himanshu ntpc

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PROJECT REPORT

INDUSTRIAL TRAINING REPORT

UNDERTAKEN AT

N.T.P.C. BADARPUR, NEW DELHI FROM: 31st MAY to 6th

July,2011

SUBMITTED TO: Mrs. RACHNA SINGH

SUBMITTED BY: BK SUMIT

MAHARAJA SURAJMAL

INSTITUTE OF

TECHNOLOGY (G.G.S.I.P.U)

3RD YEAR B.TECH

ELECTRONIC AND

COMMUNICATION


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TABLE OF CONTENT

1. Certificate

2. Acknowledgement

3. Training at BTPS

4. Introduction

NTPC

Badarpur Thermal Power Station

5. Operation

6. Control & Instrumentation

Manometer Lab

Protection and interlock Lab

Automation Lab

Water Treatment Plant

Furnace Safeguard Supervisory System

Electronic Test Lab

7. Information Technolgy

About IT department

HMS Project


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1.CERTIFICATE

This is to certify that BK SUMIT (Enroll no.-

0201502808)student of B.tech Electronics &Communication ,IIIrd Year; M. S. I. T. Janakpuri, (G.G.S.I.P.U.) hassuccessfully completed his industrial training at BadarpurThermal Power Station, New Delhi for eight week from 31stMay to 6th July 2011.

He has completed the whole training as per the training reportsubmitted by him.

Training InchargeBTPS/NTPC


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NEW DELHI

2.ACKNOWLEDGEMENT

With profound respect and gratitude, I take the opportunity to

convey my thanks to complete the training here.

I do extend my heartfelt thanks to Mrs. Rachna Singh for

providing me this opportunity to be a part of this esteemed

organization.

I am extremely grateful to all the technical staff of

BTPS/NTPC for their co-operation and guidance that helpedme a lot during the course of training. I have learnt a lot

working under them and I will always be indebted of them for

this value addition in me.

I would also like to thank the training in charge of M.S.I.T ,

Janakpuri (G.G.S.I.P.U.) and all the faculty member of

Electronics & Communication department for their effort of

constant co-operation. Which have been significant factor in

the accomplishment of my industrial training.


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3. Training at NTPC

I was appointed to do eight-week training at this esteemed

organization from 7th June to 17th July 2010.In these eight

weeks I was assigned to visit various division of the plantwhich were

1.Operation

2.Control and instrumentation (C&I)

3.Information Technology

This six-week training was a very educational adventure

for me. It was really amazing to see the plant by your selfand learn how electricity, which is one of our daily

requirements of life, is produced.

This report has been made by self-experience at BTPS. The

material in this report has been gathered from my

textbooks, senior student report, and trainer manual

provided by training department. The specification &principles are at learned by me from the employee of eachdivision of BTPS.


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About NTPC

NTPC Limited is the largest thermal power generating

company of India. A public sector company, it was

incorporated in the year 1975 to accelerate power

development in the country as a wholly owned company of

the Government of India. At present, Government of India

holds 89.5% of the total equity shares of the company and

FIIs, Domestic Banks, Public and others hold the balance10.5%. With in a span of 31 years, NTPC has emerged as a

truly national power company, with power generating

facilities in all the major regions of the country.


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4. INTRODUCTION

POWER GENERATION IN INDIA

NTPCs core business is engineering, construction and operation of power

generating plants. It also provides consultancy in the area of power plant

constructions and power generation to companies in India and abroad. As on

date the installed capacity of NTPC is 27,904 MW through its 15 coal based

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

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

(SPSCL). This JV Company operates the captive power plants of Durgapur (120

MW), Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33% stake in

Ratnagiri Gas & Power Private Limited (RGPPL) a joint venture company

between NTPC, GAIL, Indian Financial Institutions and Maharashtra SEB Co

Ltd.

NTPC has set new benchmarks for the power industry both in the area of power

plant construction and operations. Its providing power at the cheapest average

tariff in the country.NTPC is committed to the environment, generating power at minimal

environmental cost and preserving the ecology in the vicinity of the plants.

NTPC has undertaken massive a forestation in the vicinity of its plants.

Plantations have increased forest area and reduced barren land. The massive a

forestation by NTPC in and around its Ramagundam Power station (2600 MW)

have contributed reducing the temperature in the areas by about 3c. NTPC has

also taken proactive steps for ash utilisation. In 1991, it set up Ash Utilization

Division

A "Centre for Power Efficiency and Environment Protection (C.P.E.E.P.) hasbeen established in NTPC with the assistance of United States Agency for

International Development. (USAID). Cenpeep is efficiency oriented, eco


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friendly and eco nurturing initiative a symbol of NTPC's concern towards

environmental protection and continued commitment to sustainable power

development in India.

As a responsible corporate citizen, NTPC is making constant efforts to improve

the socio economic status of the people affected by its projects. Through its

rehabilitation and reconstructionhttp://www.ntpc.co.in/infocus/socialcomm.shtml _blankprogrammes, the company endeavors to improve the overall socio

economic status Project Affected Persons.

NTPC was among the first Public Sector Enterprises to enter into a

Memorandum of Understanding (MOU) with the Government in 1987 88.

NTPC has been placed under the 'Excellent category' (the best category) every

year since the MOU system became operative.

Harmony between man and environment is the essence of healthy life and

growth. Therefore, maintenance of ecological balance and a pristine

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

measures discussed below for mitigation of environment pollution due to power

generation.

Environment Policy & Environment Management System

Driven by its commitment for sustainable growth of power, NTPC has evolved a

well defined environment management policy and sound environment practices

for minimizing environmental impact arising out of setting up of power plants

and preserving the natural ecology.

National Environment Policy:At the national level, the Ministry of Environment and Forests had prepared a

draft Environment Policy (NEP) and the Ministry of Power along with NTPC

actively participated in the deliberations of the draft NEP. The NEP 2006 has

since been approved by the Union Cabinet in May 2006.

NTPC Environment Policy:

As early as in November 1995, NTPC brought out a comprehensive documententitled "NTPC Environment Policy and Environment Management System".

Amongst the guiding principles adopted in the document are company's

proactive approach to environment, optimum utilization of equipment, adoption

of latest technologies and continual environment improvement. The policy also

envisages efficient utilization of resources, thereby minimizing waste,

maximizing ash utilization and providing green belt all around the plant for

maintaining ecological balance.

Environment Management, Occupational Health and Safety Systems:

NTPC has actively gone for adoption of best international practices on

environment, occupational health and safety areas. The organization has pursued
http://www.ntpc.co.in/infocus/socialcomm.shtml#_blankhttp://www.ntpc.co.in/infocus/socialcomm.shtml#_blankhttp://www.ntpc.co.in/infocus/socialcomm.shtml#_blankhttp://www.ntpc.co.in/infocus/socialcomm.shtml#_blank


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the Environmental Management System (EMS) ISO 14001 and the Occupational

Health and Safety Assessment System OHSAS 18001 at its different

establishments. As a result of pursuing these practices, all NTPC power stations

have been certified for ISO 14001 & OHSAS 18001 by reputed national and

international Certifying Agencies.

