Shanu Ntpc Report

8/6/2019 Shanu Ntpc Report

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May-June

2011

SUBMITTED BY:

SHANU KUMAR

B.TECH (2ND

YEAR)

INSTRUMENTATION ENGINEERING

ROLL NO. - 09IE1013IIT KHARAGPUR

Summer Training Report


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ACKNOWLEDGEMENT

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

everyone for helping me complete the training here.

I do extend my heartful thanks to Ms. Rachna Singh Bahal 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 has helped me a lot during the course of training. I have learnt alot 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 incharge of IIT Kharagpur and all the faculty

members of Electical (Instrumentation) Engineering Department for their effort of constant

co- operation, which have been a significant factor in the accomplishment of my industrial

training.

SHANU KUMAR

IIT KHARAGPUR


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CERTIFICATE

This is to certify that SHANU KUMAR, a 2nd

year B.Tech student of

Instrumentation Engineering, Indian Institute of Technology, Kharagpur, has successfully

completed his Industrial Training at National Thermal Power Corporation, New Delhi for 6

week from 9th

May2011 to 18st

June2011. He has completed the whole training as per the

training report submitted by him.

Training InchargeNTPC Badarpur,

Badarpur, New Delhi


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TRAINING AT BTPS

I was appointed to do 6 week training at this esteemed organization from 9th may to 18th June,

2011. I was assigned the following division of the plant:

Control and Instrumentation ( C & I )

These 6 weeks training was a very educational adventure for me. It was really amazing

to see the plant by yourself and learn how electricity, which is one of our daily requirements

of life, is produced.

This report has been made by my experience at BTPS. The material in this report has

been gathered from my textbook, senior student reports and trainers manuals and power

journals provided by training department. The specification and principles are as learned by

me from the employees of each division of BTPS.

SHANU KUMAR


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CONTENTS


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ABOUT NTPC

NTPC Limited is the largest thermal power generating company of India, 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 the balance 10.5% is held by

FIIs, Domestic Banks, Public and others. Within a span of 35 years, NTPC has emerged as a

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

country.

NTPC's core business is engineering, construction and operation of power generating plants

and providing consultancy to power utilities in India and abroad.

The total installed capacity of the company is 34194 MW (including JVs) with 15 coal based

and 7 gas based stations, located across the country. In addition under JVs, 3 stations are coal

based & another station uses naphtha/LNG as fuel. By 2017, the power generation portfolio is

expected to have a diversified fuel mix with coal based capacity of around 53000 MW, 10000

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

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

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

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


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

18.79% of the total national capacity it contributes 28.60% of total power generation due to

its focus on high efficiency. NTPCs share at 31 Mar 2001 of the total installed capacity of

the country was 24.51% and it generated 29.68% of the power of the country in 2008-09.

Every fourth home in India is lit by NTPC. 170.88BU of electricity was produced by its

stations in the financial year 2005-2006. The Net Profit after Tax on March 31, 2006 was

INR 58,202 million. Net Profit after Tax for the quarter ended June 30, 2006 was INR 15528

million, which is 18.65% more than for the same quarter in the previous financial year.

2005).

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 forash utilization. In 1991, it set up Ash Utilization

Division.

A graphical overview
http://www.ntpc.co.in/operations/operations.shtmlhttp://www.ntpc.co.in/infocus/environment.shtmlhttp://www.ntpc.co.in/infocus/ashutilisation.shtmlhttp://www.ntpc.co.in/infocus/ashutilisation.shtmlhttp://www.ntpc.co.in/infocus/environment.shtmlhttp://www.ntpc.co.in/operations/operations.shtml


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Technological Initiatives

Introduction of steam generators (boilers) of the size of 800 MW. Integrated Gasification Combined Cycle (IGCC) Technology. Launch of Energy Technology Centre -A new initiative for development of

technologies with focus on fundamental R&D.

The company sets aside up to 0.5% of the profits for R&D. Mechanism to help get / earn Certified Emission Reduction.

Corporate Social Responsibility

As a responsible corporate citizen NTPC has taken up number of CSR initiatives. NTPC Foundation formed to address Social issues at national level NTPC has framed Corporate Social Responsibility Guidelines committing up to

0.5% of net profit annually for Community Welfare.

The welfare of project affected persons and the local population around NTPCprojects are taken care of through well drawn Rehabilitation and Resettlement

policies.

Partnering government in various initiatives

Consultant role to modernize and improvise several plants across the country. Disseminate technologies to other players in the sector. Consultant role Partnership in Excellence Programme for improvement of PLF of

15 Power Stations of SEBs.

Rural Electrification work under Rajiv Gandhi Garmin Vidyutikaran.

Environment Management

All stations of NTPC are ISO 14001 certified. Various groups to care of environmental issues. The Environment Management Group. Ash Utilization Division. Afforestation Group. Centre for Power Efficiency & Environment Protection. Group on Clean Development Mechanism


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JOURNEY OF NTPC

NTPC was set up in 1975 with 100% ownership by the Government

of India. In the last 30 years, NTPC has grown into the largest power

utility in India.

