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AN INDUSTRIAL TRAINING REPORT

ON

Study of power & water cycle in thermal power plant at B.H.E.L,Noida

BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINEERING

ByBikesh ranjan

Submitted ToMr. Shibamay mitra

DEPARTMENT OF MECHANICAL ENGINEERING

Sharda University

GREATER NOIDA-201306

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APPROVAL SHEET

Summer training report, entitled:study of power & water cycle in thermal power plant is approved for award of 04 credits

Examiners

__________________

__________________

Coordinator

__________________

Head of Department

__________________

Date:

CERTIFICATE

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This is to certify that Mr. / Ms.bikesh ranjan has partially completed / completed / not

completed the Industrial Training in our Organization / Industry during 1st June, 2015 to 15th

July, 2015. He / She was trained in the field of power &water cycle in thermal power

plant. His / Her overall performance during the period was Excellent / Very Good / Good /

Average / Poor.

Manager/Guide

ACKNOWLEDGEMENT

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I would like to place on record my deep sense of gratitude to Mr amit dixit, Bharat Heavy

Electricals Limited (B.H.E.L.),noida,for his generous guidance, help and useful

suggestions.permitting me to have training during 20th june to 24st July, 2015.

I express my sincere gratitude to Mr. Shibamay Mitra, Dept. of Mechanical and Automotive

Engineering, Sharda University, Greater Noida, for his stimulating guidance, continuous

encouragement and supervision throughout the course of present work.

I also wish to extend my thanks to our teacher and other colleagues for attending my seminars

and for their insightful comments and constructive suggestions to improve the quality of this

research work.

I am extremely thankful to Prof. shibamay mitra, Head, Dept. of Mechanical and Automotive

Engineering, Sharda University, Greater Noida, for providing me infrastructural facilities to

work in, without which this work would not have been possible.

Signature of the student

ABSTRACT

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In the era of Mechanical Engineering, Turbine, A Prime Mover (Which uses the Raw Energy of a substance and converts it to Mechanical Energy) is a well-known Machine most useful in the field of Power Generation. This Mechanical energy is used in running an Electric Generator which is directly coupled to the shaft of turbine. From this Electric Generator, we get electric Power which can be transmitted over long distances by means of transmission lines and transmission towers.

In my Industrial Training in B.H.E.L, Noida I go through all sections in Thermal power plant. First management team told me about the history of industry, Area, Capacity, Machines installed & Facilities in the Industry.

After that they told about the Steam Turbine its types, parts like Boiler, fuel, generator etc. Then they told full explanation of constructional features and procedure along with equipment used. Before telling about the machines used in Manufacturing of Blade, they told about the safety precautions, Step by Step arrangement of machines in the block with a well-defined proper format. They also told the process how water is used for generating electricity.

INDEX

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Sr. No. Topic Page no.

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INTRODUCTION 9

BHEL 9

1.1 OVERVIEW 9-10

1.2 WORKING AREAS 10

1.2.1 POWER GENERATION 10

1.2.2 POWER TRANSMISSION & DISTRIBUTION 10-11

1.2.3 INDUSTRIES 11

1.2.4 TRANSPORTATION 11

1.2.5 TELECOMMUNICATION 11

1.2.6 RENEWABLE ENERGY 11-12

1.2.7 INTERNATIONAL OPERATIONS 12\

1.3 TECHNOLOGY UPGRADATION AND RESEARCH AND DEVELOPMENT

12-13

1.3.1 HUMAN RESOURCE DEVELOPMENT INSTITUTE 13

1.4 HEALTH SAFETY AND ENVIRONMENT MANAGEMENT 13-14 1.4.1 ENVIRONMENTAL POLICY 14

1.4.2 OCCUPATIONAL HEALTH AND SAFETY POLICY 14

1.4.3 PRINCIPLE OF THE “GLOBAL COMPACT” 14-15

1.5 BHEL UNITS 15

2.0 BASIC OF THERMAL POWER PLANT 16

2.1 INSTALLED THERMAL POWER CAPACITY 16

3.0 CLASSIFICATION OF THERMAL POWER PLANT 16-17

3.1 BY FUEL 17

3.2 BY PRIME MOVER 17-18

3.3 BY DUTY 18

4.0 EFFICIENCY 19

4.1 HEAT RATE 20

5.0 POWER COMPANIES IN INDIA 21

6.0 PROSPECTUS OF SETTING UP A THERMAL POWER PLANT 22

6.1 ELECTRICITY COST 23

7.0 TYPICAL COAL THERMAL POWER SYSTEM 24

7.1 BOILER AND STEAM CYCLE 24-25

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7.2 FEED WATER HEATING AND DEAERATION 26

7.3 BOILER OPERATION 26-27

7.4 BOILER FURNACE AND STEAM DRUM 27

7.5 SUPER HEATER 27

7.6 STEAM CONDENSING 27-28

7.7 RE HEATER 29

7.8 AIR PATH 29-30

7.9 STEAM TURBINE GENERATOR 30

8.0 STACK GAS PATH AND CLEAN UP 31

8.1 FLY ASH COLLECTION 31

8.2 BOTTOM ASH COLLECTION 31

9.0 AUXILIARY SYSTEM 32

9.1 BOILER MAKE UP WATER TREATEMENT PLANT AND STORAGE

32

9.2 FUEL PREPARATION SYSTEM 32-33

9.3 BARRYING GEAR 33

9.4 OIL SYSTEM 33

9.5 GENERATOR COOLING 33

9.6 GENERATOR HIGH VOLTAGE SYSTEM 33-34

9.7 MONITORING AND ALARM SYSTEM 35

10 ADVANTAGE AND DISADVANTAGE OF THERMAL POWER PLANT

35-36

11 CONCLUSION 36

FIGURE INDEX

Sr. No. Topic Page no.

1. T-S DAIGRAMME 20

2. FEED WATER HEATER 22

3. COAL FIRED THERMAL POWER PLANT 24

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4. TYPICAL WATER COOLED SURFACE CONDENSOR 26

5. MARLEY MECHANICAL INDUCED DRAFT COOLING TOWER 28

6. STEAM TURBINE GENERATOR 29

7. FUEL PREPARATION SYSTEM 33

TABLE INDEX

Sr. No. Topic Page no.

1. BHEL UNITS 16

2. POWER COMPANIES IN INDIA 22

3. NAMING OF ALL PARTS OF COAL FIRED THERMAL POWER PLANT

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INTRODUCTION

BHEL is the largest engineering and manufacturing enterprise in India in the energy related infrastructure sector today. BHEL was established more than 40 years ago when its first plant was setup in Bhopal ushering in the indigenous Heavy Electrical Equipment Industry in India a dream which has been more than realized with a well-recognized track record of performance it has been earning profits continuously since1971-72.

