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National Thermal Power Corporation

Badarpur,New Delhi

TRAINING REPORT

Name: Bhanu Pratap Singh (615/MP/08)

Branch: MANUFACTURING PROCESS AND AUTOMATION

ENGINEERING

College: NETAJI SUBHAS INSTITUTE OF TECHNOLOGY(NSIT)

Duration:12 December, 2011 to 28th January, 2012

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CONTENTS

1.0 Introduction

1.1 NTPC

1.2 Power Generation in India

1.3 Overall Power Generation

1.4 Badarpur Thermal Power Station (BTPS)

2.0 Objective

3.0 Work Done During The Training Period

3.1 Electricity From Coal

3.2 Boiler Maintenance Division (BMD)

3.3 Plant Auxiliary Maintenance (PAM)

3.4 Turbine Maintenance Division (TMD)

3.5 Pollution Control and Waste Management

4.0 Inference

5.0 Bibliography

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ACKNOWLEDGEMENT

With profound respect and gratitude, I take the opportunity to convey my thanks to

complete the training here. I do extend my heartfelt thanks to Mr. H.S. Bhatia for providing

me this opportunity to be a part of this esteemed organization. I am extremely grateful to all

the technical staff of National Thermal Power Corporation for their co-operation and

guidance that helped me a lot during the course of training. I have learnt a lot working under

them and I will always be indebted of them for this value addition in me. I would also like

to thank the training in charge of NETAJI SUBHAS INSTITUTE OF TECHNOLOGY,

DWARKA and all the faculty member of Manufacturing Process And Automation

Department for their effort of constant co-operation. Which have been significant factor in

the accomplishment of my industrial training.

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1.0 INTRODUCTION

1.1 NTPC

NTPC Limited is the largest thermal power generating company of India. A public sector

company, it was incorporated in the year 1975 to accelerate power development in the

country as a wholly owned company of the Government of India. At present, Government of

India holds 89.5% of the total equity shares of the company and FIIs, Domestic Banks, Public

and others hold the balance 10.5%. Within a span of 35 years, NTPC has emerged as a truly

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

country.

1.2 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. Its providing

power at the cheapest average tariff in the country.

1.3 OVERALL POWER GENERATION

Unit 1997-98 2006-07 % of increase

Installed Capacity MW 16,847 26,350 56.40

Generation MUs 97,609 1,88,674 93.29

No. of employees No. 23,585 24,375 3.34

Generation/employee MUs 4.14 7.74 86.95

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The table below shows the detailed operational performance of coal based stations over the

years.

The energy conservation parameters like specific oil consumption and auxiliary power

consumption have also shown considerable improvement over the years.

1.4 BADARPUR THERMAL POWER STATION (BTPS)

Badarpur thermal power plant produces 705MW of power. In total there are 5 units in BTPS,

3 are 95MW each and 2 of 210MW each.95MW units were installed in early 70‟s and

210MW in late 70‟s to early 80‟s.Coal Requirements ( Depends On the Calorific Value Of

the Fuel):

95 MW -60 tonnes/hour

210MW-105 to 110 tonnes/hour 65MW of power is

consumed in company while rest (640MW) is provided to states of northern

region like UP, Delhi, Haryana, Rajasthan.There are 11 feeders in use at

present, 2-Okhla, 2-Sarita Vihar, 2-Mahroli, 2-Noida, 2-Ballabhgarh, 1-

Alwar.

OPERATIONAL PERFORMANCE OF COAL BASED NTPC STATIONS

Unit 97-98 98-99 99-00 00-01 01-02 02-03 03-04 04-05 05-06 06-07

Generation BU 106.2 109.5 118.7 130.1 133.2 140.86 149.16 159.11 170.88 188.67

PLF % 75.20 76.60 80.39 81.8 81.1 83.6 84.4 87.51 87.54 89.43

Availability

Factor

% 85.03 89.36 90.06 88.54 81.8 88.7 88.8 91.20 89.91 90.09

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OBJECTIVE

I was appointed to do four-week training at this esteemed organization from 12th

Dec 2011 to

28 th

Jan, 2012. In these four 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 Auxillary Maintenance (PAM)

5. Turbine Maintenance Division(TMD)

The objective of the training at NTPC is to gain experience of eight weeks on field, and to

gain practical knowledge in the field of thermal power generation.

