Industrial Summer Training Project Report

NTPC, BADARPUR

Submitted by:

ACKNOWLEDGEMENT

I wish to express my appreciation to all those with whom I worked interacted and whose

thoughts and insists helped me in increasing my knowledge and understanding of working in an

organization.

I feel great pleasure in presenting my obligation to Prof. J.D GUPTA who allowed me to

undergo training at BTPS.I acknowledge with deep sense of gratitude to Mr. G.D

SHARMA(training coordinator) for providing his esteem guidance and vast knowledge to help

me complete my training.

I would also like to thanks Mrs. RACHNA SINGH BHAL (H.R.), m y instructors

of B.M.D.,P.A.M.,T.M.D. and divisions without them I would not be able to perform such a

delightful job.

And at last I would like to thanks all the people involved in the training who helped me

in accomplishing it in such a wonderful way.

NISHTHA SAINI

110839

TRAINING SCHEDULE

DEPARTMENT PERIOD REPORTING OFFICER

B.M.D

P.A.M

T.M.D

CONTENTS

Introduction

ABOUT NTPC

Power Generation in India

Badarpur Thermal Power Station (BTPS)

Objective

Work Done During The Training Period

Basic steps of Electricity generation

Boiler Maintenance Division (BMD)

Plant Auxiliary Maintenance (PAM)

Turbine Maintenance Department(TMD)

Inference

Bibliography

INTRODUCTION

Thermal power station employs a great no of equipment performing number of complexity

process. The ultimate aim being the production of electricity in order to have stable generating

conditions always balance has to be achieved so that heat input is equal to electricity output and

losses. Efficiency of the plant is expressed in terms of heat rate which is the kilocalories burnt to

get 1 kWhr.

ABOUT NTPC

India‟s largest power company, NTPC was set up in 1975 to accelerate power development in

India. NTPC is emerging as a diversified power major with presence in the entire value chain of

the power generation business. Apart from power generation, which is the mainstay of the

company, NTPC has already ventured into consultancy, power trading, ash utilization and coal

mining. NTPC ranked 317th in the „2009, Forbes Global 2000‟ ranking of the World‟s biggest

companies.

The total installed capacity of the company is 31,704 MW (including JVs) with 15 coal based

and 7 gas based stations, located across the country. In addition under JVs, 3 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 53000 MW, 10000

MW through gas, 9000 MW through Hydro generation, about 2000 MW from nuclear sources

and around 1000 MW from Renewable Energy Sources (RES). NTPC has adopted a multi-

pronged growth strategy which includes capacity addition through green field projects,

expansion of existing stations, joint ventures, subsidiaries and takeover of stations.

NTPC has been operating its plants at high efficiency levels. Although the company has 18.10%

of the total national capacity it contributes 28.60% of total power generation due to its focus on

high efficiency.

POWER GENERATION IN INDIA

NTPC‟s core business is engineering, construction and operation of power generating plants. It

also provides consultancy in the area of power plant constructions and power generation to

companies in India and abroad. As on date the installed capacity of NTPC is 27,904 MW through

its 15 coal based (22,895 MW), 7 gas based (3,955 MW) and 4 Joint Venture Projects (1,054

MW). NTPC acquired 50% equity of the SAIL Power Supply Corporation Ltd. (SPSCL). This

JV Company operates the captive power plants of Durgapur (120 MW), Rourkela (120 MW) and

Bhilai (74 MW). NTPC also has 28.33% stake in Ratnagiri Gas & Power Private Limited

(RGPPL) a joint venture company between NTPC, GAIL, Indian Financial Institutions and

Maharashtra SEB Co Ltd. NTPC has set new benchmarks for the power industry both in the area

of power plant construction and operations. It‟s providing power at the cheapest average tariff in

the country.

DESCRIPTION OF BTPS

(BADARPUR THERMAL POWER STATION )

Badarpur thermal power station (BTPS) is designed and engineered by the central water and

power commission (CWP).

Approved capacity: 705 MW

Installed capacity: 705 MW

Location: New Delhi

Coal source: jharia coal fields

a) CCL (central coal fields)

b) BCCL (bharat cooking coals ltd.)

c) ECL (eastern coal fields ltd.)

Water source: Agra canal

Beneficiary state-New Delhi

Size of units- 3x95 MW

2x210 MW

Commissioning of units:

Unit I 95 MW 1973-75

Unit II 95 MW 1974-75

Unit III 95 MW 1974-75

Unit IV 210 MW 1978-79

Unit V 210 MW 1981-82

The management of centrally owned BTPC was handed over to NTPC on April 15th

1978.

The BTPS under the management of NTPC is generating today at a plant load factor of more

than 80% of the total capacity. The turnaround of station has been possible only due to

management of station by NTPC.

The station was designed and engineered by Central Electricity Authority (CEA) formerly

central water and power commission. The plant became operational on July 26th

, 1973.presently

the station is supplying its entire generation to New Delhi

There are 11 feeders in use at present, 2-Okhla, 2-Sarita Vihar, 2-Mahroli, 2-Noida, 2-

Ballabhgarh, and 1-Alwar.

Site selection of power plant

Availability of coal-steam power station should be located near mines so minimum cost

of fuel is maintained. However if such facility isn‟t available then adequate facilities

should be made for transportation of coal like railway lines which are provided in case of

BTPS

Availability of water-a large amount of water is necessary for condenser. Therefore such

a plant should be located at the bank of river or near a canal like Agra canal in case of

BTPS

Means of transportation-the power plant should be well interconnected with roads or

railways system for efficient transportation material

Land properties-land should be cheap and there should be enough land surrounding the

plant so that there may be option of expanding. The land should be able to withstand the

load of heavy equipment

Nearness to load centers-this is very important factor when considering dc transmission.

If an ac system is employed then this factor is less important because ac can be

transmitted at high voltage with consequent reduction transmission cost that is why it is

possible to install the plant away from load centre provided the conditions are favorable

Ash disposal facilities-quantity of ash to be handled is 1500-2000 tons per day the

disposal of large quantity of ash from the power station can be into river, sea or lake or

can be brought into useful purposes like manufacturing of bricks as done by BTPS or for

land filling as recently was used by Delhi metro

Distance from populated areas-since there is a lot of coal burnt in the power station there

will be a lot smoke and fumes that make surrounding of plant very hazardous

OBJECTIVE

I was appointed to do Six-week training at this esteemed organization from 18 JUNE to 28

JULY, 2010. In these six weeks I was assigned to visit various division of the plant which were:

1. Boiler Maintenance Division I (BMD-I)

2. Boiler Maintenance Division II (BMD-II)

3. Boiler Maintenance Division III (BMD-III)

4. Plant Auxiliary Maintenance (PAM)

5. Turbine Maintenance Department (T.M.D)

The objective of the training at NTPC is to gain experience of three weeks on field, utilize the

current engineering concepts, to gain practical knowledge in the field of thermal power

generation and understand how an organization works in harmony to produce benefits for both

the employees and customers.