Pollution Control systems:While deciding the appropriate technology for its projects, NTPC integrates

many environmental provisions into the plant design. In order to ensure that

NTPC comply with all the stipulated environment norms, various state of the

art pollution control systems / devices as discussed below have been installed to

control air and water pollution.

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

Electrostatic Precipitators (ESPs) and particulate emission is controlled well

within the stipulated norms. The ash collected in the ESPs is disposed to Ash

Ponds in slurry form.

Flue Gas Stacks:

Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous

emissions (SOX, NOX etc) into the atmosphere.

Low NOXBurners:In gas based NTPC power stations, NOx emissions are controlled by provision

of Low NOx Burners (dry or wet type) and in coal fired stations, by adopting

best combustion practices.

Neutralisation Pits:

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

pH correction of the effluents before discharge into Effluent Treatment Plant

(ETP) for further treatment and use.

Coal Settling Pits / Oil Settling Pits:In these Pits, coal dust and oil are removed from the effluents emanating from

the Coal Handling Plant (CHP), coal yard and Fuel Oil Handling areas before

discharge into ETP.

DE & DS Systems:

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

all coal fired power stations in NTPC to contain and extract the fugitive dust

released in the Coal Handling Plant (CHP).

Cooling Towers:

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

in closed cycle Condenser Cooling Water (CCW) Systems. This helps in


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reduction in thermal pollution and conservation of fresh water.

Ash Dykes & Ash Disposal systems:

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

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

lagoons and provided with garlanding arrangements for change over of the ash

slurry feed points for even filling of the pond and for effective settlement of theash particles.

Ash in slurry form is discharged into the lagoons where ash particles get settled

from the slurry and clear effluent water is discharged from the ash pond. The

discharged effluents conform to standards specified by CPCB and the same is

regularly monitored.

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

collection and disposal facility with Ash Mound formation. This has been

envisaged for the first time in Asia which has resulted in progressive

development of green belt besides far less requirement of land and less water

requirement as compared to the wet ash disposal system.

Ash Water Recycling System:

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

Recycling System (AWRS) has been provided. In the AWRS, the effluent from

ash pond is circulated back to the station for further ash sluicing to the ash pond.

This helps in savings of fresh water requirements for transportation ofash from

the plant.

The ash water recycling system has already been installed and is in operation at

Ramagundam, Simhadri, Rihand, Talcher Kaniha, Talcher Thermal, Kahalgaon,

Korba and Vindhyachal. The scheme has helped stations to save huge quantity

of fresh water required as make up water for disposal of ash.

Dry Ash Extraction System (DAES):

Dry ash has much higher utilization potential in ash based products (such as

bricks, aerated autoclaved concrete blocks, concrete, Portland pozzolana

cement, etc.). DAES has been installed at Unchahar, Dadri, Simhadri,

Ramagundam, Singrauli, Kahalgaon, Farakka, Talcher Thermal, Korba,

Vindhyachal, Talcher Kaniha and BTPS.

Liquid Waste Treatment Plants & Management System:The objective of industrial liquid effluent treatment plant (ETP) is to discharge

lesser and cleaner effluent from the power plants to meet environmental

regulations. After primary treatment at the source of their generation, the

effluents are sent to the ETP for further treatment. The composite liquid effluent

treatment plant has been designed to treat all liquid effluents which originate

within the power station e.g. Water Treatment Plant (WTP), CondensatePolishing Unit (CPU) effluent, Coal Handling Plant (CHP) effluent, floor

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


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effluents and their appropriate treatment centrally and re circulation of the

treated effluent for various plant uses.

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

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

Jhanor Gandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. These

plants have helped to control quality and quantity of the effluents dischargedfrom the stations.

Sewage Treatment Plants & Facilities:

Sewage Treatment Plants (STPs) sewage treatment facilities have beenprovided at all NTPC stations to take care of Sewage Effluent from Plantand township areas. In a number of NTPC projects modern type STPs with

Clarifloculators, Mechanical Agitators, sludge drying beds, Gas Collection

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

effluent quality is monitored regularly and treated effluent conforming to

the prescribed limit is discharged from the station. At several stations,

treated effluents of STPs are being used for horticulture purpose.

Environmental Institutional Set up :Realizing the importance of protection of the environment with speedy

development of the power sector, the company has constituted different

groups at project, regional and Corporate Centre level to carry out specific

environment related functions. The Environment Management Group, Ash

Utilisation Group and Centre for Power Efficiency & Environment

Protection (CENPEEP) function from the Corporate Centre and initiate

measures to mitigate the impact of power project implementation on the

environment and preserve ecology in the vicinity of the projects.Environment Management and Ash Utilisation Groups established at each

station, look after various environmental issues of the individual station.

Environment Reviews:

To maintain constant vigil on environmental compliance, Environmental

Reviews are carried out at all operating stations and remedial measures have

been taken wherever necessary. As a feedback and follow up of these

Environmental Reviews, a number of retrofit and up gradation measures

have been undertaken at different stations.

Such periodic Environmental Reviews and extensive monitoring of thefacilities carried out at all stations have helped in compliance with the

environmental norms and timely renewal of the Air and Water Consents.


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Up gradation & retrofitting of Pollution Control

Systems:

Waste Management

Various types of wastes such as Municipal or domestic wastes, hazardouswastes, Bio Medical wastes get generated in power plant areas, plant

hospital and the townships of projects. The wastes generated are a number of

solid and hazardous wastes like used oils & waste oils, grease, lead acid

batteries, other lead bearing wastes (such as garkets etc.), oil & clarifier

sludge, used resin, used photo chemicals, asbestos packing, e waste, metal

scrap, C&I wastes, electricial scrap, empty cylinders (refillable), paper,

rubber products, canteen (bio degradable) wastes, buidling material wastes,

silica gel, glass wool, fused lamps & tubes, fire resistant fluids etc. These

wastes fall either under hazardous wastes category or non hazardous wastes

category as per classification given in Government of Indias notification on


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

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

NTPC stations have been discussed below.

Advanced / Eco friendly TechnologiesNTPC has gained expertise in operation and management of 200 MW and500 MW Units installed at different Stations all over the country and is

looking ahead for higher capacity Unit sizes with super critical steam

parameters for higher efficiencies and for associated environmental gains. At

Sipat, higher capacity Units of size of 660 MW and advanced Steam

Generators employing super critical steam parameters have already been

implemented as a green field project.

Higher efficiency Combined Cycle Gas Power Plants are already under

operation at all gas based power projects in NTPC. Advanced clean coaltechnologies such as Integrated Gasification Combined Cycle (IGCC) have

higher efficiencies of the order of 45% as compared to about 38% for

conventional plants. NTPC has initiated a techno economic study under

USDOE / USAID for setting up a commercial scale demonstration power

plant by using IGCC technology. These plants can use low grade coals and

have higher efficiency as compared to conventional plants.

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

awareness among all concerned to keep the pollution under control and

preserve the health and quality of the natural environment in the vicinity ofthe power stations. NTPC is committed to provide affordable and sustainable

power in increasingly larger quantity. NTPC isconscious ofits role in the

national endeavour of mitigating energypoverty, heralding economicprosperity and therebycontributing towards Indias emergence as a majorglobal economy.

