report of thermal power plant

8/11/2019 Report of Thermal Power Plant

http://slidepdf.com/reader/full/report-of-thermal-power-plant 1/92

THERMAL POWER PLANT

A PROJECT REPORT

Submitted by

PRAMOD KUMAR

in partial fulfillment for the award of the degree

B.Tech

IN

MECHANICAL BRANCH

RIMT Institute of Engineering and Technoog!

Mandi "o#indgarh

P$NJAB TECHNICAL $NI%ER&IT'( JALAN)HAR *+,,-+

JAN* MA' /0+1

1



AC2NOWLE)"EMENT

I am extremely thankful for having been able to receive in-plant training and

submit this report at the )ahanu Ther3a Po4er &tation /)TP&1( a unanimous

part of the Reliance Energy Ltd. (REL)

I express my deep sense of gratitude to Mr. Prasad Rao( station head of !"#

Mr. R.Nandi( $ead (% & ') and Mrs.%an4ai chanda( $R(corporateoffice'umbai) for giving me this opportunity in this plant . I am also thankful to

Mr. A.).Pati ' 'echanical ept. & Mr. C.B.Ne3ade( $% of 'echanical

'aintenance ept. for his co- operation.

I also thank Mr. %i5a! "andhe4ar( #r. 'anager (!rg.) and Mr."irish.P.Bidi6ar

#r. 'anager ('ech. 'aintenance ept.) for their perennial help and ideas to make

the report better and uni*ue.

Last but not the least I +ish to thank the highly dedicated and motivated team at

!"# for making me a part of their team and making the training an exclusive

experience.

2



"L,! L%,!I%

,$,/ !$ER',L "%0ER #!,!I% 1ILL,E - ,0, ,$,/

R%, I#!2 !$,E- 345 647

REI#!ERE , %R"%R,!E %88IERELI,E EER9 E!RE

#,!,R/: (E,#!) '/';,I- 3444<<

3



INTRO)$CTION

In recent years India=s energy consumption has been increasing at one of the

fastest rates in the +orld due to population gro+th and economic development.

ommercial primary energy consumption in India has gro+n by about >44? in the

last four decades. !he per capita consumption in India is in the region of 344 @0$

per annum. riven by the rising population expanding economy and a *uest for

improved *uality of life energy usage in India is expected to gro+ at a exponential

rate.

espite the overall increase in energy demand per capita energy consumption in

India is still very lo+ compared to other developing countries. !oday India has one

of the highest potentials for the effective use of rene+able energy. India is the

+orld=s fifth largest producer of +ind po+er after enmark ermany #pain and

the /#,. !here is a significant potential in India for generation of po+er from

rene+able energy sources- small hydro biomass and solar energy. !he country

has an estimated #$" (small-hydro po+er) potential of about 5<444 '0.

4



ENER"' &CENARIO IN IN)IA

Energy is the prime mover of economic gro+th and is vital to the sustenance

of a modern economy. 8uture economic gro+th crucially depends on the long-term

availability of energy from sources that are affordable accessible and

environmentally friendly.

India ranks sixth in the +orld in total energy consumption and needs to

accelerate the development of the sector to meet its gro+th aspirations. !he

country though rich in coal and oal meets approximately 6A percent of the

country=s total energy re*uirements. ,ccording to current estimates the reserves

are sufficient to meet India=s needs for at least another 544 years. India no+ ranks

Ard amongst the coal producing countries in the +orld

If +e look at the pattern of energy production coal and oil account for <3 percent and A3 percent respectively +ith natural gas hydro and nuclear

contributing to the balance. In the po+er generation front nearly 67 percent of

po+er generation is from coal fired thermal po+er plants and >4 percent of the

coal produced every year in India has been used for thermal generation.

%n the consumption front the industrial sector in India is a maBor energy

user accounting for about <7 percent of commercial energy consumption. "er

capita energy consumption in India is one of the lo+est in the +orld but energy

intensity +hich is energy consumption per unit of " is one of the highest in

comparison to other developed and developing countries !hus there is a huge

scope for energy conservation in the country.

5



India has huge coal reserves at least C3A6 million tonnes of proven recoverable

reserves (at the end of 744A). !his amount to almost C.6? of the +orld reserves

and it may last for about 7A4 years at the current Reserve to "roduction (RF") ratio.

In contrast the +orldGs proven coal reserves are expected to last only for 57 years

at the current RF" ratio.

Oi

%il accounts for about A6 ? of IndiaGs total energy consumption. India today is one

of the top ten oil-guDDling nations in the +orld and +ill soon overtake @orea as the

third largest consumer of oil in ,sia after hina and Hapan.

