industrial training report- without strategies and chp- aakash

8/3/2019 Industrial Training Report- Without Strategies and Chp- Aakash

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CONTENTSPage no.

Certificate 3Acknowledgment 4Introduction to the Company 5

Abo ut the company 6 Vision 9 Mission 9 Core values 9 Evolution: Major Landmarks 10 NTPC- DADRI 11

Introduction to Thermal power plant 13 Main parts of Thermal power plant 14 Electricity generation process 20

Coal cycle 21 Steam cycle 22 Condensate cycle 23 Feed water cycle 24

Boiler 25 Boiler furnace and steam drum 26 Fuel firing system and ignition system 27 Auxi lia ry sy st ems 27


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certificate


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ACKNOWLEDGMENT

I express my deepest gratitude to all who contributed in imparting me the

valuable knowledge during my summer training.

I am thankful to the Administration, NTPC who provided me the opportunity to

undergo training at NTPC- Dadri.

I feel highly obliged and greatly indebted to Mr. Sahil Ghai, Chief Engineer and

Mr. S. N. Singh, Dy. Superintendent for giving me valuable information and

guidance regarding the importance and intricacies of the mechanical works.

I am also grateful to Mr. Subhash Chand, Sr. foreman for his professional inputs

from time to time during my training at NTPC. My heartiest thanks to him for hiskind cooperation extended to me while giving me the practical experience and

knowledge of the various mechanical works.

I am also thankful to other supervisory staff as well as other engineers for their

cooperation.

Aakash Gupta

Mechanical Engg.

NIT Kurukshetra


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INTRODUCTION TO

THE COMPANY

About the Company Vision Mission Core values Evolution: Major landmark NTPC- DADRI


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ABOUT THE COMPANY

NTPC, India's largest power company, was set up in 1975 to acceleratepower development in India. It is emerging as an Integrated Power Major,

with a significant presence in the entire value chain of power generation business.

Within a span of 34 years, NTPC has emerged as a truly national power

company, with power generating facilities in all the major regions of

the country.

NTPC ranked 317th

in the 2009, Forbes Global 2000 ranking of the

Worlds biggest companies. With a current generating capacity of 32,194 MW,

NTPC has embarked on plans to become a 75,000 MW company by 2017.

The total installed capacity of the company is 32,194 MW (including JVs)

with 15 coal based and 7 gas based stations, located across the country. In

addition under JVs, 4 stations are coal based & another station uses naphtha/LNG

as fuel. By 2017, the power generation portfolio is expected to have a diversified

fuel mix with coal based capacity of around 53,000 MW, 10,000 MW through

gas, 9,000 MW through Hydro generation, about 2000 MW from nuclear sources

and around 1000 MW from Renewable Energy Sources (RES).


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National Thermal Power Corporation Limited

Type PublicFounded 1975

Headquarters Delhi, India

Key people Mr. Arup Roy Choudhury, CMDIndustry Electricity generationProducts ElectricityRevenue INR 416.37 billion (2008)

or USD 18.15 billion

Net income INR 70.47 billion (2008)or USD 1.89 billion

Employees 23867 (2006)Website http://www.ntpc.co.in
http://www.ntpc.co.in/http://www.ntpc.co.in/http://www.ntpc.co.in/


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VISION

To be the worlds largest and best power producer, powering Indias growth.

MISSIONDevelop and provide reliable power, related products and services at competitive

prices, integrating multiple energy sources with innovative and eco-friendly

technologies and contribute to society.

CORE VALUESCore ValuesBCOMIT

Business Ethics Customer Focus Organisational & Professional Pride Mutual Respect & Trust Innovation & Speed

Total Quality for Excellence


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EVOLUTION: MAJOR LANDMARKS

NTPC was set up in 1975 with 100% ownership by theGovernment of India. In the last 30 years, NTPC has

grown into the largest power utility in India.

Total installed capacity crossed 10,000 MW.

NTPC celebrated 20 years of its existence . A new logowas adopted.

Government of India granted NTPC status of

Navratna being one of the nine jewels of India,

enhancing the powers to the Board of Directors

NTPC became a listed company with majority

Government ownership of 89.5%.

The companys name changed to NTPC Ltd.