ELECTRICITY FROM COAL

Coal from the coal wagons is unloaded with the help of wagon tipplers in the

C.H.P. this coal is taken to the raw coal bunkers with the help of conveyor belts.

Coal is then transported to bowl mills by coal feeders where it is pulverized andground in the powered form.


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

of hot and cold mixture P.A fan. This fan takes atmospheric air, a part of which

is sent to pre heaters while a part goes to the mill for temperature control.

Atmospheric air from F.D fan in the air heaters and sent to the furnace as

combustion air.

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

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

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

sides of the furnace. Due to heat density difference the water rises up in the

water wall tubes. This steam and water mixture is again taken to the boiler drum

where the steam is sent to super heaters for super heating. The super heaters are

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

and finally it goes to the turbine.

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

maintains balance draft in the furnace with F.D fan. These fuel gases heat

energy to the various super heaters and finally through air pre heaters and goes

to electrostatic precipitators where the ash particles are extracted. This ash is

mixed with the water to from slurry is pumped to ash period.

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

through stop valve and control valve that automatically regulate the supply ofsteam to the turbine. Stop valves and controls valves are located in steam chest

and governor driven from main turbine shaft operates the control valves the

amount used.

Steam from controlled valves enter high pressure cylinder of turbines, where it

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

and direct the steam into a second ring of moving blades mounted on the disc

secured in the turbine shaft. The second ring turns the shaft as a result of force

of steam. The stationary and moving blades together.

THERMAL POWER PLANT

A Thermal Power Station comprises all of the equipment and a subsystem

required to produce electricity by using a steam generating boiler fired with

fossil fuels or befouls to drive an electrical generator. Some prefer to use the

term ENERGY CENTER because such facilities convert forms of energy, likenuclear energy, gravitational potential energy or heat energy (derived from the

combustion of fuel) into electrical energy. However, POWER PLANT is the


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most common term in the united state; While POWER STATION prevails in

many Commonwealth countries and especially in the United Kingdom.

Such power stations are most usually constructed on a very large scale and

designed for continuous operation.

Typical diagram of a coal fired thermal power station

1. Cooling water pump2. Three phase transmission line

3. Step up transformer

4. Electrical Generator

5. Low pressure steam

6. Boiler feed water pump

7. Surface condenser

8. Intermediate pressure steam turbine

9. Steam control valve

10. High pressure steam turbine

11. Deaerator Feed water heater

12. Coal conveyor

13. Coal hopper

14. Coal pulverizer

15. boiler steam drum

16. Bottom ash hoper

17. Super heater

18. Forced draught(draft) fan

19. Reheater

20. Combustion air intake

21. Economizer

22. Air preheater

23. Precipitator

24. Induced draught (draft) fan

25. Fuel gas stack

The description of some of the components written above is described asfollows:

1. Cooling towers

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

medium to near the ambivalent web bulb air temperature. Cooling tower use

evaporation of water to reject heat from processes such as cooling the

circulating water used in oil refineries, Chemical plants, power plants and

building cooling, for example. The tower vary in size from small roof top units

to very large hyperboloid structures that can be up to 200 meters tall and 100


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meters in diameter, or rectangular structure that can be over 40 meters tall and

80 meters long. Smaller towers are normally factory built, while larger ones are

constructed on site.

The primary use of large , industrial cooling tower system is to remove the heat

absorbed in the circulating cooling water systems used in power plants ,

petroleum refineries, petrochemical and chemical plants, natural gas processingplants and other industrial facilities . The absorbed heat is rejected to the

atmosphere by the evaporation of some of the cooling water in mechanical

forced draft or induced draft towers or in natural draft hyperbolic shaped

cooling towers as seen at most nuclear power plants.

2.Three phase transmission line

Three phase electric power is a common method of electric power transmission.It is a type of polyphase system mainly used to power motors and many other

devices. A Three phase system uses less conductor material to transmit electric

power than equivalent single phase, two phase, or direct current system at the

same voltage. In a three phase system, three circuits reach their instantaneous

peak values at different times. Taking one conductor as the reference, the other

two current are delayed in time by one third and two third of one cycle of the

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

power transfer over each cycle of the current and also makes it possible to

produce a rotating magnetic field in an electric motor.At the power station, an electric generator converts mechanical powerinto a setof electric currents, one from each electromagnetic coil or winding of the

generator. The current are sinusoidal functions of time, all at the same frequency

but offset in time to give different phases. In a three phase system the phases are

spaced equally, giving a phase separationof one third one cycle . Generatorsoutput at a voltage that ranges from hundreds of volts to 30,000 volts. At the

power station, transformers: step up this voltage to one more suitable for

transmission.

After numerous further conversions in the transmission and distribution network

the power is finally transformed to the standard mains voltage (i.e. the

household voltage).

The power may already have been split into single phase at this point or it may

still be three phase. Where the step down is 3 phase, the output of this

transformer is usually star connected with the standard mains voltage being the

phase neutral voltage. Another system commonly seen in North America is to

have a delta connected secondary with a center tap on one of the windings

supplying the ground and neutral. This allows for 240 V three phase as well as

three different single phase voltages( 120 V between two of the phases and

neutral , 208 V between the third phase ( known as a wild leg) and neutral and


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240 V between any two phase) to be available from the same supply.

3.Electrical generator

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

energy, generally using electromagnetic induction. The task of converting the

electrical energy into mechanical energy is accomplished by using a motor. The

source of mechanical energy may be a reciprocating or turbine steam engine, ,

water falling through the turbine are made in a variety of sizes ranging from

small 1 hp (0.75 kW) units (rare) used as mechanical drives for pumps,

compressors and other shaft driven equipment , to 2,000,000 hp(1,500,000 kW)

turbines used to generate electricity. There are several classifications for modern

steam turbines.

Steam turbines are used in all of our major coal fired power stations to drive thegenerators or alternators, which produce electricity. The turbines themselves are

driven by steam generated in Boilers or steam generators as they are

sometimes called.

Electrical power station use large stem turbines driving electric generators to

produce most (about 86%) of the worlds electricity. These centralized stations

are of two types: fossil fuel power plants and nuclear power plants. The turbines

used for electric powergeneration are most often directly coupled to their generators .As the generators must rotate at constant synchronous speeds

according to the frequency of the electric power system, the most commonspeeds are 3000 r/min for 50 Hz systems,and 3600 r/min for 60 Hz systems.Most large nuclear sets rotate at half those speeds, and havea 4 pole generatorrather than the more common 2 pole one.

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

as it passes through the turbine. The turbine normally consists of several stage

with each stages consisting of a stationary blade (or nozzle) and a rotating

blade. Stationary blades convert the potential energy of the steam into kinetic

energy into forces, caused by pressure drop, which results in the rotation of theturbine shaft. The turbine shaft is connected to a generator, which produces the

electrical energy.

4.Boiler feed water pump

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

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

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

type or positive displacement type.


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Construction and operation

Feed water pumps range in size up to many horsepower and the electric motor is

usually separated from the pump body by some form of mechanical coupling.

Large industrial condensate pumps may also serve as the feed water pump. In

either case, to force the water into the boiler; the pump must generate sufficientpressure to overcome the steam pressure developed by the boiler. This is usually

accomplished through the use of a centrifugal pump.

