ABOUT NTPC

India’s largest power company, NTPC was set up in 1975 to accelerate power

development in India. NTPC is emerging as a diversified power major with presence in

the entire value chain of the power generation business. Apart from power generation,

which is the mainstay of the company, NTPC has already ventured into consultancy,

power trading, ash utilization and coal mining. NTPC ranked 341st in the ‘2010, Forbes

Global 2000’ ranking of the World’s biggest companies. NTPC became a Maharatna

company in May, 2010, one of the only four companies to be awarded this status. 

The total installed capacity of the company is 39,174 MW (including JVs) with 16 coal

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

stations are coal based & another station uses naptha/LNG as fuel.  The company has set

a target to have an installed power generating capacity of 1,28,000 MW by the year 2032.

The capacity will have a diversified fuel mix comprising 56% coal, 16% Gas, 11%

Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032, non-fossil

fuel based generation capacity shall make up nearly 28% of NTPC’s portfolio.

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

17.75% of the total national capacity, it contributes 27.40% of total power generation due

to its focus on high efficiency.

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UNIT 1

In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of 5.25% as

fresh issue and 5.25% as offer for sale by Government of India. NTPC thus became a

listed company in November 2004 with the Government holding 89.5% of the equity

share capital. In February 2010, the Shareholding of Government of India was reduced

from 89.5% to 84.5% through Further Public Offer. The rest is held by Institutional

Investors and the Public.

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Strategies of NTPC

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.

Roadmap developed for adopting µClean Development.

Mechanism to help get / earn µCertified Emission Reduction.

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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

to0.5% of net profit annually for Community Welfare.

The welfare of project affected persons and the local population around

NTPC projects are taken care of through well drawn Rehabilitation and

Resettlement policies.

The company has also taken up distributed generation for remote rural areas

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 ³Partnership 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 tilization Division.

Afforestation Group.

Centre for Power Efficiency & Environment Protection.

Group on Clean Development Mechanism.

NTPC is the second largest owner of trees in the country after the

Forest department

Vision

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“To be the world’s largest and best power producer, powering India’s growth.”

Mission

“Develop and provide reliable power, related products and services at competitive prices,

integrating multiple energy sources with innovative and eco-friendly technologies and

contribute to society.”

Core Values – BE COMMITTED

B Business Ethics

E Environmentally & Economically Sustainable

C Customer Focus

O Organizational & Professional Pride

M Mutual Respect & Trust

M Motivating Self & others

I Innovation & Speed

T Total Quality for Excellence

T Transparent & Respected Organization

E Enterprising

D Devoted

JOURNEY OF NTPC

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NTPC Environment Policy

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 3°c.

NTPC has also taken proactive steps for ash utilization. In 1991, it set up Ash Utilization

Division A

"Centre for Power Efficiency and Environment Protection- CENPEE" has been

established in NTPC with the assistance of United States Agency for International

Development- USAID. CENPEEP is efficiency oriented, eco-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 Resettlement

programmes, 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.

NTPC is the second largest owner of trees in the country after the Forest department.

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As early as in November 1995, NTPC brought out a comprehensive document entitled

"NTPC Environment Policy and Environment Management System". Amongst the

guiding principles adopted in the document is 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 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 complies

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.

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Flue Gas Stacks:

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

(SOX, NOX etc.) into the atmosphere.

Low-NOX Burners:

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

NOX Burners (Dry or wet type) and in coal fired stations, by adopting best combustion

practices.

Neutralization Pits:

Neutralization 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 reduction in

thermal pollution and conservation of fresh water.

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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 arrangement for changeover of the ash slurry feed points for

even filling of the pond and for effective settlement of the ash particles.

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

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

conform to standards specified by CPCB and the same is regularly monitored.

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

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

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

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

system.

Ash Water Recycling System:

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

System (AWRS) has been provided. In the AWRS, the effluent from ash pond is

circulated back to the station for further ash sluicing to the ash pond. This helps in

savings of fresh water requirements for transportation of ash from the plant.

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

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

and Vindhyachal. The scheme has helped stations to save huge quantity of fresh water

required as make-up water for disposal of ash.