BHEL caters to core sectors of the Indian Economy viz., Power Generation's & Transmission, Industry, Transportation, Telecommunication, Renewable Energy, Defence, etc. The wide network of BHEL's 14 manufacturing division, four power

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Sector regional centres, over 150 project sites, eight service centres and 18 regional offices, enables the Company to promptly serve its customers and provide them with suitable products, systems and services – efficiently and at competitive prices. BHEL has already attained ISO 9000 certification for quality management, and ISO 14001certification for environment management.

The company’s inherent potential coupled with its strong performance make this one of the “NAVRATNAS”, which is supported by the government in their endeavor to become future global players.

B.H.E.L .

1.1. OERVIVEW

• Bharat Heavy Electricals Limited (B.H.E.L.) is the largest engineering and manufacturing enterprise in India. BHEL caters to core sectors of the Indian Economy viz., Power Generation's & Transmission, Industry, Transportation, Telecommunication, Renewable Energy, Defense and many more.

• Established in 1960s under the Indo-Soviet Agreements of 1959 and 1960 in

the area of Scientific, Technical and Industrial Cooperation. • BHEL has its setup spread all over India namely New Delhi, Gurgaon,

Haridwar, Rudrapur, Jhansi, Bhopal, Hyderabad, Jagdishpur , Tiruchirapalli, Bangalore and many more.

• Over 65% of power generated in India comes from BHEL-supplied equipment.Overall it has installed power equipment for over 90,000 MW.

• BHEL's Investment in R&D is amongst the largest in the corporate sector in

India. Net Profit of the company in the year 2011-2012 was recorded as 6868crore having a high of 21.2% in comparison to last year.

• BHEL has already attained ISO 9000 certification for quality management,

and ISO 14001 certification for environment management. • It is one of India's nine largest Public Sector Undertakings or PSUs, known as

the NAVRATNAS or 'The Nine Jewels’. • The power plant equipment manufactured by BHEL is based on contemporary

technology comparable to the best in the world.

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• The wide network of BHEL's 14 manufacturing divisions, 4 Power Sector

regional centre, over 100 project sites, 8 Service Centre and 18 regional offices, enables the Company to promptly serve its customers and provide them with suitable products, systems and services efficiently.

1.2. WORKING AREAS

1.2.1. POWER GENERATION

Power generation sector comprises thermal, gas, hydro and nuclear power plant business as of 31.03.2001, BHEL supplied sets account for nearly 64737 MW or 65% of the total installed capacity of 99,146 MW in the country, as against nil till 1969-70.

BHEL has proven turnkey capabilities for executing power projects from concept to commissioning, it possesses the technology and capability to produce thermal sets with super critical parameters up to 1000 MW unit rating and gas turbine generator sets of up to 240 MW unit rating. Co-generation and combined-cycle plants have been introduced to achieve higher plant efficiencies. To make efficient use of the high-ash-content coal available in India, BHEL supplies circulating fluidized bed combustion boilers to both thermal and combined cycle power plants.

The company manufactures 235 MW nuclear turbine generator sets and has commenced production of 500 MW nuclear turbine generator sets.

Custom made hydro sets of Francis, Pelton and Kaplan types for different head discharge combination are also engineering and manufactured by BHEL.

In all, orders for more than 700 utility sets of thermal, hydro, gas and nuclear have been placed on the Company as on date. The power plant equipment manufactured by BHEL is based on contemporary technology comparable to the best in the world and is also internationally competitive.

The Company has proven expertise in Plant Performance Improvement through renovation modernization and upgrading of a variety of power plant equipment besides specialized know how of residual life assessment, health diagnostics and life extension of plants.

1.2.2. POWER TRANSMISSION & DISTRIBUTION (T & D)

BHEL offer wide ranging products and systems for T & D applications. Products manufactured include power transformers, instrument transformers, dry type transformers, series and stunt reactor, capacitor tanks, vacuum and SF circuit breakers gas insulated switch gears and insulators. A strong engineering base enables the Company to undertake turnkey delivery of electric substances up to 400 kV level series compensation systems (for increasing power transfer capacity of transmission

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lines and improving system stability and voltage regulation), shunt compensation systems (for power factor and voltage improvement) and HVDC systems (for economic transfer of bulk power). BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines). Presently a 400 kV Facts (Flexible AC Transmission System) project under execution.

1.2.3. INDUSTRIES

BHEL is a major contributor of equipment and systems to industries. Cement, sugar, fertilizer, refineries, petrochemicals, paper, oil and gas, metallurgical and other process industries lines and improving system stability and voltage regulation, shunt compensation systems (for power factor and voltage improvement) and HVDC systems(for economic transfer of bulk power) BHEL has indigenously developed the state-of-the-art controlled shunt reactor (for reactive power management on long transmission lines).Presently a 400 kV FACTS (Flexible AC Transmission System) projects is under execution. The range of system & equipment supplied includes: captive power plants, co-generation plants DG power plants, industrial steam turbines, industrial boilers and auxiliaries. Water heat recovery boilers, gas turbines, heat exchangers and pressure vessels, centrifugal compressors, electrical machines, pumps, valves, seamless steel tubes, electrostatic precipitators, fabric filters, reactors, fluidized bed combustion boilers, chemical recovery boilers and process controls.

The Company is a major producer of large-size thruster devices. It also supplies digital distributed control systems for process industries, and control & instrumentation systems for power plant and industrial applications. BHEL is the only company in India with the capability to make simulators for power plants, defense and other applications. The Company has commenced manufacture of large desalination plants to help augment the supply of drinking water to people.

1.2.4. TRANSPORTATION

BHEL is involved in the development design, engineering, marketing, production, installation, and maintenance and after-sales service of Rolling Stock and traction propulsion systems. In the area of rolling stock, BHEL manufactures electric locomotives up to 5000HP, diesel-electric locomotives from 350 HP to 3100 HP, both for mainline and shunting duly applications. BHEL is also producing rolling stock for special applications viz., overhead equipment cars, Special well wagons, Rail-cum-road vehicle etc., Besides traction propulsion systems for in-house use, BHEL manufactures traction propulsion systems for other rolling stock producers of electric locomotives, diesel-electric locomotives, electrical multiple units and metro cars. The electric and diesel traction equipment on India Railways are largely powered by electrical propulsion systems produced by BHEL. The company also undertakes retooling and overhauling of rolling stock in the area of urban transportation systems. BHEL is geared up to turnkey execution of electric trolley bus systems, light rail systems etc. BHEL is also diversifying in the area of port handing equipment and pipelines transportation system.

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1.2.5. TELECOMMUNICATION

BHEL also caters to Telecommunication sector by way of small, medium and large switching system.

1.2.6. RENEWABLE ENERGY

Technologies that can be offered by BHEL for exploiting non-conventional and renewable sources of energy include: wind electric generators, solar photo voltaic systems, solar lanterns and battery-powered road vehicles. The Company has taken up R&D efforts for development of multi-junction amorphous silicon solar cells and fuel based systems.

