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HINDALCO INDUSTRIES LIMITED

(RENUPOWER DIVISION)

Summer Vocational Training-2016

BOILER OPERATION & PLANT OVERVIEW

Submitted By

RAM PRAKASH TRIPATHI

Id No. - 14N31A03E4

MALLA REDDY COLLEGE OF ENGG. & TECH.

Maisammaguda, Dhulapally, Secundarabad-500100

TELANGANA STATE

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ACKNOWLEDGEMENT

I take immense pleasure in thanking the Department of Mechanical Engineering having permitted me to carry

out this project work.

I wish to express my deep sense of gratitude to my Internal Guide, Astt.Prof. DAMODAR REDDY of

Mechanical Department(Thermal Engg.) and Mr. Hem Raj, HOD-TTMDC at Renusagar Power

Division(Hindalco Industries Limited) for giving me permission. His proficient, enthusiastic guidance,

encouragement and suggestions given by him undoubtedly helped in supplementing my thoughts in the right

direction for attaining the desired objective.

I would like to express a deep sense of gratitude and thank profusely to Mr. S. B. Verma (H.O.D,

OPERATION DEPT.) for his sincere & invaluable guidance. My heartfelt gratitude goes to Mr.Naveen

Gupta, Mr.Sumanth Kumar, Mr. Rajesh Mishra (T.T.M.D.C) for providing all the guidance required for

the completion of my project. I would like to thank the staff of boiler operation dept., Mr. S.N.Srivastava,

Mr.S.D.Dubey, Mr.Santosh Gupta, Mr.Sanoj Kumar, Mr.Animesh Kumar, and all the workshop staff

who helped me in various aspects of my project. I would also like to thank Mr. R.K.Tripathi (Turb. Oprtn.)

for his invaluable guidance.

I am very much thankful to employees of Hindalco Industries Limited, Renusagar Power Division, Renusagar

for who have contributed directly or indirectly towards the successful completion of my project work on time.

All above, I express my indebtedness to thee “ALMIGHTY” for all His blessings and kindness.

RAM PRAKASH TRIPATHI

Id No. - 14N31A03E4

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DECLARATION

I hereby declare that the project work entitled OVERVIEW OF BOILER is an authentic record of my own

work carried out at HINDALCO INDUSTRIES LTD., RENUSAGAR POWER DIVISION as

requirements of six weeks vocational training programme for the professionalism in degree of B.Tech.

Mechanical Engineering, MALLA REDDDY COLLEGE OF ENGINEERING AND TECHNOLOGY,

HYDERABAD under the guidance of Mr. HEM RAJ (HOD-TTMDC) & Mr. Naveen Gupta.

RAM PRAKASH TRIPATHI

Id No. - 14N31A03E4

Certified that the above statement made by the student is correct to the best of our knowledge and belief.

Dr. V.S.K.Reddy

Principal

MALLA REDDY COLLEGE OF ENGINEERING AND TECHNOLOGY

Mr. P.H.V.Shesha Thalpa Sai Mr. Hem Raj

Head of Department HOD

MECHANICAL ENGINEERING TTMDC

Hindalco Renusagar

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THE ADITYA BIRLA GROUP: A PREMIUM GLOBAL CORPORATION

A US $41 billion (Rs. 2,50,000 crore) corporation, the Aditya Birla Group is in the League of

Fortune 500. Anchored by an extraordinary force of over 120,000 employees, belonging to 42

nationalities. Over 50 per cent of its revenues flow from its overseas operations spanning 36

countries.

The Aditya Birla Group has been ranked fourth in the world and first in Asia Pacific in the ‘Top

Companies for Leaders’ study 2011, conducted by Aon Hewitt, Fortune Magazine and RBL (a

strategic HR and leadership Advisory firm). The Group has topped the Nielsen's Corporate Image

Monitor 2014-15 and emerged as the Number one corporate, the 'Best in Class', for the third

consecutive year.