BASIC STEPS OF ELECTRICITY GENERATION:

The basic steps in the generation of electricity from coal involves following steps:

.Coal to steam

.Steam to mechanical power

.Mechanical power to electrical power

Coal to steam:

Coal from the coal wagons is unloaded in the coal handl ing p lant . This Coal i s

t ranspor ted up to the raw coal bunkers with the help of belt conveyors. Coal is

transported to Bowl Mi l l s b y Coal f eeders The coal i s pulver ized in the B o w l

M i l l , w h e r e i t i s g r o u n d t o a p o w d e r f o r m . T h e m i l l consists of a round

metallic table on which coal particles fall .This table is rotated with the help of a motor. There

are three large steel rollers which are spaced 120" apart. When there is no coal, these rollers does

not rotate but when the coal is fed to the table it packs up between roller and the table

and this forces the ro l l ers t o ro t a t e . Coal i s crushed b y the crushing action

between the rollers and rotating table. This crushed coal is taken away to the furnace

through coal pipes with the help of hot and cold air mixture from P.A. Fan.

Water from the boiler feed pump passes through economize r and reaches the

boi le r d rum. Wate r f rom the drum passes through down comers and goes to

bottom ring header. Water from the bottom ring header is divided to all the four

s ides of t he fu rnace . Due to heat and - the dens i t y difference the water rises up in

the water wall tubes. "Water is partly converted to steam 'as it rises up in the furnace. This

s team and water mix ture i s again t aken to the boi l er drum where the steam is

separated from water. Water follows the s a m e p a t h w h i l e t h e s t e a m i s

s e n t t o s u p e r h e a t e r s f o r s u p e r h e a t i n g . T h e s u p e r h e a t e r s a r e

l o c a t e d i n s i d e t h e furnace and the steam is superheated (540"C) and finally it

goes to turbine.

Steam to mechanical Power

From the boiler, a steam pipe conveys steam to the turbine through a stop valve (which can

be used to shut off s t e a m i n a n e m e r g e n c y ) a n d t h r o u g h c o n t r o l v a l v e s

t h a t au tomat i ca l l y regula t e the suppl y of s t eam to the tu rb ine where it passes

through a ring of stationary blades fixed to the cylinder wall. These act as nozzles

and direct the steam i n t o a s e c o n d r i n g o f m o v i n g b l a d e s m o u n t e d o n a

d i s c which rotates the blades and its passage of some heat energy is changed into mechanical

energy.

The thermal (steam) power plant uses a dual (vapour + l iquid) phase cyc l e . I t i s

a c losed cyc l e to enable the working f lu id (water ) to be used again and

again . The c y c l e u s e d i s " R a n k i n e C y c l e " m o d i f i e d t o i n c l u d e

s u p e r h e a t i n g o f s t e a m , r e g e n e r a t i v e f e e d w a t e r h e a t i n g a n d

reheating of steam.

Mechanical to electrical

As the blades of the turbine rotate, the shaft of the generator, which is coupled to turbine, also

rotates. It results in rotation of the coil of generator, which causes induced electricity to be

produced.

BASIC POWER PLANT CYCLE:

Factors affecting thermal efficiency:

. Initial steam pressure

. Initial steam temperature

. Condenser pressure

.Regenerative feed water heating

.Whether reheat is used or not, and if used reheat pressure and temperature

On large turbines, it becomes economical to increase the cycle efficiency by using reheat,

which is a way o f p a r t i a l l y o v e r c o m i n g t e m p e r a t u r e

l i m i t a t i o n s . B y returning partially expanded steam, to a reheat, the average

t e m p e r a t u r e a t w h i c h h e a t i s a d d e d , i s i n c r e a s e d a n d , b y expanding this

reheated steam to the remaining stages of the t u r b i n e , t h e e x h a u s t w e t n e s s i s

c o n s i d e r a b l y l e s s t h a n i t would o therwise be converse l y, i f the max imum

to le rable wetness is allowed, the initial pressure of the steam can be appreciably

increased.

Typical diagram of coal based thermal power plant:

The description of some of the components written above is described as follows: 1. Cooling towers

Cooling Towers are evaporative coolers used for cooling water or other working medium

to near the ambivalent web-bulb air temperature. Cooling tower use evaporation of water

to reject heat from processes such as cooling the circulating water used in oil refineries,

Chemical plants, power plants and building cooling, For example : The tower vary in size

from small roof-top 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 cooling water systems used in power plants ,

petroleum refineries, petrochemical and chemical plants, natural gas processing plants

and other industrial 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 as seen at most nuclear power

plants.

2. Electrical generator

An Electrical generator is a device that converts kinetic energy to electrical energy,

generally using electromagnetic induction. The task of converting the electrical energy into

mechanical energy is accomplished by using a motor. The source of mechanical energy may

be a reciprocating or turbine steam engine, , water falling through the turbine are made in a

variety of sizes ranging from small 1 hp (0.75 kW) units (rare) 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.

3. Turbines

There are several classifications for modern steam turbines.

Steam turbines are used in all of our major coal fired power stations to drive the generators or

alternators, which produce electricity. The turbines themselves are driven by steam generated

in „Boilers‟ or „steam generators‟ as they are sometimes called.

Electrical power station use large steam turbines driving electric generators to produce most

(about 86%) of the world‟s electricity. These centralized stations are of two types: fossil fuel

power plants and nuclear power plants. The turbines used for electric power generation are

most often directly coupled to their-generators .As the generators must rotate at constant

synchronous speeds according to the frequency of the electric power system, the most

common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for 60 Hz systems. Most

large nuclear sets rotate at half those speeds, and have a 4-pole generator rather than the more

common2-pole one.

Energy in the steam after it leaves the boiler is converted into rotational energy as it passes

through the turbine. The turbine normally consists of several stage with each stages

consisting of a stationary blade (or nozzle) and a rotating blade. Stationary blades convert the

potential energy of the steam into kinetic energy into forces, caused by pressure drop, which

results in the rotation of the turbine shaft. The turbine shaft is connected to a generator,

which produces the electrical energy.

4. Steam-powered pumps

Steam locomotives and the steam engines used on ships and stationary applications such as

power plants also required feed water pumps. In this situation, though, the pump was often

powered using a small steam engine that ran using the steam produced by the boiler. A

means had to be provided, of course, to put the initial charge of water into the boiler(before

steam power was available to operate the steam-powered feed water pump).the pump was

often a positive displacement pump that had steam valves and cylinders at one end and feed

water cylinders at the other end; no crankshaft was required.

In thermal plants, the primary purpose of surface condenser is to condense the exhaust steam

from a steam turbine to obtain maximum efficiency and also to convert the turbine exhaust

steam into pure water so that it may be reused in the steam generator or boiler as boiler feed

water. By condensing the exhaust steam of a turbine at a pressure below atmospheric

pressure, the steam pressure drop between the inlet and exhaust of the turbine is increased,

which increases the amount heat available for conversion to mechanical power. Most of the

heat liberated due to condensation of the exhaust steam is carried away by the cooling

medium (water or air) used by the surface condenser.

5.Control valves

Control valves are valves used within industrial plants and elsewhere to control operating

conditions such as temperature, pressure, flow, and liquid Level by fully partially opening or

closing in response to signals received from controllers that compares a “set point” 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.

6. 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 or any other large combustion device. Fuel

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 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 the concentration of the

pollutants to the levels required by governmental environmental policies and regulations.

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

residential abodes, restaurants , hotels or other stacks are referred to as chimneys.

BMD

BOILER MAINTENANCE

DEPARTMENT

BOILER MAINTENANCE DIVISION I (BMD - I)

BOILER MAINTENANCE DIVISION II (BMD- II)

BOILER MAINTETNANCE DIVISION III (BMD – III)

As the name suggests this unit maintains the boiler and checks out its proper functioning. There

are 5 boilers 3 of 95 MW and 2 of 210 MW each. Each boiler is considered as one unit.