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

or other similar level sensing device energizing the pump when it detects a

lowered liquid level in the boiler is substantially increased. Some pumps contain

a two stage switch. As liquid lowers to the trigger point of the first stage, the

pump is activated. I f the liquid continues to drop (perhaps because the pump

has failed, its supply has been cut off or exhausted, or its discharge is blocked);

the second stage will be triggered. This stage may switch off the boilerequipment (preventing the boiler from running dry and overheating), trigger an

alarm, or both.

5. Steam powered pumpsSteam locomotives and the steam engines used on ships and stationary

applications such as power plants also required feed water pumps. In this

situation, though, the pump was often powered using a small steam engine that

ran using the steam produced by the boiler. A means had to be provided, ofcourse, to put the initial charge of water into the boiler(before steam power wasavailable to operate the steam powered feed water pump).the pump was often a

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

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

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

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

convert the turbine exhaust steam into pure water so that it may be reused in the

steam generator or boiler as boiler feed water. By condensing the exhaust steam

of a turbine at a pressure below atmospheric pressure, the steam pressure drop

between the inlet and exhaust of the turbine is increased, which increases the

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

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

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

6. Control valves

Control valves are valves used within industrial plants and elsewhere to controloperating conditions such as temperature,pressure,flow,and liquid Level by fully

partially opening or closing in response to signals received from controllers that


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compares a set point to a process variable whose value is provided by

sensors that monitor changes in such conditions. The opening or closing of

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

7. Deaerator

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

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

to make it non corrosive. A dearator typically includes a vertical domed

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

boiler requires that the circulating steam, condensate, and feed water should be

devoid of dissolved gases, particularly corrosive ones and dissolved or

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

will deposit on the heating surfaces giving rise to localized heating and tuberuptures due to overheating. Under some conditions it may give to stress

corrosion cracking.

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

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

operated properly, most deaerator vendors will guarantee that oxygen in the

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

8. Feed water heater

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

delivered to a steam generating boiler. Preheating the feed water reduces the

irreversible involved in steam generation and therefore improves the

thermodynamic efficiency of the system.[4] This reduces plant operating costs

and also helps to avoid thermal shock to the boiler metal when the feed water is

introduces back into the steam cycle.

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

heaters allow the feed water to be brought up to the saturation temperature very

gradually. This minimizes the inevitable irreversibilitys associated with heat

transfer to the working fluid (water). A belt conveyor consists of two pulleys,

with a continuous loop of material the conveyor Belt that rotates about them.

The pulleys are powered, moving the belt and the material on the belt forward.

Conveyor belts are extensively used to transport industrial and agricultural

material, such as grain, coal, ores etc.

9. Pulverizer

A pulverizer is a device for grinding coal for combustion in a furnace in a fossil


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fuel power plant.

10. Boiler Steam Drum

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

water/steam at the top end of the water tubes in the water tube boiler. They store

the steam generated in the water tubes and act as a phase separator for the

steam/water mixture. The difference in densities between hot and cold water

helps in the accumulation of the hotter water/and saturated steam into steam

drum. Made from high grade steel (probably stainless) and its working involves

temperatures 390C and pressure well above 350psi (2.4MPa). The separated

steam is drawn out from the top section of the drum. Saturated steam is drawn

off the top of the drum. The steam will re enter the furnace in through a super

heater, while the saturated water at the bottom of steam drum flows down to themud drum /feed water drum by down comer tubes accessories include a safety

valve, water level indicator and fuse plug. A steam drum is used in the company

of a mud drum/feed water drum which is located at a lower level. So that it acts

as a sump for the sludge or sediments which have a tendency to the bottom.

11. Super Heater

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

the boiler again increasing its thermal energy and decreasing the likelihood thatit will condense inside the engine. Super heaters increase the efficiency of the

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

logically known as superheated steam; non superheated steam is called saturated

steam or wet steam; Super heaters were applied to steam locomotives in quantity

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

engines including power stations.

12. EconomizersEconomizer, or in the UK economizer, are mechanical devices intended to

reduce energy consumption, or to perform another useful function like

preheating a fluid. The term economizer is used for other purposes as well.

Boiler, power plant, and heating, ventilating and air conditioning. In boilers,

economizer are heat exchange devices that heat fluids , usually water, up to but

not normally beyond the boiling point of the fluid.The pulleys are powered,

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

extensively used to transport industrial and agricultural material, such as grain,

coal, ores etc.

A pulverizer is a device for grinding coal for combustion in a furnace in a fossil


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fuel power plant

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

water/steam at the top end of the water tubes in the water tube boiler. They store

the steam generated in the water tubes and act as a phase separator for the

steam/water mixture. The difference in densities between hot and cold water

helps in the accumulation of the hotter water/and saturated steam into steamdrum. Made from high grade steel (probably stainless) and its working involves

temperatures 390C and pressure well above 350psi (2.4MPa). The separated

steam is drawn out from the top section of the drum. Saturated steam is drawn

off the top of the drum. The steam will re enter the furnace in through a super

heater, while the saturated water at the bottom of steam drum flows down to the

mud drum /feed water drum by down comer tubes accessories include a safety

valve, water level indicator and fuse plug. A steam drum is used in the company

of a mud drum/feed water drum which is located at a lower level. So that it acts

as a sump for the sludge or sediments which have a tendency to the bottom.

13. Air Preheater

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

another process (for example, combustion in a boiler). The purpose of the air

preheater is to recover the heat from the boiler flue gas which increases the

thermal efficiency of the boiler by reducingthe useful heat lost in the fuel gas.

As a consequence, the flue gases are also sent to the flue gas stack (or chimney)at a lower temperature allowing simplified design of the ducting and the flue gas

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

14. Precipitator

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

device that removes particles from a flowing gas (such As air) using the force of

an induced electrostatic charge. Electrostatic precipitators are highly efficient

filtration devices, and can easily remove fine particulate matter such as dust andsmoke from the air steam.

ESPs continue to be excellent devices for control of many industrial particulate

emissions, including smoke from electricity generating utilities (coal and oil

fired), salt cake collection from black liquor boilers in pump mills, and catalyst

collection from fluidized bed catalytic crackers from several hundred thousand

ACFM in the largest coal fired boiler application.

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

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

today focusing on rigid discharge electrodes to which many sharpened spikes


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are attached , maximizing corona production. Transformer rectifier systems

apply voltages of 50 100 Kilovolts at relatively high current densities. Modern

controls minimize sparking and prevent arcing, avoiding damage to the

components. Automatic rapping systems and hopper evacuation systems remove

the collected particulate matter while on line allowing ESPs to stay in operation

for years at a time.

15. Fuel gas stack

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

structure through which combustion product gases called fuel gases are

exhausted to the outside air. Fuel gases are produced when coal, oil, natural gas,

wood or any other large combustion device. Fuel gas is usually composed of

carbon dioxide and water vapour as well as nitrogen and excess oxygenremaining from the intake combustion air. It also contains a small percentage of

pollutants such as particulates matter, carbon mono oxide, nitrogen oxides and

sulphur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300

feet) or more, so as to disperse the exhaust pollutants over a greater aria and

thereby reduce the concentration of the pollutants to the levels required by

governmental environmental policies and regulations.When the fuel gases exhausted from stoves, ovens, fireplaces or other small

sources within residential abodes, restaurants , hotels or other stacks are referred

to as chimneys.