1.2.7. INTERNATIONAL OPERATIONS

BHEL has, over the years, established its references in around 60 countries of the world, ranging for the United States in the west to New Zealand in the far east. These references encompass almost the entire product range of BHEL, covering turnkey power projects of thermal, hydro and gas-based types, substation projects, rehabilitation projects, besides a wide variety of products, like transformers, insulators, switch gears, heat exchangers, castings and forgings, valves, wellhead equipment, centrifugal compressors, photo-voltaic equipment etc. apart from over 1110mw of boiler capacity contributed in Malaysia, and execution of four prestigious power projects in Oman, some of the other major successes achieved by the company have been in Australia, Saudi Arabia, Libya, Greece, Cyprus, Malta, Egypt, Bangladesh, Azerbaijan, Sri Lanka, Iraq etc.

The company has been successful in meeting demanding customer's requirements in terms of complexity of the works as well as technological, quality and other requirements viz. extended warrantees, associated O&M, financing packages etc. BHEL has proved its capability to undertake projects on fast-track basis. The company has been successful in meeting varying needs of the industry, be it captive power plants, utility power generation or for the oil sector requirements. Executing of overseas projects has also provided BHEL the experience of working with world renowned consulting organizations and inspection agencies.

In addition to demonstrated capability to undertake turnkey projects on its own, BHEL possesses the requisite flexibility to interface and complement with international companies for large projects by supplying complementary equipment and meeting their production needs for intermediate as well as finished products.

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The success in the area of rehabilitation and life extension of power projects has established BHEL as a comparable alternative to the original equipment manufacturers (OEM’S) for such plants.

1.3. TECHNOLOGY UPGRADATION AND RESEARCH & DEVELOPMENT

To remain competitive and meet customers' expectations, BHEL lays great emphasis on the continuous up gradation of products and related technologies, and development of new products. The Company has upgraded its products to contemporary levels through continuous in house efforts as well as through acquisition of new technologies from leading engineering organizations of the world.

The Corporate R&D Division at Hyderabad, spread over a 140 acre complex, leads BHEL's research efforts in a number of areas of importance to BHEL's product range. Research and product development centers at each of the manufacturing divisions play a complementary role.

BHEL's Investment in R&D is amongst the largest in the corporate sector in India. Products developed in-house during the last five years contributed about 8.6% to the revenues in 20002001.

BHEL has introduced, in the recent past, several state-of-the-art products developed in-house: low-NOx oil / gas burners, circulating fluidized bed combustion boilers, high-efficiency Pelton hydro turbines, petroleum depot automation systems, 36kV gas-insulated sub-stations, etc. The Company has also transferred a few technologies developed in-house to other Indian companies for commercialization.

Some of the on-going development & demonstration projects include: Smart wall blowing system for cleaning boiler soot deposits, and micro-controller based governor for diesel-electric locomotives. The company is also engaged in research in futuristic areas, such as application of super conducting materials in power generations and industry, and fuel cells for distributed, environment-friendly power generation.

1.3.1 HUMAN RESOURCE DEVELOPMENT INSTITUTE

The most prized asset of BHEL is its employees. The Human Resource Development Institute and other HRD centers of the Company help in not only keeping their skills updated and finely honed but also in adding new skills, whenever required .Continuous training and retraining, positive, a positive work culture and participative style of management, have engendered development of a committed and motivated workforce leading to enhanced productivity and higher levels of quality.

1.4. HEALTH, SAFETY AND ENVIRONMENT MANAGEMENT

BHEL, as an integral part of business performance and in its endeavor of becoming a world-class organization and sharing the growing global concern on issues related to Environment. Occupational Health and Safety, is committed to protecting

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Environment in and around its own establishment, and to providing safe and healthy working environment to all its employees. For fulfilling these obligations, Corporate Policies have been formulated as.

1.4.1. ENVIRONMENTAL POLICY

• Compliance with applicable Environmental Legislation/Regulation. • Continual Improvement in Environment Management Systems to protect our

natural environment and Control Pollution.

• Promotion of activities for conservation of resources by Environmental Management.

• Enhancement of Environmental awareness amongst employees, customers and suppliers. BHEL will also assist and co-operate with the concerned Government Agencies and Regulatory Bodies engaged in environmental activities, offering the Company's capabilities is this field.

1.4.2. OCCUPATIONAL HEALTH AND SAFETY POLICY

• Compliance with applicable Legislation and Regulations. • Setting objectives and targets to eliminate/control/minimize risks due to

Occupational and Safety Hazards.

• Appropriate structured training of employees on Occupational Health and Safety (OH&S) aspects.

• Formulation and maintenance of OH&S Management programs for continual improvement.

• Periodic review of OH&S Management System to ensure its continuing suitability, adequacy and effectiveness.

• Communication of OH&S Policy to all employees and interested parties.

The major units of BHEL have already acquired ISO 14001 Environmental Management System Certification, and other units are in advanced stages of acquiring the same. Action plan has been prepared to acquire OHSAS 18001 Occupational Health and Safety Management System certification for all BHEL units. In pursuit of these Policy requirements, BHEL will continuously strive to improve work particles in the light of advances made in technology and new understandings in Occupational Health, Safety and Environmental Science Participation in the "Global Compact" of the United Nations.

The "Global Compact" is a partnership between the United Nations, the business community, international labor and NGOs. It provides a forum for them to work together and improve corporate practices through co-operation rather than confrontation.

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BHEL has joined the "Global Compact" of United Nations and has committed to support it and the set of core values enshrined in its nine principles.

1.4.3. PRINCIPLES OF THE "GLOBAL COMPACT"

HUMAN RIGHTS 1. Business should support and respect the protection of internationally

proclaimed human rights and. 2. Make sure they are not complicit in human rights abuses.

LABOUR STANDARDS 1. Business should uphold the freedom of association and the effective

recognition of the right to collective bargaining. 3. Eliminate discrimination. 4. The elimination of all form of forces and compulsory labour. 5. The effective abolition of child labour. 6. Eliminate discrimination.

ENVIRONMENT Businesses should support a precautionary approach to environmental

challenges. Undertake initiatives to promote greater environmental responsibility and Encourage the development and diffusion of environmentally friendly technology.

By joining the "Global Compact", BHEL would get a unique opportunity of networking with corporate and sharing experience relating to social responsibility on global basis.

1.5 BHEL UNITS

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UNIT TYPE PRODUCT

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1. Bhopal Heavy Electrical Part Steam Turbines, Turbo Generators, Hydro Sets, Switch Gear Controllers

2. Haridwar HEEP CFFP

Heavy Electrical Equipement Plant Central Foundry Forge Plant

Hydro Turbines, Steam Turbines, Gas Turbines, Turbo Generators, Heavy Castings and Forging, Control Panels, Light Aircrafts, Electrical Machines.

