Final Report Power

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Abhijeet MADC Nagpur Energy Private Limited

(AMNEPL)

INDUSTRIAL TRAINING REPORT

SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENT OF THE COURSE OF

B.Tech

Undertaken at

MIHAN THERMAL POWER PLANT, NAGPUR (MAHARASHTRA)

FROM: 31 May to 28 June, 2012

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C E R T I F I C A T E

This is to certify that Mr.Abhay Khedia( 09BME261) student of Bachelor of Technology in

Mechanical engineering Stream, 4th Year of VELLORE INSTITUTE OF

TECHNOLOGY,VELLORE has successfully completed his industrial training at MIHAN

Thermal power station Nagpur for four weeks from 31 may to 28th

june, 2012.

Date : 15/06/2012

Training Incharge

(Abhijeet MADC Nagpur

energy pvt Ltd )

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ACKNOWLEDGEMENT

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

complete the training here.

I do extend my heartfelt thanks to Mr.NCSV Raju (AGM-HR) and Mr. Ninad Sherekar

(HOD-C&I) for providing me this opportunity to be a part of this esteemed organization.

I sincerely thank to,Mr. Prashant Wagadre (HR) and Mr. our co-ordinators

for their co-operation and support.

I am extremely grateful to all the technical staff of Mihan Power Plant for their co-operation

and guidance that helped me a lot during the course of training. I have learnt a lot working

under them and I will always be indebted of them for this value addition in me.

I would also like to thank the training in charge of and all the faculty member of Electrical &

Electronics department for their effort of constant co-operation, which have been significant

factor in the accomplishment of my industrial training.

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Training at MIHAN POWER PLANT (MPP)

I was appointed to do four-weeks training at this well established organization from 26

th

April to 24th

May 2012. In these four weeks I was allotted the job to visit various division of

the plant and to study instrumentation used in plant.

This four-week training was a very educational adventure for me. It was really amazing to see

the Power Plant by yourself and learn how electricity, which is one of our daily requirements

of life, is generated.

This report has been made by self-experience at MPP. The material in this report has been

gathered from my textbooks, senior student report, and trainer manual provided by training

department. The specification & principles are learned by me from the employee of each

division of MPP.

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INTRODUCTION

ABHIJEET GROUP

Abhijeet Group of Nagpur promoted by Mr. Manoj Jayaswal The Group is a well-diversified

business entity with significant presence in the core sector areas of Power, Mining,

Ferroalloys, Steel and Roads. Abhijeet Group is a thorough professionally managed

organization and takes immense pride in its highly committed, dedicated and dynamic

workforce. Various companies of the Abhijeet group in past have successfully completed

Build-Operate-Transfer (BOT) projects.

MADCL- Maharashtra Airport Development Company Limited

MADCL was incorporated in 2002, by the Government of Maharashtra as the nodal agency

for implementing project Multi-modal International Cargo Hub and Airport at

Nagpur(MIHAN )along with development of airports in the State of Maharashtra. As on

March 31, 2009 the company was managed by a 14-memberBoard of Directors with Mr. A.S.

Chavan ( Hon’ble Chief Minister of Maharashtra) being the Chairman

AMNEPL- ABHIJEET MADC NAGPUR ENERGY PRIVATE LIMITED

AMNEPL is promoted by Abhijeet Infrastructure Limited (AIL) (74% stake) and

MADCL(26%). Mr. Manoj Jayaswal is the Chairman of the company and Mr. B. K. Bonde is

the representative Director from MADCL. They are assisted by a team of qualified,

professional and experienced management with significant experience in the industry.

AMNEPL is setting up a thermal power plant at Nagpur for exclusively supplying power to

the upcoming SEZ and MIHAN

MIHAN POWER PALNT

The MIHAN Power Plant, being developed by our 74.00% owned Subsidiary, Abhijeet

MADC Nagpur Energy Private Limited (AMNEPL) near Khairy Khurd village, in Nagpur

district, Maharashtra, will have four coal-fired sub-critical generating units of 61.5 MW each

and a 25 MW back-up diesel generator , with a combined installed capacity of 271 MW. This

MPP is basically built to fullfil the requirements of MIHAN. The engineering, procurement

and construction contracts for the power project have been awarded to Abhijeet Projects

Limited (APRL), a Group Company. In turn, APRL has awarded the boiler, turbine and

generator contract to DF Power Systems Private Limited. First unit of 61.5 MW was

commissioned in January 2011 and the second unit of 61.5 MW was commissioned in April