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5.OPERATION

POWER GENERATION

Currently NTPC owns 15 Coal Based Power Plants with a generating capacity of 24,395 MW,

and 7 Gas/Liquid Fuel Based Power Plants with a generating capacity of 3,955 MW.Apart from this it has 4 other Coal and Gas Based Power Plants with power generating

capacity of 2,294 MW as joint ventures with other organizations.

Regional spread of Generating Facilities

REGION COAL GAS TOTAL

Northern 7,035 2,312 9,347

Western 6,360 1,293 7,653

Southern 3,600 350 3,950

Eastern 7,400 7,400

Joint Ventures 814 1,480 2,294

TOTAL 25,209 5,435 30,644

Hydro Based Power Projects

NTPC has increased thrust on hydro development for a balanced portfolio for long term

sustainability. The first step in this direction was taken by initiating investment in Koldam

Hydro Electric Power Project (800 MW capacity) located on Satluj river in Bilaspur district

of Himachal Pradesh. Two other hydro projects under construction are Tapovan Vishnugad

(600 MW capacity) and Loharinag Pala (520 MW capacity) in Uttarakhand. On all these

projects construction activities are in full swing.

Performance

In terms of operations, NTPC has always been considerably above the national average. The

availability factor for coal based power stations has increased from 89.32% in 1998 99 to92.47% in 2008 09, which compares favourably with international standards. The PLF has

increased from 76.6% in 1998 99 to 91.14% during the year 2008 09.


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OPERATIONAL PERFORMANCE OF COAL BASED NTPC STATIONS

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

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

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

Availability

Factor

% 85.03 89.36 90.06 88.54 81.8 88.7 88.8 91.20 89.91 90.09

BASIC FUNCTIONING

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

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

connected to a generator. When the turbine turns, electricity is generated andgiven as output by the generator, which is then supplied to the consumers

through high-voltage power lines.


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Process of a Thermal Power Plant

Detailed process of power generation in a thermal power plant:

1) Water intake: Firstly, water is taken into the boiler through a water source. If

water is available in a plenty in the region, then the source is an open pond or

river. If water is scarce, then it is recycled and the same water is used over and

over again.

2) Boiler heating: The boiler is heated with the help of oil, coal or natural gas. A

furnace is used to heat the fuel and supply the heat produced to the boiler. The

increase in temperature helps in the transformation of water into steam.

3) Steam Turbine: The steam generated in the boiler is sent through a steam


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turbine. The turbine has blades that rotate when high velocity steam flows

across them. This rotation of turbine blades is used to generate electricity.

4) Generator: A generator is connected to the steam turbine. When the turbine

rotates, the generator produces electricity which is then passed on to the power

distribution systems.

5) Special mountings: There is some other equipment like the economizer and

air pre-heater.

An economizer uses the heat from the exhaust gases to heat the feed water. An

air pre-heater heats the air sent into the combustion chamber to improve the

efficiency of the combustion process.

6) Ash collection system: There is a separate residue and ash collection system

in place to collect all the waste materials from the combustion process and toprevent them from escaping into the atmosphere.

Apart from this, there are various other monitoring systems and instruments in

place to keep track of the functioning of all the devices. This prevents any

hazards from taking place in the plant.

There are basically two main units of a thermal power plant:

5.1. Steam Generator or Boiler

5.2. Steam Turbine and Electric Generator

We have discussed about the processes of electrical generation further. A

complete detailed description of two (except 2) units is given further.

Coal is conveyed (14) from an external stack and ground to a very fine powder

by large metal spheres in the pulverised fuel mill (16). There it is mixed with

preheated air (24) driven by the forced draught fan (20). The hot air-fuel

mixture is forced at high pressure into the boiler where it rapidly ignites. Waterof a high purity flows vertically up the tube-lined walls of the boiler, where it

turns into steam, and is passed to the boiler drum, where steam is separated

from any remaining water. The steam passes through a manifold in the roof of

the drum into the pendant super heater (19) where its temperature and pressure

increase rapidly to around 200 bar and 540C,


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sufficient to make the tube walls glow a dull red. The steam is piped to the high

pressure turbine (11), the first of a three-stage turbine process. A steam governorvalve (10) allows for both manual control of the turbine and automatic set-point


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following. The steam is exhausted from the high pressure turbine, and reduced

in both pressure and temperature, is returned to the boiler reheater (21). The

reheated steam is then passed to the intermediate pressure turbine (9), and from

there passed directly to the low pressure turbine set (6). The exiting steam, now

a little above its boiling point, is brought into thermal contact with cold water

(pumped in from theCooling tower) in the condenser (8), where it condenses rapidly back into water,

creating near vacuum-like conditions inside the condensor chest. The condensed

water is then passed by a feed pump (7) through a deaerator (12), and pre-

warmed, first in a feed heater (13) powered by steam drawn from the high

pressure set, and then in the economiser (23), before being returned

to the boiler drum. The cooling water from the condensor is sprayed inside a

cooling tower (1), creating a highly visible plume of water vapour, before being

pumped back to the condensor (8) in cooling water cycle. The three turbine sets

are sometimes coupled on the same shaft as the three-phase electrical generator(5) which generates an intermediate level voltage (typically 20-25 kV). This is

stepped up by the unit transformer (4) to a voltage more suitable for

transmission (typically 250-500 kV) and is sent out onto the three-phase

transmission system (3). Exhaust gas from the boiler is drawn by the induced

draft fan (26) through an electrostatic precipitator (25) and is then vented

through the chimney stack (27).

5.1.Steam Generator/BoilerThe boiler is a rectangular furnace about 50 ft (15 m) on a side and 130 ft (40

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

(60 mm) in diameter. Pulverized coal is air-blown into the furnace from fuel

nozzles at the four corners and it rapidly burns, forming a large fireball at the

center. The thermal radiation of the fireball heats the water

that circulates through the boiler tubes near the boiler perimeter. The water

circulation rate in the boiler is three to four times the throughput and is typically

driven by pumps. As the water in the boiler circulates it absorbs heat andchanges into steam at 700 F (370 C) and 3,200 psi (22.1MPa). 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. The steam generating boiler has

to produce steam at the high purity, pressure and temperature required for the

steam turbine that drives the electrical generator. The generator includes the

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

with its steam generating tubes and the superheater coils. Necessary safetyvalves are located at suitable points to avoid excessive boiler pressure. The air

and flue gas path equipment include: forced draft (FD) fan, air preheater (APH),


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boiler furnace, induced draft (ID) fan, fly ash collectors (electrostatic

precipitator or baghouse) and the flue gas stack.

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

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

fan with isolating dampers. On some units of about 60 MW, two boilers per unitmay instead be provided.

Schematic diagram of a coal-fired power plant steam generator

Boiler Furnace and Steam Drum

Once water inside the boiler or steam generator, the process of adding the latentheat of vaporization or enthalpy is underway. The boiler transfers energy to the

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

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

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

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

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

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

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

turned into steam/vapour in the water walls, the steam/vapour once again entersthe steam drum.