Globally, the Aditya Birla Group is:

A metals powerhouse, among the world's most cost-efficient aluminium and copper

producers. Hindalco-Novelis is the largest aluminium rolling company. It is one of the three

biggest producers of primary aluminium in Asia, with the largest single location copper smelter

No.1 in viscose staple fibre

No.1 in carbon black

The fourth-largest producer of insulators

The fifth-largest producer of acrylic fibre

Among the top 10 cement producers globally

Among the best energy-efficient fertiliser plants

The largest Indian MNC with manufacturing operations in the USA, wherein 95 per cent of the

workforce comprises of Americans

Aditya Birla Group – The Indian Scenario

A top fashion (branded apparel) and lifestyle player

The second-largest player in viscose filament yarn

The largest producer in the chlor-alkali sector

Among the top three mobile telephony companies

A leading player in life insurance and asset management

Among the top two supermarket chains in the retail business

Aditya Birla Group – Beyond Business

Reaches out annually to 7.5 million people through the Aditya Birla Centre for Community

Initiatives and Rural Development, spearheaded by Mrs. Rajashree Birla.

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Works in 5,000 villages globally.

Focuses on: health-care, education, the girl child, sustainable livelihood, women empowerment

projects, infrastructure and espousing social reform.

Runs 42 schools which provide quality education to 45,000 children. Of these 18,000 students

belong to the underprivileged segment. Merit Scholarships are given to 24,000 children from the

interiors.

Its 18 hospitals tend to more than a million villagers.

Ongoing education, healthcare and sustainable livelihood projects in Philippines, Thailand,

Indonesia, Egypt, Korea and Brazil, lift thousands of people out of poverty.

Set up the Aditya Birla India Centre at the London Business School.

The Aditya Birla Group transcends conventional barriers of business because we believe it is our

duty to facilitate inclusive growth.

OVERVIEW OF HINDALCO INDUSTRIES LIMITED

Hindalco Industries Limited is a flagship company of the Aditya Birla group. This company

has been growing ever since it was established in 1958. Today, it has emerged as a market leader

in aluminium and copper. After the latest controversy of Vedanta regarding the closure of plants

of Sterlite and stay order at Niamgiri, Hindalco and Nalco are the two giants in the field of

Aluminium industry.

Hindalco has two broad Business Segments:

1. Aluminium: It consists of Primary Aluminium, Aluminium Extrusion, Rolled Products,

Aluminium Foil & Packaging.

2. Copper: It consists of Copper Cathodes, Continuous cast copper roads.

The revenue contribution by each segment is

Hindalco's journey has been challenging at times, but truly exhilarating. Novelis became a

Hindalco's subsidiary with the completion of the acquisition process in May of the year 2007.

The transaction makes Hindalco the world's largest aluminium rolling company and one

of the biggest producers of primary aluminium in Asia, as well as being India's leading copper

producer.

The fact file of the company in two areas covers, World's largest aluminium rolling

company, one of the biggest producers of primary aluminium in Asia, ISO 9001:2000 and 14001

certified, One of the lowest-cost producers of aluminium in the world and India's leading copper

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producer, India's largest copper smelting and refining plant at Dahej, Gujarat, with two

copper mines in Australia, ISO 9001,14001 and OSHAS 18001 certified, Smelting and refining

capacity 500,000 tpa, the largest single location smelter in the world.

Domestic consumption growth for both aluminium and copper augurs well for Hindalco,

which has embarked on the growth plan through low cost Greenfield projects of the company.

OVERVIEW OF RENUSAGAR POWER DIVISION

Renusagar Power Division (RPD) is a Captive Power Plant of Hindalco Industries Limited,

country’s leading aluminium producer and a flagship company of The Aditya Birla Group. It has

the distinction of being the first Captive Power Plant for Aluminium Company in India.

The great visionary Late Syt G.D. Birla conceptualized the Power Plant at Renusagar way

back in 1964. Renusagar Power Division is located at the pithead of Singrauli Coal Seam of

Northern Coal Fields Limited (NCL) and on the banks of Rihand Lake.

It is situated in Sonebhadra District of Uttar Pradesh (U.P.) on the border of U.P. and M.P. It

is 200 KM from Varanasi and 40 KM from Renukoot. This region is known as Power Capital of

the country and contributes approximately 10000 MW to the national economy.