NTPC became the largest power generation company in

India. Forbes Global 2000 for 2008 ranked it 411th

in

the world.

Total installed capacity becomes 31134 MW. Govt. of

India granted MAHARATNA status to it. NTPC

ranked 317th

in the 2009, Forbes Global 2000ranking of the Worlds biggest companies.

1975

1990

1997

2004

2005

1995

2008

2010


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NTPCDADRI

Approved capacity 1820 MWLocation Distt. Gautam Budh Nagar, Uttar Pradesh

Coal source Piparwar Mines, Jharkhand

Water source Upper Ganga Canal, Mat BranchBeneficiary states Delhi, U.P.Approved cost Rs. 1669.21 crore

Unit sizes 4 x 210 MW + 2 x 490 MW

Units commissioned Unit I - 210 MW October 1991Unit II - 210 MW December 1992

Unit III - 210 MW March 1993

Unit IV - 210 MW March 1994

Unit V - 490 MW January 2010

Unit VI - 490 MW July 2010

International Assistance International Bank for Reconstruction andDevelopment (IBRD)


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NTPC dadri is model project of NTPC. Also it is the best project of

NTPC also known as NCPS (National capital power station). Situated 60 kms

away from Delhi in the District of gautam budh Nagar, Uttar Pradesh. The station

has an installed capacity of 1669 MW of power840 MW from Coal based units

and 829 MW Gas Based Station. The station is excelling in performance ever

since its commercial operation. consistently in receipts of meritorious projectivity

awards, the coal based units of the station stood first in the country in terms of

PLF for the financial year 1999 2000 by generating an all time national high

PLF of 96.12 % with the most modern O & M Practices. NTPC Dadri is

committed to generated clean and green Power. The Station also houses the first

HVDC station of the country (GEP project) in association with Centre for power

efficiency and Environment protection (CENEEP) NTPC & USAUID. The

station has bagged ISO 14001 & ISO 9002 certification during the financial year

1999 2000, certified by Agency of International repute M/s DNV Netherlands

M/s DNV Germany respectively.


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MAIN PARTS OF THERMAL POWER

PLANT

1. Cooling tower 10. Steam governor valve 19. Superheater

2. Cooling water pump 11. High pressure turbine 20. Forced draught fan

3. Transmission Line (3- phase) 12. Deaerator 21. Reheater

4. Unit transformer ( 3- phase) 13. Feed Heater 22. Air intake

5. Electric generator (3- phase) 14. Coal Conveyor 23. Economiser

6. Low pressure turbine 15. Coal hopper 24. Air preheater

7. Condensate extraction pump 16. Pulverized fuel mill 25. Precipitator

8. Condenser 17. Boiler drum 26. Induced draught fan

9. Intermediate pressure turbine 18. Ash hopper 27. Chimney stack


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The description of some of the components above is as follows:

1. Cooling towers-

Cooling towers are evaporative coolers used for cooling water. Coolingtower use evaporation of water to reject heat from processes such as cooling the

circulating water used in oil refineries, chemical plants, power plants, etc. The

tower vary in size from small rooftop units to very large hyperboloid structures

that can be up to 200 meters tall and 100 meters in diameter, or rectangular

structure that can be over 40 meters tall and 80 meters long. Smaller towers are

normally factory built while larger ones are constructed on site. The primary use

of large, industrial cooling tower system is to remove the heat absorbed in the

circulating water system used in power plants, petroleum refineries,

petrochemical and chemical plants, natural gas processing plants and otherindustrial facilities.

The absorbed heat is rejected to the atmosphere by the evaporation of some

of the cooling water in mechanical forced draft or induced draft towers or in

natural draft hyperbolic shaped cooling towers.