"as tur#ine 8o4er 8ants /Natura "as1

atural gas accounts for about C.? of energy consumption in the country. !he

current demand for natural gas is about 6 million cubic meters per day (mcmd) as

against availability of 6> mcmd. ;y 744> the demand is expected to be around

744 mcmd. atural gas reserves are estimated at 664 billion cubic meters.

Eectrica Energ!

!he all India installed capacity of electric po+er generating stations under utilities

+as 557<C5 '0 as on A5st 'ay 7443 consisting of 7CC64 '0- hydro >>A5

'0 - thermal and 7>74 '0- nuclear and 5C6 '0- +ind ('inistry of "o+er).

!he gross generation of po+er in the year 7447-744A stood at <A5 billion units

(k0h).

Nucear Po4er 8ant

7



uclear "o+er contributes to about 7.3 per cent of electricity generated in India.

India has ten nuclear po+er reactors at five nuclear po+er stations producing

electricity. 'ore nuclear reactors have also been approved for construction.

H!dro Po4er 8ant

India is endo+ed +ith a vast and viable hydro potential for po+er generation of

+hich only 5<? has been harnessed so far. !he share of hydropo+er in the

countryGs total generated units has steadily decreased and it presently stands at 7<?

as on A5st 'ay 7443. It is assessed that exploitable potential at 64? load factor is

C3444 '0.

&ource units +::,*:; 0+*0 0-*< 0++*0+0

Eectricit! #iion

units 7C.A6 3C4.4C >57.6> 546>.CC

Coa 3iion tonnes >6.6> 54.45 5A3. 5>A.3>

Lignite 3iion tones

3.C<

55.6 56.47 5.>4

Natura gas 3iion

cu#ic 3eters CC4 5<>A4 5C75 74C<A

Oi 8roducts 3iion

tonnes 6A.<<

.C 5A.< 56.3>

The actua fina energ! consu38tion /8ast and 8ro5ected1 is gi=en in Ta#e*0

8



;,#I 0%R@I %8 !$ER'EL "%0ER "L,!

, modern pulveriDed coal-fired electricity generation facility that uses the most

commonly employed Rankine-based thermodynamic cycle .#team at the desired

pressure temperature and mass flo+ is produced in a steam generator and

expanded through a turbine generator. !he exhausted stem is no+ condensed in a

condenser and the condensed li*uid is used again in the steam generator.

oal is delivered to the facility by rail+ay +agons barges or trucks using sea link.

!he coal handling system unloads the coal stocks reclaims crushes and conveys it

to storage silos. oal from the silos is then pulveriDed to a fine po+der and then

blo+n into the steam generator +here it is mixed +ith air and combusted to release

energy for the generation of steam .!he steam generators produces superheats and

reheats steam as it proceeds through the cycle.

!he steam turbine generator converts the thermal energy of the superheated and

reheated steam to electrical energy. #team exhausted from the turbine is condensed

to li*uid in the condenser. !he condensate pump feed the +ater through the I.p

regenerative feed +ater heaters to a deaerator .boiler feed pumps move thedeaerated li*uid through the h.p feed +ater heaters back to the steam generator

8orced draught fan (8. fan) supply combustion air to the steam generator and the

primary air fan ("., 8an) transport pulveriDed coal into the burners. Induced

9



draught fans remove the flue gases from the furnace and exhaust them through the

stack into the atmosphere.

ooling +ater from the condenser is supplied by the circulating +ater system

+hich takes the heat removed from the condenser and reBects it to cooling to+ers

or another heat sink such as cooling lake river or sea.

ombustion gases coming out of the steam generator re*uire additional treatment

for removal of fly ash particulates sulphur dioxide and nitrogen oxides before the

gases are released through the exhaust stack

10



ABO$T

)AHAN$ THERMAL POWER PLANT

/RELIANCE ENER"' LT).1

11



CONTENT&

+. OR"ANI&ATION PRO7ILE +,

+.+ Introduction +,

+.0 A#out )ahanu Ther3a Po4er &tation +;

+.> Po4er "eneration Process +:

0. MECHANICAL MAINTENANCE )EPARTMENT 0;

0.+ Boier Maintenance 0;

0.0 Boier Pressure Parts Maintenance 0;

0.> Boier Rotar! Parts Maintenance ><

0., Tur#ine Maintenance ,;

>. O77&ITE A$?ILIAR' $NIT& -,

>.+ Ash handing 8u38 house -,

>.0 Coa handing area -<

>.> C.W 8u38 house <:>., Water 8retreat3ent 8ant @+

>.; )e3ineraisation 8ant @,

12



+. OR"ANI&ATION PRO7ILE

+.+ INTRO)$CTION9

!he ;#E# (;ombay #uburban Electricity #upply) is incorporated in 57.

