A Practical Training Report

Undertaken at

Nashik Thermal Power Station,

Eklahare, MAHAGENCO

Dist. Nashik (Maharashtra)

Submitted in Partial Fulfilment of the Requirement

For the Award of Degree

of

Bachelor of Technology

In Department of Mechanical Engineering

to

Rajasthan Technical University,

Kota

2014-2015

Submitted to: - Submitted by: - Dr. JP Bhamu Sagar Mehta Associate Professor B.Tech. VII Sem Department of Mechanical Engineering 11EEBME753

GOVERNMENT ENGINEERING COLLEGE, BIKANER

August, 2014

ACKNOWLEDGEMENT

It is often said that life is a mixture of achievements, failure, experiences, exposures and

efforts to make your dream come true. There are people around you who help you realize

your dream. I acquire this opportunity with much pleasure to acknowledge the invaluable

assistance of Nasik Thermal Power Station and all the people who have helped me through

the course of my journey in successful completion of the summer training.

I would like to take this opportunity to thank all those who have contributed in this report

directly or indirectly. I offer my thanks to Mr. Santosh Kulkarni (Dy. Executive Engineer),

Mr. N.M. Shinde (Dy.Chief Engineer), Mr. K.M. Mane (Superintendent Engineer), Mr.

Kimbahune Vikrant V. (Power User, EAM), and O.R.Usrete (Sr. Chemist) for providing

whole hearted Co-operation.

I would personally like to my thank Mr. A.P. Netke (Assistant Engineer and Training In-

charge) for helping me throughout my training.

I feel deep sense of gratitude towards Dr. JP Bhamu, Associate Professor in Govt.

Engineering College Bikaner, being a constant source of motivation and guidance. I also like

to thank all Faculty and all staff members of mechanical department of Govt. Engineering

College Bikaner.

I want to thank to all Staff and Workers of NTPS for their guidance and co-operation at each

& every step of my training.

I also acknowledge thank to my fellow students for discussing various points during the

course of training which proved very useful in preparing this report. I am grateful to my

friends who gave me the moral support in my times of difficulties. Last but not the least I

would like to express my special thanks to my family for their continuous motivation and

support.

Sagar Mehta

11EEBME753

Table of Contents

S. No. Topics Page No.

1 HISTORY OF POWER SECTOR 1

1.1 Introduction 1

1.2 Market Reform 2

2 HISTORY OF INDIAN POWER SECTOR 3

2.1 Introduction 3

2.2 Present Energy Scenario In India 4

3 HISTORY OF THERMAL POWER GENERATION 6

3.1 Introduction 6

3.2 Thermal Power Generation In India 6

4 NASIK THERMAL POWER STATION 7

4.1 Introduction 7

4.2 Installed Capacity 8

4.3 Transport 9

4.4 Shaktiman A Symbol Of Visionary Resourcefulness 9

5 STEAM POWER PLANT 10

5.1 Power Plant 10

5.2 Steam Power Plant 10

5.3 Rankine or Steam Cycle 11

6 THERMAL POWER STATION VIEWS 13

7 POWER PLANT WATER INTAKE 14

7.1 Introduction 14

7.2 Methodology 14

8 COAL HANDLING PLANT 15

8.1 Introduction 15

12 TURBINE OPERATION, MAINTAINANCE AND 31

ITS AUXILIARIES

12.1 Introduction 31

12.2 Working Principle of Steam Turbine 31

12.3 Types of Steam Turbine 31

12.4 Construction and Steam Flow 31

12.5 Valves 32

12.6 Turbine Governing System 32

12.7 Oil Supply System 33

12.8 Turbine Monitoring System 33

12.9 Fixed Points 33

12.10 Steam Turbine starts up 36

12.11 Precautions during Running 36

8.2 Coal 15

8.3 Types of Coal 15

8.4 Coal in India 16

8.5 General Working of CHP 16

9 WATER TREATMENT PLANT 18

9.1 Introduction 18

9.2 Water Treatment Process 18

10 BOILER WATER MONITORING 21

11 BOILER OPERATION, MAINTAINANCE AND 22

ITS AUXILIARIES

11.1 Introduction 22

11.2 Boiler Main Process 22

11.3 Types of Boiler Used in Power Plant 22

11.4 Boiler Main Auxiliaries 24

11.5 Improving Boiler and Overall Efficiency of Plant 27

11.6 Flue Gas Path 27

11.7 Boiler Auxiliaries Specifications 29

12.12 Materials for Steam Turbine Design 36

13 GENERATOR 37

13.1 Introduction 37

13.2 Principle of Generation 37

14 STEAM CONDESING SYSTEM 39

14.1 Introduction 39

14.2 Steam Condensing System Components 39

15 BOILER FEED WATER PUMP 43

15.1 Introduction 43

15.2 Construction and Operation 43

16 ASH HANDLING PLANT 44

16.1 Introduction 44

16.2 Types of Coal Ash 44

16.3 Bottom Ash System 45

16.4 Fly Ash System 45

16.5 Areas of Fly Ash Utilization 45

17 ENERGY CONSERVATION AND ENERGY AUDIT 48

17.1 Energy Conservation 48

17.2 Audit 48

18 CONCLUSION 49

19 SUGGESTIONS 50

List of Figures and Tables

S. No. Figure Name Page No.

1 2.1 India’s Installed Capacity by Source 4

2 2.3 Indian Generation Capacity (in MW) 5

3 2.3 India’s GDP Variation with Energy Consumption 5

4 4.1 Nashik Thermal Power Station 9

5 5.1 Rankine or Steam Cycle 11

6 5.2 T-s Diagram of Modified Rankine (Reheat) Cycle 12

7 5.3 Energy Conversion in TPS 12

8 6.1 Plant Layout 13

9 6.2 Typical View of Thermal Power Plant 13

10 8.1 Constituents of Coal 15

11 8.2 Coal Handling Plant 16

12 9.1 Pre-Treatment Plant Flow Diagram 19

13 9.2 Softening Plant Flow Diagram 19

14 11.1 Tangential Fired Boiler 23

15 11.2 Balance Draft Boiler 23

16 11.3 Coal and Flue Gas Cycle 26

17 12.1 Steam Turbine and Regenerative Heating 33

18 12.2 Steam Turbine Rotor 33

19 13.1 Turbo-Generator 36

20 13.2 Generator Transformer 36

21 14.1 Diagram of Typical Water Cooled Condenser 40

22 16.1 Electrostatic Precipitator 46

23 16.2 Typical View of Ash Handling Plant 47

Table Name

24 4.1 Capacity of Units 8

25 8.1 Coal Mill Technical Specifications 17

26 8.2 Coal Feeder Technical Specifications 17

27 9.1 Boiler Water Parameters 20

28 11.1 Boiler Technical Specifications 23

29 11.2 Boiler Parameters 24

30 11.3 Required Boiler Auxiliaries 25

31 11.4 Flue Gas Parameters at Various Stages 28

32 11.5 Materials for Boiler Tubes 29

33 11.6 ID Fan Technical Specifications 29

34 11.7 PA Fan Technical Specifications 29

35 11.8 FD Fan Technical Specifications 30

36 11.9 Air Pre-Heater Technical Specifications 30

37 12.1 Turbine Technical Specifications 34

38 12.2 Oil Pump Technical Specifications 34

39 14.1 Condenser Technical Specifications 42

40 15.1 BFP Technical Specifications 43

ABSTRACT

A thermal power station is a power plant in which the prime mover is steam driven. Water is

heated, turns into steam and spins a steam turbine which drives an electrical generator. After

it passes through the turbine, the steam is condensed in a condenser and recycled to where it

was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal

power stations is due to the different fuel sources. Some prefer to use the term energy centre

because such facilities convert forms of heat energy into electricity. Some thermal power

plants also deliver heat energy for industrial purposes, for district heating, or for desalination

of water as well as delivering electrical power. A large part of human CO2 emissions comes

from fossil fuelled thermal power plants; efforts to reduce these outputs are various and

widespread. At present 54.09% or 93918.38 MW (Data Source CEA, as on 31/03/2011) of

total electricity production in India is from Coal Based Thermal Power Station. A coal based

thermal power plant converts the chemical energy of the coal into electrical energy. This is

achieved by raising the steam in the boilers, expanding it through the turbine and coupling the

turbines to the generators which converts mechanical energy into electrical energy.

1

CHAPTER 1

HISTORY OF POWER SECTOR

1.1 INTRODUCTION: -

The electric power industry provides the production and delivery of electric energy, often

known as power, or electricity, in sufficient quantities to areas that need electricity through

a grid connection. The grid distributes electrical energy to customers. Electric power is

generated by central power stations or by distributed generation.