2. Three phase transmission line-

Three phase electric power is a common method of electric power

transmission. It is a type of polyphase system mainly used for power motors andmany other devices. In a three phase system, three circuits reach their

instantaneous peak values at different times. Taking one conductor as reference,the other two conductors are delayed in time by one-third and two-third of cycle

of the electrical current. This delay between phases has the effect of giving

constant power over each cycle of the current and also makes it impossible to

produce a rotating magnetic field in an electric motor. At the power station, an

electric generator converts mechanical power into a set of electric currents onefrom each electromagnetic coil or winding of the generator. The currents are

sinusoidal functions of time, all at the same frequency but offset in time to givedifferent phases. In a three phase system, the phases are spaced equally giving a

phase separation of one-third of one cycle. Generators output at a voltage that

ranges from hundreds of volts to 30,000 volts. At the power station. Transformers

step-up this voltage for suitable transmission. After numerous further conversionsin the transmission and distribution network, the power is finally transformed to

standard mains voltage i.e. the household voltage. The power may already have

been split into single phase at this point or it may be still three phase. Where the

step-down is three phase. The output of the transformer is usually star connected

with the standard mains voltage being the phase neutral voltage.


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3. Electrical generator-

An electrical generator is a device that coverts mechanical energy toelectrical energy, using electromagnetic induction whereas electrical energy is

converted to mechanical energy with the help of electric motor. The source of

mechanical energy may be a reciprocating turbine steam engine. Turbines aremade in variety of sizes ranging from small 1 hp(0.75 kW) used as mechanical

drives for pumps, compressors and other shaft driven equipment to 2,000,000

hp(1,500,000 kW) turbines used to generate electricity.

4. Boiler Feed Pump-

A Boiler Feed Pump is a specific type of pump used to pump water into

steam boiler. The water may be freshly supplied or retuning condensation of

steam produced by the boiler. These pumps are normally high pressure units thatuse suction from a condensate return system and can be of centrifugal pump type

or positive displacement type. Construction and Operation feed water 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 industrial

condensate pumps may also serve as the feed water pump. In either case, to forcewater 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 centrifugal pump. Feed water pumps usually run intermittently and are

controlled by a float switch or other similar level-sensing device energizing thepump when it detects a lowered liquid level in the boiler substantially increased.

Some pumps contain a two stage switch. As liquid lowers to the trigger point ofthe first stage, the pump is activated.

If the liquid continues to drop (perhaps because the pump has failed, its

supply has been cut-off or exhausted, or its discharge is blocked), the second

stage will be triggered. This stage may switch off the boiler equipment

(preventing the boiler from running dry and overheating), trigger an alarm orboth.

5. Control valves-

Control Valves are the valves used within industrial plants and elsewhere

to control operating conditions such as temperature, pressure, flow and liquidlevel by fully or partially opening or closing in response to signals received fromcontrollers that compares a setpoint to a process variable whose value is

provided by sensors that monitor changes in such conditions. The opening or

closing of control valves is done by means of electrical, hydraulic or pneumatic

systems.


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6. Deaerator-

A Deaerator is a device for air removal and used to remove dissolved gasesfrom boiler feed water to make it non-corrosive. A deaerator typically includes a

vertical domed deaeration section as the deaeration feed water tank. A steam

generating boiler requires that the circulating steam, condensate and feed watershould be devoid of dissolved gases, particularly corrosive ones and dissolved or

suspended solids. The gases will give rise to corrosion of the metal. The solids

will deposit on heating surfaces giving rise to localized heating and tube ruptures

due to overheating. Deaerator level and pressure must be controlled by adjusting

control valves-the level by regulating condensate flow and pressure by regulating

steam flow. Most deaerators guarantee that if operated properly, oxygen in

deaerated water will not exceed 7ppb by weight.

7. Feed Water Heater-

A feed water heater is a power plant component used to pre heat water

delivered to a steam generating boiler. Feed water heater improves the efficiency

of the system. This reduces plant operating costs and also helps to avoid thermal

shock to boiler metal when the feed water is introduced back into the steam cycle.Feed water heaters allow the feed water to be brought up to the saturation

temperature very gradually. This minimizes the inevitable irreversibility

associated with heat transfer to the working fluid (water). A belt conveyer

consists of two pulleys, with a continuous loop of material- the conveyer belt thatrotates around them. The pulleys are powered, moving the belt and the material

on the belt forward. Conveyer belts are extensively used to transport industrialand agricultural material, such as grain, coal, ores, etc.

8. Pulverizer-

A pulverizer is a device for grinding coal for combustion in a furnace in afossil fuel power plant.