Structure of units 1, 2, 3 is same and so is of unit 4,5

Units 1/2/3 (95 MW each)

1. I.D Fans 2 in no.

2. F.D Fans 2 in no.

3. P.A. Fans 2 in no.

4. Mill Fans 3 in no.

5. Ball mill fans 3 in no.

6. RC feeders 3 in no.

7. Slag Crushers 5 in no.

8. DM Make up Pump 2 in no.

9. PC Feeders 4 in no.

10. Worm Conveyor 1 in no.

11. Turnikets 4 in no.

Units 4/5 (210 MW each)

1. I.D Fans 2 in no.

2. F.D Fans 2 in no.

3. P.A Fans 2 in no.

4. Bowl Mills 6 in no.

5. R.C Feeders 6 in no.

6. Clinker Grinder 2 in no.

7. Scrapper 2 in no.

8. Seal Air Fans 2 in no.

9. Hydrazine and

Phosphorous Dozing

2 in no.

Boiler and its description:

A boiler is a rectangular furnace about 50 ft (15 m) on a side and 130 ft. (40m) 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-burn into the furnace from fuel nozzles at the four corners and it rapidly burn s, forming

large fireball at the centre. The thermal radiation of fireball heats the water that circulates

through boiler tubes near the boiler perimeter. The water circulation rate is three 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 degree C) and 3200 psi (22.1 MPa) . It is separated from

the water inside the drum at the top of the furnace.

Fig : Boiler side of Badarpur Thermal Power Station ,New Delhi

The saturated steam is introduced into superheat pendent tubes that hang in the hottest part of

combustion gases as they exit the furnace. Here the steam is superheated 1000 F to prepare it for

the turbine .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 boiler

includes the economizer, the steam drum, the chemical dosing equipment, and

furnace wi th i t s s t eam genera t ing tubes and the superheate r co i l s . Necessa r y

safe t y valves are l oc ated a t su i t ab l e poin t s to a v o i d e x c e s s i v e b o i l e r

p r e s s u r e . T h e a i r a n d f l u e g a s path equipment include: fo rced d raf t

(FD) fan,air preheater (APH), b o i l e r f u r n a c e , i n d u c e d d r a f t ( I D )

f a n , f l y a s h c o l l e c t o r s (electrostatic precipitator or baghouse) and theflue gas

stack .[1][2] [3]

Schematic diagram of

typical coal-fired power plant steam generator highlighting the air preheater (APH) location

Specifications:

MAIN BOILER: AT 100% LOAD

•Evaporation 700t/hr

•Feed water temperature 247°C

•Feed water leaving economizer 276°C

STEAM TEMPERATURE:

• Drum 341°C

•Super heater outlet 540°C

• Reheat inlet 332°C

• Reheat outlet 540°C

STEAM PRESSURE:

•Drum design 158.20 kg/cm2

•Drum operating 149.70 kg/cm2

•Super heater outlet 137.00 kg/cm2

•Reheat inlet 26.35 kg/cm2

•Reheat outlet 24.50 kg/cm2

FUEL:COAL DESIGN WORST

•Fixed carbon 38% 25%

•Volatile matter 26% 25%

•Moisture 8% 9%

•Grindability 50% Hardgrove 45% Hardgrove

OIL:

•Calorific value of fuel oil 10,000 kcal/kg

•Sulphur content 4.5% W/W

•Moisture content 1.1% W/W

•Flash point 66°C

AUXILLARIES OF THE BOILER:

1. FURNACE

Furnace is primary part of boiler where the chemical energy of the fuel is converted to thermal

energy by combustion. Furnace is designed for efficient and complete combustion. Major factors

that assist for efficient combustion are amount of fuel inside the furnace and turbulence, which

causes rapid mixing between fuel and air. In modern boilers, water furnaces are used.

Height - 42.797mLength - l3.868mWidth - 10.592mVolume - 52l0m

To start the production unit, firstly pulverised coal is fed to the furnace through a pump .For

fuel burning, ignition temperature and pressure are also necessary. The burning

of coal completely and raise the temperature to an approximately level. Initially air and oil are

also fed to it through F.D. fan and oil gun respectively. Then when the temperature is reached to

the required level coal starts burning and produces lots of heat and flue gases. The water tube

flowing inside the boiler containing water turns into wet steam. It is a water tube

boiler.

2. BOILER DRUM:

.Drum is of fusion-welded design with welded hemispherical dished ends. It is provided with

stubs for welding all the connecting tubes, i.e. downcomers, risers, pipes, saturated steam outlet.

The function of steam drum internals is to separate the water from the steam generated in the

furnace walls and to reduce the dissolved solid contents of the steam below the prescribed limit of 1 ppm

and also take care of the sudden change of steam demand for boiler.

.The secondary stage of two opposite banks of closely spaced thin corrugated sheets ,which

direct the steam and force the remaining entertained water against the corrugated plates. Since

the velocity is relatively low this water does not get picked up again but runs down the plates and off

the second stage of the two steam outlets.

.From the secondary separators the steam flows upwards to the series of screen dryers, extending

in layers across the length of the drum. These screens perform the final stage of the separation.

.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 bythe 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/ vapour in

the water walls, the steam/vapour once again enters the steam drum.

EXTERNAL VIEW OF THE BOILER AT BTPS, NEW DELHI

2.WATER WALLS: Water flows to the water walls from the boiler drum by natural circulation. The front and the two

side water walls constitute the main evaporation surface absorbing the bulk of rad iant heat of

the fuel bu rn t in the chamber . The f ront and rea r w a l l s a r e b e n t a t t h e

l o w e r e n d s t o f o r m a w a t e r - c o o l e d s l a g h o p p e r . T h e u p p e r p a r t o f

t h e c h a m b e r i s n a r r o w e d t o a c h i e v e perfect mix ing o f combust ion gases .

The water wal l s tubes a re connected to headers at the top and bottom. The rear

water wall stubes at the top are grounded in four rows at a wider pitch forming the grid tubes.

4. REHEATER :

Reheater is used to raise the temperature of s t eam f rom which a par t of energy has

been ex t rac t ed in h igh - pressure turbine. This is another method of increasing the

cycle efficiency. Reheating srequires additional equipment I.e. Heating surface

connecting boiler and turbine pipe safety equipment like safety valve, non-return valve,

isolating valves, high pressure feed pump, etc. Reheater is composed to two sections namely

front and r e a r p e n d a n t s e c t i o n w h i c h i s l o c a t e d a b o v e t h e f u r n a c e

a r c h between water-cooled screen wall tubes and rear wall hanger tubes.

Tubes of Reheater

5. SUPERHEATERS:

Whatever type of boiler is used, steam will leave the water at its surface and pass into the steam

space. Steam formed above the water surface in a shell boiler is always saturated a n d

c a n n o t b e c o m e s u p e r h e a t e d i n t h e b o i l e r s h e l l , a s i t i s

c o n s t a n t l y i n c o n t a c t w i t h t h e

w a t e r s u r f a c e . If superheated steam is required, the saturated

s t e a m m u s t p a s s t h r o u g h a s u p e r h e a t e r . T h i s i s s i m p l y a h e a t

exchanger where additional heat is added to the saturated steam .In water-tube boilers,

the superheater may bean additional pendant suspended in the furnace area where the hot gases

wi l l p rovide the degree of superheat requi red (see Figure 3.4.4). In other

cases, for example in CHP schemes where the gas t u r b i n e e x h a u s t g a s e s a r e

r e l a t i v e l y c o o l , a s e p a r a t e l y f i r e d superheater may be needed to provide the

additional heat.