Dry Ash Extraction System (DAES):

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

aerated autoclaved concrete blocks, concrete, Portland pozzolana cement, etc.). DAES

has been installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon,

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

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Liquid Waste Treatment Plants & Management System:

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

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

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

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

liquid effluents which originate within the power station e.g. Water Treatment Plant

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

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

effluents and their appropriate treatment centrally and re-circulation of the treated

effluent for various plant uses.

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

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

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

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

Sewage Treatment Plants & Facilities:

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

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

number of NTPC projects modern type STPs with Clarifloculators, Mechanical Agitators,

sludge drying beds, Gas Collection Chambers etc. have been provided to improve the

effluent quality. The effluent quality is monitored regularly and treated effluent

conforming to the prescribed limit is discharged from the station. At several stations

treated effluents of STPs are being used for horticulture purpose.

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ABOUT BTPS

BADARPUR THERMAL POWER STATION was established on 1973 and it was the

part of Central Government. On 01/04/1978 is was given as No Loss No Profit Plant of

NTPC. Since then operating performance of NTPC has been considerably above the

national average. The availability factor for coal stations has increased from 85.03 % in

1997-98 to 90.09 % in 2006-07, which compares favorably with international standards.

The PLF has increased from 75.2% in1997-98 to 89.4% during the year 2006-07 which is

the highest since the inception of NTPC.

 Badarpur thermal power station started 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 Notification .

The power is supplied to a 220 KV network that is a part of the northern grid. The ten

circuits through which the power is evacuated from the plant are:

1. Mehrauli

2. Okhla

3. Ballabgarh

4. Indraprastha

5. UP (Noida)

6. Jaipur

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UNIT 2

Given below are the details of unit with the year they’re installed.

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Station Location

Badarpur is situated only 20 km away from Delhi. The plant is located on the left side of the National

Highway (Delhi-Mathura Road) and it comprises of 430 hectares (678 acres) bordered by the Agra

Canal from East and by Mathura-Delhi Road from West. However, the area for ash

disposal is done in the Delhi Municipal limit and is maintained with the help of Delhi Development

Authority. The plant is also close to the project of 220 kv Double Circuit Transmission line between the

I.P. station and Ballabgarh Cooling Water is obtained from Agra Canal for the cooling

system. Additional 60 cusecs channel has also been constructed parallel to the Agra

Canal so as to obtain uninterrupted water supply during the slit removing operation in

Agra Canal.

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OPERATION OF A POWER PLANT

Basic Principle

 As per FARADAY’s Law-“Whenever the amount of magnetic flux linked with a circuit

changes, an EMF is produced in the circuit. Generator works on the principle of

producing electricity. To change the flux in the generator turbine is moved in a great

speed with steam.” To produce steam, water is heated in the boilers by burning the coal.

In a Badarpur Thermal PowerStation, steam is produced and used to spin a turbine that

operates a generator. Water is heated, turns into steam and spins a steam turbine which

drives an electrical generator. After it passes through the turbine, the steam is condensed

in a condenser; this is known as a Rankine cycle.

The electricity generated at the plant is sent to consumers through high-voltage power

lines The Badarpur Thermal Power Plant has Steam Turbine-Driven Generators which

has a collective capacity of 705MW. The fuel being used is Coal which is supplied from

the Jharia Coal Field in Jharkhand. Water supply is given from the Agra Canal.

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UNIT 3

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

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Coal to Electricity : Basics

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PARTS OF A POWER PLANT

The various parts are listed below:-

1. Cooling tower

2. Cooling water pump

3. Transmission line (3-phase)

4. Unit transformer (3-phase)

5. Electric generator (3-phase)

6. Low pressure turbine

7. Condensate extraction pump

8. Condenser

9. Intermediate pressure turbine

10. Steam governor valve

11. High pressure turbine

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UNIT 4

12. Deaerator

13. Feed heater

14. Coal conveyor

15. Coal hopper

16. Pulverised fuel mill

17. Boiler drum

18. Ash hopper

19. Super heater

20. Forced draught fan

21. Reheater

22. Air intake

23. Economiser

24. Air preheater

25. Precipitator

26. Induced draught fan

27. Flue Gas

1. Cooling Tower

Cooling towers are heat removal devices used to transfer process waste heat to the

atmosphere. Cooling towers may either use the evaporation of water to remove process

heat and cool the working fluid to near the wet-bulb air temperature or in the case of

closed circuit dry cooling towers rely solely on air to cool the working fluid to near the

dry-bulb air temperature. Common applications include cooling the circulating water

used in oil refineries, chemical plants, power stations and building cooling.