In 1997, Government of India granted NTPC status of Navratna

being one of the nine jewels of India, enhancing the powers to the

Board of Directors.

NTPC became a listed company with majority Government

ownership of 89.5%.

NTPC becomes third largest by Market Capitalization of listed

companies

The company rechristened as NTPC Limited in line with its

changing business portfolio and transforms itself from a thermal

power utility to an integrated power utility.

National Thermal Power Corporation is the largest power

generation company in India. Forbes Global 2000 for 2008 ranked it

411th in the world.

National Thermal Power Corporation is the largest power

generation company in India. Forbes Global 2000 for 2008 ranked it

317th in the world.

NTPC has also set up a plan to achieve a target of 50,000 MW

generation capacity.

NTPC has embarked on plans to become a 75,000 MW company by

2017.

1975

1997

2005

2004

2008

2009

2017

2012


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ABOUT BTPS

Badarpur thermal power station started working in 1973 with a single 95 mw unit. There

were 2 more units (95 MW each) installed in next 2 consecutive years. Now it has total five

units with total capacity of 720 MW. Ownership of BTPS was transferred to NTPC with

effect from 01.06.2006 through GOIs Gazette Not ification .Given below are the details of

unit with the year they are installed.

Address: Badarpur, New Delhi110 044

Telephone: (STD-011) - 26949523

Fax: 26949532

Installed Capacity 720 MW

Derated Capacity 705 MW

Location New Delhi

Coal Source Jharia Coal Fields

Water Source Agra Canal

Beneficiary States Delhi

Unit Sizes 3X95 MW

2X210 MW

Units Commissioned Unit I- 95 MW - July 1973

Unit II- 95 MW August 1974

Unit III- 95 MW March 1975

Unit IV - 210 MW December 1978

Unit V - 210 MW - December 1981

Transfer of BTPS to NTPC Ownership of BTPS was transferred to NTPC with

effect from 01.06.2006 through GOIs Gazette

Notification


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BASIC STEPS OF ELECTRICITY GENERATION

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

Coal to steam Steam to mechanical power

Mechanical power to electrical power

COAL TO ELECTRICITY: BASICS

The basic steps in the generation of coal to electricity are shown below:

Coal to Steam

Coal from the coal wagons is unloaded in the coal handling plant. This Coal is transported up

to the raw coal bunkers with the help of belt conveyors. Coal is transported to Bowl mills by

Coal Feeders. The coal is pulverized in the Bowl Mill, where it is ground to powder form.

The mill consists of a round metallic table on which coal particles fall. This table is rotated

with the help of a motor. There are three large steel rollers, which are spaced 120 apart.

When there is no coal, these rollers do not rotate but when the coal is fed to the table it packs


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up between roller and the table and ths forces the rollers to rotate. Coal is crushed by the

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

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

P.A. Fan takes atmospheric air, a part of which is sent to Air-Preheaters for heating while a

part goes directly to the mill for temperature control. Atmospheric air from F.D. Fan is heated

in the air heaters and sent to the furnace as combustion air.

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

Water from the drum passes through 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 and

density difference, the water rises up in the water wall tubes. Water is partly converted to

steam as it rises up in the furnace. This steam and water mixture is again taken to thee boiler

drum where the steam is separated from water.


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Water follows the same path while the steam is sent to superheaters for superheating. The

superheaters are located inside the furnace and the steam is superheated (540C) and finally it

goes to the turbine.

Flue gases from the furnace are extracted by induced draft fan, which maintains balance draft

in the furnace (-5 to 10 mm of wcl) with forced draft fan. These flue gases emit their heat


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energy to various super heaters in the pent house and finally pass through air-preheaters and

goes to electrostatic precipitators where the ash particles are extracted. Electrostatic

Precipitator consists of metal plates, which are electrically charged. Ash particles are

attracted on to these plates, so that they do not pass through the chimney to pollute the

atmosphere. Regular mechanical hammer blows cause the accumulation of ash to fall to the

bottom of the precipitator where they are collected in a hopper for disposal.

Steam to Mechanical Power

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

be used to shut-off the steam in case of emergency) and through control valves that

automatically regulate the supply of steam to the turbine. Stop valve and control valves are

located in a steam chest and a governor, driven from the main turbine shaft, operates the

control valves to regulate the amount of steam used. (This depends upon the speed of the

turbine and the amount of electricity required from the generator).

Steam from the control valves enters the high pressure cylinder of the turbine, where it passes

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

the steam into a second ring of moving blades mounted on a disc secured to the turbine shaft.

The second ring turns the shafts as a result of the force of steam. The stationary and moving

blades together constitute a stage of turbine and in practice many stages are necessary, so

that the cylinder contains a number of rings of stationary blades with rings of moving blades

arranged between them. The steam passes through each stage in turn until it reaches the end

of the high-pressure cylinder and in its passage some of its heat energy is changed into

mechanical energy.

The steam leaving the high pressure cylinder goes back to the boiler for reheating and returns

by a further pipe to the intermediate pressure cylinder. Here it passes through another series

of stationary and moving blades.