The first Unit of 67.5 MW capacity was commissioned in 1967 at RPD. In the Last 40 years

the plant has grown more than ten times, now it is having 11 Boilers & 10 Turbo-Generators and

the current installed capacity is 802 MW. The capacity growth at RPD has been in accordance

with the capacity growth of Aluminium plant at Hindalco – Renukoot

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BOILERS

Boilers convert de-mineralized water into high-pressure steam using the heat generated from

coal firing. Renusagar has eleven (11) boilers (including one standby boiler). These boilers are

“Top supported, Bi-drum, Radiant type, Balanced Draft, Natural Circulation, Tangential Tilting

Firing System with Pulverized Coal Firing”.UV-40 Capacities of boilers vary from 275 to 345

tons steam per hour.

Statutory requirement of annual Boiler survey led to Renusagar installing a spare boiler to supply

uninterrupted power to Hindalco-Renukoot. Concept of spare boiler is a unique feature of

Renusagar Power Plant. Standby boiler ensures higher plant availability. All the eleven boilers

and 10 turbines are connected with common feed water and steam header.

The common header ensures the inter-connection of Boilers & Turbines on need to need basis.

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Water & Steam Cycle

Raw water is taken from Rihand Lake and is demineralised in Demineralization Plant (D.M.

Plant), and is fed to boiler for producing steam. The saturated steam in the upper drum of boiler is

separated with the help of drum internals and then superheated to 510°C-535°C in super-heater

tubes.

High-pressure superheated steam coming out from boiler enters the steam turbine and rotates

it. Generator is coupled to the rotating Turbine to produce Electrical Power.

The exhaust steam coming out of turbine is condensed and pumped back to boiler for steam

generation

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RANKINE CYCLE

Steam Turbine

Renusagar has ten numbers impulse reaction type turbines, each connected to a generator &

an exciter. Turbines are having five extraction points for regenerative feed water heating.

Electricity Generation

Steam turbine coupled generators run at 3000 rpm and generates electricity at 10.5 & 13.8

KV. The power generated at 10.5 & 13.8 KV is stepped up to 132 KV with the help of generator

transformer and exported to Hindalco through ten (10) transmission lines.

The Auxiliary power consumption at Renusagar comes out to be 7.97%, this is the power

required to run our own equipments.

Ash Handling System

Ash handling system consists of Bottom Ash System, Electrostatic Precipitators (ESP) & Fly

Ash System. Around 15-20% ash is taken out through Bottom Ash System and rest through Fly

Ash System.

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All the eleven (11) boilers are fitted with Electrostatic Precipitators (ESP). The efficiency of

ESP is 99%, with the result that stacks are smokeless and area is pollution free.

Fly ash disposal is done through - Wet & Dry Ash disposal system. Bulk of the fly ash is

transported to ash pond through wet ash disposal system. A FAL-G Brick Making Plant

manufactures fly ash bricks & blocks from Dry fly ash.

Renupower is promoting use of fly ash as raw material among cement manufacturers. For

easy handling of fly ash into tankers, a separate DFAT (Dry Fly Ash Transportation) system has

been setup outside the plant premises.

Power generation by the turbines at R.P.D

UNIT DESIGN

CAPACITY(MWH) GENERATION(MWH)

#1 67.5 71 #2 67.5 71 #3 80 83

#4 80 83

#5 68 70

#6 74 83

#7 74 83

#8 77 80

#9 80 89

#10 80 89

TOTAL 748 802

Power generation of R.P.D

PLF=( ACTUAL GENERATION/INSTALLED CAPACITY)×100

BEST GENERATION =818.75 (29/06/15) Therefore Best PLF =(805.75/748)×100 =107.72

*PLF= Plant load factor

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BOILER AND ITS AUXILIARIES

Definition of Boiler (As per IBR 1950):

Any closed vessel exceeding 22.75 litres (5 gallons) in capacity, which is used expressly for

generating steam under pressure and includes mountings or fitting attached to such vessel, which

is wholly or partly under pressure when steam is shut off.

At Renusagar Power Division, there are 11 boilers (1 spare) and are top supported, bi-drum, dry

bottom, water tube, tangential tilted corner fired, natural circulation, balanced draft boilers.

COMBUSTION:

The function of boiler is to produce steam from water using the heat from combustion of the fuel.