2011. The third unit of 61.5 MW is commissioned in May 2011. The power project is

expected to be fully commissioned by June-2011

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INDEX

1. Coal to electricity basics…………………………………………8

1.1 Coal to steam

1.2 Steam to mechanical

1.3 Mechanical to electrical

2. Basic power plant cycle…………………………………………10

2.1 factors affecting thermal cycle efficiency

2.2 regenerative feed water heating

3. Coal handling plant…………………………………………… 12

3.1 Components of coal handling plant

3.2 Coal lab overview

4. Boiler…………………………………………………………… 15

4.1 Boiler specification

4.2 Structure of boiler

4.3 Flow of water and steam

4.4 High efficiency cyclone separator

4.5 Drum and its specification

4.6 Combustion equipment

4.7 Economizer

4.8 Air pre heater

4.9 Soot blower

5. Fan…………………………………………………………………21

6. Turbine…………………………………………………………… 22

6.1 Main technical specification

6.2 Steam turbine cycle

6.3 Components of turbine

6.4 Lubrication system for turbine and generator

7. Water treatment plant………………………………………………26

7.1 Pre treatment plant

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7.2 Demineralization

7.3 Water softening plant

7.4 Effluent treatment plant

8. Cooling towers…………………………………………………………29

9. Ash handling plant……………………………………………………..29

9.1 Bottom ash handling system

9.2 Economizer and air pre heater ash removal syatem

9.3 Dry fly ash extraction and transportation system

9.4 Dry ash disposal system

10. Mechanical maintenance……………………………………………….31

11. Switch yard……………………………………………………………..32

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1. Coal to electricity basics The basic steps in the generation of electricity from coal involves following steps:

Coal to steam

Steam to mechanical power

Mechanical to electrical power

Coal to electricity basics

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

1.1 COAL TO STEAM

Coal from the coal trucks is unloaded in the coal yard .In the C.H.P, this coal is taken to the

raw coal bunkers with the help of conveyor belts. Coal is then transported to crushers by coal

feeders where it is reduced to size from 9mm.

This crushed coal is taken away to the furnace through coal belt conveyor with the help of

Primary air fan. This fan takes atmospheric air, a part of which is sent to pre heaters while a

part goes to the mill for temperature control. Atmospheric air from S.A. fan in the air heaters

and sent to the furnace as combustion air.

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

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

from the bottom ring header is divided to all the four sides of the furnace. Due to density

difference the water rises up in the water wall tubes. This steam and water mixture is again

taken to the boiler drum where the steam is sent to super heaters (LTSH and HTSH) for super

heating. The super heaters are located inside the furnace and the steam is super heated (540

degree Celsius) and finally it goes to the turbine.

COAL Super heated

steam Turbine torque AC in stator

ASH HEAT

ENERGY

LOSS IN

CONDENSOR

MECHANICAL

ENERGY LOSS ELECTRICAL

ENERGY LOSS

CHEMICAL

ENERGY

THERMAL

ENERGY KINETIC

ENERGY

ELECTRICAL

ENERGY

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

balance draft in the furnace with P.A and S.A fans. These fuel gases heat energy to the

various super heaters and finally through air pre heaters and goes to electrostatic precipitators

where the ash particles are extracted. This ash is mixed with the water to form slurry and is

pumped to ash dyke.

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

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

and controls valves are located in steam chest and governor driven from main turbine shaft

operates the control valves the amount used.

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

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

into a second ring of moving blades mounted on the disc secured in the turbine shaft. The

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

together.

After that the steam is taken out from the 6 extractions and fed to the feed-water heaters (LP

and HP).

1.2 Steam to mechanical power

From boiler a steam pipe conveys steam to the turbine to the stop valve (which can be use dto

shut off the steam in case of emergency ) and through control valves that automatically

regulate the supply of the steam to the turbine . stop valve and control valve are located in

steam chest and 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 amount of

the electricity required from the generator )

1.3 Mechanical to electrical power

As the blades of the turbine rotates, the shaft of the generator,which is coupled to that of the

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

electricity to be produced.

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2. Basic power plant cycle

The ideal Rankine cycle consists of the following four processes:

1-2 Isentropic compression in a pump

2-3 Constant pressure heat addition in a boiler

3-4 Isentropic expansion in a turbine

4-1 Constant pressure heat rejection in a condenser

Water enters the pump at state 1 as saturated liquid and is compressed isentropically to the

operating pressure of the boiler. The water temperature increases somewhat during this

isentropic compression process due to a slight decrease in the specific volume of water. The

vertical distance between states 1 and 2 on the T-s diagram is greatly exaggerated for clarity.

Water enters the boiler as a compressed liquid at state 2 and leaves as a superheated vapor at

state 3. The boiler is basically a large heat exchanger where the heat originating from

combustion gases, nuclear reactors, or other sources is transferred to the water essentially at

constant pressure. The boiler, together with the section where the steam is superheated (the

superheater), is often called the steam generator. The superheated vapor at state 3 enters the

turbine, where it expands isentropically and produces work by rotating the shaft connected to

an electric generator. The pressure and the temperature of steam drop during this process to

the values at state 4, where steam enters the condenser. At this state, steam is usually a

saturated liquid–vapor mixture with a high quality. Steam is condensed at constant pressure

in the condenser, which is basically a large heat exchanger, by rejecting heat to a cooling

medium such as a lake, a river, or the atmosphere. Steam leaves the condenser as saturated

liquid and enters the pump, completing the cycle. In areas where water is precious, the power

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plants are cooled by air instead of water. This method of cooling, which is also used in car

engines, is called dry cooling. Remembering that the area under the process curve on a T-s

diagram represents the heat transfer for internally reversible processes, we see that the area

under process curve 2-3 represents the heat transferred to the water in the boiler and the area

under the process curve 4-1 represents the heat rejected in the condenser. The difference

between these two (the area enclosed by the cycle curve) is the net work produced during the

cycle.

2.1 Factors affecting thermal cycle efficiency

Initial steam pressure

Initial steam temperature

Whether reheat is used or not,if used reheat pressure and temperature

Condenser pressure

Regenerative feedwater heating

In our plant we are using regenerative feed water heating to increase the efficiency of

thermal power plant .