The towers vary in size from small roof-top units to very large hyperboloid structures that

can be up to 200 meters tall and 100 meters in diameter, or rectangular structures 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 absorbed heat is rejected to the atmosphere

by the evaporation of some of the cooling water in mechanical forced-draft or induced

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Draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear

power plants.

2. Cooling Water Pump

it pumps the water from the cooling tower which goes to the condenser.

3. 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 conductive 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 current in one conductor as the reference, the currents in the other two are delayed

in time by one-third and two-third of one cycle .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 power into a set of 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 separation of one-third of one cycle. Generators output at a voltage that ranges

from hundreds of volts to 30,000 volts.

4. Unit transformer (3-phase)

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-

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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 ( or wild leg) and

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

5. 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 maybe water falling through the turbine or steam turning a turbine (as is the case

with thermal power plants). There are several classifications for modern steam turbines.

Steam turbines are used in our entire major coal fired power stations to drive the

generators 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 stations use large steam turbines driving electric generators to produce

most (about 86%) of the world’s electricity. These centralized stations are of two types:

fossil fuel power plants and nuclear power plants. The turbines used for electric power

generation are most often directly coupled to their-generators .As the generators must

rotate at constant synchronous speeds according to the frequency of the electric power

system, the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for

60 Hz systems. Most large nuclear sets rotate at half those speeds, and have a 4-pole

generator rather than the more common 2-pole one.

6. Low Pressure Turbine

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 stages 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 and direct the flow onto the

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rotating blades. The rotating blades convert the kinetic energy into impulse and reaction

forces, caused by pressure drop, which results in the rotation of the turbine shaft. The

turbine shaft is connected to a generator, which produces the electrical energy.

Low Pressure Turbine (LPT) consists of 4x2 stages. After passing through Intermediate

Pressure Turbine steam is passed through LPT which is made up of two parts- LPC

REAR & LPC FRONT. As water gets cooler here it gathers into a HOTWELL placed in

lower parts of turbine.

7. Condensation Extraction 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 returning condensation of the steam

produced by the boiler. These pumps are normally high pressure units that use suction

from a condensate return system and can be of the centrifugal pump type or positive

displacement type.

Construction and operation:

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

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

condensate pumps may also serve as the feed water pump. In either case, to force the

water into the boiler, the pump must generate sufficient pressure to overcome the steam

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

centrifugal pump. Feed water pumps usually run intermittently and are controlled by a

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

lowered liquid level in the boiler. Some pumps contain a two-stage switch. As liquid

lowers to the trigger point of the first stage, the pump is activated. If 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

boiler equipment (preventing the boiler from running dry and overheating), trigger an

alarm, or both.

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8. Condenser

The steam coming out from the Low Pressure Turbine (a little above its boiling pump) is

brought into thermal contact with cold water (pumped in from the cooling tower) in the

condenser, where it condenses rapidly back into water, creating near Vacuum-like

conditions inside the condenser chest.

9. Intermediate Pressure Turbine

Intermediate Pressure Turbine (IPT) consists of 11 stages. When the steam has been

passed through HPT it enters into IPT. IPT has two ends named as FRONT & REAR.

Steam enters through front end and leaves from Rear end.