Although electricity had been known to be produced as a result of the chemical reactions that

take place in an electrolytic cell since Alessandro Volta developed the voltaic pile in 1800, its

production by this means was, and still is, expensive. In 1831, Faraday devised a machine

that generated electricity from rotary motion, but it took almost 50 years for the technology to

reach a commercially viable stage. In 1878, in the US, Thomas Edison developed and sold a

commercially viable replacement for gas lighting and heating using locally generated and

distributed direct current electricity.

Additionally, Robert Hammond, in December 1881, demonstrated the new electric light in

the Sussex town of Brighton in the UK for a trial period. In early 1882, Edison opened the

world’s first steam-powered electricity generating station at Holborn Viaduct in London,

where he had entered into an agreement with the City Corporation for a period of three

months to provide street lighting. In time he had supplied a number of local consumers with

electric light. The method of supply was direct current (DC).

It was later on in the year in September 1882 that Edison opened the Pearl Street Power

Station in New York City and again it was a DC supply. It was for this reason that the

generation was close to or on the consumer's premises as Edison had no means of voltage

conversion. The voltage chosen for any electrical system is a compromise. Increasing

the voltage reduces the current and therefore reduces the required wire thickness.

Unfortunately it also increases the danger from direct contact and increases the required

insulation thickness. Furthermore some load types were difficult or impossible to make work

with higher voltages. The overall effect was that Edison's system required power stations to

1

2

be within a mile of the consumers. While this could work in city centres, it would be unable

to economically supply suburbs with power.

The mid to late 1880's saw the introduction of alternating current (AC) systems in Europe and

the U.S. AC power had an advantage in that transformers, installed at power stations, could

be used to raise the voltage from the generators, and transformers at local substations could

reduce voltage to supply loads. Increasing the voltage reduced the current in the transmission

and distribution lines and hence the size of conductors and distribution losses. This made it

more economical to distribute power over very long distances. Generators (such

as hydroelectric sites) could be located far from the loads. AC and DC competed for a while,

during a period called the War of Currents. The DC system was able to claim slightly greater

safety, but this difference was not great enough to overwhelm the enormous technical and

economic advantages of alternating current which eventually won out.

1.2 MARKET REFORM: -

There has been a movement towards separating the monopoly parts of the industry, such as

transmission and distribution sectors from the contestable sectors of generation and retailing

across the world. This has occurred prominently since the reform of the electricity supply

industry in England and Wales in 1990. In some countries, wholesale electricity markets

operate, with generators and retailers trading electricity in a similar manner to share and

accuracy.

3

CHAPTER 2

HISTORY OF INDIAN POWER SECTOR

2.1 INTRODUCTION: -

The Indian Power Industry before independence was controlled firmly by the British. The

first demonstration of electric light in Calcutta was conducted on 24 July 1879 by P W

Fleury & Co. On 7 January 1897, Kilburn & Co secured the Calcutta electric lighting license

as agents of the Indian Electric Co, which was registered in London on 15 January 1897. A

month later, the company was renamed the Calcutta Electric Supply Corporation. The control

of the company was transferred from London to Calcutta only in 1970. Enthused by the

success of electricity in Calcutta, power was thereafter introduced in Bombay. Mumbai saw

electric lighting demonstration for the first time in 1882 at Crawford Market, and Bombay

Electric Supply & Tramways Company (B.E.S.T.) set up a generating station in 1905 to

provide electricity for the tramway. The first hydroelectric installation in India was installed

near a tea estate at Sidrapong for the Darjeeling Municipality in 1897. The first electric train

ran between Bombay's Victoria Terminus and Kurla along the Harbour Line, in 1925. In

1931, electrification of the metre gauge track between Madras Beach and Tambaram was

started.

The power sector in India has undergone significant progress after Independence. When India

became independent in 1947, the country had a power generating capacity of 1,362

MW. Hydro power and coal based thermal power have been the main sources of generating

electricity. Generation and distribution of electrical power was carried out primarily by

private utility companies. Notable amongst them and still in existence is Calcutta Electric.

Power was available only in a few urban centres; rural areas and villages did not have

electricity. After 1947, all new power generation, transmission and distribution in the rural

sector and the urban centres (which was not served by private utilities) came under the

purview of State and Central government agencies. State Electricity Boards (SEBs) were

formed in all the states. Nuclear power development is at slower pace, which was introduced,

in late sixties. The concept of operating power systems on a regional basis crossing the

political boundaries of states was introduced in the early sixties. In spite of the overall

4

development that has taken place, the power supply industry has been under constant pressure

to bridge the gap between supply and demand.

2.2 PRESENT ENERGY SCENARIO IN INDIA: -

The electricity sector in India had an installed capacity of 205.34 Gigawatt (GW) as

of June 2013, the world's fifth largest.

Thermal power plants constitute 70% of the installed capacity, hydroelectric about

15% and rest being a combination of wind, small hydro, biomass, waste-to-

electricity, and nuclear.

India generated 855 BU (855 000 MU i.e. 855 TW) electricity during 2011-12 fiscal.

Fig. 2.1 India’s Installed Capacity by Source

In terms of fuel, coal-fired plants account for 56% of India's installed electricity

capacity, compared to South Africa's 92%; China's 77%; and Australia's 76%. After

coal, renewal hydropower accounts for 19%, renewable energy for 12% and natural

gas for about 9%.

5

Fig. 2.2 Indian Generation Capacity (in MW)

As of January 2012, one report found the per capita total consumption in India to be

778 kWh.

India is the world's fourth largest energy consumer after United States, China and

Russia.

Fig. 2.3 India’s GDP Variation with Energy Consumption

6

CHAPTER 3

HISTORY OF THERMAL POWER GENERATION

3.1 INTRODUCTION: -

Almost all coal, nuclear, geothermal, solar thermal electric, and waste incineration plants, as

well as many natural gas power plants are thermal. The initially developed reciprocating

steam engine has been used to produce mechanical power since the 18th Century, with

notable improvements being made by James Watt. When the first commercially developed

central electrical power stations were established in 1882 at Pearl Street Station in New York

and Holborn Viaduct power station in London, reciprocating steam engines were used. The

development of the steam turbine in 1884 provided larger and more efficient machine designs

for central generating stations. By 1892 the turbine was considered a better alternative to

reciprocating engines; turbines offered higher speeds, more compact machinery, and stable

speed regulation allowing for parallel synchronous operation of generators on a common bus.

After about 1905, turbines entirely replaced reciprocating engines in large central power

stations.

3.2 THERMAL POWER GENERATION IN INDIA: -

Thermal power plants convert energy rich fuel into electricity and heat. Possible fuels

include coal, natural gas, petroleum products, agricultural waste and domestic trash /

waste.

Coal and lignite accounted for about 70% of India's installed capacity.

India's electricity sector consumes about 80% of the coal produced in the country. A

large part of Indian coal reserve is similar to Gondwana coal.

The installed capacity of Thermal Power in India, as of June 30, 2011, was 115649.48

MW which is 65.34% of total installed capacity.

The state of Maharashtra is the largest producer of thermal power in the country.

7

CHAPTER 4

NASIK THERMAL POWER STATION

4.1 INTRODUCTION: -

Nashik Thermal Power Plant is located at Eklahare village near Nashik in Maharashtra. The

power plant is one of the coal based power plants of Mahagenco (Maharashtra State Power

Generation Company Limited – MSPGCL). Mahagenco has the highest overall generation

capacity and the highest thermal installed capacity amongst all the state power generation

utilities in India. In terms of installed capacity, it is the second highest generation company

after NTPC. Nasik Thermal Power Station comprises of 2x140 MW and 3x210 MW units.

The first 140 MW unit was synchronized on 16th

August 1970 followed by second unit on

21st of March 1971.The cost of unit including civil work was Rs. 56.5 crores each.

Boilers are front fired type from Babcock Wilcock France. Turbines are also from France.

NTPS Stage-II comprises of three units of 210 MW each of BHEL Make. The first 210 MW

units were synchronized on 26th

April 1979 at total project cost of Rs. 94.73 crores. The next

two units i.e. Unit No. 4 and 5 of 210 MW were constructed at the cost of Rs. 143.95 crores

and commissioned on 10th

July 1980 and 30th

January 1981 respectively. Thus total cost of

Stage-II is Rs. 238.68 crores.

Boilers are corner fired of American design. Turbines are of Russian design.

The power station campus include self contained township with all amenities. The entire

complex measures 472 hectare of land on the bank of river Godavari.

The power station with its auxiliary equipment comprise intake pump house on the bank of

river Godavari, a large raw water reservoir divided in two halves, and reservoir pump house,

Water Treatment Plant for clarified and filter water, cooling towers with canals and CW

pump houses and the power station proper with concrete stack, dust collecting plant, boiler

plant, steel building housing the plant and equipment in bunker bay, heater bay, and turbine

bay. Beyond the turbine bay is the outdoor installation of generator transformers, auxiliary

reserve and unit transformers.