Finally, the steam is taken to the low-pressure cylinders, each of which enters at the centre

flowing outwards in opposite directions through the rows of turbine blades through an

arrangement called the double flow- to the extremities of the cylinder. As the steam gives

up its heat energy to drive the turbine, its temperature and pressure fall and it expands.


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Because of this expansion the blades are much larger and longer towards the low pressure

ends of the turbine.

Mechanical Power to Electrical Power

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

turbine, also rotates. It results in rotation of the coil of the generator, which causes induced

electricity to be produced.

BASIC POWER PLANT CYCLE

A simplified diagram of a thermal power plant

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

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

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

reheating of steam.


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

which is a way of partially overcoming temperature limitations. By returning partially

expanded steam, to a reheat, the average temperature at which the heat is added, is increased

and, by expanding this reheated steam to the remaining stages of the turbine, the exhaust

wetness is considerably less than it would otherwise be conversely, if the maximum tolerable

wetness is allowed, the initial pressure of the steam can be appreciably increased.

Bleed Steam Extraction: For regenerative system, nos. of non-regulated extractions is taken

from HP, IP turbine.

Regenerative heating of the boiler feed water is widely used in modern power plants; the

effect being to increase the average temperature at which heat is added to the cycle, thus

improving the cycle efficiency.

FACTORS AFFECTING THERMAL CYCLE EFFICIENCY

Thermal cycle efficiency is affected by following:

Initial Steam Pressure. Initial Steam Temperature. Whether reheat is used or not, and if used reheat pressure and temperature. Condenser pressure. Regenerative feed water heating.


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UNITS OF A THERMAL POWER PLANT

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

1.) Steam Generator or Boiler

2.) Steam Turbine

3.) Electric Generator

Steam Generator/Boiler

The 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 and

changes 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


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with its steam generating tubes and the 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 (APH),

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 unit

may instead be provided.

Schematic diagram of a coal-fired power plant steam generator


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Boiler Furnace and Steam Drum

Once water inside the boiler or steam generator, the process of adding the latent

heat of vaporization or enthalpy is underway. The boiler transfers energy to the

water 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 andis eventually turned into steam due to the heat being generated by the burners

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

steam/vapour in the water walls, the steam/vapour once again enters the steam

drum.

External View of an Industrial Boiler at BTPS, New Delhi


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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 the

furnace 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 plants

also 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 theboilers. The coal is next pulverized into a very fine powder. The pulverisers

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 100C before being

pumped through the furnace fuel oil spray nozzles.


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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 to

enhance mixing of the coal powder with the incoming preheated combustion air

and thus to enhance the combustion. To provide sufficient combustion

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


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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 avoidbackfiring 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 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.


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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. Some

arrangement 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. The

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 leadto overheating and failure of the tubes. Thus, the salts have to be removed from

the water and that is done by a


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Water Demineralising Treatment Plant (DM).

Ash Handling System at Badarpur Thermal Power Station, New Delhi

A DM plant generally consists of cation, anion and mixed bed exchangers. The

final water from this process consists essentially of hydrogen ions and

hydroxide 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


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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.

Steam Turbine

MAIN TURBINE:

The 210MW turbine is a cylinder tandem compounded type machine

comprising of H.P. and I.P and L.P cylinders. The H.P. turbine comprises of 12

stages the I.P turbine has 11 stages and the L.P has four stages of double flow.

The H.P and I.P. turbine rotor are rigidly compounded and the I.P. and L.P rotor

by lens type semi flexible coupling. All the 3 rotors are aligned on five bearings

of which the bearing number is combined with thrust bearing.

The main superheated steam branches off into two streams from the boiler and

passes through the emergency stop valve and control valve before entering the

governing wheel chamber of the H.P. Turbine. After expanding in the 12 stages

in the H.P. turbine then steam is returned in the boiler for reheating.

The reheated steam from boiler enters I.P. turbine via the interceptor valves and

control valves and after expanding enters the L.P stage via 2 numbers of cross

over pipes.

In the L.P. stage the steam expands in axially opposed direction to counteract

the thrust and enters the condenser placed directly below the L.P. turbine. The

cooling water flowing through the condenser tubes condenses the steam and the

condensate the collected in the hot well of the condenser.

The condensate collected the pumped by means of 3x50% duty condensate

pumps through L.P heaters to deaerator from where the boiler feed pump

delivers the water to the boiler through H.P. heaters thus forming a closed cycle.


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STEAM TURBINE

A steam turbine is a mechanical device that extracts thermal energy from

pressurized steam and converts it into useful mechanical work.

From a mechanical point of view, the turbine is ideal, because the propelling

force is applied directly to the rotating element of the machine and has not as in

the reciprocating engine to be transmitted through a system of connecting links,

which are necessary to transform a reciprocating motion into rotary motion.

Hence since the steam turbine possesses for its moving parts rotating elements

only if the manufacture is good and the machine is correctly designed, it ought

to be free from out of balance forces.