9. Boiler Steam Drum-

Steam Drums are a regular feature of water tube boilers. It is reservoir of

water/steam at the top end of the water tubes in the water-tube boiler. They storethe steam generated in the water tubes and act 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 steam

drum. Made from high-grade steel (probably stainless) and its working involvestemperatures 390C and pressure well above 350psi (2.4MPa). The separatedsteam is drawn out from the top section of the drum.


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Saturated steam is drawn off the top of the drum. The steam will reenter the

furnace in through a super heater, while the saturated water at the bottom of

steam drum flows down to the mud- drum /feed water drum by down comer tubesaccessories include a safety valve, water level indicator and fuse plug. A steam

drum is used in the company of a mud-drum/feed water drum which is located at

a lower level. So that it acts as a sump for the sludge or sediments which have atendency to the bottom.

10. Super Heater-

A Super heater is a device in a steam engine that heats the steam generated

by the boiler again increasing its thermal energy and decreasing the likelihood

that it will condense inside the engine. Super heaters increase the efficiency of the

steam engine, and were widely adopted. Steam which has been superheated is

logically known as superheated steam; non-superheated steam is called saturatedsteam or wet steam; Super heaters were applied to steam locomotives in quantity

from the early 20th century, to most steam vehicles, and so stationary steam

engines including power stations.

11. Economizers-

Economizer, or in the UK economizer, are mechanical devices intended to

reduce energy consumption, or to perform another useful function like preheating

a fluid. The term economizer is used for other purposes as well. Boiler, powerplant, and heating, ventilating and air conditioning. In boilers, economizer are

heat exchange devices that heat fluids , usually water, up to but not normallybeyond the boiling point of the fluid. Economizers are so named because they can

make use of the enthalpy and improving the boilers efficiency. They are a device

fitted to a boiler which saves energy by using the exhaust gases from the boiler to

preheat the cold water used the fill it (the feed water). Modern day boilers, such

as those in cold fired power stations, are still fitted with economizer which isdecedents of Greens original design. In this context they are turbines before it is

pumped to the boilers. A common application of economizer is steam powerplants is to capture the waste hit from boiler stack gases (flue gas) and transfer

thus it to the boiler feed water thus lowering the needed energy input , in turn

reducing the firing rates to accomplish the rated boiler output .

Economizer lower stack temperatures which may cause condensation of acidiccombustion gases and serious equipment corrosion damage if care is not taken in

their design and material selection.


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12. Air Preheater-

Air preheater is a general term to describe any device designed to heat airbefore another process (for example, combustion in a boiler). 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 fuel gas. Asa consequence, the flue gases are also sent to the flue gas stack (or chimney) at a

lower temperature allowing simplified design of the ducting and the flue gas

stack. It also allows control over the temperature of gases leaving the stack.

13. Precipitator-

An Electrostatic precipitator (ESP) or electrostatic air cleaner is a

particulate device that removes particles from a flowing gas (such As air) using

the force of an induced electrostatic charge. Electrostatic precipitators are highlyefficient filtration devices, and can easily remove fine particulate matter such as

dust and smoke from the air steam. 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 pump mills, and catalyst collection from fluidized bed catalytic crackersfrom several hundred thousand. Transformerrectifier systems apply voltages of

50-100 Kilovolts at relatively high current densities. Modern controls minimize

sparking and prevent arcing, avoiding damage to the components. Automatic

rapping systems and hopper evacuation systems remove the collected particulatematter while on line allowing ESPs to stay in operation for years at a time.

14. Fuel gas stack-

A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar

structure through which combustion product gases called fuel gases are exhausted

to the outside air. Fuel gases are produced when coal, oil, natural gas, wood orany other large combustion device. Fuel gas is usually composed of carbon

dioxide (CO2) and water vapor as well as nitrogen and excess oxygen remainingfrom the intake combustion air. It also contains a small percentage of pollutants

such as particulates matter, carbon mono oxide, nitrogen oxides and sulfur oxides.

The flue gas stacks are often quite tall, up to 400 meters (1300 feet) or more, so

as to disperse the exhaust pollutants over a greater aria and thereby reduce theconcentration of the pollutants to the levels required by governmental

environmental policies and regulations.


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ELECTRICITY GENERATION PROCESS

In a thermal power plant, one of coal, oil or natural gas is used to heat the

boiler to convert the water into steam. The steam is used to turn a turbine, which

is connected to a generator. When the turbine turns, electricity is generated and

given as output by the generator, which is then supplied to the consumers through

high-voltage power lines.