About 100 meters away from the powerhouse stack and further beyond are the installations

for fuel oil day storage and pump houses and bulk storages with pump house. Near the power

8

station is the coal storage yard and coal handling plant, comprising crusher house, surge and

reclaim hoppers, wagon tipplers, connecting belt conveyor system with inclined belt

conveyors leading to the power station.

NTPS… a major driving force since 1971 pouring 910 MW and an apex of Golden triangle

of Mumbai, Pune & Nashik. Industrial house of giants like Mahindra, MICO, VIP, Siemens,

Gabriel, CEAT, Raymond, Crompton Greaves, HAL(Hindustan Aeronautics Limited),

Security Press are HT Consumers more than110 MW. The power plant has got ISO

Certification on April 2002.

4.2 INSTALLED CAPACITY: -

Nashik Thermal Power Station has an installed capacity of 890 MW. The plant has 5 units

under operation. The individual units have the generating capacity as follows.

Stage Unit

Number

Installed

Capacity (MW)

Date of

Commissioning Status

Stage I 1 140 August, 1970 Stopped(under

renovation)

Stage I 2 140 March, 1971 Stopped(under

renovation)

Stage II 3 210 April, 1979 Running

Stage II 4 210 July, 1980 Running

Stage II 5 210 January, 1981 Running

Table 4.1 Capacity of Units

9

4.3 TRANSPORT: -

It is on the Bhusawal-Kalyan section of Central Railway. Coal-based thermal power stations

consume large quantities of coal. For example, the Nasik Thermal Power Station consumed

4,626,000 tonnes of coal in 2006-07. Around 80 per cent of the domestic coal supplies in

India are meant for coal based thermal power plants and coal transportation forms 42 per cent

of the total freight earnings of Indian railways.

4.4 SHAKTIMAN A SYMBOL OF VISIONARY RESOURCEFULNESS: -

NTPS built a scrap metal sculpture "SHAKTIMAN”, weighing 27 tones, 17 meter tall one of

its kinds in ASEA recorded in the GUINNES book of records. No doubt it’s a symbol of

innovative idea emerged in word and sprit, inspiring visitors that wealth from waste can be a

reality.

Fig. 4.1 Shaktiman Statue in Guinness Book of World Records In 1991

10

CHAPTER 5

STEAM POWER PLANT

5.1 POWER PLANT: -

A power station (also referred to as generating station, power plant, powerhouse, generating

plant) is an industrial facility for the generation of electric power.

Types of energy available for generation of electrical energy are follows.

1. Thermal Energy

2. Solar Energy

3. Atomic Energy

4. Hydro Power

5. Wind Power

6. Tidal Power

7. Geo-Thermal

8. From Gas

5.2 STEAM POWER PLANT: -

A steam-electric power station is a power station in which the electric generator

is steam driven. Water is heated, turns into steam and spins a steam turbine. After it passes

through the turbine, the steam is condensed in a condenser. The greatest variation in the

design of steam-electric power plants is due to the different fuel sources.

For a steam power plant, practical thermal cycle was suggested by Rankine called Ideal cycle

or Rankine cycle. A steam power plant continuously convert the energy stored in fossil fuels

(Coal, Oil, Natural Gas) or fissile fuels (Uranium, Thorium) into shaft power into shaft work

and ultimately into electricity. The working fluid is water, which is sometimes in liquid phase

and sometimes in the vapour phase during its cycle of operations. Figure below illustrate a

fossil-fuelled power plant as a bulk energy converter from fuel to electricity using water as

working medium. Energy released by burning of fuel is transferred to water by boiler (B) to

generate steam at a high pressure and temperature, which expands in the turbine (T) to a low

pressure to produced shaft work. The steam leaving the turbine condensed into water in the

condenser (C) where cooling water from river or sea circulates carrying away the heat

11

released during condensation. The water (condensate) is then fed back to the boiler by the

pump (P), and the cycle goes on repeating itself.

5.3 THERMAL POWER STATION WORKS ON ‘RANKINE CYCLE’

Main Components of TPS

1. Boiler

2. Turbine

3. Condenser

4. Boiler feed pump

5. Generator

Fig. 5.1 Rankine or Steam Cycle

12

Fig. 5.2 T-s Diagram of Modified Rankine (Reheat) Cycle

Fig. 5.3 Energy Conversion in TPS

Furnace Chemical to

Heat

Boiler

Heat energy converts water to saturated

Steam

Turbine

Heat energy into Kinetic

Energy

Turbine

Kinetic energy into Mechanical

Work

Generator Mechanical to Electrical

Energy

13

CHAPTER 6

THERMAL POWER STATION VIEWS

Fig. 6.1 Plant Layout

Fig. 6.2 Typical View of Thermal Power Plant

14

CHAPTER 7

POWER PLANT WATER INTAKE

7.1 INTRODUCTION: -

A systematic study has been carried out to assess the water quality at downstream of

Godavari river at Nashik city and its impact on Nashik Thermal Power Station, Eklahare.

Water samples from six sampling stations were collected monthly, during period March 08 –

April 09 and physic-chemical and chemical parameters were analyzed by the standard

methods. The pollution level over a period of time is increasing on the river water mainly due

to sewage, industrial and other wastewaters are directly discharge in the river. The use of

Godavari river water is, mainly for domestic, industrial, agricultural purpose and huge

amount of water is also utilized by Nashik Thermal Power Station for electricity generation.

The intake water lifted by Nashik Thermal Power Station is from downstream of the

Godavari River i.e. after Gangawadi. For treatment of such contaminated water huge

chemicals are required for production of filtered water (sump water), which leading to high

chemical cost. To overcome from these difficulties due to polluted water, the quality

assessment of intake water of Nashik Thermal Power Station is necessary for cost effective

generation.

7.2 METHODOLOGY: -

The pumping station consists of a box open on the riverside. Two, equally spaced pillar walls

at the inside base of the box dived the river approach into three equal bay. Trash racks are

provided at the entry of each bay to arrest the floating debris coming with river water. Due to

shifting flow of river water bunds with the help of sand bags are sometimes used to diver the

flow of river water along the pump house. Sand also accumulates in front of pump house. A

dredging arrangement is there to remove the sand from front of the Pump House.

There are four vertical mixed flow type water pumps. These are placed in line in a common

basin behind three partitioned bays. All the pumps are motor driven. Motor operated,

butterfly types discharge valves are provided for the pumps.

15

CHAPTER 8

COAL HANDLING PLANT

8.1 INTRODUCTION: -

In thermal power plant coal is a principal fuel, hence design & layout of coal handling plant

is important.

8.2 COAL: -

Coal is a non renewable solid fuel formed by a series of geochemical process from the

plant remains accumulated together with other sediments.

For calculating usefulness of coal as a fuel it is analyzed by two types

i. Proximate Analysis: Determines moisture, ash, volatile matter and fixed carbon

percentage

ii. Ultimate Analysis: Determines carbon, hydrogen, nitrogen, sulfur and oxygen within

coal.

Main constituents of coal are

ffffffigFf

Fig. 8.1 Constituents of Coal

8.3 TYPES OF COAL: -

According to quality (carbon content), the coal may be divided into following classes:

16

i. Anthracite: - It is the best quality coal and its carbon content is as much as 92% with

a low volatile matter and very little moisture. It is hard and heavy and burns with

great heat.

ii. Bituminous: - It is also of good quality coal next to Anthracite. Its carbon content is

up to 85%. Coal mined in India, is mainly of bituminous type of Gondwana age.

iii. Sub-bituminous: -It is a type of coal whose properties range from those of lignite to

those of bituminous coal and are used primarily as fuel for steam-electric power

generation. Sub-bituminous coals may be dull, dark brown to black, soft. They

contain 15-30% inherent moisture by weight and are non-coking.

iv. Lignite: - It is inferior quality coal, full of moisture and volatile matter. Its carbon

content is less than 50%. It is also known as ‘brown coal’.

v. Peat: - It is the first stage in the formation of coal. It is light and woody and has poor

heating capacity.

8.4 COAL IN INDIA: -

The common coals used in Indian industry are bituminous and sub-bituminous coal. The

calorific value of Indian coal ranges from 4000-5000 Kcal/kg. Apart from low calorific value,

Indian coal suffers from high ash content (15-45%) which is about 30-40%.The good thing

about Indian coal is its low sulphur content.

