler. This is usually accomplished through the use of a centrifugal pump. Another common form of feedwater pumps run constantly and are provided with a minimum flow device to stop overpressuring the pump on low flows.The minimum flow usually returns to the tank or deaerator.

6.Control valves Control valves are valves used to control conditions such as flow, pressure, temperature,

and liquid level by fully or partially opening or closing in response to signals received from controllers

that compare a "setpoint" to a "process variable" whose value is provided by sensors that monitor

changes in such conditions.[1]

Control Valve is also termed as the Final Control Element.

The opening or closing of control valves is usually done automatically

by electrical, hydraulic or pneumatic actuators. Positioners are used to control the opening or closing

of the actuator based on electric, or pneumatic signals. These control signals, traditionally based on

3-15psi (0.2-1.0bar), more common now are 4-20mA signals for industry, 0-10V for HVAC systems,

and the introduction of "Smart" systems, HART, Fieldbus Foundation, and Profibus being the more

common protocols. Some of the control valve available are Reverse Double-Ported Globe-Style

Valve Body,Three-Way Valve with Balanced Valve Plug, Flanged Angle-style control valve body and

. Valve Body with Cage-Style Trim, Balanced Valve Plug, and Soft Seat.[2]

A control valve consists of three main parts in which each part exist in several types and designs:

Valve's actuator

Valve's positioner

Valve's body

7.Deaerator A deaerator is a device that is widely used for the removal of oxygen and other

dissolved gases from the feedwater to steam-generatingboilers. In particular, dissolved oxygen in

boiler feedwaters will cause serious corrosion damage in steam systems by attaching to the walls of

metal piping and other metallic equipment and forming oxides (rust). Dissolved carbon

dioxide combines with water to form carbonic acidthat causes further corrosion. Most deaerators are

designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less as well as

essentially eliminating carbon dioxide.[1][2][3]

There are two basic types of deaerators, the tray-type and the spray-type:[2][4][5][6][7]

The tray-type (also called the cascade-type) includes a vertical domed deaeration section

mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feedwater

storage tank.

The spray-type consists only of a horizontal (or vertical) cylindrical vessel which serves as both

the deaeration section and the boiler feedwater storage tank.

8.Feedwater heater A feedwater heater is a power plant component used to pre-heat water delivered to

a steam generatingboiler. Preheating the feedwater reduces the irreversibilities involved in steam

generation and therefore improves the thermodynamic efficiency of the system.[4]

This reduces plant

operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is

introduced back into the steam cycle.

In a steam power plant (usually modeled as a modified Rankine cycle), feedwater heaters allow the

feedwater to be brought up to the saturation temperature very gradually. This minimizes the

inevitable irreversibilities associated with heat transfer to the working fluid (water). See the article on

the Second Law of Thermodynamicsfor a further discussion of such irreversibilities.

9.Pulverizer A pulverizer or grinder is a mechanical device for the grinding of many different types of materials. For example, a pulverizer mill is used to pulverize coal for combustion in the steam-generating furnaces of fossil fuel power plants.

10.Boiler steam drum

A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam at the top

end of the water tubes. The drum stores the steam generated in the water tubes and acts as a

phase-separator for the steam/water mixture. The difference in densities between hot and cold water

helps in the accumulation of the "hotter"-water/and saturated-steam into the steam-drum. The

separated steam is drawn out from the top section of the drum and distributed for process. Further

heating of the saturated steam will make superheated steam normally used to drive a steam turbine.

Saturated steam is drawn off the top of the drum and re-enters the furnace in through a superheater.

The steam and water mixture enters the steam drum through riser tubes, drum internals consisting

of demister separate the water droplets from the steam producing dry steam. The saturated water at

the bottom of the steam drum flows down through the downcomer pipe, normally unheated, to

headers and water drum. Its accessories include a safety valve, water-level indicator and level

controller. Feed-water of boiler is also fed to the steam drum through a feed pipe extending inside

the drum, along the length of the steam drum.