So, combustion of coal /air mixture (or oil during light up) is an important phenomenon in a

boiler. It is of two types:

1. Primary combustion:

The primary combustion occurs in the furnace due to combustion of coal or oil.

2. Secondary combustion:

The combustion that takes place outside the furnace is called secondary combustion. It is

the main cause of accidents and explosions. If the fuel does not get the required fuel supply, it

may not fully burn in the furnace and some unburnt fuel will travel with the fuel gases and

stick to the part of boiler, super heater, economizer or APH &start accumulating over there

and the moment the ignition temperature is reached, it explodes as secondary combustion.

TANGENTIAL FIRING

The coal burners (or oil guns) are fitted at the corners and fire in such a way that a fire ball

generated at the centre of the furnace and so the firing is done along the tangents to the fire ball

circle at the centre and carries away the flue gases. There is scrubbing action due to tangential

firing, which results in proper combustion of fuel. The burners can also be tilted (+30 to -30) to

raise or reduce the degree super heat of the steam.

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SCANNER

The scanner is an optical lens for sensing the flame inside the boiler furnace and transmits it to

the DCS.the air supplied by scanner air fan, which removes the soot deposition over the scanner,

also cools it.

OIL GUN

Oil gun is used to supply oil to furnace during the light up by flowing oil through LONV and

flow of air through AONV thus atomized of the oil by striking it against the diffuser plate and

then the atomized oil is sprayed in the furnace through small holes. Proper atomization is

necessary for total combustion of oil.

Burner management system:

Burner management system (BMS) based on distributed digital control system (DDCS) for

large utility boilers. The BMS system is responsible for the safety of the furnace and boiler. The

system protects personnel and machinery from unsafe condition in furnace, and it helps the

operator in safe operation, startup, and shutdown of the boiler.

Furnace:

A furnace is a chamber of combustion. In addition to this it provides support and enclosure for

the combustion equipment, burners or stockers. The design of the furnace requires co-ordination

of several important factors:

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1. Type of combustion equipment.

2. Character of fuel used, specially its ash content.

3. Draft equipment employed.

4. Air supply and degree of preheating.

5. Boiler and its baffling arrangement.

MAIN PARTS OF BOILER & ITS AUXILIARIES

NON PRESSURE PARTS:

Draft Fans:

The fans used for creating draft are:

1. PA Fan: primary air fan supplies coal /air mixture by pressurized hot air. The air is heated

by APH and supplied to coal mill and thus the pressurized hot air supplies coal to coal

pipes.

2. FD Fan: forced draft fan is used to supply air for burning of coal in the boiler furnace, it

also supplies cold air to the pressurized hot air to obtain the desired temperature in the

coal mill for drying the coal.

3. ID Fan: induced draft fan is used to suck the flue gases in the duct connected to the boiler

and discharge the gases to the atmosphere through the chimney.

AIR PREHEATER: - The APH also helps in increasing the efficiency of the boiler by

increasing the temperature of the primary as well as the secondary air. It is of two types:

Regenerative APH: - It contains a rotating cylindrical structure fitted with fins and

through 50% of its area flue gases pass and through 35% primary air and 15% for

auxiliary air. Since it is rotating so flue gases transfers its heat to the primary and

auxiliary air and raises its temperature.

Recuperative or Tubular APH: - It contains tubular arrangement through which

primary and auxiliary air pass in the tubes and are heated by the flow of the flue

gases over the tubes. It has higher efficiency than regenerative APH and requires

lesser maintenance

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PRESSURE PARTS

STEAM DRUM: - The upper drum of the boiler is called the steam drum. It contains both the

steam as well as water, and due to lesser density steam occupies upper portion of the drum and

water lies beneath it. It receives saturated water from the economizer and supplies saturated steam

to the super heater after evaporation if water, it is connected to the lower drum through the boiler

bank tubes, which take water from the upper drum to the lower drum and the water wall tubes

eject the steam produced in the upper drum. Its upper portion has a mechanical separator separate

the steam from the water droplet carried.

WATER DRUM: - the lower drum is called the water drum. It receives water from the upper drum

through the boiler bank tubes and it receives heat from the flue gases to raise the temp of the

water. It is connected to the down comer, which supplies water from the lower drum to the ring

header. This distributes the water to the water walls tubes. It has a stuffing box, which receives

steam from the south side tubes and sends it to the upper drum.