8.5 GENRAL WORKING OF CHP

Fig. 8.2 Coal Handling Plant

17

Coal Mill: -

A pulveriser or grinder is a mechanical device for the grinding of many different types of

materials. For example, a pulveriser mill (Coal Mill) is used to produce pulverize coal for

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

Types of Coal Mills

i. Bowl Mill (Medium Speed)

ii. Ball & Race Mill (Medium Speed)

iii. Ball and Tube Mill (Low Speed)

TECHNICAL SPECIFICATIONS OF COAL MILL AND COAL FEEDER:-

Coal Mill

MAKE BHEL MAKE BHEL

CAPACITY

31.4 T/HR CAPACITY 320 KW

TYPE XRP 763 BOWL MILLS VOLTAGE 6.6 KV

HRDGROOVE

IN 72 % ( 200 MESH) CURRENT 37 AMP

MILL

OUTLET T 80-85 ºC SPEED 990 RPM

Table 8.1 Coal Mill Technical Specifications

Coal Feeder

MAKE MITSUBHISHI SPEED 1430 RPM

TYPE

PIV ROTARY COAL

FEEDER CURRENT 7.6 AMP

CAPACITY

3.7 KW VOLTAGE 415 V

Table 8.2 Coal Feeder Technical Specifications

18

CHAPTER 9

WATER TREATMENT PLANT

9.1 INTRODUCTION: -

Nashik Thermal Power Station is situated at the bank of Godavari River at Eklahare Village.

Godavari River is the only source of raw water for Nashik Thermal Power Station for

Electricity Generation and other purpose. Raw water quality at Nashik TPS is much typical

and contaminated due to release of raw sewage, untreated effluents from various Chemical

Industries, various domestic effluents etc. from up-stream. Most of the period during the year,

the water contains impurities beyond removal by way of existing conventional system. Due

to deteriorated Godavari river water quality, separate arrangement of Darna River water for

drinking purpose is made for NTPS colony residents.

9.2 WATER TREATMENT PROCESS: -

i. River water contains a lot of impurities such as algae, fungi, dead vegetation and

mineral matter in the form of dissolved solids.

ii. This water is fed after treatment to boiler water system, cooling water system and for

domestic purpose.

The treatment is done in two stages –

i. First Stage: - Pre-treatment

Maximum impurities except total dissolved solids and colloidal silica are removed in

this treatment.

ii. Second Stage: - Post Treatment

a) Demineralization: - Perfectly pure water is produced by ion exchange process by

passing the filtered water through the resins. This water is fed to the boiler feed water

system.

b) Softening: - Hardness causing elements such as Calcium and Magnesium are

removed in this process. This water is used for cooling water system.

c) Domestic water: - Chlorination / Bleaching Powder dosing is arranged to the filtered

water so as to make it suitable for drinking purpose.

Average Incoming River water Parameters are –

19

TH – Min – 90 ppm Max – 350 ppm

TCl – Min – 20 ppm Max – 250 ppm

Details of above treatment processes is as under-

Pretreatment Plant: -

i. River water is taken at river water inlet chamber at W. T. Plant where the chemicals

such as alum, lime /bleaching powder, PAC etc. are added.

ii. In this process flocks are formed due to addition of alum / lime which are removed in

settling tank / clarifier.

Fig. 9.1 Pre-Treatment Plant Flow Diagram

Softening Plant: -

Water is passed through base exchangers where hardness causing elements i.e. calcium and

magnesium are removed to get soft water.

Fig. 9.2 Softening Plant Flow Diagram

R – Na + Ca / Mg = R – Ca / Mg + Na

Resin Hard Water Soft Water

Regeneration of Base Exchanger resin is done by using Common Salt, Reaction of which is –

R- Ca / Mg + NaCl = R – Na + Ca / Mg

Salt Resin Effluent

Demineralization: -

Minerals are removed from the filtered water by ion exchange process. Cations (positive

ions) and Anions (Negative ions) are removed from the water one by one using Resin which

FILTERED FILTERED BASE

WATER WATER EXCHANGER SOFT C. T.

SUMP PUMP WATER POND

RIVER Alum,Lime SETTLING RAPID FILTERED

WATER KmnO4 TANK(STG-1) SAND WATER

INTAKE PAC,Bleaching CLARIFIER GRAVITY SUMP

CHAMBER Powder (STG-2) FILTER

RIVER

PUMP

20

is an organic material having the capacity to exchange ions in the water with the active group

on the resin.

Chemical reactions in Regular Process are

i. Reaction in Cation Exchanger-

Na Cl Na Cl

Ca CO3 + R – H = R ---Ca + H --- CO3

Mg SiO3 Resin Mg SiO3

ii. Reaction in Anion Exchanger-

Cl Cl

H--- SO4 + R – OH = R--- SO4 + OH - H / H2O

SiO3 Resin SiO3

Chemical reactions during Regeneration Process are

i. Reaction in Cation Exchanger-

Na Na Cl

R ---Ca + HCl = R-H + Ca Cl2

Mg Mg Cl2

ii. Reaction in Anion Exchanger-

Cl Cl

R ---SO4 + NaOH = ROH + Na--- SO4

SiO3 SiO3

Recommended Boiler water parameters – Stage – II (210 MW)

Table 9.1 Boiler Water Parameters

Drum Operating Pressure

Kg / cm2

126 – 165

M/S BHEL

Recommendation

Parameters at NTPS

Treatment Type

Phosphate

Phosphate

pH at 25 0 C

9.4 - 9.7

9.4 to 9.6

Conductivity at 25 0 C

mhos/cm

100

< 35

21

CHAPTER 10

BOILER WATER MONITERING

i. D. M. water which is produced for feeding to boiler water system is having pH 7.0 and

Conductivity less than 1.0 micromhos / cm, Silica - NIL.

ii. This water is very sensitive and atmospheric CO2 gets immediately mixed with it to

make it acidic which is not desirable, so chemical dosing is done in boiler feed water.

iii. Dissolved oxygen is also present in the D.M. water which is responsible for corrosion.

85 % of dissolved oxygen is removed in deaerator in feed water system.

iv. Hydrazine dosing is arranged through L.P dosing pump at BFP suction for scavenging

residual dissolved oxygen in the system water to avoid corrosion of metal surface.

v. pH of D. M. make up water at condenser is about 6.8 to 6.9 ( which is not desirable ) is

increased to about 8.8 by dosing Ammonia solution along with Hydrazine through L.P.

dosing pump.

vi. Colloidal Silica (which is not removed in D.M. Plant) gets transformed to active silica at

Temp. Above 250 deg. Cent. And it appears in boiler drum water.

vii. Silica in the form of silicates is hazardous in boiler water as it gets evaporated to steam

and gets deposited directly on the turbine blades as too hard deposits.

CONCLUSION: -

i. The rotation of water is decided by the Govt. as per the agricultural requirement.

ii. Normally the water cycle is about 10 days per month throughout the year.

iii. Due to these reasons, water gets contaminated for about 200 days per year.

iv. Such type of contaminated water has to be treated in W.T. Plant before its utilization

for electricity generation.

v. Nashik TPS is situated on the downstream of Godavari River and all the waste water

effluents from Nashik City, Nashik Road area, chemical effluent released from MIDC

Industries etc. gets mixed with the Godavari River which lastly comes to NTPS Dam.

22

CHAPTER 11

BOILER OPERATION, MAINTAINANCE AND ITS AUXILIARIES

11.1 INTRODUCTION: -

Steam boiler or simply a boiler is basically a closed vessel into which water is heated until

the water is converted into steam at required pressure. The utility boilers are large capacity

steam generators used purely for the electrical power generation. In boiler heat energy is

released from the combustion of fossils fuel and heat is transferred to different fluids in the

system and a part of it is lost or left out as unutilized.

The basic working principle of boiler is very simple and easy to understand. The boiler is

essentially a closed vessel inside which water is stored. Fuel (generally coal) is bunt in a

furnace and hot gasses are produced. These hot gasses come in contact with water vessel

where the heat of these hot gases transfer to the water and consequently steam is produced in

the boiler. Then this steam is piped to the turbine of thermal power plant. There are many

different types of boiler utilized for different purposes like running a production unit,

sanitizing some area, sterilizing equipment, to warm up the surroundings etc.

11.2 BOILER MAIN PROCESS: -

i. Send DM water to the boiler through boiler drum to boiler tubes.

ii. Sending fuel (furnace oil and coal) to the boiler through dampers (3000 MT/day).

iii. Sending required amount of primary (300T/hr) and secondary air (600T/hr) to the

boiler.

iv. Supplies superheated steam (5400C) of adequate temperature and pressure to turbines.

v. Extracting flue gases from the boiler and discharging them to atmosphere.

vi. Removing bottom ash formed as a result of combustion process.

vii. Removing fly ash from electrostatic precipitator hoppers.

11.3 TYPES OF BOILER USED IN POWER PLANTS: -

Conventional, Single Drum, Tangentially fired, balanced draught, Natural Circulation,

Radiant Reheat Type, Dry Bottom with Direct Fired Pulverized Coal with Bowl Mill or with

Fuel Oil.