A steam drum is used without or in the company of a mud-drum/feed water drum which is located at

a lower level. A boiler with both steam drum and mud/water drum is called a bi-drum boiler and a

boiler with only a steam drum is called a mono-drum boiler. The bi-drum boiler construction is

normally intended for low pressure-rating boiler while the mono-drum is mostly designed for higher

pressure-rating.[1]

On steam locomotives the steam drum is also called a steam dome

11.Superheater

A superheater is a device used to convert saturated steam or wet steam into dry steam used

in steam engines or in processes, such as steam reforming. There are three types of superheaters

namely: radiant, convection, and separately fired. A superheater can vary in size from a few tens of

feet to several hundred feet (a few metres to some hundred metres). The main advantages of using

a superheater are reduced fuel and water consumption but there is a price to pay in increased

maintenance costs. In most cases the benefits outweighed the costs and superheaters were widely

used. An exception was shunting locomotives (switchers). British shunting locomotives were rarely

fitted with superheaters. In locomotives used for mineral traffic the advantages seem to have been

marginal. For example, the North Eastern Railway fitted superheaters to some of its NER Class

P mineral locomotives but later began to remove them.

Without careful maintenance superheaters are prone to a particular type of hazardous failure in the

tube bursting at the U-shaped turns in the superheater tube. This is difficult to both manufacture, and

test when installed, and a rupture will cause the superheated high-pressure steam to escape

immediately into the large flues, then back to the fire and into the cab, to the extreme danger of the

locomotive crew.

12.Economizer

economisers , are mechanical devices intended to reduce energy consumption, or to

perform another useful function such as preheating a fluid. The term economizer is used for

other purposes as well. Boiler, power plant, heating, ventilating, and air conditioning (HVAC)

uses are discussed in this article. In simple terms, an economizer is a heat exchanger.

Modern-day boilers, such as those in coal-fired power stations, are still fitted with economizers which

are descendants of Green's original design. In this context they are often referred to as feedwater

heaters and heat the condensate from turbines before it is pumped to the boilers.

Economizers are commonly used as part of a heat recovery steam generator in a combined

cycle power plant. In an HRSG, water passes through an economizer, then a boiler and then

a superheater. The economizer also prevents flooding of the boiler with liquid water that is too cold

to be boiled given the flow rates and design of the boiler.

A common application of economizers in steam power plants is to capture the waste heat

from boiler stack gases (flue gas) and transfer it to the boiler feedwater. This raises the temperature

of the boiler feedwater, lowering the needed energy input, in turn reducing the firing rates needed for

the rated boiler output. Economizers lower stack temperatures which may cause condensation of

acidic combustion gases and serious equipment corrosion damage if care is not taken in their design

and material selection

13.Air preheater An air preheater (APH) is a general term to describe any device designed to heat air before another

process (for example,combustion in a boiler) with the primary objective of increasing the thermal

efficiency of the process. They may be used alone or to replace a recuperative heat system or to

replace a steam coil.

In particular, this article describes the combustion air preheaters used in large boilers found

in thermal power stationsproducing electric power from e.g. fossil fuels, biomass or waste.[1][2][3][4][5]

The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the

thermal efficiency of the boiler by reducing the useful heat lost in the flue gas. As a consequence,

the flue gases are also conveyed to the flue gas stack (or chimney) at a lower temperature, allowing

simplified design of the conveyance system and the flue gas stack. It also allows control over the

temperature of gases leaving the stack.

14. Electrostatic precipitator An electrostatic precipitator (ESP) is a highly efficient filtration device that removes fine particles,

like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally

impeding the flow of gases through the unit. [1]

In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies

energy only to the particulate matter being collected and therefore is very efficient in its consumption

of energy (in the form of electricity). ESPs continue to be excellent devices for control of many

industrial particulate emissions, including smoke from electricity-generating utilities (coal and oil

fired), salt cake collection from black liquor boilers in pulp mills, and catalyst collection from fluidized

bed catalytic cracker units in oil refineries to name a few. These devices treat gas volumes from

several hundred thousand ACFM to 2.5 million ACFM (1,180 m³/s) in the largest coal-fired boiler

applications. For a coal-fired boiler the collection is usually performed downstream of the air

preheater at about 160 °C (320 °F) which provides optimal resistivity of the coal-ash particles. For

some difficult applications with low-sulfur fuel hot-end units have been built operating above 370 °C

(698 °F).