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

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

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

This process is known as natural circulation. The boiler furnace auxiliary

equipment includes coal feed nozzles and igniter guns, soot blowers, water

lancing and observation ports (in the furnace walls) for observation of thefurnace interior. Furnace explosions due to any accumulation of combustible

gases after a tripout are avoided by flushing out such gases from the combustion

zone before igniting the coal. The steam drum (as well as the superheater coils

and headers) have air vents and drains needed for initial start-up. The steam

drum has an internal device that removes moisture from the wet steam entering

the drum from the steam generating tubes. The dry steam then flows into the

superheater coils. 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. Nuclear plantsalso boil water to raise steam, either directly passing the working steam through

the reactor or else using an intermediate heat exchanger.

Fuel Preparation System

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 pulverisers maybe 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 100C before being

pumped through the furnace fuel oil spray nozzles.

Boiler Side of the Badarpur Thermal Power Station, New Delhi

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.

Fuel Firing System and Igniter System

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

burners at an angle which imparts a swirling motion to the powdered coal toenhance mixing of the coal powder with the incoming preheated combustion air

and thus to enhance the combustion. To provide sufficient combustion


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temperature in the furnace before igniting the powdered coal, the furnace

temperature is raised by first burning some light fuel oil or processed natural

gas (by using auxiliary burners and igniters provide for that purpose).

Air Path

External fans are provided to give sufficient air for combustion. The forced draft

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 opening. At the furnace outlet and before the furnace gases are

handled by the ID fan, fine dust carried by the outlet gases is removed to avoid

atmospheric pollution. This is an environmental limitation prescribed by law,

and additionally minimizes erosion of the ID fan.

Auxiliary Systems

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 thecollection 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.

Bottom Ash Collection and Disposal

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

bottom ash from the bottom of the furnace. This hopper is always filled with

water to quench the ash and clinkers falling down from the furnace. Somearrangement is included to crush the clinkers and for conveying the crushed

clinkers and bottom ash to a storage site.

Boiler Make-up Water Treatment Plant and Storage

Since there is continuous withdrawal of steam and continuous return of

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

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

this, continuous make-up water is added to the boiler water system. Theimpurities 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


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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. The

final water from this process consists essentially of hydrogen ions andhydroxide ions which is the chemical composition of pure water. The DM water,

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

atmosphere because of its very high affinity for oxygen absorption. The

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

water input. However, some storage is essential as the DM plant may 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 atmospheric air. DM water make-up

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

side). This arrangement not only sprays the water but also DM water gets

deaerated, with the dissolved gases being removed by the ejector of the

condenser itself.

5.2.Steam Turbine and Electric Generator

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.

Barring Gear (or Turning Gear)

Barring gear is the term used for the mechanism provided for rotation of the

turbine generator shaft at a very low speed (about one revolution per minute)

after unit stoppages for any reason. Once the unit is "tripped" (i.e., the turbine

steam inlet valve is closed), the turbine starts slowing or "coasting down".

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 deflection is becausethe heat inside the turbine casing tends to concentrate in the top half of the

casing, thus making the top half portion of the shaft hotter than the bottom half.


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The shaft therefore warps or bends by millionths of inches, only detectable by

monitoring eccentricity meters. But this small amount of shaft deflection would

be enough to cause vibrations and damage the entire steam turbine generator

unit when it is restarted. Therefore, the shaft is not permitted to come to a

complete stop by a mechanism known as "turning gear" or "barring gear" that

automatically takes over to rotate the unit at a preset low speed. If the unit isshut down for major maintenance, then the barring gear must be kept in service

until the temperatures of the casings and bearings are sufficiently low.

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 usesteam ejectors or rotary motor-driven exhausters for continuous removal of air

and gases from the steam side to maintain vacuum. A Typical Water Cooled

Condenser

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 vapour pressure of water is much less than

atmospheric pressure, the condenser generally works under vacuum. Thus leaks

of noncondensible air into the closed loop must be prevented. Plants operatingin 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.


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A typical water cooled condensor

Feedwater Heater

A Rankine cycle with a two-stage steam turbine and a single feedwater heater.

In the case of a conventional steam-electric power plant utilizing a drum boiler,

the surface condenser removes the latent heat of vaporization from the steam as

it changes states from vapour to liquid. The heat content (btu) in the steam is

referred to as Enthalpy. The condensate pump then pumps the condensate water

through a feedwater heater. The feedwater heating equipment then raises the

temperature of the water by utilizing extraction steam from various stages of the

turbine. Preheating the feedwater reduces the irreversibilitys involved in steamgeneration and therefore improves the thermodynamic efficiency of the system.

[9] This reduces plant operating costs and also helps to avoid thermal shock to

the boiler metal when the feedwater is introduced back into the steam cycle.


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A Rankine cycle with a 2-stage steam turbine and a single feedwater

heater

Superheater

As the steam is conditioned by the drying equipment inside the drum, it is piped

from the upper drum area into an elaborate set up of tubing in different areas of

the boiler. The areas known as superheater and reheater. The steam vapour picks

up energy and its temperature is now superheated above the saturation

temperature. The superheated steam is then piped through the main steam linesto the valves of the high pressure turbine.


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Deaerator

A steam generating boiler requires that the boiler feed water should be devoid of

air and other dissolved gases, particularly corrosive ones, in order to avoidcorrosion of the metal. Generally, power stations use a deaerator to provide for

the removal of air and other dissolved gases from the boiler feedwater. A

deaerator typically includes a vertical, domed deaeration section mounted on

top of a horizontal cylindrical vessel which serves as the deaerated boiler

feedwater storage tank.

Boiler Feed Water DeaeratorThere are many different designs for a deaerator and the designs will vary from

one manufacturer to another. The adjacent diagram depicts a typical

conventional trayed deaerator. If operated properly, most deaeratormanufacturers will guarantee that oxygen in the deaerated water will not exceed

7 ppb by weight (0.005 cm3/L).


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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 apreset speed of the turbine during start-ups, a pump driven by the turbine main

shaft takes over the functions of the auxiliary system.

Generator Heat Dissipation

The electricity generator requires cooling to dissipate the heat that it generates.

While small units 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 transfercoefficient of any gas and for its low viscosity which reduces windage losses.

This system requires special handling during start-up, with air in the chamber

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 outside air ingress. The hydrogen must be sealed

against outward leakage where the shaft emerges from the casing. Mechanical

seals around the shaft are installed with a very small annular gap to avoid

rubbing between the shaft and the seals. Seal oil is used to prevent the hydrogengas leakage to atmosphere. The generator also uses water cooling. Since the

generator coils are at a potential of about 15.75kV and water is conductive, an

insulating barrier such as Teflon is used to interconnect the water line and the

generator high voltage windings. Demineralised water of low conductivity is

used.

Generator High Voltage System

The generator voltage ranges from 10.5 kV in smaller units to 15.75 kV inlarger units. The generator high voltage leads are normally large aluminum

channels because of their high current as compared to the cables used in smaller

machines. They are enclosed in well-grounded aluminum bus ducts and are

supported on suitable insulators. The generator high voltage channels are

connected to step-up transformers for connecting to a high voltage electrical

substation (of the order of 220 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. In smaller units, generating at 10.5kV, a breaker is provided to connect it toa common 10.5 kV bus system.