23

Fig. 11.1 Corner Fired Boiler Fig. 11.2 Balance Draft Boiler

210 MW BOILERS TECHNICAL SPECIFICATIONS: -

BOILER TYPE

TANGENTIALLY FIRED OR CORNER FIRED

COAL

BITUMINOUS COAL

FC VM MOIST

37.30% 27.60% 10%

ASH GRINDABILITY CV

25% 50 HGI 5000 KCAL/KG

FURNACE WIDTH DEPTH VOLUME

13.8C8M 10.592M 5495 M³

TYPE FUSION WELDED TYPE

WARM UP OIL

LIGHT DIESEL OIL

TOTAL HEATING

SURFACE AREA

22862.10 SQ.M

Table 11.1 Boiler Technical Specifications

24

FEED WATER CYCLE: -

DM Water – Feed Storage Tank – Boiler Feed Pump – HP Heaters –LP Heaters – Feed

Station – Economizer – Boiler Drum – Boiler Tubes

BOILER PARAMETERS: -

MAIN STEAM FLOW @ SH OUTLET

700 T/HR

MAIN STEAM TEMP @ SH OUTLET

540 ºC

MAIN STEAM PRES @ SH OUTLET

137 KG/CM²

REHEAT STEAM FLOW

578.3T/HR

REHEAT STEAM TEMP @REHEAT OUTLET

540 ºC

REHEAT STEAM PRESSURE@REHEAT OUTLET

25.1 KG/CM²

REHEAT STEAM PRESSURE@REHEAT INLET

27 KG/CM²

FEED WATER TEMP. ECONOMISER INLET

247 ºC

Table 11.2 Boiler Parameters

11.4 BOILER MAIN AUXILIARIES: -

Auxiliaries of steam boiler are devices that be installed to the steam boiler, and can make it

operates efficiently. These devices should be maintained and controlled, so steam boiler can

run in good condition. Some of auxiliaries which are installed in steam boiler are:

11.4.1 COAL CYCLE: -

Coal is pulverized and feed into the boiler in the following steps-

• Coal mine - unshaped, unsized raw bituminous coal –crusher – bunker (stack).

• Coal bunkers (20mm size coal) – coal feeders (controlling input to coal mill) – coal

mills.

• Powder, pulverized coal lifted by primary air and sending through coal pipes - coal

dampers - to furnace for combustion.

25

11.4.2 FUEL (FO / LDO) OIL CYCLE: -

• Furnace Oil (FO) / Light Diesel Oil (LDO) Tanks – Fuel Oil Pumps – Heaters

(Steam) – Oil Dampers - Oil Guns – To Furnace

• Furnace Oil Is Non Explosive, Difficult To Ignite In Bulk, No Spontaneous

Combustion

• Expensive Rs. 45-60 Thousand/Kl

BOILER AUXILIARIES QUANTITY IN NUMBERS

AIR HEATERS 02 NOS.

FUEL OIL PUMPS 03 NOS.

OIL GUNS / IGNITORS 12 NOS. (4 NOS. AT 1 ELEVATION)

COAL MILLS 06 NOS.

PRIMARY AIR FANS 02 NOS.

FORCE DRAFT FANS 02 NOS.

INDUCED DRAFT FANS 02 NOS.

BOILER FEED PUMPS 03 NOS.

EMERGENCY LIFT PUMPS 02 NOS.

SEAL AIR FANS 02 NOS.

SCANNER FANS 02 NOS.

BOTTOM ASH GRINDERS 04 NOS.( 2NOS. FOR ONE PASS)

ELECTROSTATIC PRECIPETATOR 24 ESP FIELDS (48 HOPPERS)

Table 11.3 Required Boiler Auxiliaries

11.4.3 AIR CYCLE: -

• Primary Air Fans: – Mixture cold & hot air supplies to lifting coal to furnace.

• Forced Draft Fans: – Supplies hot air required for combustion. The function of

forced draft fans is to supply the combustion air initially, when no coal firing is taking

place. But once the coal firing starts, the function of forced draft fan remains only to

supply air required for completing combustion process.

26

• Balanced Draft: - Balanced draft is obtained through use of both induced and forced

draft. This is more common with larger boilers where the flue gases have to travel a

long distance through many boiler passes. The induced draft fan works in conjunction

with the forced draft fan allowing the furnace pressure to be maintained slightly

below atmospheric.

• Induced Draft Fans: – Maintain continuity of combustion and maintain negative

pressure (-ve). Extract flue gases from furnace and discharge them to atmosphere.

• Primary Air: - This air lifts the pulverized coal from the coal mills & enters the

boiler with it. The primary air quantity is less with pressure higher so that it can lift

the coal. This air is also used to dry the coal.

• Secondary Air: - As air supplied wet coal (Primary air) is less in quantity it is not

sufficient for complete combustion & some quantity of air must be supplied

additionally to complete combustion. This is called secondary air.

• Seal Air Fans: - These fans take the suction from cold air duck of primary air system

& their discharge goes to the sealing of gear box of coal mills & its rollers for bearing

sealing.

• Scanner Fans: - Scanner fans air supply the cooling air necessary for the cooling of

costly scanner heads. Scanner heads may get damaged if not cooled, leading to outage

of units. These fans take their suction from the discharge of FD in the discharge of

these fans goes to scanner after getting filtered. In case of AC failure when FD fans

trip, there is provision to provide suction to these fans from atmosphere.

• Soot Blower System: - The fuel used in thermal power plants causes soot and this is

deposited on the boiler tubes, economizer tubes, air pre heaters, etc. This drastically

reduces the amount of heat transfer of the heat exchangers. Soot blowers control the

formation of soot and reduce its corrosive effects. The types of soot blowers are fixed

type, which may be further classified into lane type and mass type depending upon the

type of spray and nozzle used. The other type of soot blower is the retractable soot

blower. The advantages are that they are placed far away from the high temperature

zone, they concentrate the cleaning through a single large nozzle rather than many

small nozzles and there is no concern of nozzle arrangement with respect to the boiler

tubes.

27

11.5 IMPROVING BOILER AND OVERALL EFFICIENCY OF PLANT: -

• Economizer: - Absorbs heat from flue gas and add this sensible heat to feed water

before water enters to Boiler. The justifiable cost of the economizer depends on the

total gain in efficiency. In turn this depends on the flue gas temperature leaving the

boiler and the feed water inlet temperature.

• Air Pre-Heater: -Flue gases passes through Heater tubes and Cold air passes through

air heater heated up and Hot air used for combustion. An air preheater or air heater is

a general term to describe any device designed to heat air before another process (for

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

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

system or to replace a steam coil.

• Super Heaters: - The super heater is a heat exchanger in which heat is transferred to

the saturated steam to increase its temperature. It raises the overall cycle efficiency. In

addition, it reduces the moisture content in the last stages of the turbine and thus

increases the turbine efficiency. The superheater consists of a superheater header and

superheater elements. Steam from the main steam pipe arrives at the saturated steam

chamber of the superheater header and is fed into the superheater elements.

Superheated steam arrives back at the superheated steam chamber of the superheater

header and is fed into the steam pipe to the cylinders. Superheated steam is more

expansive.

• Reheater: - The reheater functions similar to the superheater in that it serves to

elevate the steam temperature. Primary steam is supplied to the high pressure turbine.

After passing through the high pressure turbine, the steam is returned to the steam

generator for reheating (in a reheater) after which it is sent to the low pressure turbine.

A second reheat cycle may also be provided.

11.6 FLUE GAS PATH: -

• Whenever combustion takes place chemical energy converted into heat energy

(depends on CV).

• Various gases CO2, SO2, N2, water vapor produced.

• Heat carried away through flue gas is used in Air Heater & Economizer to improve

Boiler Efficiency.

28

• Temperature of the flue gases at various stages is given below in the index for (210

MW) Rated output plant. Parameters of flue gas may vary from one plant to other.