!he company got license to distribute electricity in areas of 'umbai. It generates

and supply electricity to 'umbai city and its suburbs. 8rom the modest license

supplying po+er to suburbs of 'umbai ;#E# today is a multi occasional and

multi dimensional enterprise.

In the process the company has emerged as the country leading integrated

po+er company +ith activities spanning the entire po+er process right from

concept to the consumption of the electric energy.

;#E# +ith its corporate lineage going back to 57 is India=s premier /tility

engaged in the generation transmission and distribution of electricity in and

around 'umbai. It provides portfolio of value added services in electrical

13



REL and its affiliate po+er companies rank among the top 7< listed private

sector companies on maBor financial parameters. REL is part of the Reliance

industries-IndiaGs private sector company ranked among the +orldGs 5>< largest

companies in terms of net profit and the <44 largest companies in terms of sales.

REL is committed to creating superior value for all its stakeholders and be

amongst the most admired and trusted utility companies in the +orld by setting

ne+ benchmarks in standards of corporate governance operational and financial

excellence responsible corporate citiDenship and profitable gro+th.

+.0 ABO$T )AHAN$ THERMAL POWER &TATION9

eneration division is located at ahanu ist. !hane in orth-0est of

'aharashtra nearly about 574 @m from 'umbai. It is called as ahanu !hermal

"o+er #tation (!"#). !he second unit +as test synchroniDed in a record time of

less than three months. !his <44 '0 "o+er #tation +as declared commercial in

Hune #ince then it has crossed several milestones and achieved a number of

laurels as best operating po+er station and for its environment friendly operation.

!he manpo+er of the company incorporates the services of 74> executive and A43

non executives (i.e. +orkers). It also employee=s 644->44 contract labours. It

makes use of combustion process for the generation of heat.

15



Reliance Energy .!.".#. is coal based !hermal po+er station +hich takes

coal sea +ater oil as inputs for producing electricity as one of the maBor output

including ash flue gases other outputs.

BA&IC PRINCIPLE O7 PLANT9

ahanu !hermal "o+er #tation is totally based on modified Rankine=s

cycle.'odified Rankine=s cycle is a vapour cycle having t+o basic characteristics2

!he +orking fluid is condensable vapour +hich is in li*uid phase during part

of the cycle.

!he cycle consist of succession of steady flo+ process +ith each process

carried out in a separate components +hich is specially design for the

purpose. Each consists an open system and all the components are

connected in series so that the cycle is close.

&ALIENT 7EAT$RE& O7 )TP&9

5. I#% 447 uality management

7. I#% 53445 Environmental 'anagement

A. In 5C certified by ;1I.

16



The Technica &8ecifications a#out the 8ant are as foo4s9

18



+.>. POWER "ENERATION PROCE&& $&E) AT )TP&9

19

!ype of #tation 9 !hermal

#tation apacity 9 <44 '0 ( 7 x 7<4 '0)

8uel 9 544 ? oal

oal #ource 9

Indian oal- 8 rade

,ustralian oal J , rade

!ransportation 9 ;y Rail & #hip

onsumption 9 7.<6 'illion tones F year ,ssuming C444hrs

ooling 0ater #ource 9 8rom ,rabian #ea

onsumptive Re*uirement 9 >6444 mA F hr.

,sh isposal 9 0et ,sh disposal system

himney 9

R multi flue (7 flue) chimney +ith flue

height 7><.A m

'ake up 0ater 9 KA ?

Land Re*uirement 9 In $ectors

"lant ,rea 9 A<5.<C $ectors

,sh isposal ,rea 9 A>4 $ectors

olony ,rea 9 544 $ectors



ahanu !hermal "o+er #tation is coal based po+er station having t+o sets

of 7<4 '0 each. !he chemical energy in the coal is released as heat on

combustion in the furnace of the boiler. !he heat is utiliDed to convert feed +ater to

steam and further superheat the steam. !his steam flo+n over the turbine +here the

steam is used to produce shaft +ork. !his steam is utiliDed as medium to carry the

heat energy +hich is converted to mechanical energy (shaft +ork) in the turbine.

!he turbine shaft is in turn coupled rigidly to the generator shaft +hich bears the

excitation +inding. !he excitation system is of brushless type +ith pilot exciter

and the main exciter mounted on the generator shaft itself. !he rotating magnetic

field induces E'8 in the stator +inding of the generator. !hus chemical energy

from coal is received as electrical energy at the terminals of the generator .