WORK DONE DURING THE TRAINING PERIOD 3.1 ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P. (Coal

Handling Plant) this coal is taken to the raw coal bunkers with the help of conveyor belts.

Coal is then transported to bowl mills by coal feeders where it is pulverized and ground in the

powered form.

This crushed coal is taken away to the furnace through coal pipes with the help of hot and

cold mixture P.A fan. This fan takes atmospheric air, a part of which is sent to pre heaters

while a part goes to the mill for temperature control. Atmospheric air from F.D fan in the air

heaters and sent to the furnace as combustion air.

Water from boiler feed pump passes through economizer and reaches the boiler drum . Water

from the drum passes through the down comers and goes to the bottom ring header. Water

from the bottom ring header is divided to all the four sides of the furnace. Due to heat density

difference the water rises up in the water wall tubes. This steam and water mixture is again

taken to the boiler drum where the steam is sent to super heaters for super heating. The super

heaters are located inside the furnace and the steam is super heated (540 degree Celsius) and

finally it goes to the turbine.

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Fuel gases from the furnace are extracted from the induced draft fan, which maintains

balance draft in the furnace with F.D fan. These fuel gases heat energy to the various super

heaters and finally through air pre heaters and goes to electrostatic precipitators where the ash

particles are extracted. This ash is mixed with the water to from slurry is pumped to ash

period. The steam from boiler is conveyed to turbine through the steam pipes and through

stop valve and control valve that automatically regulate the supply of steam to the turbine.

Stop valves and controls valves are located in steam chest and governor driven from main

turbine shaft operates the control valves the amount used. Steam from controlled valves enter

high pressure cylinder of turbines, where it passes through the ring of blades fixed to the

cylinder wall. These act as nozzles and direct the steam into a second ring of moving blades

mounted on the disc secured in the turbine shaft. The second ring turns the shaft as a result of

force of steam on the stationary and moving blades together.

Typical components of a coal fired thermal power station

1. Cooling water pump

2. Three-phase transmission line

3. Step up transformer

4. Electrical Generator

5. Low pressure steam

6. Boiler feed water pump

7. Surface condenser

8. Intermediate pressure steam turbine

9. Steam control valve

10. High pressure steam turbine

11. Deaerator Feed water heater

12. Coal conveyor

13. Coal hopper

14. Coal pulverizer

15. boiler steam drum

16. Bottom ash hoper

17. Super heater

18. Forced draught (draft) fan

19. Reheater

20. Combustion air intake

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21. Economizer

22. Air preheater

23. Precipitator

24. Induced draught (draft) fan

25. Fuel gas stack

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. TurbinesThere 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

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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

common 2-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. Boiler feed water pump

A Boiler feed water pump is a specific type of pump used to pump water into a steam boiler.

The water may be freshly supplied or retuning condensation of the steam produced by the

boiler. These pumps are normally high pressure units that use suction from a condensate

return system and can be of the 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 force the water

into the boiler; the pump must generate sufficient pressure to overcome the steam pressure

developed by the boiler. This is usually accomplished through the use of a centrifugal pump.

Feed water pumps usually run intermittently and are controlled by a float switch or other

similar level-sensing device energizing the pump when it detects a lowered liquid level in the

boiler is substantially increased. Some pumps contain a two-stage switch. As liquid lowers to

the trigger point of the first stage, the pump is activated. I f the liquid continues to drop

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(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, or

both.

5. 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.

6. 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

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7. Deaerator

A Dearator is a device for air removal and used to remove dissolved gases (an

alternate would be the use of water treatment chemicals) from boiler feed water to

make it non-corrosive. A deaerator typically includes a vertical domed deaeration

section as the deaeration boiler feed water tank. A Steam generating boiler requires

that the circulating steam, condensate, and feed water should 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 the heating surfaces

giving rise to localized heating and tube ruptures due to overheating. Under some

conditions it may give to stress corrosion cracking.

Deaerator level and pressure must be controlled by adjusting control valves- the level

by regulating condensate flow and the pressure by regulating steam flow. If operated

properly, most deaerator vendors will guarantee that oxygen in the deaerated water

will not exceed 7 ppb by weight (0.005 cm3/L)

8. Feed water heater

A Feed water heater is a power plant component used to pre-heat water delivered to a

steam generating boiler. Preheating the feed water reduces the irreversible involved in

steam generation and therefore improves the thermodynamic efficiency of the

system.[4] This reduces plant operating costs and also helps to avoid thermal shock to

the boiler metal when the feed water is introduces back into the steam cycle.