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Other Systems

Monitoring and Alarm system

Most of the power plants 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.

Battery Supplied Emergency Lighting & 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 safe, damage-free shutdown of the

units in an emergency situation.


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ELECTRICITY GENERATION PROCESS

(A BASIC OVERVIEW)

HOW ELECTRICITY IS GENERATED?

Thermal power station burns fuel and uses the resultant heat to raise steam

which drives the TURBO GENERATOR. The fuel may be

fossil(coal,oil,natural gas) or it may be fissionable, whichever fuel is used, the

objective is same to convert the mechanical energy into electricity by rotating a

magnet inside a set of winding.

COAL TO STAEM

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

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

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

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

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

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

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

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

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

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

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

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

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

bunker for sale while the clean flue gases are passed on through IP fans to be

discharged through chimneys.

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

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

is transformed by heat into staemat high temperature and pressure.. The steam

superheated in further tubes (superheaters) passes to turbine where it is

discharged through the nozzle on the turbine blades. Just as the energy of wind

turns the sail of the windmill, the energy of steam striking the blade makes the

turbine rotate.

Coupled to the end of the turbine is the rotor of the generator. The rotor is

housed inside the stator having heavy coils of the bars in which electricity is

produced through the movement of magnetic field created by the rotor.


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Electricity passes from stator windings to step-up transformer which increases

its voltage so that it can be transmited efficiently over lines of grid.

The staem which has given up its heat energy is cahnged back into water in a

condenser so that it is ready for re-use. The condenser contains many kilometers

of tubing through which cold water is constantly pumped. The staem passingaround the tubes looses heat.Thus it is rapidly changed back into water.

But, the two lots of water, that is, the boiler feed and cooling water must never

mix. Cooling water is drawn from river- bed, but the boiler feed water must be

absolutely pure, far purer than the water we drink(de-mineralized water),

otherwise it may damage the boiler tubes.


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6.CONTROL AND INSTRUMENTATION

I was assigned to do training in control and instrumentation from

10th June 2010 to 28th 2010

CONTROL AND INSTRUMENTATION

This division basically calibrates various instruments and takes care of any

faults occur in any of the auxiliaries in the plant.This department is the brain of the plant because from the relays to

transmitters followed by the electronic computation chipsets and recorders

and lastly the controlling circuitry, all fall under this.

It has following labs:

1. MANOMETRY LAB

2. PROTECTION AND INTERLOCK LAB

3. AUTOMATION LAB

4. WATER TREATEMENT LAB

5. FURNACE SAFETY SUPERVISORY SYSTEM(FSSS)

6. ELECTRONICS TEST LAB

6.1.MANOMETRY LAB:

6.1.1 TRANSMITTERS:

It is used for pressure measurements of gases and liquids, its working principle

is that the input pressure is converted into electrostatic capacitance and from

there it is conditioned and amplified. It gives an output of 4 20 mA dc. It can be

mounted on a pipe or a wall. For liquid or steam measurement transmitters is

mounted below main process piping and for gas measurement transmitter is

placed above pipe.

6.1.2 MANOMETER:


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Its a tube which is bent, in U shape. It is filled with a liquid. This device

corresponds to a difference in pressure across the two limbs.

6.1.3 BOURDEN PRESSURE GAUGE

Its an oval section tube. Its one end is fixed. It is provided with a pointer toindicate the pressure on a calibrated scale. It is of 2 types:

(a) Spiral type: for Low pressure measurement.

(b) Helical Type: for High pressure measurement.

6.2.PROTECTION AND INTERLOCK LAB:

6.2.1 INTERLOCKING:

It is basically interconnecting two or more equipments so that if one equipments

fails other one can perform the tasks. This type of interdependence is also

created so that equipments connected together are started and shut down in the

specific sequence to avoid damage.

For protection of equipments tripping are provided for all the equipments.

Tripping can be considered as the series of instructions connected through ORGATE. When a fault occurs and any one of the tripping is satisfied a signal is

sent to the relay, which trips the circuit. The main equipments of this lab are

relay and circuit breakers. Some of the instrument uses for protection are:

6.2.1.1 RELAY:

It is a protective device. It can detect wrong condition in electrical circuits by

constantly measuring the electrical quantities flowing under normal and faulty

conditions. Some of the electrical quantities are voltage, current, phase angleandvelocity.

6.2.1.2 FUSES:

It is a short piece of metal inserted in the circuit, which melts when heavy

current flows through it and thus breaks the circuit. Usually silver is used as a

fuse material because:

a) The coefficient of expansion of silver is very small. As a result nocriticalfatigue occurs and thus the continuous full capacity normal current ratings are

assured for the long time.


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b) The conductivity of the silver is unimpaired by the surges of the current that

produces temperatures just near the melting point.

c) Silver fusible elements can be raised from normal operating temperature to

vaporization quicker than any other material because of its comparatively low

specific heat.

6.2.2 MINIATURE CIRCUIT BREAKER:

They are used with combination of the control circuits to.

a) Enable the staring of plant and distributors.

b) Protect the circuit in case of a fault.

In consists of current carrying contacts, one movable and other fixed. When a

fault occurs the contacts separate and are is stuck between them. There arethree types of

MANUAL TRIP

THERMAL TRIP

SHORT CIRCUIT TRIP

6.2.3 P ROTECTION AND INTERLOCK SYSTEM:

1. HIGH TENSION CONTROL CIRCUIT:

For high tension system the control system are excited by separate D.C supply.

For starting the circuit conditions should be in series with the starting coil of the

equipment to energize it. Because if even a single condition is not true then

system will not start.

2.LOW TENSION CONTROL CIRCUIT:

For low tension system the control circuits are directly excited from the 0.415

KV A.C supply. The same circuit achieves both excitation and tripping. Hence

the tripping coil is provided for emergency tripping if the interconnection fails.


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3. AUTOMATION LAB:

This lab deals in automating the existing equipment and feeding routes.

Earlier, the old technology dealt with only (DAS) Data Acquisition System and

came to be known as primary systems. The modern technology or the secondarysystems are coupled with (MIS) Management Information System. But this lab

universally applies the pressure measuring instruments as the controlling force.

However, the relays are also provided but they are used only for protection and

interlocks.

Once the measured is common i.e. pressure the control circuits can easily be

designed with single chips having multiple applications. Another point is the

universality of the supply, the laws of electronic state that it can be any where

between 12V and 35V in the plant. All the control instruments are excited by

24V supply (4 20mA) because voltage can be mathematically handled with easetherefore all control systems use voltage system for computation. The latest

technology is the use of ETHERNET for control signals.5.3

PYROMETER LAB

(1) LIQUID IN GLASS THERMOMETER:Mercury in the glass thermometer boils at 340 degree Celsius which limits the

range of temperature that can be measured. It is L shaped thermometer which is

designed to reach all inaccessible places.

(2) ULTRA VIOLET CENSOR:

This device is used in furnace and it measures the intensity of ultra violet rays

there and according to the wave generated which directly indicates the

temperature in the furnace.

(3) THERMOCOUPLES:This device is based on SEEBACK and PELTIER effect. It comprises of two

junctions at different temperature. Then the emf is induced in the circuit due to

the flow of electrons. This is an important part in the plant.