If the load on a turbine is kept constant the torque developed at the coupling is

also constant. A generator at a steady load offers a constant torque. Therefore, a

turbine is suitable for driving a generator, particularly as they are both high-

speed machines.

A further advantage of the turbine is the absence of internal lubrication. Thismeans that the exhaust steam is not contaminated with oil vapour and can be

condensed and fed back to the boilers without passing through the filters. It also

means that turbine is considerable saving in lubricating oil when compared with

a reciprocating steam engine of equal power.

A final advantage of the steam turbine and a very important one is the fact that a

turbine can develop many time the power compared to a reciprocating enginewhether steam or oil.

OPERATING PRINCIPLES

A steam turbines two main parts are the cylinder and the rotor. The cylinder

(stator) is a steel or cast iron housing usually divided at the horizontal

centerline. Its halves are bolted together for easy access. The cylinder contains

fixed blades, vanes and nozzles that direct steam into the moving blades carried


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by the rotor. Each fixed blade set is mounted in diaphragms located in front of

each disc on the rotor, or directly in the casing. A disc and diaphragm pair a

turbine stage. Steam turbines can have many stages. A rotor is a rotating shaft

that carries the moving blades on the outer edges of either discs or drums. The

blades rotate as the rotor revolves. The rotor of a large steam turbine consists of

large, intermediate and low-pressure sections.

In a multiple-stage turbine, steam at a high pressure and high temperature enters

the first row of fixed blades or nozzles through an inlet valve/valves. As the

steam passes through the fixed blades or nozzles, it expands and its velocity

increases. The high velocity jet of stream strikes the first set of moving blades.

The kinetic energy of the steam changes into mechanical energy, causing the

shaft to rotate. The steam that enters the next set of fixed blades strikes the next

row of moving blades.

As the steam flows through the turbine, its pressure and temperature decreases

while its volume increases. The decrease in pressure and temperature occurs asthe steam transmits energy to the shaft and performs work. After passing

through the last turbine stage, the steam exhausts into the condenser or process

steam system.

The kinetic energy of the steam changes into mechanical energy through the

impact (impulse) or reaction of the steam against the blades. An impulse turbine

uses the impact force of the steam jet on the blades to turn the shaft. Steamexpands as it passes through thee nozzles, where its pressure drops and its

velocity increases. As the steam flows through the moving blades, its pressure

remains the same, but its velocity decreases. The steam does not expand as it

flows through the moving blades.


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STEAM CYCLE

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

closed cycle to enable the working fluid (water) to be used again and again. The

cycle used is Rankine cycle modified to include superheating of steam,

regenerative feed water heating and reheating of steam.

MAIN TURBINE

The 210 MW turbine is a tandem compounded type machine comprising of H.P.

and I.P. cylinders. The H.P. turbines comprise of 12 stages, I.P. turbine has 11

stages and the L.P. turbine has 4 stages of double flow.

The H.P. and I.P. turbine rotors are rigidly compounded and the L.P. motor by

the lens type semi flexible coupling. All the three rotors are aligned on fivebearings of which the bearing no. 2 is combined with the thrust bearing

The main superheated steam branches off into two streams from the boiler and

passes through the emergency stop valve and control valve before entering the

governing wheel chamber of the H.P. turbine. After expanding in the 12 stages

in the H.P. turbine the steam is returned in boiler for reheating.


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The reheated steam for the boiler enters the I.P> turbine via the interceptor

valves and control valves and after expanding enters the L.P. turbine stage via 2

nos of cross-over pipes.

In the L.P. stage the steam expands in axially opposite direction to counteract

the trust and enters the condensers placed below the L.P. turbine. The cooling

water flowing throughout the condenser tubes condenses the steam and the

condensate collected in the hot well of the condenser.

The condensate collected is pumped by means of 3*50% duty condensate

pumps through L.P. heaters to deaerator from where the boiler feed pump

delivers the water to boiler through H.P. heaters thus forming a close cycle.

The Main Turbine

TURBINE CYCLE

Fresh steam from the boiler is supplied to the turbine through the emergency

stop valve. From the stop valves steam is supplied to control valves situated in


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H.P. cylinders on the front bearing end. After expansion through 12 stages at the

H.P. cylinder, steam flows back to the boiler for reheating steam and reheated

steam from the boiler cover to the intermediate pressure turbine through two

interceptor valves and four control valves mounted on I.P. turbine.

After flowing through I.P. turbine steam enters the middle part of the L.P.

turbine through cross-over pipes. In L.P. turbine the exhaust steam condenses in

the surface condensers welded directly to the exhaust part of L.P. turbine.

The Turbine Cycle

The selection of extraction points and cold reheat pressure has been done with a

view to achieve a high efficiency. These are two extractors from H.P. turbine,

four from I.P. turbine and one from L.P. turbine. Steam at 1.10 and 1.03 g/sq.

cm. Abs is supplied for the gland sealing. Steam for this purpose is obtained

from deaerator through a collection where pressure of steam is regulated.


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From the condenser, condensate is pumped with the help of 3*50% capacity

condensate pumps to deaerator through the low-pressure regenerative

equipments.