In a steam power (usually modeled as a modified Ranking cycle), feed water heaters

allow the feed water to be brought up to the saturation temperature very gradually.

This minimizes the inevitable irreversibility‟s associated with heat transfer to the

working fluid (water). A belt conveyor consists of two pulleys, with a continuous loop

of material- the conveyor Belt – that rotates about them. The pulleys are powered,

moving the belt and the material on the belt forward. Conveyor belts are extensively

used to transport industrial and agricultural material, such as grain, coal, ores etc.

9. Pulverizer :A pulverizer is a device for grinding coal for combustion in a furnace in

a fossil fuel power plant.

10. Boiler Steam Drum

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

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at the top end of the water tubes in the water-tube boiler. They store the 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 involves temperatures 390‟C and pressure well

above 350psi (2.4MPa). The separated steam is drawn out from the top section of the

drum. Saturated steam is drawn off the top of the drum. The steam will re-enter 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 tubes

accessories 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 a tendency to

the bottom.

11. 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 saturated steam 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.

12. 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, power plant, and heating,

ventilating and air conditioning. In boilers, economizer are heat exchange devices that

heat fluids , usually water, up to but not normally beyond the boiling point of the

fluid. Economizers are so named because they can make use of the enthalpy and

improving the boiler‟s 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

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fill it (the feed water). Modern day boilers, such as those in cold fired power stations,

are still fitted with economizer which is decedents of Green‟s original design. In this

context they are turbines before it is pumped to the boilers. A common application of

economizer is steam power plants 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 acidic

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

design and material selection.

13. Air Preheater

Air preheater is a general term to describe any device designed to heat air before

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. As a

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.

14. 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 highly efficient filtration devices,

and can easily remove fine particulate matter such as dust and smoke from the air

steam.

ESP‟s 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 crackers from several hundred thousand ACFM in the

largest coal-fired boiler application.

The original parallel plate-Weighted wire design (described above) has evolved as

more efficient ( and robust) discharge electrode designs were developed, today

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focusing on rigid discharge electrodes to which many sharpened spikes are attached ,

maximizing corona production. Transformer –rectifier 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 particulate matter while on line

allowing ESP‟s to stay in operation for years at a time.

15. 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.

3.2 BOILER MAINTENANCE DIVISION I/II/III (BMD-I/II/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.

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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.

2/3 in no.

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Coal Handling Plant and New Coal Handling Plant (CHP/ NCHP)

The old coal handling plant caters to the need of units 2,3,4,5 and 1 whereas the latter

supplies coal to units 4 and V.O.C.H.P. supplies coal to second and third stages in the

advent coal to usable form to (crushed) form its raw form and send it to bunkers, from

where it is send to furnace.

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Major Components

1. WAGON TIPPLER: - Wagons from the coal yard come to the tippler and are emptied

here. The process is performed by a slip –ring motor of rating: 55 KW, 415V, 1480 RPM.

This motor turns the wagon by 135 degrees and coal falls directly on the conveyor

through vibrators. Tippler has raised lower system which enables is to switch off motor

when required till is wagon back to its original position. It is titled by weight balancing

principle. The motor lowers the hanging balancing weights, which in turn tilts the

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conveyor. Estimate of the weight of the conveyor is made through hydraulic weighing

machine.

2. CONVEYOR: - There are 14 conveyors in the plant. They are numbered so that their

function can be easily demarcated. Conveyors are made of rubber and more with a speed of

250-300m/min. Motors employed for conveyors has a capacity of 150 HP. Conveyors have a

capacity of carrying coal at the rate of 400 tons per hour. Few conveyors are double belt, this

is done for imp. Conveyors so that if a belt develops any problem the process is not stalled.

The conveyor belt has a switch after every 25-30 m on both sides so stop the belt in case of

emergency. The conveyors are 1m wide, 3 cm thick and made of chemically treated

vulcanized rubber. The max angular elevation of conveyor is designed such as never to

exceed half of the angle of response and comes out to be around 20 degrees.

3. ZERO SPEED SWITCH:-It is safety device for motors, i.e., if belt is not moving and the

motor is on the motor may burn. So to protect this switch checks the speed of the belt and

switches off the motor when speed is zero.