The original parallel plate–weighted wire design[further explanation needed]

has evolved as more efficient

(and robust) discharge electrode designs were developed, today focusing on rigid (pipe-frame)

discharge electrodes to which many sharpened spikes are attached (barbed wire),

maximizing corona production. Transformer-rectifier systems apply voltages of 50–100 kV at

relatively high current densities. Modern controls, such as an automatic voltage control,

minimize electric sparking and prevent arcing (sparks are quenched within 1/2 cycle of the TR set),

avoiding damage to the components. Automatic plate-rapping systems and hopper-evacuation

systems remove the collected particulate matter while on line, theoretically allowing ESPs to stay in

continuous operation for years at a time.

15.Flue-gas stack

A flue-gas stack is a type of chimney, a vertical pipe, channel or similar structure through which

combustion product gases called flue gases are exhausted to the outside air. Flue gases are

produced when coal, oil, natural gas, wood or any other fuel is combusted in an industrial furnace,

apower plant's steam-generating boiler, or other large combustion device. Flue gas is usually

composed of carbon dioxide (CO2) and water vapor as well as nitrogen and

excess oxygen remaining from the intake combustion air. It also contains a small percentage of

pollutants such asparticulate matter, carbon monoxide, nitrogen oxides and sulfur oxides. The flue

gas stacks are often quite tall, up to 400 metres (1300 feet) or more, so as to disperse the exhaust

pollutants over a greater area and thereby reduce the concentration of the pollutants to the levels

required by governmental environmental policy and environmental regulation.

When the flue gases are exhausted from stoves, ovens, fireplaces, or other small sources within

residential abodes, restaurants, hotels, or other public buildings and small commercial enterprises,

their flue gas stacks are referred to as chimneys.

Elements Of Thermal Power Plant

1. COAL HANDLING UNIT

2.BOILER OR STEAM GENERATOR UNIT

3.TURBINE &ELECTRIC GENERATOR UNIT

4.CONDENSATION AND COOLING WATER UNIT

5.ASH HANDLING UNIT

Elements of Coal Handling Plant (CHP)

TRACK HOOPER

PADDLE FEEDER

CONVEYER BELT

MAGNETIC SEPERATOR

CRUSHER HOUSE

VGF

TRANSFER POINTS

STACKER

STOCKYARD/COAL PILES A coal preparation plant (CPP) is a facility that washes coal of soil and rock, crushes it into

graded sized chunks (sorting), stockpiles grades preparing it for transport to market, and

more often than not, also loads coal into rail cars, barges, or ships. A CPP may also be

called a coal handling and preparation plant (CHPP), coal handling plant, prep

plant, tipple orwash plant.

The more of this waste material that can be removed from coal, the lower its total ash

content, the greater its market value and the lower its transportation costs.

PADDLE FEEDERS

Then this raw coal is scooped onto conveyer by PADDLE FEEDER

CONVEYER BELT

Belt conveyor is a kind of machine that to transfer the material continuously. The belt works

under the effect of frictional force. It is not only the components to transfer the material

The belt conveyor is advanced and simple in structure, easy to maintain. Its transfer capacity

is high, transfer distance is long.

They are widely used in mining, metallurgical and coal industry to transfer sandy or lump

material, or packaged material. In many situation, it is a very important component of

nonstandard machinery.

The conveyors which are produced by break-day consist of standard parts, which are

advanced and simple in structure, easy to maintain

They are widely used in mining, metallurgical and coal industry to transfer sandy or lump

material, or packaged material.

CRUSHER HOUSE After hand picking foreign material, coal is transported to the Crush house by conveyor belts

where it is crushed to small pieces of about 20 mm diameter. The crushed coal is then transported

to the store yard. Coal is transported to bowl mills by coal feeders.

Crushers may be used to reduce the size, or change the form, of waste materials so they can be

more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in

rock ore), so that pieces of different composition can be differentiated. Crushing is the process of

transferring a force amplified by mechanical advantage through a material made of molecules that

bond together more strongly, and resist deformation more, than those in the material being crushed

do. Crushing devices hold material between two parallel or tangent solid surfaces, and apply

sufficient force to bring the surfaces together to generate enough energy within the material being

crushed so that its molecules separate from (fracturing), or change alignment in relation to

(deformation), each other. The earliest crushers were hand-held stones, where the weight of the

stone provided a boost to muscle power, used against a stone anvil. Querns and mortars are types

of these crushing devices.

STACKER AND STOCK YARD

A stacker is a large machine used in bulk material handling. Its function is to pile bulk

material such as limestone, ores and cereals on to a stockpile. A reclaimer can be used to

recover the material.