Feed water is pumped from deaerator to the boiler through the H.P. heaters by

means of 3*50% capacity feed pumps connected before the H.P. heaters.

SPECIFICATIONS OF THE TURBINE

Type: Tandem compound 3 cylinder reheated type. Rated power: 210 MW. Number of stages: 12 in H.P., 11 in I.P. and 4*2 in L.P. cylinder. Rated steam pressure: 130 kg /sq. cm before entering the stop valve. Rated steam temperature: 535C after reheating at inlet. Steam flow: 670T / hr. H.P. turbine exhaust pressure: 27 kg /sq. cm., 327C Condenser back pressure: 0.09 kg /sq. cm. Type of governing: nozzle governing. Number of bearing; 5 excluding generator and exciter. Lubrication Oil: turbine oil 14 of IOC. Gland steam pressure: 1.03 to 1.05 kg /sq. cm (Abs) Critical speed: 1585, 1881, 2017. Ejector steam parameter: 4.5 kg /sq. cm. Condenser cooling water pressure: 1.0 to 1.1 kg /sq. cm. Condenser cooling water temperature: 27000 cu. M /hr. Number of extraction lines for regenerative heating of feed water;

seven.


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TURBINE COMPONENTS

Casing. Rotor. Blades. Sealing system. Stop & control valves. Couplings and bearings. Barring gear.

TURBINE CASINGS

HP Turbine Casings:

Outer casing: a barrel-type without axial or radial flange. Barrel-type casing suitable for quick startup and loading. The inner casing- cylindrically, axially split. The inner casing is attached in the horizontal and vertical planes in the

barrel casing so that it can freely expand radially in all the directions and

axially from a fixed point (HP- inlet side).

IP Turbine Casing:

The casing of the IP turbine is split horizontally and is of double-shellconstruction.

Both are axially split and a double flow inner casing is supported in theouter casing and carries the guide blades.

Provides opposed double flow in the two blade sections and compensatesaxial thrust.

Steam after reheating enters the inner casing from Top & Bottom.


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LP Turbine Casing:

The LP turbine casing consists of a double flow unit and has a triple shellwelded casing.

The shells are axially split and of rigid welded construction. The inner shell taking the first rows of guide blades is attached

kinematically in the middle shell.

Independent of the outer shell, the middle shell, is supported at fourpoints on longitudinal beams.

Steam admitted to the LP turbine from the IP turbine flows into the innercasing from both sides.

ROTORS

HP Rotor:

The HP rotor is machined from a single Cr-Mo-V steel forging withintegral discs.

In all the moving wheels, balancing holes are machined to reduce thepressure difference across them, which results in reduction of axial thrust.

First stage has integral shrouds while other rows have shroudings, rivetedto the blades are periphery.

IP Rotor:

The IP rotor has seven discs integrally forged with rotor while last fourdiscs are shrunk fit.

The shaft is made of high creep resisting Cr-Mo-V steel forging while theshrunk fit discs are machined from high strength nickel steel forgings.

Except the last two wheels, all other wheels have shrouding riveted at thetip of the blades. To adjust the frequency of thee moving blades, lashing

wires have been provided in some stages.


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LP Rotor:

The LP rotor consists of shrunk fit discs in a shaft. The shaft is a forging of Cr-Mo-V steel while the discs are of high

strength nickel steel forgings.

Blades are secured to the respective discs by riveted fork root fastening. In all the stages lashing wires are provided to adjust the frequency of

blades. In the last two rows, satellite strips are provided at the leading

edges of the blades to protect them against wet-steam erosion.

BLADES

Most costly element of the turbine. Blades fixed in stationary part are called guide blades/ nozzles and those

fitted in moving part are called rotating/working blades.

Blades have three main parts:o Aerofoil: working part.o Root.o Shrouds.

Shroud are used to prevent steam leakage and guide steam to next set ofmoving blades.

VACUUM SYSTEM

This comprises of:

Condenser: 2 for 200 MW unit at the exhaust of LP turbine. Ejectors: One starting and two main ejectors connected to the condenser

locared near the turbine.

C.W. Pumps: Normally two per unit of 50% capacity.


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CONDENSER

There are two condensers entered to the two exhausters of the L.P. turbine.

These are surface-type condensers with two pass arrangement. Cooling water

pumped into each condenser by a vertical C.W. pump through the inlet pipe.

Water enters the inlet chamber of the front water box, passes horizontally

through brass tubes to the water tubes to the water box at the other end, takes a

turn, passes through the upper cluster of tubes and reaches the outlet chamber in

the front water box. From these, cooling water leaves the condenser through the

outlet pipe and discharge into the discharge duct.

Steam exhausted from the LP turbine washes the outside of the condenser tubes,

losing its latent heat to the cooling water and is connected with water in the

steam side of the condenser. This condensate collects in the hot well, welded to

the bottom of the condensers.

A typical water cooled condensor


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been made for providing sealing. The pump is generally rated for 160 m3/ hr at a

pressure of 13.2 kg/ cm2

.