3. Hyderabad HPEP

Heavy Power Equipement Plant

Industrial Turbo-Sets, Compressor Pumps and Heaters, Bow Mills, Heat Exchangers Oil Rings, Gas Turbines, Switch Gears, Power Generating Sets.

4. Trichy HPBP

High Pressure Boiling Plant

Seamless Steel Tubes, Spiral Fin Welded Tubes.

5. Jhansi TP

Transformer Plant

Transformers, Diesel Shunt Less AC locos and EC EMU.

6. Banglore EDN EPD

Electronics Division Electro Porcelains Devision

Energy Meters, Watt Meters, Control Equipement, Capacitors, Photo Voltic Panels, Simulator, Telecommunication System, Other Advanced Microprocessor based Control System, Insulator and Bushing, Ceramic Liners

7. Ranipet BAP

Boiler Auxilary Plant

Electrostatic Precipitator, Air Pre-Heater, Fans, Wind Electric Generators, Desalination Plants.

8. Goindwal Industrial Valves Plant Industrial Valves & Fabrication

9. Jagdishpur IP

Insulator Plant

High tension ceramic, Insulation Plates and Bushings

10. Rudrapur Component Fabrication Plant Windmill, Solar Water Heating system

11. Gurgaon Amorphous Silicon Solar Cell Plant.

Solar Photovoltaic Cells, Solar Lanterns, Chargers ,Solar clock

Table-1

2.0 BASICS OF THERMAL POWER PLANT

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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 center 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.

2.1 Installed thermal power capacity

The installed capacity of Thermal Power in India, as of October 31, 2012, was 140206.18 MW which is 66.99%of total installed capacity.

Current installed base of Coal Based Thermal Power is 120,103.38 MW which comes to 57.38% of total installed base.

Current installed base of Gas Based Thermal Power is 18,903.05 MW which is 9.03% of total installed capacity.

Current installed base of Oil Based Thermal Power is 1,199.75 MW which is 0.57% of total installed capacity.

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

In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations. An important class of power stations in the Middle East uses by-product heat for the desalination of water.The efficiency of a steam turbine is limited by the maximum temperature of the steam produced and is not directly a function of the fuel used. For the same steam conditions, coal, nuclear and gas power plants all have the same theoretical efficiency. Overall, if a system is on constantly (base load) it will be more efficient than one that is used intermittently (peak load).Besides use of reject heat for process or district heating, one way to improve overall efficiency of a power plant is to combine two different thermodynamic cycles. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.

3.0 Classification of Thermal power plant

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3.1 By fuel

•Fossil-fuel power stations may also use a steam turbine generator or in the case of natural gas-fired plants may use a combustion turbine. A coal-fired power station produces electricity by burning coal to generate steam, and has the side-effect of producing large amounts of sulfur dioxide which pollutes air and water and carbon dioxide, which contributes to global warming. About 50% of electric generation in the USA is produced by coal-fired power plants.

•Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator. About 20% of electric generation in the USA is produced by nuclear power plants.

•Geothermal power plants use steam extracted from hot underground rocks.

•Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.

•In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.

•Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.

•Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.

3.2 By prime mover

•Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90% of all electric power produced in the world is by use of steam turbines.

•Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Princeton being the world's first, commissioned in 1959.

•Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new base load power plants are combined cycle plants fired by natural gas.

•Internal combustion reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office

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buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas, and landfill gas.

•Micro turbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.

3.3 By duty

Power plants that can be dispatched (scheduled) to provide energy to a system include:

•Base load power plants run nearly continually to provide that component of system load that doesn't vary during a day or week. Base load plants can be highly optimized for low fuel cost, but may not start or stop quickly during changes in system load. Examples of base-load plants would include large modern coal-fired and nuclear generating stations, or hydro plants with a predictable supply of water.

•Peaking power plants meet the daily peak load, which may only be for a one or two hours each day. While their incremental operating cost is always higher than base load plants, they are required to ensure security of the system during load peaks. Peaking plants include simple cycle gas turbines and sometimes reciprocating internal combustion engines, which can be started up rapidly when system peaks are predicted. Hydroelectric plants may also be designed for peaking use.

•Load following power plants can economically follow the variations in the daily and weekly load, at lower cost than peaking plants and with more flexibility than base load plants.Non-dispatch able plants include such sources as wind and solar energy; while their long-term contribution to system energy supply is predictable, on a short-term (daily or hourly) base their energy must be used as available since generation cannot be deferred. Contractual arrangements (“take or pay") with independent power producers or system interconnections to other networks may be effectively non-dispatch able.

Thermal power plants can deploy a wide range of technologies. Some of the major technologies include:

Steam cycle facilities (most commonly used for large utilities); Gas turbines (commonly used for moderate sized peaking facilities);

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Cogeneration and combined cycle facility (the combination of gas turbines or internal combustion engines with heat recovery systems); and

Internal combustion engines (commonly used for small remote sites or stand-by power generation).

India has an extensive review process, one that includes environment impact assessment, prior to a thermal power plant being approved for construction and commissioning. The Ministry of Environment and Forests has published a technical guidance manual to help project proposers and to prevent environmental pollution in India from thermal power plants.

4.0EFFICIENCY

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Fig.1 A Rankine cycle with a two-stage steam turbine and a single feed water heater.

The energy efficiency of a conventional thermal power station, considered salable energy produced as a percent of the heating value of the fuel consumed, is typically 33% to 48% As with all heat engines, their efficiency is limited, and governed by the laws of thermodynamics. By comparison, most hydropower stations in the United States are about 90 percent efficient in converting the energy of falling water into electricity.

The energy of a thermal not utilized in power production must leave the plant in the form of heat to the environment. This waste heat can go through a condenser and be disposed of with cooling water or in cooling towers. If the waste heat is instead utilized for district heating, it is called co-generation. An important class of thermal power station are associated with desalination facilities; these are typically found in desert countries with large supplies of natural gas and in these plants, freshwater production and electricity are equally important co-products.

The Carnot efficiency dictates that higher efficiencies can be attained by increasing the temperature of the steam. Sub-critical fossil fuel power plants can achieve 36–40% efficiency. Super critical designs have efficiencies in the low to mid 40% range, with new

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"ultra critical" designs using pressures of 4400 psi (30.3 MPa) and multiple stage reheat reaching about 48% efficiency. Above the critical point for water of 705 °F (374 °C) and 3212 psi (22.06 MPa), there is no phase transition from water to steam, but only a gradual decrease in density.

Currently most of the nuclear power plants must operate below the temperatures and pressures that coal-fired plants do, since the pressurized vessel is very large and contains the entire bundle of nuclear fuel rods. The size of the reactor limits the pressure that can be reached. This, in turn, limits their thermodynamic efficiency to 30–32%. Some advanced reactor designs being studied, such as the very high temperature reactor, advanced gas-cooled reactor and supercritical water reactor, would operate at temperatures and pressures similar to current coal plants, producing comparable thermodynamic efficiency.