Table 11.4 Flue Gas Parameters at Various Stages

Eco

Drum

S/H R/H S/H

LTSH

Boiler

WindBox

APH

S/H

ESP

ID fan

Coal

Bunker

Coal Mill

Feeder

FD Fan

PA Fan

Coal from

CHP

Chimney

COAL AND FLUE GAS CYCLE

HFO

Fig. 11.3 Coal and Flue Gas Cycle

FLUE GAS PATH OUTLET TEMPERATURE

IN 0 C

FURNACE 1123

PLATTERN SUPER HEATER 1010

REHEATER FRONT 823

REHEATER REAR 765

FINAL SUPER HEATER 662

HORIZONTAL SUPER HEATER 479

ECONOMISER 369

AIR HEATER 140

E.S.P. 125

I.D.FAN 120

CHIMNEY 120

29

Materials used for the boiler tubes as per ASME: -

Material

ASTM

Specification

Grade

Temperature

Carbon Steel

SA 210

A1

450oC

Carbon ¼ % MO Steel

SA 209

T1

480Oc

1 % Cr, ½ % MO Steel

SA 213

T11

550oC

2 ½ % Cr, 1 % MO Steel

SA 213

T22

580oC

18% Cr, 8 % Ni Stainless Steel

SA 213

T304

Up to 700oC

Table 11.5 Materials for Boiler Tubes

11.7 BOILER AUXILIARIES SPECIFICATIONS: -

Induced Draft Fan: -

MOTOR UNIT NO.3 UNIT NO.4 UNIT NO.5 FAN

MAKE BHEL BHEL BHEL MAKE BHEL

CAPACITY 1700 1300 1300 CAPACITY 232.5M³/SEC

SPEED 990 990 990 TYPE

AXIAL

IMPULSE

VOLTAGE 6.6 6.6 6.6 SPEED 990 RPM

CURRENT 175 138 138 NO. OF

FAN /

BOILER 2

Table 11.6 ID Fan Technical Specifications

Primary Air Fan: -

MAKE BHEL MAKE BHEL , KKK

CAPACITY 1250 KW TYPE SINGLE SUCTION RADIAL

VOLTAGE 6.6 KV FAN SIZE NDF-21 b U#3

FAN SIZE NDFV-22b U#4&5

SPEED 1480 RPM CAPACITY 70.33 M³/SEC

Table 11.7 PA Fan Technical Specifications

30

Forced Draft Fan: -

Table 11.8 FD Fan Technical Specifications

Air Pre-Heater: -

TYPE

TRISECTOR ROTARY AIR

PREHEATER(LIUNGSTORM) MAIN DRIVE MOTOR

SIZE 27 VI 72 MAKE

CROMPTON

GREAVES

NO OF AIR HEATERS 2 CAPACITY 11 KW

INSTALLED POSITION VERTICAL VOLTAGE 415 V

HEIGHT OF HOT END

LAYER 1067 MM CURRENT 22 AMP

HEIGHT OF

INTERMEDIATE LAYER 457 MM SPEED 1440 RPM

HEIGHT OF COLD END

LAYER 305 MM DRIVE

MOTOR 2 NOS.

GAS TEMP. 141 ºC

Table 11.9 Air Pre-Heater Technical Specifications

MOTOR UNIT NO.3 UNIT NO.4 UNIT NO.5 FAN

MAKE BHEL BHEL BHEL MAKE BHEL

CAPACITY 630 750 750 CAPACITY 105.5 M³/SEC

SPEED 990 1491 1491 TYPE OF

FAN

AXIAL

IMPULSE

VOLTAGE 6.6 6.6 6.6 FAN TYPE AN 20e6 U#3

CURRENT 68 79 79 TYPE OF

FAN

AXIAL

REACTION

IGV

OPERATIO PNEUMATIC HYDRAULIC HYDRAULIC FAN TYPE

API-18/11

U#4&5

31

CHAPTER 12

TURBINE OPERATION, MAINTAINANCE AND ITS AUXILIARIES

12.1 INRODUCTION: -

Turbine is an engine that converts energy of fluid into mechanical energy. The steam turbine

is steam driven rotary engine.Steam Turbine Converts the Heat Energy (Kinetic Energy) into

Mechanical Energy.

12.2 WORKING PRINCIPLE OF STEAM TURBINE: -

i. A steam turbine works on the principle of conversion of High pressure & temperature

steam into high Kinetic energy, thereby giving torque to a moving rotor.

ii. For above energy conversion there is requirement of converging /Converging-

Diverging Sections.

iii. Such above requirement is built up in the space between two consecutive blades of

fixed and moving blades rows.

12.3 TYPES OF STEAM TURBINE: -

According to the principle of action of the steam, turbine can be classified as:

i. Impulse Turbine: - In a stage of Impulse turbine the pressure/Enthalpy drop takes

place only in fixed blades and not in the moving blades.

ii. Reaction Turbine: - In a stage of Reaction Turbine the Pressure/enthalpy drop takes

place in both the fixed and moving blades.

TURBINES IN NTPS NASHIK: -

210 MW Turbine at Nashik is three cylinders (HP, IP, LP) Tandem compound with nozzle

governing, condensing & regenerative feed heating type.

• The HPT comprises of 12 stages, the first stage being governing stage.

• The IPT comprises of 11 stages.

• The LPT has 4+4 stages .Steam enters at middle & flows in opposite paths having

four stages.

Turbine rotors are supported on five bearings .The common bearing of HP & IP rotor is a

combined journal & radial thrust bearing. Rest four bearings are journal bearings.

12.4 CONSTRUCTION AND STEAM FLOW: -

32

The turbine is tandem compound machine with HP, IP, & LP parts. The HP part is a

single flow cylinder & IP & LP parts are double flow cylinders.

The individual rotors & generator rotor are connected by rigid couplings.

The HP cylinder has a throttle control. The initial steam is admitted before the blading

by two combined main steam stop & control valves.

The lines leading from the two HP exhaust branches to the re heater are provided with

swing a check valve which prevents hot steam from re heater flowing back in to the

HP cylinder.

The steam coming from the re heater is passed to the IP part via two combined reheat

stop & control valves cross around pipes connect the IP & LP cylinders.

Bleeds are arranged at several points of the turbine.

12.5 VALVES: -

It is a mechanical device to control the flow of fluid in pipe. Valves are said to be nerve

centre of power plant controlling high pressure steam & water.

The HP turbine is fitted with two initial steam stop & control valves.

A stop & control valve with stems arranged right angle to each other are combined in

a common body.

The stop valves are spring operated single-seat valves, the control valves, are also of

single seat design, have diffusers to reduce pressure losses.

The IP turbine has two combined reheat stop &control valves.

The reheat stop valves are spring loaded single seat valves.

The control valves, also spring loaded, have diffusers. The control valves operate in

parallel & are fully open in the upper load range.

In the lower load range, they control the steam flow to the IP turbine & ensure stable

operation even when turbo set is supplying only the station load.

Both the main & reheat stop & control valves are supported kinematically on

foundation ceiling below the machine floor before the turbo set.

All valves are individually operated by oil hydraulic servomotors.

12.6 TURBINE GOVERNING SYSTEM: -

33

The turbine has an electro-hydraulic governing system backed with a hydraulic

governing system.

An electric system measures & controls speed & output, & operate the control valves

hydraulically in conjunction with an electro hydraulic converter.

The electro hydraulic governing system permits run up control of turbine up to rated

speed & keeps speed swings following sudden load shedding low.

The linear output frequency characteristic can be very closely set even during

operation.

12.7 OIL SUPPLY SYSTEM: -

A single oil supply system lubricates & cools the bearing, governs the machine

operates the hydraulic actuators & safety and protective devices & drives the

hydraulic turning gear.

The main pump is driven by the turbine shaft draws oil from the main oil tank.

Auxiliary oil pumps maintain the oil supply on start up & shut down. During turbine

gear operation & when MOP is faulted.

When the turning gear is stared, jacking oil pumps force high pressure oil under the

shaft journals to prevent boundary lubrication.

The lubricating & cooling oil is passed through oil coolers before oil supply.

12.8 TURBINE MONITORING SYSTEM: -

In addition to measuring instruments & instruments indicating pressures,

temperatures, valve positions &speed, the monitoring system also includes measuring

instruments & indicators for the following values.

Absolute expansion, measured at the front & rear bearing pedestal of the HP turbine.

Differential expansion between the shafting & turbine casing, measured at several

points.

Bearing pedestal vibrations, measured at all turbine bearings.

Relative shaft vibrations measured at all turbine bearings .absolute shaft vibrations,

obtained from bearing pedestal vibration & relative shaft vibration by calculation.

12.9 FIXED POINTS: -

There is no restriction on axial movement of the casings.

34

In designing the supports of the turbine on the foundation, attention is given to the

expansion and contraction of the machine during thermal cycling.

Excessive stresses would be caused in the components if the thermal expansion or

contractions were restricted any way.

The method of attachment of the machine components, and their coupling together,

are also decisive factors in determining the magnitude of the relative axial expansion

between the rotor system & turbine casings, which is given careful attention when

determining the internal clearances in the design.

TURBINE MAIN DATA: -

RATED OUTPUT OF TURBINE

210 MW

RATED SPEED

3000 RPM

RATED PRESSUE OF STEAM BEFORE

EMERGENCY STOP VALVE

130 KG/CM²

RATED LIVE STEAM TEMPERATURE

535 ºC

RATED STEAM PRESSURE

23.20 KG /CM²

RATED STEAM PRESS. AF

535 ºC

STEAM FLOW

616 TON/HR

STEAM FLOW AT VALVE WIDE OPEN

CONDITION

670 TON/HR

RATED PRESSURE AT THE EXHAUST OF LPT

63.3 MM HG COL

RATED CIRCULATING WATER TEMP.