10. Steam Governor Valve

Steam locomotives and the steam engines used on ships and stationary applications such

as power plants also required feed water pumps. In this situation, though, the pump was

often powered using a small steam engine that ran using the steam produced by the boiler

a means had to be provided, of course, to put the initial charge of water into the boiler

(before steam power was available to operate the steam-powered feed water pump).The

pump was often a positive displacement pump that had steam valves and cylinders at one

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

plants, the primary purpose of surface condenser is to condense the exhaust steam from a

steam turbine to obtain maximum efficiency and also to convert the turbine exhaust

steam into pure water so that it may be reused in the steam generator or boiler as boiler

feed water. By condensing the exhaust steam of a turbine at a pressure below atmospheric

pressure, the steam pressure drop between the inlet and exhaust of the turbine is

increased, which increases the amount heat available for conversion to mechanical

power. Most of the heat liberated due to condensation of the exhaust steam is carried

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

are valves used within industrial plants and elsewhere to control operating conditions

such as temperature, pressure, flow and liquid level by fully or partially opening or

closing in response to signals received from controllers that compares a “set point” to a

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“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.

11.High Pressure Turbine

Steam coming from Boiler directly feeds into HPT at a temperature of 540°C and at a

pressure of 136 kg/cm2. Here it passes through 12 different stages due to which its

temperature goes down to 329°C and pressure as 27 kg/cm2. This line is also called as

CRH – COLD REHEAT LINE. It is now passed to a REHEATER where its temperature

rises to 540°C and called as HRH-HOT REHEATED LINE.

12. Deaerator

A Deaerator 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 tube ruptures due to overheating. Under some conditions it may give rise 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)

13. 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 irreversibility involved in

steam generation and therefore improves the thermodynamic efficiency of the system.

This reduces plant operating costs and also helps to avoid thermal shock to the boiler

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metal when the feed water is introduced back into the steam cycle. In a steam power

(usually modelled as a modified Rankine cycle), feed water heaters allow the feed water

to be brought up to the saturation temperature very gradually. This minimizes the

inevitable irreversibility associated with heat transfer to the working fluid (water).

14. Coal conveyor

Coal conveyors are belts which are used to transfer coal from its storage place to Coal

Hopper. 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.

15. Coal Hopper

Coal Hoppers are the places which are used to feed coal to Fuel Mill. It also has the

arrangement of entering Hot Air at 200°C inside it which solves our two purposes:-

1. If our Coal has moisture content then it dries it so that a proper combustion takes place.

2. It raises the temperature of coal so that its temperature is more near to its Ignite

Temperature so that combustion is easy.

16. Pulverized Fuel Mill

A pulveriser is a device for grinding coal for combustion in a furnace in a fossil fuel

power plant.

17. Boiler 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

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(probably stainless) and its working involve temperature of 390°C and pressure well

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

drum.

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

through a super heater, while the saturated water at the bottom of steam drum flows down

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

valve, water level indicator and fuse plug.

18. Ash Hopper

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 accumulate

at the bottom.

19. 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. 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 also stationary steam engines including power stations.

20. Force Draught Fan

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

takes air from the atmosphere and, warms it in the air preheater for better combustion,

injects it via the air nozzles on the furnace wall.

21. Reheater

Reheater is a heater which is used to raise the temperature of steam which has fallen from

the intermediate pressure turbine.

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22. Air Intake

Air is taken from the environment by an air intake tower which is fed to the fuel.

23. Economizers

Economizer, or in the UK economizer, are mechanical devices intended to reduce energy

consumption, or to perform another useful function like preheating a fluid. The term

economizer is used for other purposes as well-Boiler, power plant, heating, ventilating

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

usually water, up to but not normally beyond the boiling point of the fluid. Economizers

are so named because they can make use of the enthalpy and improving the boiler’s

efficiency. They are devices fitted to a boiler which save energy by using the exhaust

gases from the boiler to preheat the cold water used to fill it (the feed water). Modern day

boilers, such as those in cold fired power stations, are still fitted with economizer which

is decedents of Green’s original design. In this context there are turbines before it is

pumped to the boilers. A common application of economizer in steam power plants is to

capture the waste heat from boiler stack gases (flue gas) and transfer thus it to the boiler

feed water thus lowering the needed energy input , in turn reducing the firing rates to

accomplish the rated boiler output . Economizer lower stack temperatures which may

cause condensation of acidic combustion gases and serious equipment corrosion damage

if care is not taken in their design and material selection.