L.P. Heaters

Turbine has been provided with non-controlled extractions, which are utilized

for heating the condensate, from turbine bleed steam. There are 410 W pressure

heaters in which the last four extractions are used. L.P. Heater-1 has two parts

LPH-1A and LPH-1B located in the upper parts of the condenser A and

condenser B, respectively. These are of horizontal type with shell and tube

construction. L.P.H. 2,3 and 4 are of similar construction and they are mounted

in a row of 5m level. They are of vertical construction with brass tubes the ends

of which are expanded into tube plate. The condensate flows in the U tubes in

four passes and extraction steam washes the outside of the tubes. Condensate

passes through these four L.P. heaters in succession. These heaters are equipped

with necessary safety valves in the steam space level indicator for visual level

indication of heating steam condensate pressure vacuum gauges formeasurement of steam pressure, etc:

Deaerator

The presence of certain gases, principally oxygen, carbon dioxide and ammonia,

dissolved in water is generally considered harmful because of their corrosive

attack on metals, particularly at elevated temperatures. One of the mostimportant factors in the prevention of internal corrosion in modern boilers and

associated plant therefore, is that the boiler feed water should be free as far as

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

embodying into the boiler feed system a deaerating unit, whose function is to

remove the dissolved gases from the feed water by mechanical means.

Particularly the unit must reduce the oxygen content of the feed water to a lower

value as far as possible, depending upon the individual circumstances. Residual


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oxygen content in condensate at the outlet of deaerating plant usually specified

are 0.005/ litre or less.

A Deaerator

PRINCIPAL OF DEAERATION

It is based on following two laws.

Henrys Law Solubility

The Deaerator comprises of two chambers:

Deaerating column Feed storage tank

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

construction with dished ends welded to it. The tray stack is designed to ensure

maximum contact time as well as optimum scrubbing of condensate to achieve

efficient deaeration. The deaeration column is mounted on the feed storage tank,

which in turn is supported on rollers at the two ends and a fixed support at the

centre. The feed storage tank is fabricated from boiler quality steel plates.


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

inspection and maintenance.

The condensate is admitted at the top of the deaerating column flows

downwards through the spray valves and trays. The trays are designed to expose

to the maximum water surfaces for efficient scrubbing to affect the liberation of

the associated gases steam enters from the underneath of the trays and flows in

counter direction of condensate. While flowing upwards through the trays,

scrubbing and heating is done. Thus the liberated gases move upwards

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

condensate. Liberated gases escapes to atmosphere from the orifice opening

meant for it. This opening is provided with a number of dlflectors to minimize

the loss of steam.

FEED WATER SYSTEM

The main equipments coming under this system are:

Boiler feed Pump: Three per unit of 50% capacity each located in the 0meter level in the T bay.

High Pressure Heaters: Normally three in number and are situated inthe TG bay.

Drip Pumps: generally two in number of 100% capacity each situatedbeneath the LP heaters.

Turbine Lubricating Oil System: This consists of the Main Oil Pump(MOP), Starting Oil Pump (SOP), AC standby oil pumps and emergency

DC Oil Pump and Jacking Oil Pump (JOP). (one each per unit)

Boiler Feed Pump

This pump is horizontal and of barrel design driven by an Electric Motor

through a hydraulic coupling. All the bearings of pump and motor are forced


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lubricated by a suitable oil lubricating system with adequate protection to trip

the pump if the lubrication oil pressure falls below a preset value.

The high pressure boiler feed pump is a very expensive machine which calls for

a very careful operation and skilled maintenance. Operating staff must be able

to find out the causes of defect at the very beginning, which can be easily

removed without endangering the operator of the power plant and also without

the expensive dismantling of the high pressure feed pump.

Function

The water with the given operating temperature should flow continuously to the

pump under a certain minimum pressure. It passes through the suction branch

into the intake spiral and from there; it is directed to the first impeller. After

leaving the impeller it passes through the distributing passages of the diffuser

and thereby gets a certain pressure rise and at the same time it flows over to the

guide vanes to the inlet of the next impeller. This will repeat from one stage to

the other till it passes through the last impeller and the end diffuser. Thus thefeed water reaching into the discharge space develops the necessary operating

pressure.

Booster Pump

Each boiler feed pump is provided with a booster pump in its suction line which

is driven by the main motor of the boiler feed pump. One of the major damageswhich may occur to a boiler feed pump is from cavitation or vapor bounding at

the pump suction due to suction failure. Cavitation will occur when the suction

pressure of the pump at the pump section is equal or very near to the vapor

pressure of the liquid to be pumped at a particular feed water temperature. By

the use of booster pump in the main pump suction line, always there will be

positive suction pressure which will remove the possibility of cavitation.


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Therefore all the feed pumps are provided with a main shaft driven booster

pump in its suction line for obtaining a definite positive suction pressure.

Lubricating Pressure

All the bearings of boiler feed pump, pump motor and hydraulic coupling are

force lubricated. The feed pump consists of two radial sleeve bearings and one

thrust bearing. The thrust bearing is located at the free end of the pump.