If accurate control of the degree of superheat is required, as would be the case if the

steam is to be used to drive turbines, then an attemperator (desuperheater) is fitted.

This is a device installed after the superheater, which injects water into the

superheated steam to reduce its temperature.

6. ECONOMISER:

The function of an economizer in a steam generating unit is to absorb heat from the flue

gases and add as a s e n s i b l e h e a t t o t h e f e e d - w a t e r b e f o r e t h e w a t e r

e n t e r s t h e evaporation circuit of the boiler .Earlier economizer were introduced mainly to

recover the heat available in flue gases that leaves the boiler and provision of th i s

addi t i on hea t ing su rfac e inc reases the ef f i c iency of s te am generators. In the

modern boilers used for power generation feed-water heaters were used to increase

the efficiency of turbine unit and feed-water temperature.

An Economiser

Location &Maintenance:

It is usual to locate economizer ahead of air heate r . Counte r f l ow a rrangement i s

normal l y se l ec ted so that h e a t i n g s u r f a c e r e q u i r e m e n t i s k e p t

m i n i m u m f o r t h e s a m e temperature drop in flue gas. Water flow is from bottom to

top so that steam if any formed during the heat transfer can move along with water and

the lock up steam which will cause overheating and failure of economizer tube. Manholes and

adequate spacing between the banks of tubes are provided for inspection and maintenance works.

7. AIR PREHEATER:

Air preheater absorbs waste heat from the flue gases and transfers this heat to incoming

cold a i r , b y means of cont inuous l y ro t a t ing heat t ransfe r e lement of specially

formed metal plates. Thousands of these high efficiency elements are spaced and compactly

arranged within 12 sections. Sloped compartments of a radially divided cylindrical shell

called the rotor. The housing surrounding the rotor is provided with duct connect ing

both the ends and i s adequate l y scaled b y rad i a l and circumferential scaling.

Air preheater consists of:

.1.Connecting plates. Housing 2. Rotor 3. Bearing

4. Sector plates & Sealing Arrangement

.5.Heating surface elements

8. PULVERISER:

A pulver iz er i s a mechan ical device for the gr inding of man y d i f f e r e n t

t y p e s o f m a t e r i a l s . F o r e x a m p l e , t h e y a r e u s e d t o pulverize coal

for combustion in the steam-generating furnaces of fossil fuel power plants.

Types of Pulverizers

Ball and Tube Mills

A ball mill is a pulverizer that consists of a h o r i z o n t a l r o t a t i n g c y l i n d e r , u p

t o t h r e e d i a m e t e r s i n l e n g t h , containing a charge of tumbling or cascading

steel balls, pebbles, or rods. A tube mill is a revolving cylinder of up to five diameters in

length used for fine pulverization of ore, rock, and other such materials; the material,

mixed with water, is fed into the chamber from one end, and passes out the other end as slime.

Ring and Ball Mill

This type of mill consists of two rings separated by a series of large balls. The lower ring

rotates, while the upper r i n g p r e s s e s d o w n o n t h e b a l l s v i a a s e t o f

s p r i n g a n d a d j u s t e r a ssembl ies . The mate r ia l t o be pulver ized i s

in t roduced in to the center or side of the pulverizer (depending on the design) and

is ground as the lower ring rotates causing the balls to orbit between the upper and lower rings.

The pulverized material is carried out of t h e m i l l b y t h e f l o w o f a i r m o v i n g

t h r o u g h i t . T h e s i z e o f t h e pulverized particles released from the grinding

section of the mill is determined by a classifer separator.

MPS Mill

Similar to the Ring and Ball Mill, this mill uses large "tires" to crush the coal. These are

usually found in utility plants.

Bowl Mill

Similar to the MPS mill, it also uses tires to crush coal. There are two types, a deep bowl mill,

and a shallow bowl mill.

Advantage of pulverized coal

• Efficient utilization of cheap and low grade coal

•Flexibility to meet fluctuating load

•Elevation of bending lose

An external view of coal pulverizer

MILLING SYSTEM:

RC bunker

These are in process storage silos used for s tor ing c rushed coal f rom the coal

handl ing s ys tem. General l y , these are made up of welded steel plates.' Normally, there

are six such bunkers supplying coal of the corresponding mills. These are located on top of the

mills so as to aid in gravity feeding of coal.

Rc feeder:

It transports pre crust coal from raw coal bunker to mill. The quantity of raw coal fed in mill can

be controlled by speed control of aviator drive controlling damper and aviator change. These are

6 in number.

Ball Mill:

The ball mill crushes the raw coal to a certain height and then allows it to fall down. Due to

impact of ball on coal and attraction as per the particles move over each other as well as over the

Armor lines, the coal gets crushed. Large particles are broken by impact and full grinding is done

by attraction. The Drying and grinding option takes place simultaneously inside the mill.

Mills

There are six mill (25% capacity each), for every 200 .MW unit, located adjacent to the

furnace at '0' M level. These mills pulverize coal to the desired fineness to be fed to the furnace

for combustion.

Mills Fans: - It is of 3 types

Six in all and are running condition all the time.

(a) ID Fans: - Located between electrostatic precipitator and chimney.

Type-radical

Speed-1490 rpm

Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil

(b) FD Fans: - Designed to handle secondary air for boiler. 2 in number and

provide ignition of coal.

Type-axial

Speed-990 rpm

Rating-440 KW

Voltage-6.6 KV

(c) Primary Air Fans: - Designed for handling the atmospheric air up to 50

degrees Celsius, 2 in numbers, and they transfer the powered coal to burners

to firing.

Type-Double suction radial

Rating-300 KW

Voltage-6.6 KV

Lubrication-by oil

Type of operation-continuous

ESP (ELECTROSTATIC PRECIPITATOR)

When coal is burnt in the boiler ash is liberated and carried along with flue gases if these ashes

are exhausted to the atmosphere. It will create pollution resulting in health hazard .Hence it is

necessary to precipitate the dust from the flue gases and in this process is ESP f inds p l ace in

the power p l an t . In 21OMw 11OT of coal burns pe r hour and i f coal contents

30% ash then ash carried along with flue gases will be 33Tonns\hr.

ADVANTAGES

1. Higher efficiency2. Minimum cost 3. Low maintenance4. Large volume of ash particle5.

Creates less pollution

DISADVANTAGES

1. High initial cost2. Loss of efficiency when flow is above the desired rate3. Unpredictable

efficiency

FUEL FIRING

There are mainly three components which are used in fuel firing:-1. Pulverised coal2. High

pressure air 3. Oil

COAL

The coal has various varieties. The coal which is used out they should have high calorific value,

produce maximum heat produce less ash and pollution on burning easily available ,low cost etc.

these features are available in bituminous coal, which is used in the plant. It has about 90-95%

carbon and its caloric value varies between 3600-4200. Coal is brought in large pieces, so in first

stage the coal is finally crushed so that it burns completely .Then i t i s sen t the furnace

through conveyor bel t . In t he furnace the coal burns and produces steam. The ash

which gets collected in the scraper is removed time to time with the help of water. Its main

function is to produce lot of heat so ass to convert water into steam.