4.1 Heat rate

A form of expressing efficiency of an engine or turbine. The fuel heating value consumed per unit of useful output (usually electrical output). Common unit is kJ/kWh. To convert to efficiency divide by 3600 and invert.

Heat Rate (Generated) (kJ/kWh)

Quantity fuel (kg) * higher heating value of fuel consumed (kJ/kg) divided by:

Total energy generated (kWh)

Heat Rate (gen) is related to Efficiency (gen) by:

Heat Rate (gen) (kJ/kWh) = 3600 * 100 divided by:/ Efficiency (gen) (%)

Heat Rate (Sent Out) (kJ/kWh)

Quantity fuel (kg) * higher heating value of fuel consumed (kJ/kg) divided by:/ Total energy generated (kWh) - Total auxiliary energy (kWh)

Heat Rate (s/o) is related to Efficiency (s/o) by

Heat Rate (s/o) (kJ/kWh) = 3600 * 100 ./ Efficiency (s/o) (%)

5.0 POWER COMPANIES IN INDIA.

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A G N

Adani Power Gujarat Urja Vikas NigamNuclear Power Corporation

of IndiaAndhra Pradesh Central

Power Distribution CompanyH O

Andhra Pradesh Power Generation Corporation

Haryana Power Generation Corporation

Orissa Power Generation Corporation

Astonfield I P

BIndraprastha Power

GenerationPaschim Gujarat Vij

Bombay Electric Supply & Tramways Company Limited

JPunjab State Power

CorporationBrihanmumbai Electric

Supply and TransportJindal Steel and Power R

British Electric Traction Company

JSW EnergyRajasthan Rajya Vidyut

Utpadan NigamC K Reliance Infrastructure

CESC LimitedKarnataka Power Corporation

LimitedRural Electrification

Corporation LimitedChamundeshwari Electricity

Supply Corporation LimitedL S

Chhattisgarh State Power Generation Company Limited

Lanco Infratech Sterlite Energy Limited

Clarke EnergyList of electricity

organisations in IndiaT

D MTamil Nadu Generation and

Distribution Corporation Limited

Dabhol Power Company Madhya Gujarat VijTamil Nadu Transmission

Corporation LimitedDakshin Gujarat Vij

Company Ltd.Madhya Pradesh Power

Generation Company LimitedTata Power

Dakshin Haryana Bijli Vitran Nigam

Maharashtra State Electricity Distribution Company Limited

TNEB

Damodar Valley Corporation

Maharashtra State Power Generation Company Limited

Torrent Power

Delhi Transco LimitedMangalore Electricity Supply

Company LimitedTransmission Corporation of

Andhra Pradesh

E MSPL Limited U

Essar Energy N Uttar Gujarat Vij

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G Neyveli Lignite CorporationUttar Haryana Bijli Vitran

Nigam

User talk:Gkd1981 NHPC LimitedUttar Pradesh Rajya Vidyut

Utpadan NigamGujarat State Electricity

Corporation LimitedNorth Eastern Electric Power

Corporation LimitedW

Gujarat State Energy Generation

NSPCL Welspun Energy

Table-2

6.0 PROSPECTS OF SETTING UP A THERMAL POWER PLANT

The current and future projected cost of new electricity generation capacity is a critical input into the development of energy projections and analyses. The cost of new generating plants plays an important role in determining the mix of capacity additions that will serve growing loads in the future. New plant costs also help to determine how new capacity competes against existing capacity, and the response of the electricity generators to the imposition of environmental controls on conventional pollutants or any limitations on greenhouse gas emissions.Planning of Power Plant involves decision on two basic parameters:

1. Total power output to be installed (e.g. 1000 MW)

Installed capacity is determined from:

• Estimated Demand: - Before setting up a power plant, we need to critically analyze demand which gives us the idea to determine capacity which needs to be installed. The installation capacity should match the demand and hence estimation of demand is the critical fact while setting up a power plant.

• Growth of Demand anticipated: - While determining demand, future prospects needs to be considered so that the return on capital would be maximized and future demand could be met easily.

• Reserve Capacity required:- Considering the various type of demand in a market how much reserve capacity is required to be installed is determined and hence this will help in determining installation capacity.

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2. Size of generating units (e.g. 4 units of 250 MW each)

Size of the generating units will depend on:

• Variation of Load (Load Curve):- During the different hour of the day and in various seasons the demand varies, so the load curves. Now the number of units has to be determined to run the operations optimally and meeting the requirement daily.

• Minimum start-up and shut down periods of the units

• Maintenance programme planned

6.1ELECTRICITY COST

The direct cost of electric energy produced by a thermal power station is the result of cost of fuel, capital cost for the plant, operator labour, maintenance, and such factors as ash handling and disposal. Indirect, social or environmental costs such as the economic value of environmental impacts, or environmental and health effects of the complete fuel cycle and plant decommissioning, are not usually assigned to generation costs for thermal stations in utility practice, but may form part of an environmental impact assessment.

7.0 TYPICAL COAL THERMAL POWER STATION

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Fig.2 Typical diagram of a coal-fired thermal power station

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

2. Cooling water pump11. High pressure steam turbine

20. Forced draught (draft) fan

3. transmission line (3-phase) 12. Deaerator 21. Reheater4. Step-up transformer (3-phase)

13. Feedwater heater 22. Combustion air intake

5. Electrical generator (3-phase) 14. Coal conveyor 23. Economiser

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

7. Condensate pump16. Coal pulverizer

25. Precipitator

Table-3

For units over about 200 MW capacity, redundancy of key components is provided by installing duplicates of the forced and induced draft fans, air preheaters, and fly ash collectors. On some units of about 60 MW, two boilers per unit may instead be provided.

7.1 BOILER AND STEAM CYCLE

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In the nuclear plant field, steam generator refers to a specific type of large heat exchanger used in a pressurized water reactor (PWR) to thermally connect the primary (reactor plant) and secondary (steam plant) systems, which generates steam. In a nuclear reactor called a boiling water reactor (BWR), water is boiled to generate steam directly in the reactor itself and there are no units called steam generators.

In some industrial settings, there can also be steam-producing heat exchangers called heat recovery steam generators (HRSG) which utilize heat from some industrial process. The steam generating boiler has to produce steam at the high purity, pressure and temperature required for the steam turbine that drives the electrical generator.

Geothermal plants need no boiler since they use naturally occurring steam sources. Heat exchangers may be used where the geothermal steam is very corrosive or contains excessive suspended solids.

A fossil fuel steam generator includes an economizer, a steam drum, and the furnace with its steam generating tubes and superheater coils. Necessary safety valves are located at suitable points to avoid excessive boiler pressure. The air and flue gas path equipment include: forced draft (FD) fan, air preheater (AP), boiler furnace, induced draft (ID) fan, fly ash collectors (electrostatic precipitator or baghouse) and the flue gas stack.