WATER WALL TUBES:- The tubes receives water from the ring header and are spread vertically

around the furnace, so the water in these tubes get heated and get converted into steam, which due

to lower density rise up setting up natural circulation. The steam is supplied to the upper drum by

three sides of the water wall tubes i.e. north, east & west and to lower drum by the south side

tubes.

CONVECTION TUBE: - It connects upper drum to lower drum. Large numbers of convection

tubes are found in boilers. These tubes are not welded to upper drum and lower drum; these tubes

are connected by spanding process.

DOWN COMMER PIPE:- A pipe for leading the hot gases from the top of a blast furnace

downward to the regenerators, boilers, etc.

In some water-tube boilers, a tube larger in diameter than the water tubes to

conduct the water from each top drum to a bottom drum, thus completing the circulation.

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SUPER HEATERS: - These are of two types:

a. Radiant Superheater: It is also called the primary super heater. It receives heat

from the furnace by radiation as it hangs above the furnace and receives saturated

steam from the upper drum, which is superheated to the desired temperature.

b. Convective Superheater: It is also called secondary or platen or final superheater.

It receives heat by convection from the counter flow of flue gases. The superheated

steam from the final superheater is supplied to the turbine.

c. Desuperheater: The de Superheater lies between the primary and the secondary

super heaters. The main function of the desuperheater is to reduce the temp of the

superheated steam coming from primary superheater by spraying water tapped

before economizer from the feed line.

ECONOMISER: - The economizer is used to add sensible heat to the feed water and utilize the heat

of the flue gases. It consists of KMs of tubes lying in the path of the flue gases and thus absorbs

the heat from flue gases by counter flow of water. Thus it helps in increasing the efficiency of

boiler by reducing the amount of heat required to raise the temperature of the water in the water

wall tubes.

SAFETY VALVES: - Total 4 nos. Safety valves are provided in each unit. 2 nos. on upper drum

and 2 nos. after final super heater on steam line. It opens when the boiler pressure exceeds the

working pressure.

PRESSURE GAUGE: -Pressure gauge is generally constructed to indicate unto double the

maximum working pressure. So that the pointer is vertical when the valve is blow off. A siphon is

connected before the pressure gauge for preventing steam from entering the gauge and keeping it

comparatively cool.

DRAINS OR STEAM TRAPS: Drains are provided in equipments to insure safety of equipments

and human. The function of steam trap is to drain off water resulting from partial condensation

of steam from steam pipe and jacket without allowing steam to escape through it. Generally

steams traps are divided into two groups:

1. Bucket type or float type.

2. Thermal expansion type.

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STOP VALVE: The stop valve is mounted on top of boiler forming outlet steam. It is fully in open

position during boiler on load. It is used only (closed) when boiler is under overhauling or

shutdown for auxiliary maintenance.

FEED CHECK VALVE: It is a non return cum isolating valve used between boiler feed control

valve(CV1 & CV2) and economizer it’s main function is to check the water returning from

boiler during any trouble in the boiler feed make up system.

FUSIBLE PLUG: The main function of fusible plug is to protect the crown plate or the fire tube

burning when the level of water in water shells down.

BLOW DOWN TANK: It is used to remove sludge or sediments collected at the bottom most point

in water space in boiler but it is not used in large power generating units

TURBINE AND ITS AUXILIARIES

The steam turbine is a device, which is used to convert the kinetic energy of the steam into

rotating motion of the rotor shaft, coupled to the generator, by allowing it to expand adiabatically.

The steam passes through the main steam connection, the steam strain and emergency stop valve

before the servo valves, into the inlet port of the outer casting. After opening of servo valve,

steam flows into steam chamber to pass through jet groups and into the expansion area of the

turbine, by giving off its energy capacity & expanding up to the final pressure in the exhaust port.