(4) RTD (RESISTANCE TEMPERATURE DETECTOR):It performs the function of thermocouple basically but the difference is of a

resistance. In this due to the change in the resistance the temperature difference

is measured.

In this lab, also the measuring devices can be calibrated in the oil bath or just


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boiling water (for low range devices) and in small furnace (for high range

devices).

4. FURNACE SAFETY AND SUPERVISORY SYSTEM

LAB:This lab has the responsibility of starting fire in the furnace to enable theburning of coal. For first stage coal burners are in the front and rear of the

furnace and for the second and third stage corner firing is employed. Unburnt

coal is removed using forced draft or induced draft fan. The temperature inside

the boiler is 1100 degree Celsius and its height is 18 to 40 m. It is made up of

mild steel. An ultra violet sensor is employed in furnace to measure the intensity

of ultra violet rays inside the furnace and according to it a signal in the same

order of same mV is generated which directly indicates the temperature of the

furnace.

For firing the furnace a 10 KV spark plug is operated for ten seconds over a

spray of diesel fuel and pre heater air along each of the feeder mills. The

furnace has six feeder mills each separated by warm air pipes fed from forced

draft fans. In first stage indirect firing is employed that is feeder mills are not fed

directly from coal but are fed from three feeders but are fed from pulverized

coalbunkers. The furnace can operate on the minimum feed from three feeders

but under not circumstances should any one be left out under operation, to

prevent creation of pressure different with in the furnace, which threatens to

blast it.

5.ELECTRONICS LAB:

This lab undertakes the calibration and testing of various cards. It houses

various types of analytical instruments like oscilloscopes, integrated circuits,cards auto analyzers etc.

Various processes undertaken in this lab are:

1. Transmitter converts mV to mA.

2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts the

magnetic portion.

3. ANNUNCIATION CARDS

They are used to keep any parameter like temperature etc. within limits. It gets a

signal if parameter goes beyond limit. It has a switching transistor connected to

relay that helps in alerting the UCB.


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PRESSURE MONITORING

Pressure can be monitored by three types of basic mechanisms

Switches Gauges Transmitter type

For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressuremeasurement device. It is widely used in applications where inexpensive static

pressure measurements are needed.

A typical Bourdon tube contains a curved tube that is open to external pressureinput on one end and is coupled mechanically to an indicating needle on the

other end, as shown schematically below.

Typical Bourdon Tube Pressure Gages

For Switches pressure swithes are used and they can be used for digital meansof monitoring as swith being ON is referred as high and being OFF is as low.All the monitored data is converted to either Current or Voltage parameter.

The Plant standard for current and voltage are as under

Voltage : 0 10 Volts range Current : 4 20 milliAmperes

We use 4mA as the lower value so as to check for disturbances and wire breaks.

Accuracy of such systems is very high .ACCURACY : + - 0.1 %

The whole system used is SCADA based.


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Normally used Thermocouple is K Type Thermocouple:Chromel(Nickel-Chromium Alloy) /Alumel(Nickel-Aluminium Alloy)This is the most commonly used general purpose thermocouple. It is

inexpensive and, owing to its popularity, available in a wide variety of probes.

They are available in the 200 C to +1200 C range. Sensitivity isapproximately 41 V/C.

RTDs are also used but not in protection systems due to vibrational errors.

We pass a constant curre t through the RTD. So that if R changes then the

Voltage also changes RTDs used in Industries are Pt100 and Pt1000

Pt100 : 0 0C 100 ( 1 = 2.5 0C )

Pt1000 : 00

C - 1000Pt1000 is used for higher accuracyThe gauges used for Temperature measurements are mercury filled Temperature

gauges. For Analog medium thermocouples are used And for Digital medium

Switches are used which are basically mercury switches.

FLOW MEASUREMENT

Flow measurement does not signify much and is measured just for meteringpurposes and for monitoring the processes

ROTAMETERS:A Rotameter is a device that measures the flow rate of liquid or gas in a closed

tube. It is occasionally misspelled as 'rotometer'.

It belongs to a class of meters called variable area meters, which measure flow

rate by allowing the cross sectional area the fluid travels through to vary,

causing some measurable effect.A rotameter consists of a tapered tube, typically made of glass, with a float

inside that is pushed up by flow and pulled down by gravity. At a higher flow

rate more area (between the float and the tube) is needed to accommodate the

flow, so the float rises. Floats are made in many different shapes, with spheres

and spherical ellipses being the most common. The float is shaped so that it

rotates axially as the fluid passes. This allows you to tell if the float is stuck

since it will only rotate if it is not.

For Digital measurements Flap system is used.

For Analog measurements we can use the following methods :

Flowmeters


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Venurimeters / Orifice meters Turbines Massflow meters ( oil level ) Ultrasonic Flow meters Magnetic Flowmeter ( water level )

Selection of flow meter depends upon the purpose , accuracy and liquid to be

measured so different types of meters used.Turbine type are the simplest of all.They work on the principle that on each rotation of the turbine a pulse is

generated and that pulse is counted to get the flow rate.

VENTURIMETERS :

Referring to the diagram, using Bernoulli's equation in the special case of

incompressible fluids (such as the approximation of a water jet), the theoretical

pressure drop at the constriction would be given by (/2)(v22 - v1

2).

And we know that rate of flow is given by:

Flow = k (D.P)Where DP is Differential Presure or the Pressure Drop.

CONTROL VALVES

A valve is a device that regulates the flow of substances (either gases,fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing

various passageways. Valves are technically pipe fittings, but usually are

discussed separately.

Valves are used in a variety of applications including industrial, military,commercial, residential, transportation. Plumbing valves are the most obvious in


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everyday life, but many more are used.

Some valves are driven by pressure only, they are mainly used for safety

purposes in steam engines and domestic heating or cooking appliances. Others

are used in a controlled way, like in Otto cycle engines driven by a camshaft,

where they play a major role in engine cycle control.

Many valves are controlled manually with a handle attached to the valve stem.

If the handle is turned a quarter of a full turn (90) between operating positions,

the valve is called a quarter-turn valve. Butterfly valves, ball valves, and plug

valves are often quarter-turn valves. Valves can also be controlled by devices

called actuators attached to the stem. They can be electromechanical actuators

such as an electric motor or solenoid, pneumatic actuators which arecontrolled by air pressure, orhydraulic actuators which are controlled by the

pressure of a liquid such as oil or water.

So there are basically three types of valves that are used in power industries

besides the handle valves. They are :

Pneumatic Valves they are air or gas controlled which iscompressed to turn or move them

Hydraulic valves they utilize oil in place of Air as oil has bettercompression

Motorised valves these valves are controlled by electric motors

FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSSis also called as Burner Management System (BMS). It is a

microprocessor based programmable logic controller of proven design

incorporatingall protection facilities required for such system. Main objective

of FSSS is to ensure safety of the boiler.

The 95 MW boilers are indirect type boilers. Fire takes place in front and in rearside. Thats why its called front and rear type boiler. The 210 MW boilers are

direct type boilers (which mean that HSD is in direct contact with coal) firing

takes place from the corner. Thus it is also known as corn

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