Stackers are nominally rated for capacity in tonnes per hour (tph). They normally travel on a

rail between stockpiles in the stockyard. A stacker can usually move in at least two

directions: horizontally along the rail and vertically by luffing (raising and lowering) its boom.

The boom is luffed upwards as the height of the stockpile increases. Some stackers can

rotate the boom. This allows a single stacker to form two stockpiles, one on either side of

the conveyor. Stackers are used to stack in different patterns, such as cone stacking and

chevron stacking. Stacking in a single cone tends to cause size segregation, with coarser

material moving out towards the base. In raw cone ply stacking, additional cones are added

next to the first cone. In chevron stacking, the stacker travels along the length of the

stockpile adding layer upon layer of material.

BOILER OR STEAM GENERATOR

ELEMENTS OF BOILER FUEL PREPARATION SYSTEM

AIR &FUEL GAS SYSTEM

WATER AND STEAM SYSTEM

FUEL FIRING SYSTEM

DEARATION NAND DEED PUMPING SYSTEM

Fuel preparation system

In coal-fired power stations, the raw feed coal from the coal storage area is first crushed into small

pieces and then conveyed to the coal feed hoppers at the boilers. The coal is next pulverized into a

very fine powder. The pulverizers may be ball mills, rotating drum grinders, or other types of

grinders.

Some power stations burn fuel oil rather than coal. The oil must kept warm (above its pour point) in

the fuel oil storage tanks to prevent the oil from congealing and becoming unpumpable. The oil is

usually heated to about 100 °C before being pumped through the furnace fuel oil spray nozzles.

Boilers in some power stations use processed natural gas as their main fuel. Other power stations

may use processed natural gas as auxiliary fuel in the event that their main fuel supply (coal or oil) is

interrupted. In such cases, separate gas burners are provided on the boiler furnaces.

Superheater

Fossil fuel power plants often have a superheater section in the steam generating furnace.

The steam passes through drying equipment inside the steam drum on to the superheater, a

set of tubes in the furnace. Here the steam picks up more energy from hot flue gases outside

the tubing and its temperature is now superheated above the saturation temperature. The

superheated steam is then piped through the main steam lines to the valves before the high

pressure turbine.

Nuclear-powered steam plants do not have such sections but produce steam at essentially

saturated conditions. Experimental nuclear plants were equipped with fossil-fired super

heaters in an attempt to improve overall plant operating cost.

Reheater Power plant furnaces may have a reheater section containing tubes heated by hot flue gases

outside the tubes. Exhaust steam from the high pressure turbine is passed through these

heated tubes to collect more energy before driving the intermediate and then low pressure

turbines.

The main advantage of reheat cycle is to reduce the specific steam consumption and

consequently reduce the size of the boiler and other auxiliaries for the same power.The

reheat cycle is only preferred for the high capacity (above 100MW and when the pressure

of the steam is as high as 100 bar).

Turbine generator The turbine generator consists of a series of steam turbines interconnected to each other

and a generator on a common shaft. There is a high pressure turbine at one end, followed by

an intermediate pressure turbine, two low pressure turbines, and the generator. As steam

moves through the system and loses pressure and thermal energy it expands in volume,

requiring increasing diameter and longer blades at each succeeding stage to extract the

remaining energy. The entire rotating mass may be over 200 metric tons and 100 feet (30 m)

long. It is so heavy that it must be kept turning slowly even when shut down (at 3 rpm) so

that the shaft will not bow even slightly and become unbalanced. This is so important that it

is one of only five functions of blackout emergency power batteries on site. Other functions

are emergency lighting, communication, station alarms and turbogenerator lube oil.

Superheated steam from the boiler is delivered through 14–16-inch (360–410 mm) diameter

piping to the high pressure turbine where it falls in pressure to 600 psi (4.1 MPa) and to

600 °F (320 °C) in temperature through the stage. It exits via 24–26-inch (610–660 mm)

diameter cold reheat lines and passes back into the boiler where the steam is reheated in

special reheat pendant tubes back to 1,000 °F (540 °C). The hot reheat steam is conducted

to the intermediate pressure turbine where it falls in both temperature andpressure and exits

directly to the long-bladed low pressure turbines and finally exits to the condenser.