20



RE"ENERATI%E 7EE) HEATIN" C'CLE9*

In regenerative feed +ater heating cycle part of the steam is extracted after partial

expansion in the turbine and is used to heat up the feed +ater before going to the

boiler. In the process superheat and latent heat of extracted steam is transferred to

feed +ater to raise its temperature i.e. sensible heat addition in the feed +ater is

carried out before reaching the boiler. !he drop formed due to the condensation of

extracted steam is recycled in to feed +ater cycle at appropriate point.

7L$E "A& C'CLE9

!he boiler has furnace and heating parts. "ulveriDed coal is fired in the

furnace along +ith air re*uired for combustion. !o ignite the fire first light diesel

oil (L%) is fired in atomiDed form. , spark from Igniter 8lame 'onitoring (I8')

system ignites this oil. %nce the flame is stabiliDed on L% pulveriDed coal (>4-C4

micron siDe) is fired. !he arrangement of oil and coal burners is of tilting tangential

type (!!8). !his results in a vortex of flame revolving at a very speed. !his results

in a turbulent fire ball +hich ensures complete combustion. ;alanced draft of -< to

-54 mm of +ater column is maintained inside the boiler. !his ensures smooth flo+

of flue gas and proper dissipation of heat to the heating surfaces.

!he flue gas is finally passed over regenerative devices viD. economiDer

and ,ir preheater (,"$) to Electrostatic precipitator. $ere the ash from the flue

21



gas is collected and the flue gas consisting of #%7 is desulphuriDed in the 8 unit

and is then set out to atmosphere through chimney.

!he pulveriDed coal is carried to the boiler by hot "rimary ,ir. !his air is

made available by "rimary ,ir 8an. "art of cold primary air is passed through air

preheater +here it gets heated. It is then mixed +ith the cold primary air. $ot

primary air at desired temperature is then passed to coal mill from +here it carries

the coal. 8orced raft fan gives the (#,) +hich is actually the excess air re*uired

for combustion. !his air is also heated in ,"$ before passing to furnace. !hus

L% is fired initially. "ulveriDed coal "rimary ,ir and #econdary air form the

input to the furnace.

&TEAM C'CLE9

!he +alls of the first pass of boiler are made up of numerous tubes carrying

feed +ater (emineralised +ater). !herefore these +alls are called as +ater +alls.

!he furnace is located in the first pass itself +ith burner and air inBection assembly

being at the four corners formed by the +ater +alls. !hese +ater +alls originate

from a ;ottom Ring $eader (;R$) +hich is supplied +ith feed +ater from boiler

drum through do+n comers. !he boiler drum consists of a steam compartment and

+ater compartment. It has t+o turbo separators +ith AA separators in each ro+.

!urbo separators separate steam from steam +ater mixture.

22



!he heat evolved from combustion is transmitted to heating surfaces by

radiation and convection. !he +ater in the +ater +alls is heated and converted to

steam. ue to density difference the steam rises in the +ater +alls +hich are

terminated into top headers. !hese top headers are connected to the turbo

separators in the boiler drum. $ere +ater is separated by centrifugal action and it

falls back into drum and mixes +ith drum +ater. ry steam (C4?) rises up through

compartment. 8rom here the steam is passed through various superheating coils

located in the second pass and horiDontal pass in the boiler. !he steam from final

super heater header is passed to $igh "ressure !urbine through main steam pipe.

T$RBINE9

!he steam turbine at !"# is a A cylinder tandem compound @0/ make

(@raft 0orks /nion i.e. erman esign) 7<4 '0 steam turbine. It consists of

$igh "ressure turbine ($"!) Intermediate "ressure turbine (I"!) and Lo+

"ressure turbine (L"!). !he shafts of these turbines are axially coupled to each

other +ith rigid couplings. !he L"! shaft is coupled rigidly to the generator shaft

on the other end.

!he main steam from left and right side of the final super heater is

admitted at 53<-5<4 kgFcm7 pressure and <344 temperature to the $"!. ,t the exit

of $"! the steam has reduced parameters of around 34 kgFcm7 & A344. !he steam

is sent back to reheater in the boiler for reheating through old Reheat line (R$).

23



Reheating facilitates expansion of steam at reduced pressure due to comparative

higher temperatures. %ther+ise moisture formation may result at the ultimate

stages of L"!. !he reheated steam from left and right sides of the reheater header

is passed to the I"!.