24. Air Preheater

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

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

recover the heat from the boiler flue gas which increases the thermal efficiency of the

boiler by reducing the useful heat lost in the flue 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.

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25. Precipitator

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

removes particles from a flowing gas (such as air) using the force of an induced

electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and

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

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 applications. The original parallel plate-Weighted wire design (described

above) has evolved as more efficient (and robust) discharge electrode designs, today

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

maximizing corona production. Transformer –rectifier systems apply voltages of

50-100 Kilovolts at relatively high current densities. Modern controls minimize sparking

and prevent arcing, avoiding damage to the components. Automatic rapping systems and

hopper evacuation systems remove the collected particulate matter while on line allowing

ESPs to stay in operation for years at a time.

26. Induced Draught Fan

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, which additionally

minimizes erosion of the ID fan.

27. Flue gas stack

A Flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through

which combustion product gases called flue gases are exhausted to the outside air. Flue

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gases are produced when coal, oil, natural gas, wood or any other large combustion

device. Flue gas is usually composed of carbon dioxide (CO2) and water vapour as well

as nitrogen and excess oxygen remaining from the intake combustion air. It also contains

a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen

oxides and 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 area and thereby

reduce the concentration of the pollutants to the levels required by government's

environmental policies and regulations. The flue gases are exhausted from stoves, ovens,

fireplaces or other small sources within residential abodes, restaurants, hotels through

other stacks which are referred to as chimneys.

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VARIOUS CYCLES AT POWER STATION

PRIMARY AIR CYCLE

SECONDARY AIR CYCLE

COAL CYLCE

ELECTRICITY CYCLE

FLUE GAS CYCLE

CONDENSATE CYCLE

FEED WATER CYCLE

STEAM CYCLE

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UNIT 5

32

33

Coal Cycle

34

35

Flue Gas Cycle

36

37

38

39

CONTROL & INSTRUMENTATION

 

INTRODUCTION

C&I LABS

CONTROL & MONITORING MECHENISM

PRESSURE MONITORING

TEMPERATURE MONITORING

FLOW MEASUREMENT

CONTROL VALVES

INTRODUCTION

This division basically calibrates various instruments and takes care of any faults occur in

any of the auxiliaries in the plant.

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

measure and control the physical and chemical properties of a material.”

 

C&I LABS

Control and Instrumentation Department has following labs:

 

Manometry Lab.

Protection and Interlocks Lab.

Automation Lab.

Electronics Lab.

Water Treatment Plant.

Furnaces Safety Supervisory System Lab

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OPERATION AND MAINTAINANCE

Control and Instrumentation Department has following Control Units:1.

 

1. Unit Control Board2.

2. Main Control Board3.

3. Analog & Digital Signal Control4.

4. Current Signal Control

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.

 A View of Control Room at BTPS

 

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1. MANOMETRY LAB

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.

MANOMETER

It’s 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.

BOURDEN PRESSURE GAUGE

It’s an oval section tube. Its one end is fixed. It is provided with a pointer to indicate the

pressureon a calibrated scale. It is of 2 types :

(a) Spiral type: for Low pressure measurement.

(b) Helical Type: for High pressure measurement. While selecting Pressure Gauge these

parameters should keep in mind-

1. Accuracy

2. Safety

3. Utility

4. Price

ACCURACY 

Higher Accuracy implies Larger Dial Size for accuracy of small and readable pressure

scale increments.

SAFETY 

While selecting Pressure Gauge it should consider that Gauge Construction Material

should be chemically compatible with the environment either inside or outside it.

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UTILITY 

It should keep it mind that range of the Gauge should be according to our need else

Overpressure Failure may occur resulting in damage of Gauge.

PRICE

Lager the Gauge’s Dial size larger would be our price. Better Gauge’s Construction

material also increases the cost. So they must be chosen according to our need.

 

2. PROTECTION AND INTERLOCKING

INTERLOCKING

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

which trips the circuit. The main equipments of this lab are relay and circuit breakers.