The turbine consists of the following main assembly groups:

1. turbine casting

2. front and rear bearings

3. turbine rotor and bearing

4. the blade mounts

5. the sealing shells

6. The emergency stops & regulating valves with their actuators.

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Operation of turbine and its auxiliaries;

The main steam from the boiler passes through the Intermediate Valve and then

Emergency Stop Valve to the valve block, which has control valves to control the flow of steam

into the turbine. When steam enters the turbine, its pressure is reduced and its velocity increased

by passing through nozzles fitted in the casing. Then the steam falls on the Curtis wheel and

maximum expansion of the steam takes place here and then steam expands adiabatically and

looses pressure and velocity during the successive expansion stages. The energy is transferred to

rotate the motor. Five extractions from the turbine, at different stages are taken and supplied to

the HP heaters (1 & 2 ), deararator and LP heaters( 1 & 2 ). The steam at the end of expansion

passes into the condenser where it is cooled by the water, circulating b/w cooling tower and

condenser, flowing in tubes and thus condenses top form water which is collected in the hot well

below the condenser, from where this water goes to steam jet air ejector (SJAE) which removes

the air from the condenser and then the condensate water goes to condensate extractor pump

(CEP). The CEP pumps the condensate water to LP heater1, where the condensate water, flows in

tubes, and absorbs the heat of the extracted steam and similarly absorbs heat in the LPH2 to raise

t5he temperature to 115 degree Celsius after LPH2. Then the water goes to deaerator where gases

like co2, o2 and other gases are mechanically and chemically removed. Then the condensate

water goes to the boiler feed pump (BEP) , which increases the pressure of feed water and pumps

it to the HP heaters, where also the temperature of water is increased to 236 degree Celsius and

the feed water is send to the economizer.

Condenser:

The condenser is equipment in which the working fluid gives up, to the cooling water, that

quantity of heat by virtue of which as per the second law of thermodynamics, which cannot be

converted into work.

The condenser tubing array on which the exhaust steam from the turbine condenses, consists of

straight tubes with smooth surfaces and runs at right angles to the turbine axis. The exhaust steam

from the LP turbine flows through the condenser steam dome and enters the condenser tubing

array from above. The steam condenses on the outer surface of the smooth condenser tubes. The

heat of condensation is transferred to the circulating water in tubes.

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Deaerator:

The water generally contains O2, CO2, air, H2S, and other gases in dissolved condition. It is

absolutely necessary to remove these gases before supplying the water to the boiler, as they are

responsible for corrosion. The removal of gases is accomplished by heating the water to 105-130

degree Celsius with subsequent agitation during heating. Since absorbing capacity of water is

reduced at high temperature so the gases are removed by simple heating.

The water is first passed to the vent condenser where the gases preheat it and air is liberated from

the water. Then it is passed through a spray distributor, from where water falls over an entire

width of a heating tray like a shower. The water from the trays falls over air separating trays and

then it passes into storage space for deaerated water. The released air and part of steam is vented

passing over the condenser. O2 content can be reduced below 0.005cc/litre, CO2 is also removed

and increased pH value of water gives the indication of efficient deaeration.

Steam Jet Air Ejection (SJAE):

SJAE uses jets of high velocity steam to remove air from condenser. Live steam from boiler is

delivered to each stage of SJAE. In first stage, steam passes through the suction opening; it

attains a high velocity and entrains the air. Mixture of air and steam is compressed and delivered

to intercooler where steam is condensed and returned to a suitable point in the feed circuit. The

second jet takes the gases and air from intercooler & further compressing, delivers it to

aftercooler in which steam used for operation is recovered.

Generator and its Auxiliaries:

Generator is designed as two pole, hydrogen cooled, and turbo generator with pedestal cooling.

The rotation of the generator is counter clockwise as seen from the driving side. Sealing of the

generator on the bushings of the inductor shaft is done by the hydrogen shaft bushing of radial

type. The complete generator is covered with generator planking attached to the turbine planking,

where the hearing hood follows from the generator bearing on the excitation side onwards.

Bearing hood contains a ventilation facility with axial fans for cooling the slip ring surface.

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Stator and Stator windings: stator frame is shaped as weldment with flexural and tensional

rigidity. The high alloy core plates of 0.05mm thickness, varnish insulated on both sides, are

united in one pack by non magnetic core and plates.