#imilar to $"! I"! is also a single pass turbine. ;ut here the steam

expands in opposite direction as that in $"! thereby balancing the resultant thrust.

,t the exhaust of I"! the steam has reduced parameters of around >.<-C.4 kgFcm 7

pressure and A<4-A>44 temperature. !his steam is admitted to L"! +hich is a

double pass turbine. !he steam expands in either direction. !he exhaust of L"! is

connected to the condenser +hich is under vacuum pressure of 4.C kgFcm7.

24

LPT

B/DRUM ECO LTSH

PSH

FSH

FURNACE

IPT HPT

CONDEN. HOT WELL DEA BFP

2470c 2920c

5400c 3440

c

5400c

5030c

3930c

3510c

155 Kg/cm2

164 Kg/cm2

168 Kg/cm2173 Kg/cm2

40

Kg/cm2

37

Kg/cm2

C R

H H R

H

Sensible heat addition atent heat

FEED HEATERS



#team is passed over tubes +hich are coated +ith titanium from inside. #team

through these tubes carries the heat along +ith it. %nly latent heat from the steam

is removed so that it is converted to condensate. !his condensate is collected in a

hot +ell. ondensate Extraction "ump (E") is used to evacuate the condensate

from the hot +ell and to supply it to the regenerative circuit. !he regenerative

circuit consists of a land #team ooler rain cooler (3<42 77 kgFcm7) Lo+

pressure heaters (L"$) eaerator ;oiler 8eed "ump (;8"2 56442 54-5<

kgFcm7) $igh "ressure $eaters ($"$) and EconomiDer. ,s seen after the drain

cooler the condensate can be passed through the condensate polishing unit to

maintain its *uality ("$). !he gland steam cooler receives heat from the turbine

gland seal steam coming to condenser +hereas turbine drains are connected to the

drain cooler.

!he L"$5 is placed directly inside the condenser +hereas L"$

7 and L"$

A

receive heat from extractions from L"!. !he hot condensates pass to deaerator

+here dissolved gases are removed. 8eed +ater thus available is stored in 8eed

+ater storage tank. !his tank is connected to the suction of the booster pump. !he

discharge of the booster pump is connected to the suction of the main feed +ater

pump (80"). !he booster pump and main feed +ater pump form the boiler feeder

pump. ;oth the pumps are run by a single motor. ;ooster pump is directly

connected +hereas main 80" is coupled via hydraulic coupling. $ydraulic

25



coupling facilities stepless control for feed flo+. !he ;oiler 8eeder "ump

discharge is connected to $"$6 through $"$

<. !hese heaters receive heat from

extractions from I"!. !he discharge of $"6 is connected to the economiDer via

8eed Regulating 1alves station.

!he economiDer outlet is connected to the +ater compartment of boiler

drum. !hus the feed and condensate cycle is completed as a close loop. !he drips

of all the regenerative heaters are connected back to the condenser to avoid loss of

emineralised +ater.

"ENERATION O7 POWER9

In pilot exciter permanent magnet on the rotating shaft induces emf in its

stator +indings. !he output is passed through a complex thyristor based

circuit. !he controlled .. supply is fed to the main exciter stator +inding.

Emf induced in the rotor +inding of the main exciter is rectified and

connected to the rotor +inding. !he level being 7AC6 ,mperes at A5 1 ..

Emf is induced in the stator +inding of the generator at 56.<@1 and 5474

,mperes at 4.C< p.f. lagging.

, part of the po+er generated is evacuated by a step do+n /nit ,uxiliary

!ransformer (/,!) 56.< @1F6.6 @1 to meet the auxiliary po+er

re*uirement.

26



!he generator bus duct is further connected to the enerator !ransformer

(!) +hich steps the voltage up to 7741 at around 5444 ,mperes. !he

output of the enerator !ransformer is connected to the s+itchyard +hich

feed the consumers through a net+ork of substation connected by

transmission lines.

,dditionally a #tation !ransformer (#!) connected to grid is provided +hich

is used at the initial start-up of the plant +hen both the units are not in

service.

0. MECHANICAL MAINTENANCE )EPARTMENT

7.5. ;oiler maintenance

7.5.5. ;oiler "ressure "art 'aintenance

7.5.7. ;oiler Rotary "art maintenance

7.7. !urbine 'aintenance

0.+.+ BOILER PRE&&$RE PART& MAINTENANCE

• ;oiler

• EconomiDer

• ;oiler rum

• o+n comers

• /p risers

27



• 0ater +alls

• #team cooled +alls

• #uper heaters

• Reheater

• esuperheater

• #afety valve

•#oot blo+ers

• Expansion and sealing

• ;uckstays

• 0ind box ,ssembly

BOILER9

!he boiler in !"# is a natural circulation single drum radiant heat

negative draft type +ith tilting tangential burner type. 8iring e*uipment

consists of remotely controllable $E, igniters air cooled oil guns and coal

noDDles.