Some of the instrument uses for protection are:

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. 

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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.

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 are three types of trips.

I. MANUAL TRIP

II. THERMAL TRIP

III. SHORT CIRCUIT TRIP

Protection and Interlock System-

1) HIGH TENSION CONTROL CIRCUIT for high tension system the control

system is 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 secondary systems 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.

4. PYROMETRY LAB

LIQUID IN GLASS THERMOMETER

Mercury in the glass thermometer boils at 340° C which limits the range of temperature

that can be measured. It is L shaped thermometer which is designed to reach all

inaccessible places.

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.

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.

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 boiling water

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

.

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5. FURNACE SAFETY AND SUPERVISORY SYSTEM LAB

This 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°C and its heights 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 no circumstances should anyone 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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ANNUNCIATIN 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.

CONTROL & MONITORING MECHANISMS

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

1. Metallurgical

2. Mechanical

Mechanical Problem can be related to Turbines that is the max speed permissible for a

turbine is3000 rpm so speed should be monitored and maintained at that level.

Metallurgical Problem can be view as the max Inlet Temperature for Turbine is 1060°

C so temperature should be below the limit. Monitoring of all the parameters is necessary

for the safety of both:

1. Employees

2. Machines

So the Parameters to be monitored are:

1. Speed

2. Temperature

3. Current

4. Voltage

5. Pressure

6. Eccentricity

7. Flow of Gases

8. Vacuum Pressure

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9. Valves

10. Level

11. Vibration

PRESSURE MONITORING

Pressure can be monitored by three types of basic mechanisms

1. Switches

2. Gauges

3. Transmitter type

For gauges we use Bourdon 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 shows schematically below.

Typical Bourdon Tube Pressure Gages

For Switches pressure switches are used and they can be used for digital means of

monitoring as switch being ON is referred as high and being OFF is as low.

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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 milli-Amperes

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 %

Programmable Logic Circuits (PLCs) are used in the process as they are the heart

of Instrumentation.

49

TEMPERATURE MONITORING

We can use Thermocouples or RTDs for temperature monitoring. Normally RTDs are

used for low temperatures.

Thermocouple selection depends upon two factors:

1. Temperature Range

2. Accuracy Required

Normally used Thermocouple is K Type Thermocouple:

In this we use Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy) as

two metals. 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 μV/°C.

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

We pass a constant current through the RTD. So that if R changes then the Voltage also

changes

RTDs used in Industries are Pt100 And Pt1000

 Pt100: 0°C – 100 Ω ( 1 Ω = 2.5 0C )

 Pt1000: 0°C - 1000Ω

 

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.

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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 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 :

1. Flow meters

2. Venturimeters / Orifice meters

3. Turbines

4. Mass flow meters (oil level)

5. Ultrasonic Flow meters

6. Magnetic Flow meter (water level )

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

different types of meters used.

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TURBINE TYPE:

They are 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), and the theoretical pressure drop at the

constriction would be given by (ρ/2)(v22- v1

2).

And we know that rate of flow is given by:

Flow = k √ (D.P)

Where DP is Differential Pressure 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 cycleengines 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 isturned a quarter of a full turn (90°) between operating

positions, the valve is called a quarter-turnvalve. Butterfly valves, ball valves, and

plug valves are often quarter-turn valves. Valves can also becontrolled by devices

called actuators attached to the stem. They can be electromechanicalactuators such as an

electric motor or solenoid,

pneumatic actuators

which are controlled by airpressure, or

hydraulic actuators

whichare 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 is compressed to turn or movethem·

HYDRAULIC VALVES

 

 –

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They utilize oil in place of Air as oil has better compression

54

 

·

MOTORISED VALVES

 

 –

These valves are controlled by electric motors

FURNACE SAFEGUARD SUPERVISORY SYSTEM

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

basedprogrammable logic controller of proven design incorporating all protection

55

facilities required forsuch 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 it’s

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 infront of the oil guns, which spray aerated HSD on the coal for coal combustion.

There is a 5 minutedelay 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 switchunder 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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