2.2 Regenerative feed water heating :-

In Rankine cycle heat is transferred to the working fluid in boiler at a relatively low

temperature. This lowers the average heat addition temperature and thus the cycle efficiency.

To remedy this shortcoming, we look for ways to raise the temperature of the liquid leaving

the pump (called the feedwater) before it enters the boiler.A practical regeneration process in

steam power plants is accomplished by extracting, or “bleeding,” steam from the turbine at

various points. This steam, which could have produced more work by expanding further in

the turbine, is used to heat the feedwater instead. The device where the feedwater is heated

by regeneration is called a regenerator, or a feedwater heater (FWH). Regeneration not

only improves cycle efficiency, but also provides a convenient means of deaerating the

feedwater (removing the air that leaks in at the condenser) to prevent corrosion in the boiler.

It also helps control the large volume flow rate of the steam at the final stages of the turbine

(due to the large specific volumes at low pressures).

A feedwater heater is basically a heat exchanger where heat is transferred from the steam to

the feedwater either by mixing the two fluid streams (open feedwater heaters) or without

mixing them (closed feedwater heaters).

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3.Coal handling plant (CHP)

As coal is the prime fuel for the thermal power plant , adequate emphasis should be given for

its proper handling and storage.also it is equally important to have a sustained flow of this

fuel to maintain uninterrupted power generation.

There are four units of power generation. Each unit requires 700-800 tonnes of coal per day

to generate 61.5 MW of electricity.

Basic coal handling plant cycle

3.1 Components of coal handling plant :

Primary crusher :

In primary crusher there are two horizontal cylinders between it 70mm space. It crushes coal

below 70mm size. It capacity is 440TPH.( tonnes per hour). It has two rollers one is fixed and

one is flexible and both are rotating in opposite directions. There are two primary crushers in

the plant.

Secondary crusher :

The secondary crusher is reversible impact type of crusher. impact is made by hammer to

crush the coal. There are 64 hammers of average weight of 12 kg which rotates at 440 rpm. It

crushes the coal below 9mm. its capacity is 550 tph. There are total 4 secondary crushers in

the plant.

Vibrating screen:

The function of vibrating screen to send the coal to the secondary crusher if the size of the

coal is greater than 9 mm.the screen house consist of three vibrating screens. These screens

have rotational as well as translational motion in order to have uniform distribution and to

protect the screen from getting damaged.There are three screens arranged linearly as follows :

Coal yard Primary crusher Secondary

crusher

Screening

house

boiler

250mm ≤70mm ≤9mm

If ≥ 9mm

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1 screen - 20×30mm

2 screen-9×16mm

3 screen-9×16mm.

Hopper and vibrating feeder.

Each crusher has surge hopper in order to distribute the coal uniformly. Vibrating feeder is

used to feed the coal on the underground conveyor belt from where coal goes to bunkers .

coal from the stock yard with the help of JCBs is taken to the vibrating feeder via hopper and

underground conveyor belt. A tripper is provided in conveyor to stack the material at the

desired location on either side or along the conveyor with the help of chute or chute fitted

with the tripper itself. The tripper is provided with wheels which move on rails parallel to

conveyor. There are three types of trippers :

1. Motorized tripper

2. Bell-propelled manually operated tripper

3. Winch driven tripper.

Conveyor Belts

There are 14 conveyors in the plant. They are numbered so that their function can be easily

demarcated. Conveyors are made of rubber and move with a speed of 150-180 m/min. Motors

employed for conveyors has a capacity of 150 HP. Conveyors have a capacity of carrying

coal at the rate of 400 tons per hour. Few conveyors are double belt, this is done for

emergency so that if a belt develops any problem the process is not stalled. The conveyor belt

has a switch after every 25-30 m on both sides so stop the belt in case of emergency. The

conveyors are 1m wide, 3 cm thick and made of chemically treated vulcanized rubber. The

max angular elevation of conveyor is designed such as never to exceed half of the angle of

response and comes out to be around 20 degrees.

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3.2 Coal lab overview

FLOW CHART

Purchase of coal from supplier

Sample of coal is collected from coal yard

Record this detail in proper formed

Collection of the sample on random basis as per SOP

Received the sample and prepare as per lab size

Preparation of five number Quality sample packet

Three sample after One quality sample One quality sample

signatue & seal packet send to coal packet reefed for

kept in the plant lab sample

Analysis of sample as per SOP

Preparation of test report at Lab

Circulating Quality report to top management

The following test are performed in coal lab :

Inherent moisture : inherent misture means moisture that exists as an integral part to

the coal seam in its natural state, including water in pores, but excluding that present

in macroscopically visible fractures.

Total moisture : the coal which has been exposed to the contact with water in seam or

in washery , or coal or coke wetted by rain may carry free or visible moisture .this

water plus the moisture within the material is referred as total moisture.

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Volatile matter: it is the amount of gases that are entrapped in the coal.

Fixed carbon : the amount of elemental carbon present in the coal

GCV(gross calorific value): the amount of heat generated by burning 1 gm of coal

completely in presence of oxygen.