4. METAL SEPERATORS: - As the belt takes coal to the crusher, No metal pieces should go

along with coal. To achieve this objective, we use metal separators. When coal is dropped to

the crusher hoots, the separator drops metal pieces ahead of coal. It has a magnet and a belt

and the belt is moving, the pieces are thrown away. The capacity of this device is around 50

kg. .The CHP is supposed to transfer 600 tons of coal/hr, but practically only 300-400 tons

coal is transferred.

5. CRUSHER: - Both the plants use TATA crushers powered by BHEL motors. The crusher

is of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed to crush the pieces

to 20 mm size i.e. practically considered as the optimum size of transfer via conveyor.

6. ROTARY BREAKER: - OCHP employs mesh type of filters and allows particles of 20mm

size to go directly to RC bunker, larger particles are sent to crushes. This leads to frequent

clogging. NCHP uses a technique that crushes the larger of harder substance like metal

impurities easing the load on the magnetic separators.

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Milling System

1. RC Bunker: - Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4

& ½ tons of coal are fed in 1 hr. the depth of bunkers is 10m.

2. 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.

3. 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.

4. Classifier:- It is an equipment which serves separation of fine pulverized coal particles

medium from coarse medium. The pulverized coal along with the carrying medium

strikes the impact plate through the lower part. Large particles are then transferred to the

ball mill.

5. Cyclone Separators: - It separates the pulverized coal from carrying medium. The

mixture of pulverized coal vapour caters the cyclone separators.

6. Turniket: - It serves to transport pulverized coal from cyclone separators to pulverized

coal bunker or to worm conveyors. There are 4 turnikets per boiler.

7. Worm Conveyor: - It is equipment used to distribute the pulverized coal from bunker

of one system to bunker of other system. It can be operated in both directions.

8. 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

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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

9. Bowl Mill: - One of the most advanced designs of coal pulverizes presently

manufactured.

Motor specification –squirrel cage induction motor

Rating-340 KW

Voltage-6600KV

Curreen-41.7A

Speed-980 rpm

Frequency-50 Hz

No-load current-15-16 A

New Coal Handling Plant (NCHP)- Flow

1. Wagon Tippler:-

Motor Specification

(i) H.P 75 HP

(ii) Voltage 415, 3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

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(v) Current rating 102 A

2. Coal feed to plant:-

Feeder motor specification

(i) Horse power 15 HP

(ii) Voltage 415V,3 phase

(iii) Speed 1480 rpm

(iv) Frequency 50 Hz

3. Conveyors Nomenclature:-

10A, 10B/11A, 11B/12A, 12B/13A, 13B/14A, 14B/15A, 15B/16A, 16B/17A, 17B/18A, 18B.

4. Transfer Point 6

5. Breaker House

6. Rejection House

7. Reclaim House

8. Transfer Point 7

9. Crusher House

10. Exit

The coal arrives in wagons via railways and is tippled by the wagon tipplers into the hoppers.

If coal is oversized (>400 mm sq) then it is broken manually so that it passes the hopper

mesh. From the hopper mesh it is taken to the transfer point TP6 by conveyor 12A ,12B

which takes the coal to the breaker house , which renders the coal size to be 100mm sq. the

stones which are not able to pass through the 100mm sq of hammer are rejected via

conveyors 18A,18B to the rejection house . Extra coal is to sent to the reclaim hopper via

conveyor 16. From breaker house coal is taken to the TP7 via Conveyor 13A, 13B. Conveyor

17A, 17B also supplies coal from reclaim hopper, From TP7 coal is taken by conveyors 14A,

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14B to crusher house whose function is to render the size of coal to 20mm sq. now the

conveyor labors are present whose function is to recognize and remove any stones moving in

the conveyors . In crusher before it enters the crusher. After being crushed, if any metal is

still present it is taken care of by metal detectors employed in conveyor 10.

3.3 PLANT AUXILIARY MAINTENANCE (PAM)

This unit of the plant mainly dealt with the auxiliary or helping parts in the plant eg: water

treatment, ash treatment, pump division etc.