30 ºC

RATED QUALITY OF CIRC 27000 M³/HR

Table 12.1 Turbine Technical Specifications

OIL PUMPS: -

MOTOR PUMP

MAKE

BHEL,HARIDWAR

MAKE

MATHER & PLATT,PUNE

CAPACITY 200 KW SPEED 970 RPM

VOLTAGE 6.6 KV HEAD 220 M

CURRENT 21.8 AMP DISCHARGE 200 M³/HR

SPEED 985 RPM

Table 12.2 Oil Pump Technical Specifications

35

Fig. 12.1 Steam Turbine and Regenerative Heating

Fig. 12.2 Steam Turbine Rotor

36

12.10 STEAM TURBINE STARTS UP: -

When warming up a steam turbine for use, the main steam stop valves (after the boiler) have

a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up

the lines in the system along with the steam turbine. Also a turning gear is engaged when

there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent

uneven expansion. After first rotating the turbine by the turning gear, allowing time for the

rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is

admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the

turbine at 10 to 15 RPM to slowly warm the turbine.

12.11 PRECAUTIONS DURING RUNNING: -

Problems with turbines are now rare and maintenance requirements are relatively small. Any

imbalance of the rotor can lead to vibration, which in extreme cases can lead to a blade letting

go and punching straight through the casing. It is, however, essential that the turbine be

turned with dry steam. If water gets into the steam and is blasted onto the blades (moisture

carryover) rapid impingement and erosion of the blades can occur, possibly leading to

imbalance and catastrophic failure. Also water entering the blades will likely result in the

destruction of the thrust bearing for the turbine shaft. To prevent this, along with controls and

baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam

piping leading to the turbine.

12.12 MATERIALS FOR STEAM TURBINE DESIGN: -

i. Blades

Stainless Steel – 403 & 422 (+Cr)

17-4 PH steel (+ Ti)

Super Alloys

ii. Rotor

High “Chrome – Moley” Steel – Cr-Mo-V

Low “Ni Chrome Steel – Ni-Cr-Mo-V

37

CHAPTER 13

GENERATOR

13.1 INTRODUCTION: -

In electricity generation, a generator is a device that converts mechanical energy to electrical

energy for use in an external circuit. The source of mechanical energy may vary widely from

a hand crank to an internal combustion engine and turbine used in power plants. Generators

provide nearly all of the power for electric power grids.

13.2 PRINCIPLE OF GENERATION: - GENERATION OF AC POWER

The basic requirements for generation of AC power are as follows.

i. Conductor

ii. Magnetic field

iii. Relative speed

Faraday's laws of electromagnetic induction

First Law: - Whenever there is change in magnetic flux associated with a coil, an emf

is induced in it.

Second law: - The magnitude of induced emf is directly proportional to the rate of

change of flux through the coil.

Maximum electric speed to be achieved is 3000 RPM being 50 cycles per sec. is the quality

of electric supply in our India.

Thus maximum speed shall be achieved by 2 poles machine. However multi pole generators

are used for Hydro Power Stations as speed depends upon depth of reservoirs i.e., water

pressure, water head available at first stage of runner of turbine.

38

Fig. 13.1 Turbo-Generator

Fig. 13.2 Generator Transformer

39

CHAPTER 14

STEAM CONDENSING SYSTEM

14.1 INTRODUCTION: -

Thermoelectric power plants boil water to create steam, which then spins turbines to generate

electricity. The heat used to boil water can come from burning of a fuel, from nuclear

reactions, or directly from the sun or geothermal heat sources underground. Once steam has

passed through a turbine, it must be cooled back into water before it can be reused to produce

more electricity. Colder water cools the steam more effectively and allows more efficient

electricity generation.

Wet-recirculating or closed-loop systems reuse cooling water in a second cycle rather than

immediately discharging it back to the original water source. Most commonly, wet-

recirculating systems use cooling towers to expose water to ambient air. Some of the water

evaporates; the rest is then sent back to the condenser in the power plant. Because wet-

recirculating systems only withdraw water to replace any water that is lost through

evaporation in the cooling tower, these systems have much lower water withdrawals than

once-through systems, but tend to have appreciably higher water consumption.

14.2 STEAM CONDENSING SYSTEM COMPONENTS: -

i. Condenser

ii. Cooling tower

iii. Hot well

iv. Condenser cooling water pump

v. Condensate air extraction pump

vi. Air extraction pump

vii. Boiler feed pump

viii. Make up water pump

ix. Deaerator

x. Air Ejector

xi. Drain Cooler

xii. Feed Water Heaters (HP/LP Heaters)

40

Condenser: -

The main purposes of the condenser are to condense the exhaust steam from the turbine for

reuse in the cycle and to maximize turbine efficiency by maintaining proper vacuum. As the

operating pressure of the condenser is lowered (vacuum is increased), the enthalpy drop of

the expanding steam in the turbine will also increase. This will increase the amount of

available work from the turbine (electrical output). By lowering the condenser operating

pressure, the following will occur:

a. Increased turbine output

b. Increased Plant efficiency

c. Reduced steam flow

Fig. 14.1 Diagram of a Typical Water-cooled Surface Condenser

Hot Well: -

These are small storage tank of condensate water below condensers. They are maintained at

required level of condensate with the help of Hot Well Level Controller, provided just before

drain cooler. They are also equipped with make-up lines from DM Storage Tank and Surge

Tank.

Suction Well: -

This is the storage well of condensate water and condensate pump is submerged in this well.

It is provided with continuous vent connection to condenser to maintain the flow of

condensate water from condenser by neglecting its vacuum.

41

Condensate Pump: -

There are two multistage centrifugal condensate pumps but both are capable of delivering

full load individually. It delivers condensate to SPE.

Cooling Tower: -

A cooling tower extracts heat from water by evaporation. In an evaporative cooling tower, a

small portion of the water being cooled is allowed to evaporate into a moving air stream to

provide significant cooling to the rest of that water stream.

Cooling Towers are commonly used to provide lower than ambient water temperatures and

are more cost effective and energy efficient than most other alternatives. The smallest cooling

towers are structured for only a few litres of water per minute while the largest cooling

towers may handle upwards of thousands of litres per minute. The pipes are obviously much

larger to accommodate this much water in the larger towers and can range up to 12 inches in

diameter.

When water is reused in the process, it is pumped to the top of the cooling tower and will

then flow down through plastic or wood shells, much like a honeycomb found in a bee’s nest.

The water will emit heat as it is downward flowing which mixes with the above air flow,

which in turn cools the water. Part of this water will also evaporate, causing it to lose even

more heat.

Steam Packing Exhauster (SPE): -

This is a surface type heat exchanger which transfers the heat energy of packing steam to the

condensate water and condenses packing steam (drip) in turn, which are drained to the

condenser through an atmospheric drain tank. Its shell is equipped with an Air Blower to

evacuate non-condensable gases to atmosphere.

Air Ejector: -

It is a double stage twin steam jet ejector which acts as an air pump. Its main function is to

maintain vacuum by pulling out air and non-condensable gases from the condenser. Exhaust

steam from jet ejector are made to pass from inter and after condenser where heat of jet steam

is transferred to condensate coming from SPE.

42

Drain Cooler: -

The air from condensate water, which is exhausted to atmosphere through a vent condenser.

The bled steam directly condenses and gets mixed with condensate water from heater, and

this is passed to storage tank.

Deaerator: -

A deaerator is a device that is used for removal of oxygen and other dissolved gases from the

feed water to steam-generating boilers. In particular, dissolved oxygen in boiler feed water

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

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

dioxide combines with water to form acid that causes further corrosion.

Feed Water Heaters: -

This item is installed to improve power generator efficiency by heating supplied water and

reducing breakage due to heat stress from temperature differences in boiler tubes. Because a

single heater consists of cooling areas, condensing areas, and heating areas, this item requires

thoughtful engineering and production.

Feed water heaters are classified as low and high pressure heaters with one heater consisting

of overheating, condensing and overcooling areas, making it difficult to design and produce.

Use one or more low pressure feed water heaters to raise the temperature of condensate from

condensate pump discharge temperature to the de-aerator inlet temperature. Use one or more

high pressure feed water heaters to raise the temperature of feed water from de-aerator outlet

temperature to the required boiler economizer inlet temperature.

Condenser Data: -

MAKE BHEL

COOLING SURFACE AREA 14650 M²

NO. OF COOLING TUBES 15652

LENGTH OF COOLING TU 10M

DIA.OF COOLING TUBE 30/28 MM

NO. OF WATER PATHS FOR EACH

CONDENSER 2

DESIGNED CONSUMPTION OF COOLING

WATER 27000 M³/HR

QUANTITY OF STEAM CONDENSING 150 TO 500 T/HR

MAIN EJECTOR 2 NOS.