Rotor and Rotor windings: rotor is made of high alloy steel and is coolant flanged on. The slots

milled into the rotor barrel accommodate directly cooled excitation winding. Rotor has a damper

winding in the excitation winding slots. Excitation current is led to field winding via slip rings

arranged outside the pedestal bearing of the generator.

Slip Rings and Bush Gear: the slip rings are steel forged, which are shrunk on steel covered

with mica build up in position. They are arranged side by side in the generator bearing at the

excite end. The surface of the slip ring is helically grooved & brushes are staggered to increase

the lift of the slip rings and brushes. The brushes are pressed on the rings by means of spying load

plunger.

Excitation System: the excitation system provides the necessary field current to the rotor

winding of the synchronous machine. The amount of excitation depends upon power factor, speed

of machine and load current.

At Renusagar Power Division, brushless excitation system is used for unit # 3, 4, 6-10 and

permanent magnet type for unit # 1&2, for unit # 5 static excitation systems is used.

ESP AND ELECTRICAL MAINTENANCE

Electrostatic Precipitator (ESP):

ESP is electrical equipment where a DC voltage is applied to discharge electrodes creating

an electric field around it. ESP is used to separate the dust particles from flue gases in many

industrial processes. Dust particles carried by the gases while passing through the field is

discharged to saturation and migrate towards the collecting electrodes, usually in the form of a

plate curtain, where they are deposited in layers and by rapping, the dust is dislodged in the

hopper.

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There are two sets of electrodes. The first set is composed of electrically grounded vertical

parallel plates called collecting electrodes & the second set consists of hanging wires with 70kv

DC supply from the transformer/rectifier set at the top of ESP, it is also called the emitting

electrode. Due to this high voltage, a luminous glow, called corona is formed and accelerates the

free electrons present in the gas, which ionizes the gaseous electrons to form negatively charged

gaseous ions, which travel towards the positive collecting electrode and settle over it.

Collected particulate matter must be removed from the collecting plates on a regular schedule to

ensure regular collection operation. For removal of this collected dust this rapping mechanism is

provided, which includes a motor driven hammer, which strikes the plates at a given time interval

with an adequate force to remove the dust from the collecting plates. This dust is collected in a

hopper and periodically removed.

TRANSFORMER

The transformer is a constant power device that transfers electrical energy from one circuit to

another through a magnetic field & without a change in frequency. The electric circuit that

receives the energy from supply mains is known as primary winding & the other is known as

secondary winding. The transformer is an electromagnetic energy transfer device.

The generator transformer is used to increase the output of generator from 10.5KV to 132KV for

transmission purpose. It is an important unit because its failure causes its unit to trip.

The unit auxiliary transformer gives the supply to various auxiliaries of the boiler, turbine &

generator etc. the auxiliaries’ motor rating ranges from fractional to several KW. The total power

required is about 6-8% of station output. The transformation ratio is 10.5:6.6 (in KV).

Station service transformer gives the supply to start the plant. In case of a shutdown or blackout

condition, the plant takes power from NTPC or rihand (grid) for start-up.

Various parts of a transformer are as follows:

Main Tank: it consists of core and winding

Radiator: it is responsible for cooling of the oil. As transformer is a closed unit, the oil is

rotated in the tank by pumps and comes through pipes into the radiator &is cooled by fans.

Conservator: the conservator tank is used to provide the space for the expansion of the oil

(due to any fault). It provides sit space and oil is changed to gas.

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Breather: it is attached to the conservator tank and helps the air to come in and go out.

The air passes through silica gel. The colour of the gel should be blue when no moisture is

there & it changes to pink when sufficient moisture has been absorbed and has to be

replaced.

Bushing: there is a terminal bushing where there is a tapping of the output of generator.

This is high terminal bushing.

Pumps: they are used to pump the oil from the main tank to the radiator for cooling.

Fans: fans are provided to cool the radiator tank. These fans are provided below the tank

and cool it using the air from the atmosphere.

D.M. PLANT AND CHEMICAL LAB

The Demineralising Plant is used to remove the minerals present in the water to protect the tubes

and equipments used in power generation units. D.M.plant consists of:

1. Pretreatment Section: the pretreatment section consists of the following:

Lime dosing: to adjust the pH and remove the hardness of water.