OIL : Oil is supplied with the help of oil gun to coal so that the coal can be easily burn.

HIGH PRESSURE AIR: High pressure air is introduced into the furnace so that the coal can be

reached at ignited temperature. The high pressure air from fan is introduced to the furnace

through F.D fan

The successfully working of an oil firing equipment depends on the following:-

I. The correct design of control flow.2. The design of combustion chamber.3. The design of the

economiser which must be able to reduce the fuel to a finally divided stay

PAM PLANT AUXILIARY MAINTENANCE

. CONTROL STRUCTURE PUMP HOUSE (CSPH)

. WATER TREATMENT PLANT (WTP)

. ASH PUMP HOUSE (APH)

. AIR COMPRESSOR HOUSE

Control Structure Pump House (CSPH)

The CSPH is just located near the entrance of BTPS at the left side of the way, the basic

work of CSPH is to treat the raw water coming from the lake, this water is first treated in

CSPH and then delivered to the other units such as WTP cooling tower ESP etc. The

water is received from lake is totally dirty and full of hard and thick impurities. The water

is first screened of using the screen wash pump rotating continuously consisting of filter .

This unit consists of all types of pumps used in plants for purposes like water supply, ash

slurry flow etc. The various types of pumps are:

The CSPH has following pumps :

S. No Types No.

1 CRW Pump 3

2 Fire Fighting Pump 2

3 Diesel Fire Pump 1

4 Low Pressure Pump 3

5 High Pressure Pump 6

6 TWS Pump 3

CHARACTERSTICS:

CRW pump is raw water pump used in CSPH, through which raw water is sent into water

treatment plant to get demineralised water.

Fire Fighting Pumps are used to pacify fire, which occurs most of the time in Coal

Handling Plant. These pumps direct the screened or strained water into the areas where

fire has started.

Diesel Fire Pump is an alternative to Fire fighting pump. It acts as spare.

Low Pressure Pump is used to direct treated water into turbines and cooling lines of units

1, 2, 3, 4, 5.

In case LP pump is not able to send water up to unit 4 or 5, HP pumps are used. High

Pressure Pumps are also used in ash lines, where the ash is directed into slurry pond.

Travelling Water Strainer or TWS pump is used to screen the catchable impurities,

plastics, dirt through screens placed in the inlet of the Agra canal channel.

WATER TREATMENT PLANT (WTP )

W.T.P.-I&II

The availability of suitable supply of water both for cooling purposes and for boiler feed make

one of the basic requirement of the power station . The water treatment plant is

meeting this requirement, the water which is used in the boiler circuit must be in very pure form

to avoid corrosion of boiler tube, scale formation on the inside surface of

various parts and to avoid silica carryover to turbine corrosion tunes leads to its failure and this

reduces boiler reliability scale formation leads to resistance to heat transfer and

over hearting of the tube metal and thus causes frequent shut downs. Silica car ies

over from boiler gets deposited on relatively cold portion of turbine and create resistance to

streamflow thrust reducing efficiency of turbine as the working pressure and

temperature of boiler goes high with unit size increasing the requirement of ver y

pure water becomes even more stringent therefore the main object of the WTP is to

remove impurities of water being sent to boiler in order that the steam generated is pure and

boiler can give an uninterrupted surface.

GEOMILLER

The name given to this unit is because 'geo miller' named company built it and started it. Its

main function is to make water pure and clean .The raw water coming from CRW goes into the

tank where alum and chlorine are added to it. With the help of chlorine and alum all the

mud and dust settles down and clean water is taken from above. From there it goes

to two separate tanks and from there 7 pumps 4 of 100Mw and 3 of 21OMw power

takes the water to various sections such as WTP-I & II etc.

Internal treatment

This final D.M effluent is then either led to hot well of the condenser directly as make up

to boilers, or being stored in D.M. Water storage tanks first and then pumped for make up

purpose to boiler feed.

As the D.M. Water has a good affinity to absorb carbon dioxide and oxygen, and both are

extremely harmful to metal surfaces for their destruction like corrosion, these have to b e

r e m o v e d b e f o r e i t i s f e d t o b o i l e r . T h i s i s b e i n g d o n e i n

desecra tor . S t i l l the res idual ox ygen which i s remain ing in the water is

neutralized by a suitable doze of hydrazine, at the point af te r desecra tor . To have

fur the r minimum corros ion , the pH o f f eed water i s t o be main ta ined a t

around 9 .0 fo r which purpose ammonia in suitable doze is added to this make up water at

a point along with hydrazine as stated above.

ASH HANDLING HOUSE

Ash utilization is one of the key concerns at NTPC. The Ash Utilization Division, set up in 1991,

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

stations. The division proactively formulates policy, plans and programme for ash utilization.

It further monitors the progress in these areas and works at developing new fields of

ash utilization.

Pumps used for ash handling:

S.NO PUMP LUBRICANT CAPACITY

1. 1 Servo 57/68 oil 1000 m3/hr

2. 2 Servo 40 oil 1300 m3 /hr

3. 3 Servo 40 oil 1300 m3 /hr

4. 4 Servo 40 oil 1300 m3 /hr

The quality of ash produced confirms to the requirements of IS3812 .The fly ash gene ra ted a t

NTPC s ta t ions i s ide al fo r use in cement , concre t e , concre t e p roduct s ,

cellular concrete, lightweight aggregates, bricks/blocks/tiles etc. This is attributed to its very low

loss on ignition value. To facilitate availability of dry ash to end-users all new units of NTPC are

provided with the facility of dry ash collection system. Partial dry ash collection systems have

also been set up at the existing stations where these facilities didnot ex i s t ea r l i er .

Augmenta t ion of these s ys t ems to 100 % capaci t y i s presen t l y in progress.

A s t h e e m p h a s i s o n g a i n f u l u t i l i z a t i o n o f a s h g r e w , t h e u s a g e o v e r

t h e y e a r s a l s o increased. From 0.3 million tonnes in 1991-1992, the level of utilization

during 2006-07stood at over 20.76 million tonnes.

T h e v a r i o u s c h a n n e l s o f a s h u t i l i z a t i o n c u r r e n t l y i n c l u d e u s e b y a

n u m b e r o f c e m e n t , a s b e s t o s - c e m e n t p r o d u c t s & c o n c r e t e

m a n u f a c t u r i n g i n d u s t r i e s , l a n d d e v e l o p m e n t , r o a d s a n d

e m b a n k m e n t s , a s h d y e r a i s i n & b u i l d i n g p r o d u c t s .

NTPC has adopted user friendly policy guidelines on ash utilization. These include actions

identified for:

. Ash collection and storage system

.facilities and incentives to users

. direct department activities

. administrative and financial aspects

In order to motivate entrepreneurs to come forward with ash utilisation schemes, NTPCoffers

several facilities and incentives. These include free issue of all types of ash viz.Dry

Fly Ash / Pond Ash / Bottom Ash & infrastructure facilities, wherever

feasible. Necessary help and assistance is also offered to facilitate procurement of land, supply

of electricity etc. from Govt. Authorities. Necessary techno-managerial assistance is

givenwherever considered necessary. Besides NTPC uses only ash based bricks &

portland pozzolana cement (FAPPC) in most of its construction activities. FAPPC (as per IS

1489P a r t - 1 ) a n d F l y A s h B r i c k s ( a s p e r I S 1 2 8 9 4 ) h a v e b e e n i n c l u d e d

i n o u r s t a n d a r d specifications. Demonstration projects are taken up in area of

Agriculture, Buildingmaterials, Mine filling etc.