High Pressure Heaters

These are regenerative feed waters heaters operating at high pressure and

located by the side of turbine. These are generally vertical type and turbine

based steam pipes are connected to them.

HP heaters are connected in series on feed waterside and by such arrangement,

the feed water, after feed pump enters the HP heaters. The steam is supplied to

these heaters to form the bleed point of the turbine through motor operated

valves. These heaters have a group bypass protection on the feed waterside.In the event of tube rupture in any of the HPH and the level of condensate rising

to dangerous level, the group protection devices divert automatically the feed

water directly to boiler, thus bypassing all the 3 H.P. heaters.

An HP heater


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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 because

the 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.

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

monitoring eccentricity meters. But this small amount of shaft deflection wouldbe 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 is

shut 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) byflowing 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. 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 100C where the vapour pressure of water is much less than atmospheric


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

noncondensible air into the closed loop must be prevented. 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.

A typical water cooled condensor


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FeedwaterHeater

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 steam

generation 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 steamcycle.

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

heater


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Superheater

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

to the valves of the high pressure turbine.

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 avoid

corrosion 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 Deaerator


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There 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 deaerator

manufacturers will guarantee that oxygen in the deaerated water will not exceed

7 ppb by weight (0.005 cm3/L).

Auxiliary Systems

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.

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, inan oil-sealed casing, is used 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 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. Mechanicalseals around the shaft are installed with a very small annular gap to avoid


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rubbing between the shaft and the seals. Seal oil is used to prevent the hydrogen

gas 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 oneunit. In smaller units, generating at 10.5kV, a breaker is provided to connect it

to a common 10.5 kV bus system.

Other Systems

Monitoring and Alarm system


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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 operatingparameters 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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PLANT LAYOUT

COAL CYCLE

Rail Wagon


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RAW WATER CYCLE

Agra Canal

Gate

Intake Channel

WTP Control Structure

DM Tank

Circulating Water pump

Make up pump Cooling Tower

Condenser

Generator Out Gate Channel C.T. Pump

Hydrogen Tank Gate

Agra canal


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FEED WATER CYCLE

PRIMARY WATER CYCLE


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SECONDARY AIR CYCLE

STEAM CYCLE


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CONDENSATE CYCLE

FLUE GAS CYCLE


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C&I

(CONTROL AND

INSTRUMENTATION)


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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.

Instrumentation can be well defined as a technology of using instruments to measure and

control the physical and chemical properties of a material.

Control and instrumentation has following labs:

1. Manometry lab2. Protection and interlocks lab3. Automation lab4. Electronics lab5. Water treatment plant6. Furnaces Safety Supervisory System Lab

1. Manometry lab Transmitters- Transmitter 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.


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Manometer- Its a tube which is bent, in U shape. It is filled with a liquid. This devicecorresponds to a difference in pressure across the two limbs.

Bourden Pressure Gauge- Its an oval section tube. Its one end is fixed. It is providedwith a pointer to indicate the pressure on a calibrated scale. It is of two types : (a)Spiral type : for low pressure measurement and (b) Helical type : for high pressure

measurement

2. Protection and Interlock Lab

Interlocking- It is basically interconnecting two or more equipments so that if oneequipments 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 OR GATE. When The main equipments of this lab are

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

velocity. 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 no critical fatigue occurs and thus the continuous full capacity normal current

ratings are assured for the long time. 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.

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


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RTD(Resistance temperature detector) - It performs the function of thermocouplebasically 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 boiling water (for low range devices)

and in small furnace (for high range devices).

5. Furnace Safety and Supervisory System LabThis lab has the responsibility of starting fire in the furnace to enable the burning 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.

6. 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.


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AUTOMATION AND CONTROL SYSTEM

AUTOMATION: THE DEFINITION

The word automation is widely used today in relation to various types of applications, such as

office automation, plant or process automation.

This subsection presents the application of a control system for the automation of a process /plant, such as a power station. In this last application, the automation actively controls the

plant during the three main phases of operation: plant start-up, power generation in stable or

put During plant start-up and shut-down, sequence controllers as well as long range

modulating controllers in or out of operation every piece of the plant, at the correct time and

in coordinated modes, taking into account safety as well as overstressing limits.

During stable generation of power, the modulating portion of the automation system keeps

the actual generated power value within the limits of the desired load demand.

During major load changes, the automation system automatically redefines new set points

and switches ON or OFF process pieces, to automatically bring the individual processes in an

optimally coordinated way to the new desired load demand. This load transfer is executed

according to pre- programmed adaptively controlled load gradients and in a safe way.


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AUTOMATION: THE BENEFITS

The main benefits of plant automation are to increase overall plant availability and efficiency.

The increase of these two factors is achieved through a series of features summarized as

follows:

Optimisation of house load consumption during plant start- up, shut-down andoperation, via:

Faster plant start-up through elimination of control errors creating delays. Faster sequence of control actions compared to manual ones. Figures 1 shows the

sequence of a rapid restart using automation for a typical coal-fired station. Even a

well- trained operator crew would probably not be able to bring the plant to full

load in the same time without considerable risks.