COAL TO STEAM

Its other raw materials are air and water. The coal brought to the station by

trains or by other means, travels handling plant by conveyer belts, travels from

pulverizing mills, which grind it as fine as the face powder of size up to 20

microns. The finely produced coal mixed with preheated air is then blown into the

boiler by a fan called primary air fan where it burns more like a gas than as a

solid, in the conventional domestic or industrial grate, with additional amount of

air, called secondary air supply, by forced draft fan.

As coal is ground so finally the resultant ash is also a fine powder. Some of

it binds together to form pumps, which falls into ash pits at the bottom of the

furnace. The water quenched ash from the bottom is conveyed to pits for

subsequent disposal or sale. Most of ash, still in fine particle form is carried out

of boilers to the precipitator as dust, where electrodes charged with high voltage

electricity trap it. The dust is then conveyed to water to disposal area or to bunker

for sale while the clean flue gases are passed on through IP fans to be dischargedthrough chimneys.

The heat released from the coal has been absorbed by the many kilometers

tubing which line the boiler walls. Inside the tubes the boiler feed water, which is

transformed by heat into steam at high temperature and pressure. Exhaust gas

from the boiler is drawn by the induced draft fan through an electrostatic

precipitator and is then vented through the chimney stack.


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Coal Stock Yard

Bunker

Feeder

Coal Mill

Furnace

Electrostatic Precipitator

Ash Mount/ Dry Ash

Chimney

COAL CYCLE


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From BoilerDrum

Super Heater

High Pressure

Turbine

Reheater

IntermediatePressure Turbine

Low PressureTurbine

To condenser

The steam produced is passes through a manifold in the roof of the drum

into the pendant superheater where its temperature and pressure increase rapidly

to around 200 bar and 540C. The steam superheated in further tubes

(superheaters) passes to high pressure turbine, the first of a three stage turbine

process, where it is discharged through the nozzle on the turbine blades. Thesteam is exhausted from the high pressure turbine, and reduced in both pressure

and temperature, is returned to the boiler reheater. The reheated steam is then

passed to the intermediate pressure turbine, and from there passed directly to the

low pressure turbine set. The exiting steam, now a little above its boiling point, is

brought into thermal contact with cold water (pumped in from the cooling tower)

in the condenser. Just as the energy of wind turns the sail of the windmill, the

energy of steam striking the blade makes the turbine rotate.

STEAM CYCLE


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Boiler FeedPump

High PressureHeater 1

High PressureHeater 2

Economizer

Boiler Drum

The condensed water is then passed by a feed pump through a deaerator,

and pre-warmed, first in a feed heater powered by steam drawn from the high

pressure set, and then in the economiser, before being returned to the boiler drum.

The cooling water from the condenser is sprayed inside a cooling tower, creating

a highly visible plume of water vapor, before being pumped back to thecondenser in cooling water cycle.

FEED WATER CYCLE


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BOILER

The boiler is a rectangular furnace about 50 ft (15 m) on a side and 130 ft

(40 m) tall. Its walls are made of a web of high pressure steel tubes about 2.3

inches (60 mm) in diameter.

Pulverized coal is air-blown into the furnace from fuel nozzles at the four

corners and it rapidly burns, forming a large fireball at the center. The thermal

radiation of the fireball heats the water that circulates through the boiler tubes

near the boiler perimeter. The water circulation rate in the boiler is three to four

times the throughput and is typically driven by pumps. As the water in the boiler

circulates it absorbs heat and changes into steam at 700 F (370 C) and 3,200 psi

(22.1 MPa). It is separated from the water inside a drum at the top of the furnace.

The saturated steam is introduced into superheat pendant tubes that hang in the

hottest part of the combustion gases as they exit the furnace. Here the steam is

superheated to 1,000 F (540 C) to prepare it for the turbine.

Schematic diagram of a coal fired power plant

The steam generating boiler has to produce steam at the high purity,

pressure and temperature required for the steam turbine that drives the electrical

generator. The generator includes the economizer, the steam drum, the chemical

dosing equipment, and the furnace with its steam generating tubes and the

superheater coils. Necessary safety valves are located at suitable points to avoid

excessive boiler pressure. The air and flue gas path equipment include: forced

draft (FD) fan, air preheater (APH), boiler furnace, induced draft (ID) fan, fly ash

collectors (electrostatic precipitator or baghouse) and the flue gas stack.