NTPC continually strives to evolve innovative and diverse means of ash utilization to further

broaden the scope. Prominent among the methods devised so far are :

. dry flash extraction systems

. use in cement and concrete

. use in ash based product including setting up of Ash technology park

.agriculture

. mine filling / stowing

NTPC, Ash Utilization Division has brought out a booklet titled 'NTPC Guide for Userso f

Coal Ash ' fo r d i s t r ibut ion amongs t prospect ive en t rep reneurs and use rs o f

ash . I t covers salient information about NTPC's power stations, facilities offered for setting

upof ash based industry, statistics about ash production and its quality, brief write-up

aboutvarious technologies available for utilization of ash, list of equipment

manufacturers,technology suppliers, agencies who may be approached for setting up the

projects fly ash system

Air Compressor house

This machine is the reciprocated device machine.

Types of compressor :

# 1st classification

Plant air compressor

Tenfold compressor

Station air compressor

Instrument air compressor

Densover air compressor

Blaster air compressor

# 2nd

classification:

Single satge compressor

Double stage compressor

Multiple stage compressor

Our compressor is double stage compressor .

1. Plant air compressors are lubricated compressors.

2. Instrument air compressors are non- lubricated compressors.

Use of air in Plant

Instrument air is required for various dampers , burner tilting devices, diaphragm valves etc. at

210 MW units. Station air meets the general requirements of power station such as light oil

atomizing air , for cleaning filters , and for various maintanence works. The control air

compressors and station air compressors have been housed separately with separate receivers and

supply headers and their tapping.Plant air compressors & Densover air is used in Ball mill, ESP

system , cleaning work, R.C Feeder , cooling the bearing. Blasting & degassing in air . Hopper

operating system , densover valve operating system , HT tank , spray & tier fighting tank ,

pressurized by air.

A compressor house

Parts of compressor :

1. Crankcase

2. Crankshaft

3. Connecting rods

4. Main bearing & big end bearing

5. Cross head

6. HP &LP cylinder

7. Pistons

8. Valves

9. Intercooler

10. After cooler

11. Oil pump

12. Coupling

13. motor

Specifications of BTD –HM compressor

1. Bore LP cylinder = 380 mm

HP cylinder = 245 mm

2. Stroke = 125 mm

3. Speed = 980 rpm

4. Piston displacement = 27.60 m3/ min

5. F.A.D at 7kg /cm/sq/g =21.25 m3/min

6. Motor kw =125/135

7. Netweight of compressor = 2900 kgs (app.)

8. Lubricating oil = 25 lt

9. Oil pressure = 2.5 to 4 kg/cm

10. Cooling water flow rate = 180 lt/ min

Reciprocating compressor

Reciprocating compressors usepistonsd r i v e n b y a c r a n k s h a f t . T h e y c a n b e

e i t h e r stationary or portable, can be single or multi-staged, and can be driven by electric

motorso r i n t e r n a l c o m b u s t i o n e n g i n e s . S m a l l r e c i p r o c a t i n g

c o m p r e s s o r s f r o m 5 t o 30horsepower (hp) are commonly seen in automotive

applications and are typically for intermittent duty. Larger reciprocating

compressors up to 1000 hp are still commonlyfound in large industrial applications, but

their numbers are declining as they are replaced by various other types of compressors.

Discharge pressures can range from low pressuret o v e r y h i g h p r e s s u r e ( > 5 0 0 0 p s i

o r 3 5 M P a ) . I n c e r t a i n a p p l i c a t i o n s , s u c h a s a i r compression, multi-stage

double-acting compressors are said to be the most efficientcompressors available, and

are typically larger, noisier, and more costly than comparable rotary units.

There are four main types of compressor used at badarpur thermal power station . these are as

follows :

Densover compressor:

I t i s the most impor tan t c ompressor used a t B.T.P .S . These a re fou r in

number . One Densveyor compressor is connected with each mill. It provides the

primary as well assecondary air to the plant. These compressors are automatically

operated. It carries thecoal directly from the mill s to the furnace. These compressors

work under a maximum pressure of 8kgf.

Plant compressor:

These compressors are two in number. Plant compressors are moisture type compressors.These

are mainly used for washing the ash formed in the furnace and disposing them off.These

compressors work under a maximum pressure of 8kgf.Instrument compressors:-These are dry

type compressors. These are used to operate different instruments. Thesecompressors

are three in number. These also work under a maximum pressure of 8kgf.

Blast air compressor:

These compressors are smaller in size and are not as important as the other three types

of compressors. The coal in the RC (raw coal) bunkers sometimes sticks to the

surface of the bunkers due to moisture content in the coal. In such cases, blast air

compressors areused to detach the coal from the surface of the RC (raw coal) bunkers.

INDUSTRIAL FANS :

The air we need for combustion in the furnace and the flue gas thatwe must evacuate would

not possible without using fans. A fan iscapable of imparting energy to the air/gas in the

form of a boost in pressure. We overcome the losses through the system by means of this

pressure boost. The boost is dependent on dens ity for a givenfan at a given speed.

The higher the temperature, the lower is the boost. Fan performance (Max. capability) is

represented as volumevs. pressure boost.

ID FAN

The induced Draft Fans are generally of Axial -Impulse Type. Impeller nominal diameter is of

the order of 2500 mm.

The fan consists of the following sub-assemblies

•Suction Chamber

•Inlet Vane Control

•Impeller

•Outlet Guide Vane Assembly

ID FAN

The outlet guides are fixed in between thecase of the d i f fuser and the cas in g. These

guide vanes se rve to direct the flow axially and to stabilize the draft-flow caused in

theimpel l er . These out le t b l ades a re removable t ype f rom outs ide . During

operation of the fan itself these blades can be replaced one by one.Periodically the outlet blades

can be removed one at a time to findout the extent of wear on the blade. If excessive wear is

noticed the blade can be replaced by a new blade.

FD FAN

The fan , no rmal l y of the same t ype as ID Fan, cons i s t s o f the following

components:

*Silencer

*Inlet bend

*Fan housing

*Impeller with blades and setting mechanism

*Guide wheel casing with guide vanes and diffuser

FD FAN

The centrifugal and setting forces of the blades are taken up by the blade bearings. The blade

shafts are placed in combined radial andaxial antifriction bearings which are sealed off to the

outside. Theangle of-incidence of the blades may be adjusted during operation.T h e

c h a r a c t e r i s t i c p r e s s u r e v o l u m e c u r v e s o f t h e f a n m a y b e c h a n g e d i n

a l a r g e r a n g e w i t h o u t e s s e n t i a l l y m o d i f y i n g t h e e f f i c i e n c y . T h e

f a n c a n t h e n b e e a s i l y a d a p t e d t o c h a n g i n g operating conditions.The

rotor is accommodated in cylindrical roller bearings and an inclined ball bearing at the

drive side adsorbs the axial thrust.Lubrication and cooling these bearings is assured by a

combinedoil level and circulating lubrication system.

PRIMARY AIR FAN :

P.A. ran if flange mounted design, single stage suction, NDFVtype, backward curved

bladed radial fan operating on the principleof energy transformation due to centrifugal

forces. Some amountof the velocity energy is converted to pressure energy in the

spiralc a s i n g . T h e f a n i s d r i v e n a t a c o n s t a n t s p e e d a n d t h e f l o w

i s controlled by varying the angle of the inlet vane control. TheSpecial feature of the fan is

that is provided with inlet guide vanecontrol with a positive and precise link mechanism.