This two week of training in this division were divided as follows:

1. Control Structure Pump House (CSPH)

2. Water Treatment Plant (WTP)

3. Ash Pump House (APH)

4. Compressed Air Systems

The details of the above sub units are as follows:

a. Control Structure Pump House (CSPH)

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 :

Sr.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

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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 Pump 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.

b. Water Treatment Plant (WTP)

The raw water from CSPH is sent to WTP where it is processed and converted into

DM water. This unit has 8 pumps in all, of which 3 pumps are of 210 MW and are

used in running plant, whereas other 5 are 100 MW pumps used in cooling water

circulation. Here, initially raw water is mixed with alum and chlorine, and then passed

through chambers of carbon filter to convert it to clarified water. This water is passed

through resin filter and then mixed with 30 % HCL solution, to form ions. Then it is

passed through cation chamber to separate cations, and similarly anions are removed

through anion chamber. Thus we get carbonated water, this water is passed through

the process of decarbonation, and thus we get DM or Demineralised water.

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The layout of water treatment plant is shown in the below figure:

25

c. Ash Pump House (APH)

In the bottom ash system the ash slag discharged from furnace bottom is collected in

two water impounded scraper troughs installed below bottom ash hoppers. The ash is

continuously transported by means of scrapper chain conveyor, on to the respective

cinker grinders which reduces the lump size to required fineness. The crushed ash

from clinker grinders falls into the ash sluice trench provided below bottom ash

hopper from where ash slurry is further transported to ash slurry sump aided by the

ash sluice channel. If the clinker grinder is not in operation , bottom ash can be

discharged directly into the sluice channel through bifurcating chute bypass the

grinder.

The Main types of hoppers used in power plants are:

Water Filter Hoppers

Quencher Cooled Ash Hopper

The various ash disposal systems are:

Fly Ash System

The fly ash collected in these hoppers drop continuously to flushing apparatus

where fly ash gets mixed with flushing water and the resulting slurry drops

into the ash sluice channel. Low pressure water is applied through the nozzle

directing tangentially yto the section of pipe to create turbulence and proper

mixing of ash with water. For the maintenance of flushing apparatus plate

valve is provided between apparatus and connecting chute.

Ash Water System

High pressure water required for B.A. hopper quenching nozzles, B.A.

hoppers window spraying, clinker grinder sealing scrapper bars, cleaning

nozzles, B.A. hopper seal through flushing, Economizer hoppers flushing

nozzles and sluicing trench jetting nozzles is tapped from the high pressure

water ring main provided in the plant area.

Low pressure water required for bottom ash hopper seal through make up,

scrapper conveyor makeup, flushing apparatus jetting nozzles for all..

F.A.hoppers excepting economiser hoppers, is tapped from low pressure water

ring mains provided in the plant area.

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Ash Slurry System

Bottom ash and fly ash slurry of the system is sluiced upto ash slurry pump

along the channel with the aid of high pressure water jets located at suitable

intervals along the channel.

Slurry pump suction line consisting of reducing elbow with drain valve

reducer and butterfly valve and portion of slurry pump delivery line consisting

of butterfly valve, pipe and fittings has also been provided.

d. Compressed Air Systems

Instrument air is required for operating various dampers , burner tilting devices,

diaphragm valves etc., in the 210 MW units. Station air meets the general requirement

of the power statin such as light oil atomising air, for cleaning filters and for various

maintenance works. The control air compressors have been housed separately with

separate receivers and supply headers and their tappings.

Control Air System

These have been installed for supplying moisture free dry air required for instrument

used. The output from the compressor is fed to air receivers via non return valves.

From the receiver air is passed through the dryers to the main instrument air line

which runs alongwith the boiler house and turbine house of 210 MW unit.

There is one interconnection between service air and instrument air headers just at the

inlet of drying units. This connection has been provided as an emergency provision to

meet the requirement of instrument air in case of non-availability of instrument air

compressor. The line connecting the service air header with instrument air header is

provided with two isolating valves , one oil separator, one activated carbon filter, one

non return valve and one regulating valve. Oil and dust free air is supplied to the

instrument air header which is then passed through air drier units. Instrument air

compressor are of double acting horizontal cross head type of two opposed cylinder.

The compressors are driven by electric motor through V belts. Gear wheel type

lubricating oil pump is provided to feed the main bearing. Connecting rod bearing and

cross heads of one side ie. to the opposite side of crank shaft rotation piston. The

compressor is equipped with water cooled inter cooler or header, pressure regulator to

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load and unload the compressor and safety valves for first and second stages. The

suction air filter is at the middle of the cylinder so that air can enter at both ends of the

piston. After compression the air passes through the delivery valves to the intercooler

where the air is cooled and enters the HP cylinder. The entrapped air in HP side is

compressed in a similar manner as in LP cylinder to the required pressure and enters

the header connected to the HP cylinders through the delivery valves and then finally

to the air receiver.