4. Boiler

4.1 Boiler specification :

Rated evaporation (MCR): 250 t/h

Peak capacity: 275 t/h（1/2 hr every 12hs）

Rated steam temperature：540（0，-5）DegC

Rated steam pressure: 9.8MPa(gauge)

Rated feed water temperature: 235 DegC

Boiler flue gas discharge temperature: ~140 DegC

Blowdown ratio: ≤2 %

Ambient temperature at design state: 35DegC

PA & SA ratio:~ 60：40

Circulation ratio: 20～30

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4.2 The structure of boiler

The boiler is of high pressure & high temperature, with single drum horizontally placed,

single furnace, natural circulation, full overhung construction and steel structure disposed in

‘π’ type. The part above the operation level is arranged at the open air and the part below the

operation level is sealed. At the elevation of 11m of the operation level the steel construction

platform is placed. The furnace adopts the membrane type water wall. The center portion of

the boiler is the scroll case type steam cooled cyclone separator. The two stages of 3 groups

of convection super heaters are arranged inside the silo flue gas path. Under the super heaters

there are three sets of economizers, three sets of primary air preheaters and two sets of

secondary air preheaters.

The boiler is circulating fluidized bed (CFB) boiler, which is a new product manufactured

based on the vast experiences of manufacturing of the CFBC boiler of WHBC in corporation

with the Physical Research Institute of Chinese Academy of Science. In the combustion

system the coal is fed into the furnace through the coal chute by means of coal feeder. The

primary and secondary air fans provide the required volume of air for combustion of the

boiler separately. The air supplied by the primary air fan will be guided into the air paths (left

and right side) after passing through the air preheater to be preheated and then the same will

enter into the combustion chamber through the air nozzles on the water cooling grid plate.

The air supplied by the secondary air fan, after passing through the air preheater to be

preheated, will be guided into the furnace of the boiler to makeup the requirements of the air

to increase the turbulence in the furnace for proper combustion. The same will enter into the

furnace through the spouts/Nozzles on the front and rear walls of the furnace.

The fuel combusts with the circulated materials under the fluidized condition inside the

furnace and when the concentration of the mixed materials reaches to a certain requirements

the majorities of the materials will move upward from the inlet portion inside the furnace and

then starts the heat exchanges process with the heating surfaces when it moves downward

along with the wall by means of the inner circulation mode. The small particles in the flue gas

(often carries large amount of carbon particles) flying out of the furnace will enter into the

cyclone separator to be separated and whatever not passed through the separator will again

return to the furnace to be combusted. The clean flue gas will be drained out from the end of

the gas path after passing through the guiding chamber, high temperature super heater, low

temperature super heater, economizer, and the primary and secondary air preheaters. Owing

to the adoption of the mode of the combustion of the circulation fluidized bed and by adding

the limestone into the furnace the content of the SO2 in the flue gas can be significantly

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reduced and at the same time the generation of the NOx can be efficiently controlled by

means of combustion technology of the low temperature and stage wise air supplies. The ash

coming out of the ash coolers and other ash drain point’s are to be removed by the customer

with proper ash handling system to avoid the environmental problems.

4.3 The flow of the water and steam:

The feed water will enter into the drum after heated by the 3 sets of economizers that are

horizontally placed. The water in the drum will first enter into the water cooled membrane

type furnace through the down comer & distribution pipes and bottom headers, after heat

transfer in the furnace water and steam mixture enter in to the drum through the upper header

and raisers. The steam and water separation device is arranged inside the drum. The saturated

steam by means of the steam connecting pipe on the top of the drum, after passing through

the steam cooled cyclone tubes, enclosure pipes on the enclosure wall, low temperature super

heater, 1st stage attemperature, screen super heater, 2nd stage attemperature, high

temperature super heater, will be guided into the steam turbine.

4.4 High efficiency cyclone separator:

The purpose of cyclone is to refeed the unburned coal into the furnace. It is based on

the centrifugal principal.

The cyclone separator is the very important component of the CFBC boiler.The

CFBC boiler adopts the high efficiency scroll case steam cooled cyclone separator

technology, which is a patent of the Chinese Academy of Science. The 2 numbers of

cyclone separators are placed parallel at the outlet of the furnace, the diameter of the

separator is 4400mm, with the shell of the cyclone made up with the Φ38×6 tubes.

The inlet mode is scroll case type. This type of separator has the features of high

efficiency separation as well as increasing the combustion. The separated materials

from the flue gas will be returned to the furnace through the return material inlet

whereas the flue gas will flow to the rear convection-heating surface. The working

temperature of the materials separation and the return materials circuit is around 950

degree.

The steam cooled heating surface of cyclone separator could absorb the heat from the

after-combustion of the material, prevent the agglomeration forming by the high

temperature, expand the scope of coal adapted for the boiler and because the flame-

resisting layer is relatively thinner, the boiler start-up time could be shorten.

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Anchors inside the separator and the special anti-wearing plastic material with the

thickness of 60mm could protect the inner surface of the separator and increase the

service life of the cyclone separator.

The outlet of the cyclone separator adopts the alloy materials for high temperature

resistance and the material adopted is 1Cr25Ni20Si2.

The inlet of the separator has the manhole and the sealing property is ensured.

The thermocouple socket as well as the peephole is designed in the return materials

device to monitor the movement of the materials.

The steam-cooled separator can be performed as part of the superheated heating

surface.