7.2 FEED WATER HEATING AND DEAERATION

The boiler feedwater used in the steam boiler is a means of transferring heat energy from the burning fuel to the mechanical energy of the spinning steam turbine. The total feed water consists of recirculated condensate water and purified makeup water. Because the metallic materials it contacts are subject to corrosion at high temperatures and pressures, the makeup water is highly purified before use. A system of water softeners and ion exchange demineralizers produces water so pure that it coincidentally becomes an electrical insulator, with conductivity in the range of 0.3–1.0 microsiemens per centimeter. The makeup water in a 500  MWe plant amounts to perhaps 120 US gallons per minute (7.6 L/s) to replace water drawn off from the boiler drums for water purity management, and to also offset the small losses from steam leaks in the system.

The feed water cycle begins with condensate water being pumped out of the condenser after traveling through the steam turbines. The condensate flow rate at full load in a 500 MW plant is about 6,000 US gallons per minute (400 L/s).

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Fig.3 Diagram of boiler feed water deaerator (with vertical, domed aeration section and horizontal water storage section).

The water is pressurized in two stages, and flows through a series of six or seven intermediate feed water heaters, heated up at each point with steam extracted from an appropriate duct on the turbines and gaining temperature at each stage. Typically, in the middle of this series of feedwater heaters, and before the second stage of pressurization, the condensate plus the makeup water flows through a deaerator that removes dissolved air from the water, further purifying and reducing its corrosiveness. The water may be dosed following this point with hydrazine, a chemical that removes the remaining oxygen in the water to below 5 parts per billion (ppb). It is also dosed with pH control agents such as ammonia or morpholine to keep the residual acidity low and thus non-corrosive.

7.3 BOILER OPEIORATN

The boiler is a rectangular furnace about 50 feet (15 m) on a side and 130 feet (40 m) tall. Its walls are made of a web of high pressure steel tubes about 2.3 inches (58 mm) in diameter.

Pulverized coal is air-blown into the furnace through burners located at the four corners, or along one wall, or two opposite walls, and it is ignited to rapidly burn, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput. As the water in the boiler circulates it absorbs heat and changes into steam. It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1,000 °F (540 °C) to prepare it for the turbine.

Plants designed for lignite (brown coal) are increasingly used in locations as varied as Germany, Victoria, Australia and North Dakota. Lignite is a much younger form of coal than

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black coal. It has a lower energy density than black coal and requires a much larger furnace for equivalent heat output. Such coals may contain up to 70% water and ash, yielding lower furnace temperatures and requiring larger induced-draft fans. The firing systems also differ from black coal and typically draw hot gas from the furnace-exit level and mix it with the incoming coal in fan-type mills that inject the pulverized coal and hot gas mixture into the boiler.

Plants that use gas turbines to heat the water for conversion into steam use boilers known as heat recovery steam generators (HRSG). The exhaust heat from the gas turbines is used to make superheated steam that is then used in a conventional water-steam generation cycle, as described in gas turbine combined-cycle plants section below.

7.4 BOILER FURNACE AND STEAM DRUM

The water enters the boiler through a section in the convection pass called the economizer. From the economizer it passes to the steam drum and from there it goes through downcomers to inlet headers at the bottom of the water walls. From these headers the water rises through the water walls of the furnace where some of it is turned into steam and the mixture of water and steam then re-enters the steam drum. This process may be driven purely by natural circulation (because the water is the denser than the water/steam mixture in the water walls) or assisted by pumps. In the steam drum, the water is returned to the down comers and the steam is passed through a series of steam separators and dryers that remove water droplets from the steam. The dry steam then flows into the superheater coils.

The boiler furnace auxiliary equipment includes coal feed nozzles and igniter guns, soot blowers, water lancing and observation ports (in the furnace walls) for observation of the furnace interior. Furnace explosions due to any accumulation of combustible gases after a trip-out are avoided by flushing out such gases from the combustion zone before igniting the coal. The steam drum (as well as the super heater coils and headers) have air vents and drains needed for initial start up.

7.5 SUPERHEATER

Fossil fuel power plants often have a superheater section in the steam generating furnace. The steam passes through drying equipment inside the steam drum on to the superheater, a set of tubes in the furnace. Here the steam picks up more energy from hot flue gases outside the tubing and its temperature is now superheated above the saturation temperature. The superheated steam is then piped through the main steam lines to the valves before the high pressure turbine.

Nuclear-powered steam plants do not have such sections but produce steam at essentially saturated conditions. Experimental nuclear plants were equipped with fossil-fired super heaters in an attempt to improve overall plant operating cost.

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7.6 STEAM CONDENSING

The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases.

Fig.4 Diagram of a typical water-cooled surface condenser.

The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum.

For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 °C where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of non-condensible air into the closed loop must be prevented.

condensible air into the closed loop must be prevented.

Typically the cooling water causes the steam to condense at a temperature of about 35 °C (95 °F) and that creates an absolute pressure in the condenser of about 2–7 kPa (0.59–2.07 inHg), i.e. a vacuum of about −95 kPa (−28 inHg) relative to atmospheric pressure. The large decrease in volume that occurs when water vapor condenses to liquid creates the low vacuum that helps pull steam through and increase the efficiency of the turbines.

The limiting factor is the temperature of the cooling water and that, in turn, is limited by the prevailing average climatic conditions at the power plant's location (it may be possible to lower the temperature beyond the turbine limits during winter, causing excessive

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condensation in the turbine). Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning.

The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river, lake or ocean.

Fig.5 A Marley mechanical induced draft cooling tower

The heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain the ability of the water to cool as it circulates. This is done by pumping the warm water from the condenser through either natural draft, forced draft or induced draft cooling towers (as seen in the image to the right) that reduce the temperature of the water by evaporation, by about 11 to 17 °C (20 to 30 °F)—expelling waste heat to the atmosphere. The circulation flow rate of the cooling water in a 500 MW unit is about 14.2 m³/s (500 ft³/s or 225,000 US gal/min) at full load.

The condenser tubes are made of brass or stainless steel to resist corrosion from either side. Nevertheless they may become internally fouled during operation by bacteria or algae in the cooling water or by mineral scaling, all of which inhibit heat transfer and reduce thermodynamic efficiency. Many plants include an automatic cleaning system that circulates sponge rubber balls through the tubes to scrub them clean without the need to take the system off-line. The cooling water used to condense the steam in the condenser returns to its source without having been changed other than having been warmed. If the water returns to a local water body (rather than a circulating cooling tower), it is tempered with cool 'raw' water to prevent thermal shock when discharged into that body of water.

Another form of condensing system is the air-cooled condenser. The process is similar to that of a radiator and fan. Exhaust heat from the low pressure section of a steam turbine runs through the condensing tubes, the tubes are usually finned and ambient air is pushed through

the fins with the help of a large fan. The steam condenses to water to be reused in the water-steam cycle. Air-cooled condensers typically operate at a higher temperature than water-cooled versions. While saving water, the efficiency of the cycle is reduced (resulting in more carbon dioxide per megawatt of electricity).