!he elevations of coal noDDles are supplied +ith pulveriDed coal from tube

mills.

28



!he various auxiliaries include t+o air preheaters three tube mills t+o

primary ,ir fans t+o forced raft fans t+o Induced raft fans six #eal ,ir

8ans and a four pass Electrostatic "recipitator.

!he drum internals act as an interface bet+een the boiler and the drum.

!he function of drum is to separate +ater and steam from the mixture

generated in the furnace +alls.

T!8es of #oiers9

epends upon pressure boilers are classified as2

Industrial ;oiler- Less "ressure (64kgFcm7) and less temp.( A<44).

/tility ;oiler- $igh "ressure and $igh !emperature and generally used in

po+er generation.

#ingle rum (#ub-critical boiler) 8; and $R# boiler.

#uper-critical boiler. (8orced circulation).

Boier s8ecifications9

'anufacturer 2 ;$EL .E. esign

!ype 2 atural irculation ;alance

29



raft ouble "ass #ingle

rum #ingle Reheat

irect pulveriDed coal 8ire

0ater Impounded bottom.

;oiler esign "ressure & 2 5C7 kgF cmM

!emperature 2 <34N

;oiler esignation 2 <734 O 55<46 5 O 537.

!ype of 8iring 2 !ilting !angential.

!otal $eating surface 2 736>4 mP.

8urnace $eight 2 A.6< m

30



Econo3ier9

!he purpose of economiDer is to preheat the boiler feed +ater before it is

introduced into the steam drum and to recover some of the heat from the flue

gases leaving the boiler. !he economiDer is located in the boiler rear gas pass

belo+ the rear horiDontal superheater. !he flue gas temperature is around 3<5o in

the economiDer the heat is recovered from the flue gas to heat the feed +ater.

Boier )ru39

!he functions of the drum are2

#eparation of saturated steam from the steam +ater mixture produced by

evaporating tubes.

'ixing feed +ater from economiDer and +ater circulated from steam +ater

mixture and re circulate through the evaporating tube.

31



arrying out blo+ do+n for reduction of boiler +ater salt concentration.

!he feed +ater is supplied to boiler drum from the economiDer through t+o

economiDer outlet links. !his separated feed +ater +hich is at about 5>4 kgFcm7

pressure and +ater from the economiDer goes to furnace bottom +ater +all headers

(or ring headers) through six do+n comers. !he resulting mixture of +ater and steam

is collected in the +ater +all headers and discharged into steam drum through a

series of riser tubes. $ere the separation of +ater and steam takes place leading the

main steam to turbine via various stages of super heaters.

)o4n co3ers

!he do+n comer pipes are connected to the bottom of the drum.

!he +ater from the drum is circulated to the evaporating tubes through the

do+n comers +hich are kept external to the heating Done of the boiler.

!he number of the do+n comers varies +ith the siDe design type etc of the

boiler.

$8 Risers

!he +ater steam mixture formed inside the evaporating tube is collected in

the top headers.

8rom the top headers the +ater steam mixture is brought to the boiler drum

through up risers.

/prisers are connected to one side of the boiler drum opposite to the side

+here feed lines are connected.

32



&8ecifications9

!otal no of tubes 3C7

% 6A.< mm!hickness <.< mm

"itch >6.< mm

esign pressure 5C<.< bar

&tea3 cooed 4as

#econd pass is made up of steam cooled +alls

0ater passes through steam cooled +alls before entering into the L!#$

#team cooled +alls minimiDes the heat loss.

&u8er heaters

#uper heaters are used to make the steam turbine moisture free (i.e. dry). It gives

heat.

'etal used for super heaters must have high temp. strength high creep

strength high resistance to oxidation.

,lloy steel having chromium & molybdenum is used.

$eat transfer of flue gases are by either by convection or by radiation.

#team from the drum passes through the follo+ing three types of super heaters2

Lo4 Te38erature &u8er heater /LT&H1

It is situated above the economiDer coil in the second pass.

34



,ccurate steam temperature can be obtained by tilting burners in the furnace

as in this by tilting the burners do+n+ards in a furnace much of the heat is

given to the +ater +alls by gas and the gas entering the superheater region is

relatively cool.