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For units over about 210 MW capacities, redundancy of key components is

provided by installing duplicates of the FD fan, APH, fly ash collectors and ID

fan with isolating dampers. On some units of about 60 MW, two boilers per unit

may instead be provided.

Bolier Furnace and Steam Drum

Once water inside the boiler or steam generator, the process of adding the

latent heat of vaporization or enthalpy is underway. The boiler transfers energy to

the water by the chemical reaction of burning some type of fuel.

The water enters the boiler through a section in the convection pass called

the economizer. From the economizer it passes to the steam drum. Once the water

enters the steam drum it goes down the down comers to the lower inlet water wall

headers. From the inlet headers the water rises through the water walls and is

eventually turned into steam due to the heat being generated by the burners

located on the front and rear water walls (typically). As the water is turned into

steam/vapor in the water walls, the steam/vapor once again enters the steamdrum.

The steam/vapor is passed through a series of steam and water separators

and then dryers inside the steam drum. The steam separators and dryers remove

the water droplets from the steam and the cycle through the water walls is

repeated. This process is known as natural circulation.

The boiler furnace auxiliary equipment includes coal feed nozzles and

igniter guns, soot blowers, water lancing and observation ports (in the furnacewalls) for observation of the furnace interior. Furnace explosions due to any

accumulation of combustible gases after a trip- out are avoided by flushing out

such gases from the combustion zone before igniting the coal.

The steam drum (as well as the superheater coils and headers) have air

vents and drains needed for initial startup. The steam drum has an internal device

that removes moisture from the wet steam entering the drum from the steam

generating tubes. The dry steam then flows into the superheater coils.


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Fuel Firing System & Ignition System

From the pulverized coal bin, coal is blown by hot air through the furnace

coal burners at an angle which imparts a swirling motion to the powdered coal to

enhance mixing of the coal powder with the incoming preheated combustion airand thus to enhance the combustion.

To provide sufficient combustion temperature in the furnace before igniting

the powdered coal, the furnace temperature is raised by first burning some light

fuel oil or processed natural gas (by using auxiliary burners and igniters provide

for that purpose).

Auxiliary SystemsFly 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 bytrucks or railroad cars.

Bottom Ash Collection and Disposal

At the bottom of every boiler, a hopper has been provided for collection of

the bottom ash from the bottom of the furnace. 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.

Boiler Make-up Water Treatment Plant and Storage

Since there is continuous withdrawal of steam and continuous return of

condensate to the boiler, losses due to blow-down and leakages have to be made

up for so as to maintain the desired water level in the boiler steam drum. For this,

continuous make-up water is added to the boiler water system. The impurities inthe raw water input to the plant generally consist of calcium and magnesium salts


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which impart hardness to the water. Hardness in the make-up water to the boiler

will form deposits on the tube water surfaces which will lead to overheating and

failure of the tubes. Thus, the salts have to be removed from the water and that is

done by water demineralising treatment plant (DM).

A DM plant generally consists of cation, anion and mixed bed exchangers.

The final water from this process consists essentially of hydrogen ions and

hydroxide ions which is the chemical composition of pure water. The DM water,

being very pure, becomes highly corrosive once it absorbs oxygen from the

atmosphere because of its very high affinity for oxygen absorption.

The capacity of the DM plant is dictated by the type and quantity of salts in

the raw water input. However, some storage is essential as the DM plant may bedown for maintenance. For this purpose, a storage tank is installed from which

DM water is continuously withdrawn for boiler make-up. The storage tank for

DM water is made from materials not affected by corrosive water, such as PVC.

The piping and valves are generally of stainless steel. Sometimes, a steam

blanketing arrangement or stainless steel doughnut float is provided on top of the

water in the tank to avoid contact with atmospheric air. DM water make-up is

generally added at the steam space of the surface condenser (i.e., the vacuum

side). This arrangement not only sprays the water but also DM water getsdeaerated, with the dissolved gases being removed by the ejector of the condenser

itself.

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