PRIMARY AIR FAN

TMD TURBINE MAINTENANCE

DEPARTMENT

TURBINE CLASSIFICATION :

IMPULSE TURBINE :

In Impulse Turbine steam expands in fixed nozzles.The high velocity steam from nozzles does

work on moving bladeswhich causes the shaft to rotate. The essential features of

impulset u r b i n e a r e t h a t a l l p r e s s u r e d r o p s o c c u r a t n o z z l e s a n d n o t

o n blades.A simple impulse turbine is not very efficient because it doesnot fully use the velocity

of the steam. Many impulse turbines arevelocity compounded. This means they have two

or more sets of moving blades in each stage.

REACTION TURBINE :

In this type of turbine pressure is reduced at both fixed& m o v i n g b l a d e s . B o t h

f i x e d & m o v i n g b l a d e s a c t a s n o z z l e s . W o r k d o n e b y t h e i m p u l s e

e f f e c t o f s t e a m d u e t o r e v e r s a l s o f d i rec t ion o f h igh veloci t y s t eam. The

expans ion o f s t eam takes place on moving blades.

A reaction turbine uses the "kickback" force of thes team as i t l eaves the moving

b lades and f ixed b l ades have thes a m e s h a p e a n d a c t l i k e n o z z l e s . T h u s ,

s t e a m e x p a n d s , l o s e s pressure and increases in velocity as it passes through both sets

of blades. All reaction turbines are pressure-compounded turbines.

COMPOUNDING:

Several problems occur if energy of steam is convertedin single step & so compounding is

done. Following are the typesof compounded turbine:

•Velocity Compounded Turbine

Like simple turbine it has only one set of nozzle &entire steam pressure drop takes place

there. The kinetic energy of steam fully on the nozzles is utilized in moving blades. The role

of fixed blades is to change the direction of steam jet & to guide it.

PRESSURE COMPOUNDED TURBINE

This is basically a no. of single impulse turbines inseries or on the same shaft.The exhaust of

first turbine enters the nozzle of the next turbine.Total pressure drop of steam does

not take on first nozzle ring butdivided equally on all of them.

Pressure Velocity Compounded Turbine

It is just the combination of the two compounding hasthe advantages of allowing bigger

pressure drops in each stage &so fewer s tages a re necessar y . Here fo r given

pressu re drop the turbine will be shorter length but diameter will be increased.

S t e a m t u r b i n e s m a y b e c l a s s i f i e d i n t o d i f f e r e n t c a t e g o r i e s

depending on their construction, the process by which heat dropis ach ieved , the in i t ia l

and f inal condi t i ons o f s t eam used and their industrial usage.

MAIN TURBINE :

The 210MW turbine is a tandem compounded typemachine compris ing o f H .P . & I .P .

cyl inders . The H.P . turb ine comprises of 12 stages the I.P. turbine has 11 stages & the

L.P. hasfour stages of double flow. The H.P. & I.P. turbine rotor are rigidlycompounded & the

I.P. & the I.P. rotor by lens type semi flexiblecoupling. All the three rotors are aligned on

five bearings of whichthe bearing no.2 is combined with thrust bearing.The main superheated

steam branches off into twostreams from the boiler and passes through the

emergency stopv a l v e a n d c o n t r o l v a l v e b e f o r e e n t e r i n g , t h e g o v e r n i n g

w h e e l chamber of the H.P. turbine. After expanding in the 12 stages in the H.P. turbine

the steam returned in the boiler for reheating.

The reheated steam from the boiler enter I.P. turbine viainterceptor valves and control

valves and after expanding entersthe L.P. turbine stage via 2 numbers of cross over pipes.In

the L.P. stage the steam expands in axially oppositedirection to counteract the trust and

enters the condenser placedd i r e c t l y b e l o w t h e L . P . t u r b i n e . T h e

c o o l i n g w a t e r f l o w i n g t h r o u g h o u t t h e c o n d e n s e r t u b e s c o n d e n s e s

t h e s t e a m a n d t h e condensate collected in the hot well of the condenser.The condensate

collected is pumped by means of 3*50% duty condensate pumps through L.P. heaters

to deaerator f r o m w h e r e t h e b o i l e r f e e d p u m p d e l i v e r s t h e w a t e r t o

b o i l e r t h r o u g h H . P . h e a t e r s t h u s f o r m i n g a

c l o s e d c y c l e

Turbine cycle :

Fresh steam from boiler is supplied to the turbinethrough the emergency stop valve.

From the stop valves steam issupplied to control valves situated on H.P. cylinders on

the front bearing end. After expansion through 12 stages at the H.P. cylinder steam flows

back to boiler for reheating and reheated steam from the bo i ler cover to t he

in te rmedia t e p res su re t urb ine t rough two in tercepto r valves and four cont ro l

valves mounted on the I .P . turbine.After flowing trough I.P. turbine steam enters the

middle part of the L.P. turbine through cross over pipes. In L.P. turbine theexhaust steam

condenses in the surface condensers welded directlyto the exhaust part of L.P. turbine.

The turbine cycle

The selection of extraction points and cold reheat pressurehas been done with a view to achieve

the highest efficiency. Theseare two extractions from H.P. turbine, four from I.P.

turbine ando n e f r o m L . P . t u r b i n e . S t e a m a t 1 . 1 0 t o 1 . 0 3 g / s q c m

A b s i s supplied for the gland sealing. Steam for this purpose is obtained from

deaera tor t hrough a co l lec t ion where pressu re of s team i s regulated.From the

condenser condensate is pumped with the helpof 3*50% capacity condensate pumps to deaerator

through the low pressure regenerative equipments. Feed water is pumped from deaerator

to the boiler through the H.P. heaters by means of 3*50% capacity feed pumpsconnected

before the H.P. heaters.

TURBINE COMPONENTS:

Casing

Rotor

Blades

Sealing System

Stop & control valves

Coupling & bearings

Bearing gear

Condensate System : This contains the following :

Condensate pumps : 3 per unit of 50% capacity each located near condenser hot well.

LP Heaters : Normally 4 in no. with 1 located at upper part of the condenser & no.s 2,3,4

around 4m level.

Deaerator : one per unit located around 181M‟ level in CD bay.

Condensate Pumps

The function of these pumps is to pumps out thecondensate to the desecrator through ejectors,

gland steam cooler,a n d L . P . h e a t e r s . T h e s e p u m p s h a v e f o u r s t a g e s a n d s i n c e

t h e suction is at a negative pressure, special arrangements have been m a d e f o r

p r o v i d i n g s e a l i n g . T h i s p u m p i s r a t e d g e n e r a l l y f o r 160m3 hr. at a pressure 13.2

Kg/cm2.

L.P. Heater

Turbine has been provided with non-controlledex t rac t ions which are u t i l i zed for

heat ing the condensate , f rom turbine bleed steam. There are 410w pressure heaters in

which thelast four extractions are used. L.P. Heater-1 has two parts LPH-1Aa n d L P H - 1 B

l o c a t e d i n t h e u p p e r p a r t s o f c o n d e n s e r A a n d condenser B

respectively. These are of horizontal type with shell and tube construction. L.P.H. 2, 3 and

4 are of similar constructionand they a re mounted in a row at 5M level . They are

of ver t ica l construction with brass tubes the ends of which are expanded intotube plate. The

condensate flows in the "U" tubes in four passesand extraction steam washes the

outside of the tubes. Condensate passes thru' these four L.P. heaters in succession.