STARTING EJECTOR 1 NO

Table 14.1 Condenser Technical Specifications

43

CHAPTER 15

BOILER FEED WATER PUMP

15.1 INTRODUCTION: -

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

boiler. The water may be freshly supplied or returning condensate produced as a result of the

condensation of the steam produced by the boiler. These pumps are normally high pressure

units that take suction from a condensate return system and can be of the centrifugal

pump type or positive displacement type.

15.2 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 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. Another

common form of feed water pumps run constantly and are provided with a minimum flow

device to stop over pressuring the pump on low flows. The minimum flow usually returns to

the tank or deaerator.

Boiler Feed Pump Data: -

MOTOR PUMP

MAKE BHEL , HARDWAR MAKE BHEL,HYDERABAD

CAPACITY 4000 KW TYPE 200 KHI

VOLTAGE 6.6 KV NO.OF STGES 6

CURRENT 408 AMP SPEED 4320 RPM

SPEED 1485 RPM LUBRICATION FORCED

Table 15.1 BFP Technical Specifications

HEAD 1830 MLC

DISCHARGE 430 T/HR

44

CHAPTER 16

ASH HANDLING PLANT

16.1 INTRODUCTION: -

To generate one unit, as per design we have to burn 0.55 kg coal. But actually we have to

burn 0.65 kg coal.

Indian coal has

Calorific Value- 5000 Kcal/ Kg.

Fixed Carbon – 38%

Volatile Matter – 26%

Moisture – 8%

Ash Content – 28%.

16.2 TYPES OF COAL ASH: -

Coal ash is the residue of the coal combustion process involved in the thermal power plants.

The types of coal ash from coal based thermal power plants are:

i. Fly Ash: - Collected from different rows of electrostatic precipitator.

ii. Bottom Ash: - Collected at the bottom of boiler furnace.

iii. Pond Ash: - Mixture of bottom ash and fly ash as available in ash disposal ponds.

One 210 mw set requires

0.65*5.04*1000=3276 tonne coal per day.

Ash content is 28%

I.e. 3276*0.28=917.28 tonne i.e. 920 tonne.

Out of this 28% ash

Bottom ash 15 to 20% i.e. 138 to 184 tonne

Fly ash 80 to 85% i.e. 734 to 780 tonne

Contents of ash-

Silica

Alumina

Iron oxide

45

Calcium

Magnesium

Sulphate

Alkalis

16.3 BOTTOM ASH SYSTEM: -

It consists following main components:

Bottom ash hopper

Clinker grinder

Ejector feed pump

Hydro ejector

16.4 FLY ASH SYSTEM: -

The system for all units is identical and following description is applied to both the units the

water compounded bottom ash hopper receives the bottom ash from the furnace from where it

is stores and discharged through the clinker grinder. Two slurry pumps are provided which is

common to all units & used to make slurry and further transportation to ash dyke through

pipeline.

Ash particles are separated by passing through electrical field (Electrostatic Precipitator).

Components in ESP: -

• Discharge electrode (-ve)

• Collecting electrode (+ve )

• Rapping mechanism

• Fly ash hopper

• High tension voltage equipment

16.5 AREAS OF FLY ASH UTILISATION: -

Fly ash can be used for various applications. Some of the major areas of fly ash utilization are

as follow:

Fly ash bricks

Fly ash cement

Reclamation of waste land

46

Fly ash based components for construction industry.

Sintered aggregate

Wood substitute – doors & panels

Granite substitute

Ceramic tiles

Paints & enamels

Reclamation of ash ponds for human settlement

Fig. 16.1 Electrostatic Precipitator

Common causes of unsatisfactory performance of ESP are:

Excessive gas volume

Overloading

Ineffective rapping

47

Overfilling of dust hoppers

Poor gas distribution

Flashover and electrical instability

Discharge wire breakage

Fig 16.2 Typical View of Ash Handling Plant

48

CHAPTER 17

ENERGY CONSERVATION AND ENERGY AUDIT

17.1 ENERGY CONSERVATION: -

Energy conservation means to reduce the quantity of energy that is used for different

purposes. This practice may result in increase of financial capital, environmental value,

national and personal security, and human comfort.

Individuals and organizations that are direct consumers of energy may want to conserve

energy in order to reduce energy costs and promote economic, political and environmental

sustainability.

On a larger scale, energy conservation is an important element of energy policy. In general,

energy conservation reduces the energy consumption and energy demand per capita. This

reduces the rise in energy costs, and can reduce the need for new power plants, and energy

imports. The reduced energy demand can provide more flexibility in choosing the most

preferred methods of energy production. By reducing emissions, energy conservation is an

important method to prevent climate change. Energy conservation makes it easier to replace

non-renewable resources with renewable energy. Energy conservation is often the most

economical solution to energy shortages.

17.2 ENERGY AUDIT: -

An Energy Audit is a systematic exercise to identify end-uses that consume a significant

amount of energy, estimate the efficiency in each of these end uses and devise methods of

improving efficiency curbing losses and wasteful use or in other words it is an inspection,

survey and analysis of energy flows for energy conservation in a building, process or system

to reduce the amount of energy input into the system without negatively affecting the output.

It attempts to balance the total energy inputs with its use and serves to identify all the energy

streams in a facility. When the object of study is an occupied building then reducing energy

consumption while maintaining or improving human comfort, health and safety are of

primary concern. Beyond simply identifying the sources of energy use, an energy audit seeks

to prioritize the energy uses according to the greatest to least cost effective opportunities for

energy savings.

49

CHAPTER 18

CONCLUSION

It was a knowledgeable experience while taking practical training at NASHIK THERMAL

POWER STATION. It proved an opportunity for encounter with such huge machines like

tippler, turbine, boiler and generator. But there are few factors that require special mention.

From all the study it can be concluded that the Nasik thermal power project of 210X3 units is

fairly organized unit with the latest machinery available. The turbine is a very sophisticated

assembly of machinery which requires specific conditions of steam temperature and pressure

to work efficiently. Any alteration of the specific requirements may prove hazardous to the

turbine. Another interesting yet worrying fact is the quantity of coal consumed which

approximately 3276 tonne per day. The level of pollution is always controlled according the

established norms, but still I consider it to be quite enough. Well, efforts are always

underway in reducing the pollution and improving the efficiency of the plant. All in all, a

thermal power project is very large establishment with many components and it awesome to

see how all the components work in a synchronized manner.

The Electricity Act 2003 and subsequent National Electricity Policy and Tariff Policy have

Opened up several opportunities for the power sector. The Act allows the IPPs and captive

Power producers open access to transmission system, thus allowing them to bypass the SEBs

and sell power directly to bulk consumers. Slowly open access in distribution system is also

being allowed.

Assessment of the financial feasibility of the Proposed Project, delivers satisfactory financial

Parameters as per base financial model. It has also assessed the viability of the project under

the impact of various scenarios, which could be at variance with the base case scenario

assumed.

Company has proposed to set-up 660 MW Coal fired Thermal Power Project based on

Super Critical Technology. State Government has supported this Project and has issued letter

of support to provide all kind of administrative support required.

50

CHAPTER 19

SUGGESTIONS

Power sector is an essential service and in the basis of industrialization and agriculture. It

plays a vital role in the socio-economic development. Therefore, improving efficiency of

these thermal power stations in addition to increasing their PLF (Plant Load Factor) has

become the need of the hour to bring the cost and maximize the generation levels. With this

objective in view, several actions have already been initiated by Ministry of Power (MOP)

and other various agencies like CEA, NTPC, State Electricity Boards, CBIP etc. to improve

the operating efficiency and PLF of thermal power stations.

Now I here make it sort with my suggestions for improving efficiency of power plant and for

various other factors on the basis of what I have learned during my training are:

With the deficit of electricity in our country, there is need of many projects and the

exposure limit should be increased to effectively assist the new projects.

Proper maintenance of ESP must be done with regular maintenance of boilers and

furnaces.

Variable speed motors should be used.

Auxiliaries power reduction.

Use of automatic system for monitoring flue gases.

Completely insulate the steam system.

Turbine driven Boiler Feed Pumps should be used.

The plant is working fine with not many hindrances, but the main concern is the

cleanliness of plant. The plant, especially 140X2 units building of the plant is not

clean enough. What I believe is that cleaner environment might help in improving of

productivity and decrease the rate of breakdowns. This might improve the efficiency

of the unit as lesser number of foreign elements will be present which prevent the

proper functioning of the unit. If the efficiency increases, the coal consumption will

be reduced for the same load and that would provide better profit to the organization.

Recover the portion of heat loss from the warm cooling water existing the steam

condenser.

Reduce air, water, steam and flue gas leakages.