Poly aluminium chloride dosing: to maintain pH.

Clarification: lime, PAC, sodium aluminate are dosed into raw water in flash mixer tank

and then led to the clariflocculator, which receives chemically, treated water for

mechanical flocculation and settlement.

2. Demineralising unit:

Cation unit: it exchanges cat ions like Ca2+, Mg2+, and Na+ due to reaction with HCL and

pH of water after this unit is 2.5-3.2.

Degasser: the decationised water enters the degasser tower where free CO2 is scrubbed

from water by means of a current counter flow of low-pressure air.

Anion unit: here anions like Cl-, SO4-, CO3-, are exchanged due to reaction with NAOH.

Mixed bed unit: the anion treated water enters the mixed bed unit containing a mixture of

anion and cation resins, which are in a mixed state. The anion treated water is further

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treated in this unit. Then the demineralised water is treated in the storage tank and supplied

for use in steam generation.

COAL HANDLING PLANT (CHP)

In Renusagar whatever coal comes, it comes through dumpers, conveyer belts, arial ropeways.

The coal is stored in Renusagar coal yard shed. The coal is crushed in crusher and then

transported to coal feeders through conveyer belts to the coal mill. The size of crushed coal is

25mm. The size of coal after crushing from coal mill is 74microns.

Analysis of Coal:

The coal supplied to the power plant has to be checked by taking samples from it samples from it

from the supply because it is the most important raw material in a power plant and its quality

affects the overall efficiency of the plant. The samples of coal collected in the laboratory are

tested in the laboratory for:

Moisture content

Ash content

Volatile matter content

Calorific value

Grind ability

Fineness

Combustible in bottom ash and fly ash

Analysis of reject of CHP

These tests help in determining the proper ignition temperature of coal, which is very important

aspect to be considered during operation of the boiler.

ASH HANDLING SYSTEM

The ash handling system removes the ash from the boiler and ESP to a remote disposal area. It

can be divided into three main systems:

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1. Bottom Ash Handling System: - bottom ash handling systems of all boilers are identical

with only slight difference in bottom hopper construction. Ash from 1 & 2 goes directly to

the disposal area while from 3-6 goes to nearby ash slurry pump.

Bottom hopper of each boiler is filled with water and receives furnace ash from the boiler.

When ash and clinker fall in water it chills, cracks and is stored in the hopper for periodic

removal. The mixture of ash and water is discharged once in 8-12 hours in a vertical feed

gate to the clinker grinder, which reduces size of clinkers below 25 mm. crushed clinkers

and ash water mixture falls into ejector feed pump and is fed to hydro ejector, which

provide the jetting action by means of pressurized water to carry the mixture through

discharge line to the desired location.

2. Fly Ash Handling System: - principally fly ash handling systems of all boilers is identical

except boiler no. 1 & 2. Vacuum is created in the ash lines near the fly ash hopper bottoms

with the help of hydro vector, which creates a circulating motion of water coming out of a

nozzle which creates a vacuum and the ash is taken out sequentially from the hoppers. Fly

ash can be carried in two ways:

Dry method

Wet method

In the dry method, this dry ash is send to the silo tank with the help of jet pump and

from there air is extracted and ash is collected in the tank. When it is to be transported,

the bottom hopper of the tank is open and is either transported to the main silo by the K

pump or directly filled into the trucks.

In the wet method the flow of air conveys the ash from the hopper to the wetting

head, where air and fly ash are mixed with water to form slurry and discharged into the

collector tank.

3. Ash Disposal System: - the slurry formed by the mixture of water and fly ash/ bottom ash

pumped from ash slurry pump to the disposal area by means of hydro seal pumps through

12/14” CI pipes. For disposal a Long Distance Ash Disposal (LDAD) system has been set

up. The slurry sump is a mild steel tank. Two sets of flushing nozzles agitate the deposited

material in the sump, which is taken out and using four slurry pups in series, the required

head is transported is generated and ash is transported to the disposal area

Interconnecting the ash flow walls between both the disposal lines gives operational flexibility

by permitting the use of any discharge lines with either of the pumps.

Make up water to the slurry sump is supplied by:

Two Bilge pumps, which lift water from the sump.

Raw water line

Ash water line

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