Air Drying Unit

Air contains moisture which tends to condense, and cause trouble in operation of

various devices by compressed air. Therefore drying of air is accepted widely in case

of instrument air. Air drying unit consists of dual absorption towers with embedded

heaters for reactivation. The absorption towers are adequetly filled with specially

selected silica gel and activated alumina .While one tower is drying the air , the other

tower is under reactivation. Thus the unit maintains continuous supply of dry air for

plant requirement. Thus the system is completely automatic.

3.4 TURBINE MAINTENANCE DIVISION (TMD)

A turbine, being a form of engine, requires in order to function a suitable working fluid, a

source of high grade energy and a sink for low grade energy. When the fluid flows through

the turbine, part of the energy content is continuously extracted and converted into useful

mechanical work.

The data about the turbine of 210 MW is shown below:

MAIN TURBINE DATA

Rated output of Turbine 210 MW

Rated speed of turbine 3000 rpm

Rated pressure of steam before emergency 130 kg/cm^2

Stop valve rated live steam temperature 535 degree Celsius

Rated steam temperature after reheat at inlet to receptor

valve

535 degree Celsius

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The thermal (steam) power plant uses a dual (vapour + liquid) phase cycle. It is a closed cycle

to enable the working fluid(water) to be used again and again. The cycle used is “Rankine

Cycle” modified to include super heating of steam, regenerative feed water heating and

reheating of steam as shown in figure.

Factors Affecting Thermal Cycle Efficiency

Thermal cycle efficiency is affected by following :

Initial Steam Pressure

Initial Steam Temperature

Steam flow at valve wide open condition 670 tons/hour

Rated quantity of circulating water through condenser 27000 cm/hour

1. For cooling water temperature (degree Celsius) 24,27,30,33

1.Reheated steam pressure at inlet of interceptor valve

in kg/cm^2 ABS

23,99,24,21,24,49,24.82

2.Steam flow required for 210 MW in ton/hour 68,645,652,662

3.Rated pressure at exhaust of LP turbine in mm of Hg 19.9,55.5,65.4,67.7

Operating Principles

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

Condenser Pressure

Regenerative feed water heating

Turbine Components

The Main Turbine

The 210 MW turbine installed in our power stations is predominantly of condensing-

tandom - compound, three cylinder, horizontal, disc and diaphragm, reheat type with

nozzle governing and regenerative system of feed water heating and is coupled

directly with A.C. generator

The various main components of the steam turbine are as follows :

Turbine casings

I. High Pressure Casing

II. Intermediate Pressure Casing

III. Low Pressure Casing

Rotors

I. High Pressure Rotor

II. Intermediate Pressure Rotor

III. Low Pressure Rotor

Blades

Blades fitted in stationary part are called guide blades or nozzles and those fitted in

the rotor are called moving or working blades. The following are three main types of

blades.

I. Cylindrical (or constant profile) blade (fig A)

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II. Tapered cylindrical (Tapered but similar profile)

III. Twisted and varying profile

Sealing glands

To eliminate the possibility of steam leakage to atmosphere from the inlet and exhaust

ends of the cylinder, labyrinth glands of the radial clearance type are provided which

provide a trouble free frictionless sealing.

Emergency Stop Valves and Control Valves

ESV‟s are provided to cut off steam supply and with control valves regulate steam

supply.

Couplings

Since the shaft is made in small parts due to forging limitations and other

technological and economic reasons , the couplings are required between any two

rotors. It permits angular misalignment, transmits axial thrust and ensures axial

location.In 210 MW turbines, coupling between HPT and IPT is of rigid type and

between IPT and LPT is of semi flexible lens type.

Bearings

Barring Gear

Arrangement Of Turbine Auxiliaries

The turbine cycle can be viewed in the form of different systems as given in following

paragraphs

Vacuum System

I. Condenser- 2 per 210 MW unit at the exhaust of LP turbine

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II. Ejectors- One starting and two main ejectors connected to the condenser

located near the turbine

III. C.W. pumps – Normally two per unit of 50 % capacity

Condensate System

I. Condensate Pumps- 3 per unit of 50% capacity each located near the

condenser hot well.