These heatersare equipped with necessary safety valves in the steam space levelindicator for

visual level indication of heating steam condensate pressure vacuum gauges for

measurement of steam pressure etc.

DEAERATOR

The presence of cerataion gases principally oxygen , carbondioxide, ammonia dissolved in water

is generally considered harmful because of their corrosive attack on metals, particularly at

elevated temperatures. One of the most important factor in prevention of internal corrosion in

modern boilers and associated plant therefore is that the boiler feed water should be free as far as

possible from all dissolved gases especially oxygen. This is achieved by embodying into the

boiler feed system deaerating unit , whose function is to remove dissolved gases from feed water

by mechanical mens. Particularly the unit must reduce the oxygen content of feed waterto lower

values as far as possible , depending upon the individual circumstances. Residual oxygen content

in condensate at the outlet of deaerating plant usuassly specified are 0.005/ lt or less.

A DEAERATOR

PRINCIPLE OF DEAERATION

It is based on following two laws.

H e n r y ‟ s Law

Solubility

The Deaerator comprises of two chambers:

Deaerating column

Feed storage tank

Deaerating column is a spray cum tray type cylindrical vessel of horizontal constructionwith

dished ends welded to it. The tray stack is designed to ensure maximum contact time aswell as

optimum scrubbing of condensate to achieve efficient deaeration. The deaerationcolumn is

mounted on the feed storage tank, which in turn is supported on rollers at the twoends and a

fixed support at the centre. The feed storage tank is fabricated from boiler qualitysteel plates.

Manholes are provided on deaerating column as well as on feed storage tank for inspection and

maintenance.The condensate is admitted at the top of the deaerating column flows downwards

through thespray valves and trays. The trays are designed to expose to the maximum water

surfaces for efficient scrubbing to affect the liberation of the associated gases steam enters from

theunderneath of the trays and flows in counter direction of condensate. While flowing upwards

through the trays, scrubbing and heating is done. Thus the liberated gases move upwards along with the

steam. Steam gets condensed above the trays and in turn heats the condensate.

Liberated gases escapes to atmosphere from the orifice opening meant for it. This opening is provided with a

number of dlflectors to minimize the loss of steam.

FEED WATER SYSTEM

The main equipments under this system are :

• B o i l e r F e e d P u m p

: T h r e e p e r u n i t o f 5 0 % c a p a C i t y e a c h located in the '0' meter level in the TG

bay.

• High Pressure Heaters

: N o r m a l l y t h r e e i n n u m b e r a n d a r e situated in the TG bay.

• Drip Pumps

: Generally two in number of 100% capacity eachsituated beneath the LP heaters.

•Turbine Lubrica t ing Oi l Sys tem

: T h i s c o n s i s t s o f M a i n O i l Pump (MOP) Starting Oil Pump (SOP), AC standby

oil pumpsand emergency DC' oil pump and Jacking Oil Pump (JOP) (oneeach per unit).

Boiler feed pumps

This pump is horizontal and of barrel design driven byan Electric motor through a hydraulic coupling. All

the bearings of pump and motor are forced lubricated by a suitable oil lubricatingsystem with adequate

protection to trip the pump if the lubricationoil pressure falls below a preset value.The high-pressure

boiler feed pump is very expensivem a c h i n e w h i c h c a l l s f o r a v e r y c a r e f u l o p e r a t i o n

a n d s k i l l e d main t enance . T he sa f e ty i n ope ra t i on and e f f i c i ency o f t he f eed pump

depends largely on the reliable operation and maintenance. Operating staff must be able to find

out the causes of defect at thevery beginning which can be easily removed without endangeringthe

ope ra to r o f t he power p l an t and a l so w i thou t t he expens ive dismantling of the high

pressure feed pump.

The feed pump consists of pump barrel, into which ismounted the inside stator together with

rotor. The hydraulic part is e n c l o s e d b y t h e h i g h p r e s s u r e c o v e r a l o n g w i t h

t h e b a l a n c i n g device . The suct ion s ide of the ba rre l and the space in the

h igh pressure cover behind the balancing device are enclosed by the low pressure covers

along with the stuffing box casings. The bracketso f t h e r a d i a l b e a r i n g o f t h e

s u c t i o n s i d e a n d r a d i a l a n d t h r u s t bearing of the discharge side are fixed to

the low pressure covers.T h e e n t i r e p u m p s a r e m o u n t e d o n a

f o u n d a t i o n f r a m e . T h e hydraulic coupling and two claws coupling with

coupling guardsa re a l so del ive red a long wi th the pump. Wate r cool ing and

o i l lubricating are provided with their accessories.

HP heater

These are regenerative feed water heaters operating ath i g h p r e s s u r e a n d l o c a t e d

b y t h e s i d e o f t u r b i n e . T h e s e a r e generally vertical type and turbine bleed steam

pipes are connectedto them.HP heaters are connected in series on feed watersideand by such

arrangement, the feed water, after feed pump enters the HP hea ters . The s t eam i s

suppl i ed to these heate rs form the bleed point of the turbine through motor

operated valves. Theseheaters have a group bypass protection on the feed waterside.In the

event f tube rupture in any of the HPH and the level of theconde nsate rising to

dangerous level, the group protection deviced i v e r t s a u t o m a t i c a l l y t h e f e e d

w a t e r d i r e c t l y t o b o i l e r , t h u s bypassing all the 3 H.P. heaters.

INFERENCE

In these six weeks at BTPS, I gained practical experience and earned quite a lot of

Information regarding thermal power engineering.

The thermal plant consists of various units. All the main plant running equipments were

divided into units, which were further sub divided into more specific units for their

maintenance and efficient working.

For my six week training, I was assigned the work of three units, which were BMD and PAM &

TMD.

Boiler and turbine are the most important part of the power plant, without which the power

plant cannot run. This plant produces 705 MW of electricity, with the help of its 5 units. 3

units of 95 MW each and 2 units of 210 MW each. The 95 MW units were the first ones to be

established followed by the 210 MW units in the later years.

As for the unit PAM, it is equally important. It takes care of all the auxiliary processes going

on in the plant. It provides water to all the parts of the plant with the help of pumps present in

CSPH. Also it produces DM water from raw water by passing it through water treatment

plant. The ash or the waste produced on burning is taken care of, by Ash handling plant. The

compressed air required in any part of the plant is provided by the unit comprising of the

compressor, also known as compressor house.

The fuel used was coal which was pulverized with the help of bowl and ball mills. This

pulverized coal was the fuel burnt in the furnace to produce heat, which then heated the water to

superheated steam. This superheated steam was passed into the turbine rotor, thus rotating the

turbine shafts. To ensure the quality of steam generated a process named as reheating is taken

into account, which increases the dryness fraction of steam or makes it superheated. Thus as the

rotor rotates, it also runs the generator, which produces electricity. This electricity is then sent to

GT junction (Generator- Transformer), through which the electricity is passed into the switching

yard. After which it is distributed into various grids.

process. Thus I learned a lot during my training and hope to use this knowledge in the future.

BIBLIOGRAPHY

NTPC Trainer Manual , By Training Department

Senior Student Training Report , NTPC Badarpur Library , New Delhi

NTPC slides , By- NTPC training Department