If the burners are turned up+ards then the heat given to boiler +ater +all is

less and hotter gas enters the superheater region to increase steam

temperature.

Reheater

!he reheater is composed of t+o stages front & rear section.

!he front section is located bet+een the rear +ater +all hanger tubes &

#$ platen coils. !he rear section is located bet+een +ater-cooled screen

tubes & rear +ater +all hanger tubes.

8unction of reheater is to reheat the steam after its expansion in $"

turbine.

'aterial used are high alloy carbon steels such as #, 75A !55!5!77.

!his material is having properties of resistance to erosion high temp

creep resistance.

)esu8erheater9

esuperheaters are provided in #uper heater connecting link and R$

line (outside boiler).

It is the provided to control the temp. of steam in the circuit itself.

!emperature control is achieved by inBecting spray +ater into the path of

steam through a noDDle.

36



!he location of the de-super heater helps to ensure against +ater

carryover to the turbine.

&afet! =a=es

'ain function is to release excess pressure developed in the system.

!he opening set pressure of super heater safety valves is maintained lo+er

than the drum safety valve opening set pressure. !his ensures the ade*uate

steam flo+.

,void starvation of super heater tubes.

!o relieve the excessive pressure over & above the permissible +orking

pressure in boiler drum.

A os. of spring loaded safety valves are fitted on the top of the drum.

!he valve must open +ithout fail +hen pressure reaches predetermined

value to release excess steam *uickly & maintained normal pressure.

umber of safety valve depends upon the pressure of drum & capacity of

units.

ormally the safety valves are set to open +hen the drum pressure exceeds

54? of operating pressure.

&oot #o4ers

37



It is necessary to remove the deposit +hich is settled on the tubes.

!his reduces the heat transfer rates of the tubes.

#oot blo+ers are used to clean these deposits so that ade*uate heat transfer

rate is maintained.

!ypes2 a) 0all blo+ers. b) LR#;.

'edium used- steam lo+ pressure air sound to remove these soots.

E8ansion and seaing

!he provision of free expansion for all the parts of the boiler is important but

in the case of furnace +ater +all tube it is vital.

#ince the boiler is suspended from the boiler house steel +ork expansion is

+holly in do+n+ard direction.

%n the typical 754 '0 and <44 '0 boilers the total expansion from cold to

full load can be greater as 774mm and A34mm respectively. Restriction to free expansion of +ater +all tubes +ill induce stress in the tubes

and their ultimate failure.

!heses seal normally consists of +ater filled trough attached to ash hopper

+hich itself is rigidly mount on the boiler house basement floor.

Buc6sta!s

;uckstays keep the +alls from bo+ing in+ard or out+ard.

It gives external support.

!o provide rigidity to the +ater +all system.

38



"resent on all four sides at different elevations and on the non firing side of

the +ater +all panels.

Wind #o

!he tangential fire system is based on the single flame envelope. ;oth fuel

and combustion air are proBected from the corners of the furnace along a line

tangent to a small circle lying in a horiDontal plane at the centre of the furnace.

Intensive mixing occurs +here these steams meet.

, rotative motion similar to that of the cyclone is imparted to the flame body

+hich spreads out and fills the furnace area.

8or this system +ind box is provided at each corner of furnace.

!he +ind box is vertically divided into number of compartments each

compartment receives hot secondary air from secondary air damper and also

+ith coal noDDles through +hich pulveriDed coal from the mill is delivered to

the furnace.

0.+.0 BOILER ROTAR' PART&

5. oal mill

7. raught system

(a) "rimary ,ir 8an

(b)8orced raught 8an

(c) Induced raught 8an

39



A. Electrostatic "recipitator (E#")

3. ,ir "re $eater

+. Coa 3i

Constructiona )etais Wor6ing

!his mill is also called tube mill or drum mill having capacity of C4-544

tonFhr.

It consists of a large heavy role plate shell having disc end or head

+ith trunions.

!he shells and heads are lined inside +ith high chromium liners.

!hese liners are sufficiently hard to last for 57 years. !here are

various types of liners.

(a) ylindrical liners 2 34Q54 344

(b) %bli*ue liners 2 34Q7 C4

(c) Long conical liners 2 74Q7 34

(d) #hort conical liners 2 74Q7 34

40



!he shell is resting on t+o bearings one at each end by means of trunions. ,t

one end of the shell a gear +heel is embedded on the shell. !his gear +heel

is meshing +ith pinion rotated by a motor through a gear box.

0ith such an arrangement the entire shell can be rotated at a speed of

5>-5 rpm.