4.5 The drum and its specification

The drum ID is 1600mm and wall thickness is 100 mm, head cover thickness 100mm

and the length of the cylinder is 14000mm the total length of the drum is ~13870mm.

The material is SA-299 GrA.

The normal water level of the drum is 180mm below the centerline of the drum. The

gap between the high water level or the low water level and the normal water level is

50mm.

The single stage vaporization system is adopted which has the arrangement of cyclone

separator, cleaning sieve plate and the top shutters, etc.

4.6 The combustion equipment

The combustion equipment consists of coal feeding system, air distribution system,

deslagging system, limestone feeding system, ignition system, materials returning system.

The coal feeding system

The boiler adopts the front feeding mode and 4 numbers of belt feeders are provided.

Interfaces for Indian coal, limestone and bed material are set on the feeders.

The feeders are connected with the coal chutes by means of expansion joints to satisfy

the expansion requirement (147mm) between the feeders and the furnace water wall.

The fed quantity of the coal is designed based on the principle that the three feeders

can guarantee to feed the sufficient quantity of coal to satisfy the 100% rated output

of the boiler even the other one feeders are not functioning.

The air distribution system

The air chamber consists of the rear water wall that is bending forward and the sides’

water walls. There is 100mm thickness concrete that is cast inside the air chamber to

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avoid the overheating of the fins during the ignition and reduce the water-cooling

degree inside the air chamber.

The required primary air by the combustion chamber is guided inside through the

side’s air ducts that are located on the left and right side. In between the air chamber

and furnace there is the air distribution plate that is welded with the water wall by flat

steel. The sectional area of the air distribution plate is 8770mm × 3200mm with 1011

uniformly scattered air nozzles.

The primary air will enter into the furnace through the air nozzles to fluidize the bed

materials. The materials of the nozzles are anti wearing and high temperature alloys,

the horizontal and vertical pitch of the nozzles are 160mm. In order to protect the air

distribution plate the cast fireproof materials on the air distribution plate is 150mm.

The deslagging system

The ash generated by the combustion of the coal will be taken out by means of the

bottom slag from the bottom of the furnace and by means of the flying ash from tail.

The type of coal, the size and the property of forming of ash will affect the ratio of the

slag and the flying ash. The bottom slag will be taken out of the furnace from the 5

slag discharge pipes that are connected to the water-cooling air distribution plate.

The limestone feeding system

The boiler is designed to add the limestone for desulfurization purpose. The limestone

will be fed into the furnace through the coal chute by means of coal feeders. the

consumption of the limestone is 1.8 tons per hour by design coal. The

desulphurization is 80% based on the calculation of the ratio of 2.5 between calcium

and sulfur.

The secondary air system

The secondary air will be guided into the different level height of the lower side of the

furnace through the air spouts that are located on the front and rear wall of the

furnace. The velocity at the air spouts is 70m/s. The working pressure of the

secondary air will not be less than 6000 Pa.

In order to control the air volume to guarantee the combustion the electric driven air

gate and the air checking devices fixed on the air pipes are designed accordingly.

The start up burner under bed

There are two start-up burners that are arranged at the rear of the water cooling air

chamber of the furnace. The start-up burner consists of oil gun, electronic ignite and

the flame sensor device. The adopted fuel is LDO(low diesel oil) and will be

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mechanical pulverized by the oil gun. Each oil gun has the output of 900Kg/hour with

the pressure of 2.5Mpa.

4.7 Economizer

The function of an economizer in a steam generating unit is to absorb heat from the

flue gases and add as a sensible heat to the feed water before the water enters the

evaporation circuit of the boiler

Earlier economizer were introduced mainly to recover the heat available in the flue

gases that leaves the boiler and provision of this addition heating surface increases the

efficiency of the steam generator.in the modern boilers used for power generations

feed water heaters are used to increase the efficiency of turbine unit and feed water

temperature

Use of economizer or air heater or both is decided by the total economy that will

result in the flexibility in operation, maintenance and selection of firing system and

other related equipment.

There are 3 sets of economizers are designed and the tube size is Dia. 32×4,with in

line arrangement. The material used for the tube is SA-210A1.

4.8 Air preheater

An air preheater absorbs heat from the flue gases and transfers the heat to incoming

cold air,by means of continuously rotating heat transfer element of especially formed

metal plates.

The 5 rows tubes of the preheater for PA and SA heating. The 2 sets of the air

preheater in the middle are used for SA preheat, while the 2 sets at the top and lower

part are used for heat the PA. Horizontal in line arrangement is applied here, and

800mm space is made between the 2 different tube banks for easy inspection and

exchange.

Special sealing arrangements are provided in the air pre heater to prevent the leakage

between the air and the gas sides. Adjustable plates are also used to help the scaling

arrangements and the prevent the leakage as expansion occurs. The air pre heaters

heating surface elements are provided with two types of cleaning devices, soot

blowers to clan normal devices and washing devices to clean the element when soot

blowing alone cannot keep the element free.

4.9 Soot blower

For the fuel alkali and sulfur content is high, by forming of ash deposit, the normal

operation of boiler could be affected. For purpose to clean the ash deposit on the

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boiler heating surface, protect the boiler efficiency and output from influenced, soot

blower points are arranged at each side wall of the back-end flue gas duct, steam soot

blowing is applied here. Retracting type soot-blowers are applied at the high

temperature superheater on the top, and other soot-blowers are the fixed type.