The generator, 30 feet (9 m) long and 12 feet (3.7 m) in diameter, contains a

stationary stator and a spinning rotor, each containing miles of heavy copper conductor—no

permanent magnets here. In operation it generates up to 21,000 amperes at

24,000 volts AC(504 MWe) as it spins at either 3,000 or 3,600 rpm, synchronized to

the power grid. The rotor spins in a sealed chamber cooled withhydrogen gas, selected

because it has the highest known heat transfer coefficient of any gas and for its

low viscosity which reduces windage losses. This system requires special handling during

startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen.

This ensures that the highly explosive hydrogen–oxygen environment is not created.

Deaerator

A deaerator is a device that is widely used for the removal of oxygen and other dissolved gases from the feedwater to steam-generatingboilers. In particular, dissolved oxygen in boiler feedwaters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). Dissolved carbon dioxide combines with water to form carbonic acidthat causes further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less as well as essentially eliminating carbon dioxide

ENTHALPY DROP IN STEAM TURBINE

Condensate system in thermal power plant

Fly ash collection

Fly ash is captured and removed from the flue gas by electrostatic precipitators or fabric bag filters

(or sometimes both) located at the outlet of the furnace and before the induced draft fan. The fly ash

is periodically removed from the collection hoppers below the precipitators or bag filters. Generally,

the fly ash is pneumatically transported to storage silos for subsequent transport by trucks or railroad

cars

Bottom ash collection and disposal At the bottom of the furnace, there is a hopper for collection of bottom ash. This hopper is always

filled with water to quench the ash and clinkers falling down from the furnace. Some arrangement is

included to crush the clinkers and for conveying the crushed clinkers and bottom ash to a storage

site. Ash extractor is used to discharge ash from Municipal solid waste–fired boilers.

ENVIRONMENT

While leading the nation’s power generation league, NTPC has remained committed to the

environment. It continues to take various pro-active measures for protection of the environment and

ecology around its projects.

NTPC was the first among power utilities in India to start Environment Impact Assessment (EIA)

studies and reinforced it with Periodic Environmental Audits and Reviews.

CenPEEP - Centre for Power Efficiency & Environmental

Protection

Towards the reduction of Greenhouse Gas (GHG) emission from Indian thermal power plants, NTPC has

been promoting and deploying efficient power generation technologies and practices from design stage to

operation stage and building local institutional capacities for continuously striving for eco-friendly

technologies.

NTPC established Centre for Power Efficiency & Environmental Protection (CenPEEP) in collaboration with

USAID with a mandate to reduce GHG emissions per unit of electricity generated by improving the overall

performance of coal-fired power plants. The centre functions as a resource centre for acquisition,

demonstration and dissemination of state-of-the-art technologies and practices for performance

improvement of coal fired power plants for the entire power sector of India.

Ash Utilisation

Sustainable ash utilization is one of the key concerns at NTPC. The Ash Utilization Division (AUD), set up in

1991, strives to derive maximum usage from the vast quantities of ash produced at its coal based power

stations. The AUD proactively formulates policies, plans and programmes for ash utilization. It further

monitors the progress in these activities and works for developing new segments of ash utilization. Ash

Utilization Cell at each station, handles ash utilization activities.

The quality of fly ash produced at NTPC’s power stations is extremely good with respect to fineness, low

unburnt carbon and has high pozzolanic activity and conforms to the requirements of IS 3812 - 2003-

Pulverized Fuel Ash for use as Pozzolana in Cement, Cement Mortar and Concrete. The fly ash generated at

NTPC stations is ideal for use in manufacture of Cement, Concrete, Concrete products, Cellular concrete

products, Bricks/blocks/ tiles etc. To facilitate availability of dry fly ash to end – users, dry fly ash

evacuation and storage system have been set up at coal based stations. Further, at NTPC-Rihand facility for

loading fly ash into rail wagons has been provided so that fly ash can be transported in bulk quantity

through railway network. Such facility is also being provided at all new up coming coal based power stations.

Over the years, the Ash Utilization level has reached from meagre 0.3 million tonne in 1991 - 1992 to 26.03

million tonne in 2010-11.

The various segments of ash utilization currently include Cement, Asbestos – Cement products & Concrete

manufacturing industries, Land development, Road embankment construction, Ash Dyke Raising, Building

Products such as Bricks/ blocks/tiles, Reclamation of coal mine and as a soil amender and source of micro

and macro-nutrients in agriculture.