II. LP heaters- Normally 4 in number with no.1 located at ther upper part of the

condenser and nos 2,3,4 around 4m level

III. Deaerator- One per unit located around 18 M level in CD bay

Feed Water System

I. Boiler Feed Pump- 3 per unit of 50% capacity each located in the „0‟ meter

level in TG bay

II. High Pressure Heaters- Normally 3 in number and are situated in the TG bay

Drip Pumps

Generally two in number of 100% capacity each situated beneath the LP heaters

Turbine Lub Oil system

This consists of Main Oil Pump(MOP), Starting Oil Pump(SOP), AC standby oil

pumps and emergency DC oil pump and Jacking Oil Pump (JOP) (one each per unit)

Auxiliary Steam System

The main 16 ata header runs parallel to BC bay at the level of around 18‟M‟.

The arrangement of turbine auxiliaries is shown in the following figure:

32

33

3.5 POLLUTION CONTROL AND WASTE MANAGEMENT

NTPC is committed to the environment, generating power at minimal environmental cost and

preserving the ecology in the vicinity of the plants.Harmony between man and environment is

the essence of healthy life and growth. Therefore, maintenance of ecological balance and a

pristine environment has been of utmost importance to NTPC. It has been taking various

measures discussed below for mitigation of environment pollution due to power generation.

Pollution Control systems:

While deciding the appropriate technology for its projects, NTPC integrates many

environmental provisions into the plant design. In order to ensure that NTPC comply with all

the stipulated environment norms, various state-of-the-art pollution control systems / devices

as discussed below have been installed to control air and water pollution.

Electrostatic Precipitators (ESP):

The ash left behind after combustion of coal is arrested in high efficiency Electrostatic

Precipitators (ESP‟s) and particulate emission is controlled well within the stipulated norms.

The ash collected in the ESP‟s is disposed to Ash Ponds in slurry form.

Flue Gas Stacks:

Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions (SOX,

NOX etc) into the atmosphere.

Low-NOX Burners:

In gas based NTPC power stations, NOx emissions are controlled by provision of Low-NOx

Burners (dry or wet type) and in coal fired stations, by adopting best combustion practices.

Neutralisation Pits:

Neutralisation pits have been provided in the Water Treatment Plant (WTP) for pH correction

of the effluents before discharge into Effluent Treatment Plant (ETP) for further treatment

and use.

Coal Settling Pits / Oil Settling Pits:

In these Pits, coal dust and oil are removed from the effluents emanating from the Coal

Handling Plant (CHP), coal yard and Fuel Oil Handling areas before discharge into ETP.

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DE & DS Systems:

Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in all coal fired

power stations in NTPC to contain and extract the fugitive dust released in the Coal Handling

Plant (CHP).

Cooling Towers:

Cooling Towers have been provided for cooling the hot Condenser cooling water in closed

cycle Condenser Cooling Water (CCW) Systems. This helps in reduction in thermal pollution

and conservation of fresh water.

Ash Dykes & Ash Disposal systems:

Ash ponds have been provided at all coal based stations except Dadri where Dry Ash

Disposal System has been provided. Ash Ponds have been divided into lagoons and provided

with garlanding arrangements for change over of the ash slurry feed points for even filling of

the pond and for effective settlement of the ash particles. Ash in slurry form is discharged

into the lagoons where ash particles get settled from the slurry and clear effluent water is

discharged from the ash pond. The discharged effluents conform to standards specified by

CPCB and the same is regularly monitored.

At its Dadri Power Station, NTPC has set up a unique system for dry ash collection and

disposal facility with Ash Mound formation. This has been envisaged for the first time in

Asia which has resulted in progressive development of green belt besides far less requirement

of land and less water requirement as compared to the wet ash disposal system.

Ash Water Recycling System:

Further, in a number of NTPC stations, as a proactive measure, Ash Water Recycling System

(AWRS) has been provided. In the AWRS, the effluent from ash pond is circulated back to

the station for further ash sluicing to the ash pond. This helps in savings of fresh water

requirements for transportation of ash from the plant.The ash water recycling system has

already been installed and is in operation at Ramagundam, Simhadri, Rihand, Talcher

Kaniha, Talcher Thermal, Kahalgaon, Korba and Vindhyachal. The scheme has helped

stations to save huge quantity of fresh water required as make-up water for disposal of ash.

Dry Ash Extraction System (DAES):

Dry ash has much higher utilization potential in ash-based products (such as bricks, aerated

autoclaved concrete blocks, concrete, Portland pozzolana cement, etc.). DAES has been

35

installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon, Farakka,

Talcher Thermal, Korba, Vindhyachal, Talcher Kaniha and BTPS.