5. FANS:

A fan is a device by which the air is made to flow at required velocity and pressure in a

defined path imparting K.E of its impellers to air/flue gases. The main function of the fans is

to supply air for combustion in the furnace with required pressure & flow and to evacuate the

product of combustion i.e. flue gases into the atmosphere via chimney. There are four type of

fans in this plant they are-

Primary air fans.

Secondary air fans.

Induced draft Fans.

J-seal blower.

PRIMARY AIR FAN: The function of P.A fan is to provide air to combustion chamber for

proper burning of the coal and also used for carrying coal in to the combustion chamber.

SECONDARY AIR FANS: The function of S.A fan is to restrict the flow of unburnt coal

with the flue gas inside the combustion chamber.

INDUSED DRAFT FANS: The function of the induced draft fan is to remove flue gases in

the atmosphere through chimney.

J-SEAL BLOWER: The function of J-SEAL BLOWER is to fluidization. Byfluidization

the unburnt coal are collected in cyclone are carry into the combustion chamber.

6. Turbine

6.1 Main technical specification

1. Type : impulse type ,high pressure,high temperature,single cylinder,condensing steam

turbine

2. Gyrantee output: 61.5 MW

3. Maximum power : 63 MW

4. Rated condition parameters

Main steam pressure : 8.83 MPa

Main steam temperature: 5370C

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Main steam flow : 238T/ph

Back pressure: 9KPa

Inlet temp of cooling water : 33oC

Make up water temp : 242.9oc

5.Maximum steam flow : 244.6t/ph

6.Rotation direction : clockwise when viewed n the direction from turbine to generator

7. Rated speed : 3000rpm

8. shafting critical speed :

1810rpm(steam turbine 1st step )

≥4610rpm(steam turbine 2nd

step)

1679.7rpm(generator 1st step)

9. number of stages : 21 stages in total,consisting of 1 governing stage+20 pressure stages

10.Regenerative extractions : 6 stages consisting of 2 HP heaters + 3 LP heaters + 1

deaerator

23

6.2 Steam turbine cycle :

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

and converts it into rotational energy. Its modern manifestation was invented by Sir Charles

Parsons.

Different types of turbine may be condensing, Non-condensing, reheat, extraction and

induction type.

No-condensing or back pressure turbines: These are most widely used for process steam

applications. The exhaust pressure is controlled by a regulating valve to suit the needs of the

process steam pressure. These are commonly found at refineries, district heating units, pulp

and paper plants, and desalination facilities where large amounts of low pressure process

steam are available.

Condensing turbines: These are most commonly found in Thermal power plants. These

turbines exhaust steam in a partially condensed state, typically of quality near 90%, at a

pressure well below atmospheric into a condenser.

Reheat turbines: These are also used almost exclusively in electrical power plants. In a

reheat turbine, steam flow exits from a high pressure section of the turbine and is returned to

24

the boiler where additional superheat is added. The steam then goes back into an intermediate

pressure section of the turbine and continues its expansion.

Extracting type turbines: These are common in all applications. In an extracting type

turbine, steam is released from various stages of the turbine, and used for industrial process

needs or sent to boiler feed water heaters to improve overall cycle efficiency. Extraction

flows may be controlled with a valve, or left uncontrolled.

Induction turbines: These introduce low pressure steam at an intermediate stage to produce

additional power.

6.3.Components of turbine :

Condenser :

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 condensate 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 of 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. The condensed water is stored in

condenser hot well at its bottom. From here it aging goes to Boiler through CEP, Heaters, De-

aerator & Economizer.

Condenser extraction pump :

The condensate water is drawn from the hot well by the extraction pump and sent to the low

pressure feed heaters. This pump has four stages and since the sucton is at negative pressure ,

special arrangements have been made for providing sealing.

Ejectors:

There are two 100% capacity ejectors of the steam eject type. The purpose of the ejector is to

Evacuate air and other non condensating gases from the condenser and thus maintain the

vaccum in the condenser.

Low pressure and high pressure heaters :

These heaters are used to pre-heat water delivered to a steam generating boiler. Preheating

the feed water reduces the irreversible involved in steam generation and therefore improves

the thermodynamic efficiency of the system.This reduces plant operating costs and also helps

25

to avoid thermal shock to the boiler metal when the feed water is introduces back into the

steam cycle.

This involves two stages-

1) Low pressure heating in LP heater (3 in no. per unit)

2) High pressure heating in HP heater (2 in no. per unit)

Out of 6, extraction 1 and 2 goes to HP heater 1 and 2 respectively , extraction 3 to Deaerator

and extraction 4,5 and 6 go to LP heater 3,2 and 1 respectively.

These heaters are equipped with necessary safety valves in the steam space level indicator for

visual level indication of heating steam condensate pressure vaccum gauges for measurement

of steam pressure.

Deaerator :

A dearator is a device for removal of non condensable gases like oxygen, co2 etc 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 deaerated boiler feed water storage 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. 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 to stress corrosion cracking.

Boiler feed pump :

This pump is horizontal and of barrel design driven by electric motor through a hydraulic

coupling. All the bearings of the pump and motor are forced 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 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 other till it passes trough the last impeller and last diffuser. Thus the feed water

reaching into the discharge space develops the necessary operating pressure.