Co-ordination of house load to the generated power output.

Ensure and maintain plant operation, even in case of disturbances in the controlsystem, via:

Coordinated ON / OFF and modulating control switchover capability from a subprocess to a redundant one.

Prevent sub-process and process tripping chain reaction following a processcomponent trip.

Reduce plant / process shutdown time for repair and maintenance as well as repaircosts, via:

Protection of individual process components against overstress (in a stable orunstable plant operation).

Bringing processes in a safe stage of operation, where process components areprotected against overstress


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PROCESS STRUCTURE

Analysis of processes in Power Stations and Industry advocates the advisability of dividing

the complex overall process into individual sub-processes having distinctly defined functions.

This division of the process in clearly defined groups, termed as FUNCTIONAL GROUPS,

results in a hierarchical process structure. While the hierarchical structure is governed in the

horizontal direction by the number of drives (motorised valves, fans, dampers, pumps, etc.) in

other words the size of the process; in the vertical direction, there is a distinction made

between three fundamental levels, these being the: -

Drive Level Function Group Level Unit Level.

To the Drive Level, the lowest level, belong the individual process equipment and associated

electrical drives.

The Function Group is that part of the process that fulfils a particular defined task e.g.,

Induced Draft Control, Feed Water Control, Blooming Mill Control, etc. Thus at the time of

planning it is necessary to identify each function group in a clear manner by assigning it to a

particular process activity. Each function group contains a combination of its associated

individual equipment drives. The drive levels are subordinate to this level. The function

groups are combined to obtain the overall process control function at the Unit Level.

The above three levels are defined with regard to the process and not from the control point

of view.


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CONTROL SYSTEM STRUCTURE

The primary requirement to be fulfilled by any control system architecture is that it be

capable of being organized and implemented on true process-oriented lines. In other words,

the control system structure should map on to the hierarchy process structure.

BHELs PROCONTROL P, a microprocessor based intelligent remote multiplexing system,

meets this requirement completely.

SYSTEM OVERVIEW

The control and automation system used here is a micro based intelligent multiplexing system

This system, designed on a modular basis, allows to tighten the scope of control hardware to

the particular control strategy and operating requirements of the process

Regardless of the type and extent of process to control provides system uniformity and

integrity for:

Signal conditioning and transmission Modulating controls


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CONTROL AND MONITORING MECHANISMS

There are basically two types of Problems faced in a Power Plant

Metallurgical Mechanical

Mechanical Problemcan be related to Turbines that is the max speed permissible for a turbine

is 3000 rpm , so speed should be monitored and maintained at that level

Metallurgical Problem can be view as the max Inlet Temperature for Turbile is 1060 oC so

temperature should be below the limit.

Monitoring of all the parameters is necessary for the safety of both:

Employees Machines

So the Parameters to be monitored are :

Speed Temperature Current Voltage Pressure Eccentricity Flow of Gases Vaccum Pressure Valves


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Level Vibration

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 pressure measurement

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 pressure input 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 means of monitoring

as swith being ON is referred as high and being OFF is as low.


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TEMPERATURE MONITORING

We can use Thernocouples or RTDs for temperature monitoring

Normally RTDs are used for low temperatures.

Thermocoupkle selection depends upon two factors:

Temperature Range Accuracy Required

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 is approximately 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


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Pt100 : 00C100 ( 1 = 2.5 0C )

Pt1000 : 00C - 1000

Pt1000 is used for higher accuracy

The 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 metering purposes 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


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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 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.


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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

- v12).

And we know that rate of flow is given by:

Flow = k (D.P)

Where DP is Differential Presure or the Pressure Drop.


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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 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 are controlled by air pressure, or hydraulic 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 Valvesthey are air or gas controlled which is compressed to turn ormove them

Hydraulic valvesthey utilize oil in place of Air as oil has better compression Motorised valvesthese valves are controlled by electric motors


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FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSS is also called as Burner Management System (BMS). It is a microprocessor based

programmable logic controller of proven design incorporating all 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 rear side. That s

why its called front and rear type boiler.

The 210 MW boilers are direct type boilers (which means that HSD is in direct contact with

coal) firing takes place from the corner. Thus it is also known as corner type boiler.

IGNITER SYSTEM

Igniter system is an automatic system, it takes the charge from 110kv and this spark is

brought in front of the oil guns, which spray aerated HSD on the coal for coal combustion.

There is a 5 minute delay cycle before igniting, this is to evacuate or burn the HSD. This

method is known as PURGING.

PRESSURE SWITCH

Pressure switches are the devices that make or break a circuit. When pressure is applied , the

switch under the switch gets pressed which is attached to a relay that makes or break the

circuit.

Time delay can also be included in sensing the pressure with the help of pressure valves.

Examples of pressure valves:

1. Manual valves (tap)2. Motorized valves (actuator)works on motor action3. Pneumatic valve (actuator) _ works due to pressure of compressed air4. Hydraulic valve


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