From the bottom of the condenser, powerful condensate pumps recycle the condensed steam (water) back to the water/steam cycle.

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7.7 REHEATER

Power plant furnaces may have a reheater section containing tubes heated by hot flue gases outside the tubes. Exhaust steam from the high pressure turbine is passed through these heated tubes to collect more energy before driving the intermediate and then low pressure turbines.

7.8 AIR PATH

External fans are provided to give sufficient air for combustion. The Primary air fan takes air from the atmosphere and, first warming it in the air preheater for better combustion, injects it via the air nozzles on the furnace wall.

The induced draft fan assists the FD fan by drawing out combustible gases from the furnace, maintaining a slightly negative pressure in the furnace to avoid backfiring through any closing.

7.9 STEAM TURBINE GENERATOR

Fig.6 steam turbine generator

The turbine generator consists of a series of steam turbines interconnected to each other and a generator on a common shaft. There is a high pressure turbine at one end, followed by an intermediate pressure turbine, two low pressure turbines, and the generator. As steam moves through the system and loses pressure and thermal energy it expands in volume, requiring increasing diameter and longer blades at each succeeding stage to extract the remaining energy. The entire rotating mass may be over 200 metric tons and 100 feet (30 m) long. It is so heavy that it must be kept turning slowly even when shut down (at 3 rpm) so that the shaft will not bow even slightly and become unbalanced. This is so important that it is one of only five functions of blackout emergency power batteries on site. Other functions are emergency lighting, communication, station alarms and turbogenerator lube oil.

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Superheated steam from the boiler is delivered through 14–16-inch (360–410 mm) diameter piping to the high pressure turbine where it falls in pressure to 600 psi (4.1 MPa) and to 600 °F (320 °C) in temperature through the stage. It exits via 24–26-inch (610–660 mm) diameter cold reheat lines and passes back into the boiler where the steam is reheated in special reheat pendant tubes back to 1,000 °F (540 °C). The hot reheat steam is conducted to the intermediate pressure turbine where it falls in both temperature and pressure and exits directly to the long-bladed low pressure turbines and finally exits to the condenser.

The generator, 30 feet (9 m) long and 12 feet (3.7 m) in diameter, contains a stationary stator and a spinning rotor, each containing miles of heavy copper conductor—no permanent magnets here. In operation it generates up to 21,000 amperes at 24,000 volts AC (504 MWe) as it spins at either 3,000 or 3,600 rpm, synchronized to the power grid. The rotor spins in a sealed chamber cooled with hydrogen gas, selected because it has the highest known heat transfer coefficient of any gas and for its low viscosity which reduces windage losses. This system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly explosive hydrogen–oxygen environment is not created.

The power grid frequency is 60 Hz across North America and 50 Hz in Europe, Oceania, Asia (Korea and parts of Japan are notable exceptions) and parts of Africa. The desired frequency affects the design of large turbines, since they are highly optimized for one particular speed.

The electricity flows to a distribution yard where transformers increase the voltage for transmission to its destination.

The steam turbine-driven generators have auxiliary systems enabling them to work satisfactorily and safely. The steam turbine generator being rotating equipment generally has a heavy, large diameter shaft. The shaft therefore requires not only supports but also has to be kept in position while running. To minimize the frictional resistance to the rotation, the shaft has a number of bearings. The bearing shells, in which the shaft rotates, are lined with a low friction material like Babbitt metal. Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated.

8.0 STACK GAS PATH AND CLEANUP

As the combustion flue gas exits the boiler it is routed through a rotating flat basket of metal mesh which picks up heat and returns it to incoming fresh air as the basket rotates, This is called the air preheater. The gas exiting the boiler is laden with fly ash, which are tiny spherical ash particles. The flue gas contains nitrogen along with combustion products carbon dioxide, sulfur dioxide, and nitrogen oxides. The fly ash is removed by fabric bag filters or electrostatic precipitators. Once removed, the fly ash byproduct can sometimes be used in the manufacturing of concrete. This cleaning up of flue gases, however, only occurs in plants that

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are fitted with the appropriate technology. Still, the majority of coal-fired power plants in the world do not have these facilities. Legislation in Europe has been efficient to reduce flue gas pollution. Japan has been using flue gas cleaning technology for over 30 years and the US has been doing the same for over 25 years. China is now beginning to grapple with the pollution caused by coal-fired power plants.

Where required by law, the sulfur and nitrogen oxide pollutants are removed by stack gas scrubbers which use a pulverized limestone or other alkaline wet slurry to remove those pollutants from the exit stack gas. Other devices use catalysts to remove Nitrous Oxide compounds from the flue gas stream. The gas travelling up the flue gas stack may by this time have dropped to about 50 °C (120 °F). A typical flue gas stack may be 150–180 metres (490–590 ft) tall to disperse the remaining flue gas components in the atmosphere. The tallest flue gas stack in the world is 419.7 metres (1,377 ft) tall at the GRES-2 power plant in Ekibastuz, Kazakhstan.

In the United States and a number of other countries, atmospheric dispersion modeling studies are required to determine the flue gas stack height needed to comply with the local air pollution regulations. The United States also requires the height of a flue gas stack to comply with what is known as the "Good Engineering Practice (GEP)" stack height. In the case of existing flue gas stacks that exceed the GEP stack height, any air pollution dispersion modeling studies for such stacks must use the GEP stack height rather than the actual stack height.

8.1 FLY ASH COLLECTION

Fly ash is captured and removed from the flue gas by electrostatic precipitators or fabric bag filters (or sometimes both) located at the outlet of the furnace and before the induced draft fan. The fly ash is periodically removed from the collection hoppers below the precipitators or bag filters. Generally, the fly ash is pneumatically transported to storage silos for subsequent transport by trucks or railroad cars .

8.2 BOTTOM ASH COLLECTION AND DISPOSAL

At the bottom of the furnace, there is a hopper for collection of bottom ash. This hopper is always filled with water to quench the ash and clinkers falling down from the furnace. Some arrangement is included to crush the clinkers and for conveying the crushed clinkers and bottom ash to a storage site. Ash extractor is used to discharge ash from Municipal solid waste–fired boilers.

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9.0 AUXILIARY SYSTEMS

9.1 BOILER MAKE-UP WATER TREATMENT PLANT AND STORAGE

Since there is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blowdown and leakages have to be made up to maintain a desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. Impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water, and that is done by a water demineralising treatment plant (DM). A DM plant generally consists of cation, anion, and mixed bed exchangers. Any ions in the final water from this process consist essentially of hydrogen ions and hydroxide ions, which recombine to form pure water. Very pure DM water becomes highly corrosive once it absorbs oxygen from the atmosphere because of its very high affinity for oxygen.