Liquid Waste Treatment Plants & Management System:

The objective of industrial liquid effluent treatment plant (ETP) is to discharge lesser and

cleaner effluent from the power plants to meet environmental regulations. After primary

treatment at the source of their generation, the effluents are sent to the ETP for further

treatment. The composite liquid effluent treatment plant has been designed to treat all liquid

effluents which originate within the power station e.g. Water Treatment Plant (WTP),

Condensate Polishing Unit (CPU) effluent, Coal Handling Plant (CHP) effluent, floor

washings, service water drains etc. The scheme involves collection of various effluents and

their appropriate treatment centrally and re-circulation of the treated effluent for various plant

uses.

NTPC has implemented such systems in a number of its power stations such as

Ramagundam, Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, Jhanor

Gandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. These plants have helped to

control quality and quantity of the effluents discharged from the stations.

Sewage Treatment Plants & Facilities:

Sewage Treatment Plants (STPs) sewage treatment facilities have been provided at all NTPC

stations to take care of Sewage Effluent from Plant and township areas. In a number of NTPC

projects modern type STPs with Clarifloculators, Mechanical Agitators, sludge drying beds,

Gas Collection Chambers etc have been provided to improve the effluent quality. The

effluent quality is monitored regularly and treated effluent conforming to the prescribed limit

is discharged from the station. At several stations, treated effluents of STPs are being used for

horticulture purpose.

Waste Management

Various types of wastes such as Municipal or domestic wastes, hazardous wastes, Bio-

Medical wastes get generated in power plant areas, plant hospital and the townships of

projects. The wastes generated are a number of solid and hazardous wastes like used oils &

waste oils, grease, lead acid batteries, other lead bearing wastes (such as garkets etc.), oil &

clarifier sludge, used resin, used photo-chemicals, asbestos packing, e-waste, metal scrap,

C&I wastes, electrical scrap, empty cylinders (refillable), paper, rubber products, canteen

(bio-degradable) wastes, buidling material wastes, silica gel, glass wool, fused lamps &

36

tubes, fire resistant fluids etc. These wastes fall either under hazardous wastes category or

non-hazardous wastes category as per classification given in Government of India‟s

notification on Hazardous Wastes (Management and Handling) Rules 1989 (as amended on

06.01.2000 & 20.05.2003). Handling and management of these wastes in NTPC stations have

been discussed below.

Advanced / Eco-friendly Technologies

NTPC has gained expertise in operation and management of 200 MW and 500 MW Units

installed at different Stations all over the country and is looking ahead for higher capacity

Unit sizes with super critical steam parameters for higher efficiencies and for associated

environmental gains. At Sipat, higher capacity Units of size of 660 MW and advanced Steam

Generators employing super critical steam parameters have already been implemented as a

green field project.

Higher efficiency Combined Cycle Gas Power Plants are already under operation at all gas-

based power projects in NTPC. Advanced clean coal technologies such as Integrated

Gasification Combined Cycle (IGCC) have higher efficiencies of the order of 45% as

compared to about 38% for conventional plants. NTPC has initiated a techno-economic study

under USDOE / USAID for setting up a commercial scale demonstration power plant by

using IGCC technology. These plants can use low-grade coals and have higher efficiency as

compared to conventional plants.

With the massive expansion of power generation, there is also growing awareness among all

concerned to keep the pollution under control and preserve the health and quality of the

natural environment in the vicinity of the power stations. NTPC is committed to provide

affordable and sustainable power in increasingly larger quantity. NTPC is conscious of its

role in the national endeavour of mitigating energy poverty, heralding economic prosperity

and thereby contributing towards India‟s emergence as a major global economy.

37

4.0 INFERENCE

In these 6 weeks in NTPC/ 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 four week training, I was assigned the work of three units, which were BMD, PAM

and TMD. These 3 units are explained above in chapter 3, of this report.

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. These

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.

The coal is basically brought from Bihar and Jharkhand coal mines, by rail wagons. The

plant has special facility or technique to unload the coal from wagon and include it in

generation process. Thus i learned a lot during my training and hope to use this knowledge

in the future.

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5.0 BIBLIOGRAPHY

NTPC Trainer Manual , By Training Department

Senior Student Training Report , NTPC Nalanda Library

Power Plant Engineering, By- N.V.Ramaswamy

NTPC slides , By- NTPC training Department