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6.4 Lubricating system for turbine and generator

It reduces friction between rotating and fixed part of turbine and generator.It also removes

heat from bearing which may either be generated by friction or by the conduction along the

shaft of turbine.

Main Oil Pump

It supplies oil in the turbine and generator system by means of an actuating mechanism which

is controlled by an LVDT depending upon requirement of speed to be achieved at high

pressure under normal conditions.

Auxiliary Oil Pump

It has two functions-

1) It supplies oil during start up and shutdown when shaft is not rotating fast enough for

the main oil pump to deliver the required pressure and flow.

2) It works as stand by oil pump when main oil pump fails.

Emergency Oil Pump

It supplies oil to the bearing during the time of slow down of turbine from running stage to

stop. This time is typically 20-45 minutes.

Jack Oil Pump

It is used in large turbine-generator systems and is used only when shaft is rotated by turning

gear.

Oil purification system

During operation the oil becomes contaminated by several undesirable impurities like water,

fibres, sludge, organic compounds metals etc. so for reuse of it, it is purified using oil

purifiers. The temperature of oil also increased so oil coolers are also provided with the unit.

Centrifugal purifiers are used for purifying oil and water or heat may be deliberately added

for the action.

7. Water treatment plant

As the types of boiler are not alike their working pressure and operating condition vary and

so do the types and methods of the water treatment . water treatment plants used in thermal

power plants are designed to process the raw water to water with the very low content of

dissolved solids known as “ demineralized water “ .

Water treatment process is generally made up of two sections :

Pre treatment section

Demineralization section

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7.1 Pre treatment section :

Pre treatment plants removes the suspended solids such as clay , silt , organic and inorganic

metal , plant and other microscopic organisms. The turbidity may be taken as of two types of

suspended solids in water , firstly the separable solids and secondly non separable

solids.(colloids). The coarse components such as sand, silt can be removed from the water by

simple sedimentation. Finer particles , however will not settle in any reasonable time and

must be flocculated to produce the large particles which are settable .

7.2 Demineralization

The filter water is now used for demineralizing purpose and is fed to cation exchanger bed,

but enroute being first dechlorinated which is either done by passing through activated carbon

filter or injecting along the flow of water an equivalent amount of sodium sulphite through

some store pumps . the residual chlorine which is maintained in clarification plant to remove

organic matter from the raw water is now detrimental to action resin and must be eliminated

before its entry to this bed.

A DM plant generally consist of cation, anion and mixed bed exchanger. The final water

from this process consist 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 DM water make up is generally added at the steam space of the surface condenser ( that

is the vaccum 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.

7.3 Water softening plant

Mainly water is softened here by removing the hardness causing ions which are calcium and

magnesium Equipment used to remove the hardness from boiler feed water. A sodium zeolite

water softener uses an ion exchange process to remove calcium and magnesium ions from

water and replaces them with sodium using NaCl.

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7.4 Effluent (Waste Water) Treatment Plant

Water quality factors affecting cooling towers are those that lead to deposition on the cooling

tower fills, such as suspended solids. Those leading to cooling tower surface scaling include

water hardness and biological fouling. All three contaminants - deposition, scaling, and

biological fouling - contribute to plugging of cooling tower fill.

Reservoir 1

Pump

house

Multi grade filter

for suspended

solids

SAC (strong

acid cation )

for Ca and

Mg ions Reservoir 2

Degasser

Blower

(for CO₂ )

WBA (weak base

anions) for Silica,

carbonates and

bicarbonates

SBA (strong

base anion-

Silica &

Carbonates

MIX BED

For

remaining

salts

removal

polishing.

Intermediate

tank

Ultra filtration

colloidal silica

removal

DM storage

TANK

(A and B)

Condensate

Storage

Tank

Holding

tank

Clarifier

(lime+polyel

ectrolite+FeC

l3)

Storage

Tank

Ultra

filtration

UF

product

tank

Reverse

osmosis (97%

salt rejection)

Degasifier CT

make-up

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8. Cooling tower :

Cooling Towers are evaporative coolers used for cooling the water. Cooling Towers

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

water used in oil refineries, Chemical plants, power plants and building cooling.

The tower varies 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. The primary

use of large, industrial cooling tower system is to remove the heat absorbed in the

circulating cooling water systems used in power plants.

The absorbed heat is rejected to the atmosphere by the evaporation of some of the

cooling water in mechanical forced-draft or induced draft towers. Cooling water

pumps are used to pump the water from CT fore-bay to Condenser.

There are 15 cooling towers in this plant. And the main function of cooling tower is to

cool the water from the different parts of the plant such as from various machines etc.

There are 16 different pumps used to draw the water from cooling tower and send it in

different plant. The pumps used are CWP, AWP etc.

9. Ash handling plant :

Ash handling plant is used to control the ash content in the smoke. There are various

processes in AHP to control the ash content such as bag filters are used in boilers to lessen

the ash content after that we purge the ash down. In AHP we used bed ash coolers to collect

the ash and pass it on to filters and then to completely minimize the ash content we then

30

purge it to ESP i.e electrostatic precipitator. In ESP we charge the plate so that all ash

particles are stucked to that plate and there is no ash content is smoke of chimney and

collected ash is then sent to ash dack by using HD PUMPS.