The capacity of the DM plant is dictated by the type and quantity of salts in the raw water input. However, some storage is essential as the DM plant may be down for maintenance. For this purpose, a storage tank is installed from which DM water is continuously withdrawn for boiler make-up. The storage tank for DM water is made from materials not affected by corrosive water, such as PVC. The piping and valves are generally of stainless steel. Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with air. DM water make-up is generally added at the steam space of the surface condenser (i.e., the vacuum side). This arrangement not only sprays the water but also DM water gets deaerated, with the dissolved gases being removed by a de-aerator through an ejector attached to the condenser.

9.2 FUEL PREPARATION SYSTEM

Fig.7 fuel preparation system

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In coal-fired power stations, the raw feed coal from the coal storage area is first crushed into small pieces and then conveyed to the coal feed hoppers at the boilers. The coal is next pulverized into a very fine powder. The pulverizers may be ball mills, rotating drum grinders, or other types of grinders.

Some power stations burn fuel oil rather than coal. The oil must kept warm (above its pour point) in the fuel oil storage tanks to prevent the oil from congealing and becoming unpumpable. The oil is usually heated to about 100 °C before being pumped through the furnace fuel oil spray nozzles.

Boilers in some power stations use processed natural gas as their main fuel. Other power stations may use processed natural gas as auxiliary fuel in the event that their main fuel supply (coal or oil) is interrupted. In such cases, separate gas burners are provided on the boiler furnaces.

9.3 BARRING GEAR

Barring gear (or "turning gear") is the mechanism provided to rotate the turbine generator shaft at a very low speed after unit stoppages. Once the unit is "tripped" (i.e., the steam inlet valve is closed), the turbine coasts down towards standstill. When it stops completely, there is a tendency for the turbine shaft to deflect or bend if allowed to remain in one position too long. This is because the heat inside the turbine casing tends to concentrate in the top half of the casing, making the top half portion of the shaft hotter than the bottom half. The shaft therefore could warp or bend by millionths of inches.

This small shaft deflection, only detectable by eccentricity meters, would be enough to cause damaging vibrations to the entire steam turbine generator unit when it is restarted. The shaft is therefore automatically turned at low speed (about one percent rated speed) by the barring gear until it has cooled sufficiently to permit a complete stop.

9.5 OIL SYSTEM

An auxiliary oil system pump is used to supply oil at the start-up of the steam turbine generator. It supplies the hydraulic oil system required for steam turbine's main inlet steam stop valve, the governing control valves, the bearing and seal oil systems, the relevant hydraulic relays and other mechanisms.

At a preset speed of the turbine during start-ups, a pump driven by the turbine main shaft takes over the functions of the auxiliary system.

9.7 GENERATOR COOLING

While small generators may be cooled by air drawn through filters at the inlet, larger units generally require special cooling arrangements. Hydrogen gas cooling, in an oil-sealed casing, is used because it has the highest known heat transfer coefficient of any gas and for its

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low viscosity which reduces windage losses. This system requires special handling during start-up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in the air.

The hydrogen pressure inside the casing is maintained slightly higher than atmospheric pressure to avoid bubble formation.

9.8 GENTOERAR HIGH-VOLTAGE SYSTEM

The generator voltage for modern utility-connected generators ranges from 11 kV in smaller units to 22 kV in larger units. The generator high-voltage leads are normally large aluminium channels because of their high current as compared to the cables used in smaller machines. They are enclosed in well-grounded aluminium bus ducts and are supported on suitable insulators. The generator high-voltage leads are connected to step-up transformers for connecting to a high-voltage electrical substation (usually in the range of 115 kV to 765 kV) for further transmission by the local power grid.

The necessary protection and metering devices are included for the high-voltage leads. Thus, the steam turbine generator and the transformer form one unit. Smaller units may share a common generator step-up transformer with individual circuit breakers to connect the generators to a common bus.

9.8 MONITORING AND ALARM SYSTEM

Most of the power plant operational controls are automatic. However, at times, manual intervention may be required. Thus, the plant is provided with monitors and alarm systems that alert the plant operators when certain operating parameters are seriously deviating from their normal range.

9.9 BATTERY-SUPPLIED EMERGENCY LIGHTING AND COMMUNICATION

A central battery system consisting of lead acid cell units is provided to supply emergency electric power, when needed, to essential items such as the power plant's control systems, communication systems, turbine lube oil pumps, and emergency lighting. This is essential for a safe, damage-free shutdown of the units in an emergency situation.

9.10 TRANSPORT OF COAL FUEL TO SITE AND TO STORAGE

Main article: Fossil fuel power plant

Most thermal stations use coal as the main fuel. Raw coal is transported from coal mines to a power station site by trucks, barges, bulk cargo ships or railway cars. Generally, when shipped by railways, the coal cars are sent as a full train of cars. The coal received at site may be of different sizes. The railway cars are unloaded at site by rotary dumpers or side tilt dumpers to tip over onto conveyor belts below. The coal is generally conveyed to crushers which crush the coal to about 3⁄4 inch (19 mm) size. The crushed coal is then sent by belt

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conveyors to a storage pile. Normally, the crushed coal is compacted by bulldozers, as compacting of highly volatile coal avoids spontaneous ignition.

The crushed coal is conveyed from the storage pile to silos or hoppers at the boilers by another belt conveyor system.

10.0 ADVANTAGES OF THERMAL POWER

1. The fuel used is quite cheap.

2. Less initial cost as compared to other generating plants.

3. It can be installed at any place irrespective of the existence of coal. The coal can be

transported to the site of the plant by rail or road.

4. It requires less space as compared to Hydro power plants.

5. Cost of generation is less than that of diesel power plants.

6. They can be located very conveniently near the load centers.

7. Does not require shielding like required in nuclear power plant

8. Unlike nuclear power plants whose power production method is difficult, for thermal

power plants it is easy.

9. Transmission costs are reduced as they can be set up near the industry.

10. The portion of steam generated can be used as process steam in different industries.

11. Steam engines and turbines can work under 25% of overload capacity.

12. Able to respond changing base loads without difficulty.

Disadvantages of Thermal Power

1. It pollutes the atmosphere due to production of large amount of smoke and fumes.

2. Large amounts of water are required.

3. Takes long time to be erected and put into action.

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4. Maintenance and operating costs are high.

5. With increase in pressure and temperature, the cost of plant increases.

6. Troubles from smoke and heat from the plant, disposal of ash.

11.0 CONCLUSION

Gone through rigorous 4 Weeks training under the guidance of capable engineers and workers of BHEL Noida in sector 16-A “study of power &water cycle in thermal power plant” headed by Senior Engineer of department Mr. amit dixit situated in noida, gautam budh nagar, (Utter pradesh). The training was specified under the Thermal power plant Department. Working under the department I came to know about the basic fuels, cleaning of exhaust gases and water cycle. The training brought to my knowledge the various machining and fabrication processes went not only in water cycle in thermal power plant but other parts of the turbine.