9.1 Bottom Ash Handling System

The Bed Ash handling system shall be of dry type with water cooled ash coolers and

for intermittent removal. The bed ash resulting from the combustion of coal in the boiler shall

fall into bottom hopper provided under the furnace bottom.The cooled ash is transported to

Silo or it can be directly to ash dyke through trucks.

9.2 Economizer and Air Pre-heater Ash Removal System

Ash collected in economizer, economizer bypass duct, primary air heater and secondary air

heater hoppers will drop continuously through suitable vertical pipe connections to the

flushing connections provided beneath each of the hoppers. The flushing equipment serves to

mix the ash with the water and discharge the ash in the form of slurry.

9.3 Dry Fly Ash Extraction and Transportation System

The dry fly ash handling system consists of ESP and duct hopper ash removal

systems. A two stage conveying system shall be provided. The first stage shall include

extraction of dry fly ash from under the various ESP / duct hoppers to the intermediate

surge/buffer hoppers/ collector tanks located near the ESPs which are known as ASH SILO.

In the second stage ash shall be conveyed/ transported from under these buffer hoppers to the

storage silos located outside plant boundary. A vacuum system shall be provided for

extraction of dry fly ash in the first stage, for second stage, viz., transportation of dry fly ash

to the main storage silos, located outside plant boundary shall be necessarily by the pressure

conveying system only.

9.4 Ash Disposal System

For both the units, bottom ash from discharge of jet pumps, economizer and air pre-

heater slurry from discharge of flushing apparatus and fly ash slurry from wetting head,

collector tanks and air-washer units provided upstream of buffer hoppers shall be led to a

common slurry sump of combined ash slurry disposal pump house. From where it can be

send to cement industries where it can be used.

In ash handling plant two different type of compressors-

Instrument air compressor.

Service air compressor.

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COMPRESSOR-The function of compressor is to compress the air. If we want

moisture free compressed air then we used instrument compressor along with tri-air.

This compressed air is used

power cylinder

Control wall

If only compressed air required then service air is used. This compressed air is used in

For conveying system there are 4 instrument compressor and 8 service air compressor in ash

handling plant.

10. Mechanical maintenance

Predictive maintenance

The art of predictive maintenance is to monitor the machine with appropriate technologies

frequently enough to detect the anticipated failure modes which is also known as “condition

based maintenance “. It results in

Increased uptime

Decreased unexpected returns

Reduced maintenance cost

Maintenance is performed and it is planned

Improve plant safety

Machines normally give off some signs before failing

The sign may be change in sound level,vibraton,pressure,temperature etc

Change in performance

Metal particles in lubricant

Change in motor current

Proactive maintenance

It is also known as precision maintenance and reliability based maintenance. The motto here

is to “Fix it once & Fix it right “

Knowledge based maintenance

Shared information among all users

Root cause analysis-design problems out off machines,fix the problems not the

symptom.

Corrective maintenance- This type of maintenance occur when any small parts gets wear

and required to replace it like change of spring, bolt, or blade of the machine.

32

Break down maintenance- It occurs when the equipment causes fail to work.

The cost of break down maintenance is more. It causes more time to repair.

Periodic maintenance- This type of maintenance occur over a period of time it include

lubrication of the equipment to increases the life of the machine.

11. Switch yard

A Switchyard or substations, consisting of large breakers and towers, is usually located in

an area close to the plant. The substation is used as the distribution centre where

Electrical power is sent from the plant.

SWITCHYARD EQUIPMENTS:-

1. BREAKERS

2. ISOLATORS

3. INSULATORS

4. CURRENT TRANSFORMER (C.T.)

5. POTENTIAL TRANSFORMER (P.T.)

6. POWER LINE CARRIER COMMUNICATION(P.L.C.C)

7. BUS BARS

1. BREAKERS:-

A circuit breakers is an automatically-operated electrical switch designed to protect

an electrical circuit from damage caused by over load or short circuit. its basic function

is to detect a fault condition and, by interrupting countinuity to immediately discontinues

electrical flow.

Types of breakers:-

1. Oil circuit breaker

2. SF-6(Sulphuric hexafluoride) breaker

3. Air circuit breaker.

2. ISOLATORS:-

It is also called as disconnect. They are used to disconnect the main supply or isolate

the busbars for the maintenance purposes.

3. INSULATORS:-

An insulator also called a dielectric, it is that material that resists the flow of electric current.

Example of insulator materials are rubber-like polymer is still good enough to insulate electrical wiring

and cables. These insulators with a conductor inside them are called Bushings.

33

4. LIGHTNING ARRESTERS:-

It is a device used on electrical power systems to protect the insulation on the system from

the damaging effect of lightning.The typical lightning arresters also known as surge arrester

has a high voltage terminal and a ground terminal.

5. CURRENT TRANSFORMER (C.T.):-

A current transformer is used for measurement of electric currents. A current transformer

together with voltage transformer (VT) are known as instrument transformers.

6. POTENTIAL TRANSFORMER (P.T.):

Potential transformer, also known as capacitor voltage transformer (CVT), or capacitance

coupled voltage transformer(CCVT) is a transformer used in power systems to step down extra high

voltage signals and provide a low voltage signal

8. BUSBAR:-

The electrical power distribution, a busbar is a thick strip of copper or aluminium that

conducts electricity within a switchboard, distribution board, substitution busbar are used

to carry very long currents, or to distribute current to multiple devices within switchgear