41



!he connecting rods present on the scre+ conveyer give the rotational

movement to the conveyer.

rease or drip oil forms a lubricating oil system lubricates the

meshing point of gear +heel and pinion.

!he inside of the shell is filled +ith little less than half +ith steel

ball(high chromium) varying from 7<-<4 mm in diameter.

oal is fed into ra+ coal feeder from bunker.

In the inlet pipe the coal and hot air (primary air) are mixed in mixing

box. !he function of the primary air is to remove moisture from the

coal.

0hen the drum is rotating the ra+ coal from the feeder falls on the

scre+ conveyer if the trunion. !he scre+ conveyer pushes the coal

inside the mill by its rotational movement +ith the help of ribbons

attached to it and the coal intermingles +ith the grinding media in the

mill.

"ulveriDation of coal is accomplished through continuous cascading of

mixture resulting from2

(a) Impact of falling balls on the coal

(b),ttrition as particles slides over each other as +ell as over the

liners.

42



raught is defined as the force re*uired to dra+. In a boiler this term is

commonly used to designate a static pressure in a furnace gas passage flue or

stack. raught pressures are referred to atmospheric pressure at the same

elevation and the plus or minus sign is used to designate +hether the value is

above or belo+ the atmospheric pressure.

)raught t!8es9

(a) atural draught

(b)'echanical draught

/a1Natura draught9

0hen the re*uired flo+ of air and flue gas through a boiler can be

obtained by stack alone the system is kno+n as natural draught

system.

0hen the gas +ithin the stack is hot its specific +eight +ill be less

than that of the cool air outside the stack. !herefore the unit pressure

at the base of stack resulting from the +eight of the column of hot gas

+ithin the stack +ill be less than that of the column of external cool

44



!he air suck by the ", fan is passed through ,"$ +here its get heated. It

then mixed +ith the coal primary air.

!he hot primary air at desired is then passed to coal mill from +here it caries

the pulveriDed coal to the furnace.

/#17orced )raught 7an /7) 7an19

!he function of 8 fan is to supply excess air re*uired for complete

combustion ;oiler is provided +ith t+o 8 fans.

!he axial reaction fans are those in +hich the air or medium enters the

impeller radially and leaves axially. !hese fans are driven at constant speed.

8 fan is installed near the base of the boiler and the atmospheric air is

forced to pass through the furnace economiDer ,"$ and to the stack.

(c) Induced )raught 7an /I) 7an19

!he function of I fan (Radial) is to suck the gases out of furnaces and

thro+ them into the stack. !he boiler is provided +ith t+o I fans.

!his results in a furnace pressure lo+er than atmosphere and affects the flo+

of air from outside to the furnace.

46



!his is an #ingle #tage ouble #uction Radial 8an and is used for

extracting flue gases from the furnace.

In this type of 8an a large part of energy transferred to the medium is

converted in to pressure energy as the medium passes through the impeller.

>. Eectrostatic Preci8itator /E&P19

Wor6ing Princi8e9

!he principle upon +hich an electrostatic precipitator operates are that the

dust laden gases pass into a chamber +here the individual particles of dust are

given an electric charge by absorption of free ions from a high voltage .

ioniDing field.

!he E#" utiliDes electrostatic forces to separate ash particles from the flue

gas to be cleaned. , very high efficiency (.3?) Electrostatic "recipitator is used

to collect fly ash generated. !he fly ash emission +ill be +ithin limits even +ith

one out of the six fields out of services.

E#" utiliDes the force acting on electrically charged particles in the presence

of in an electric field to effect the separations of the solid or li*uid particles from

the gas steam. 1arious configuration of E#" are corona effect particle charging

47



particle collection and particle removal and the process generated inside E#" is

Scorona dischargeD

CRO&& &ECTIONAL %IEW O7 E&P

48



,.AIR PREHEATER9

,ir "reheater is an important boiler auxiliary +hich primarily pre heats the

combustion air for rapid and efficient combustion in the furnace.

,ir "reheater recovers the +aste heat from the outgoing flue gas of the

boiler and transfer the same to combustion area.

8urther the air preheater may also be used for heating the air to dry the coal

in pulveriDing plant.

0.0 T$RBINE

Introduction9

#team turbine is the heart of the "o+er "lant +hich is a rotating machine

+hich converts heat energy of steam to mechanical energy.

#team turbines are of different capacities from 5< '0 to <44 '0. !he design

material and auxiliaries depend on the capacity of the system (!urbine)

#team turbines of t+o type designs such as

LMW * &o=iet Russian 3ade /Leningrad Meta 4or6s1

2W$ * "er3an 3ade /2raft Wor6s $nion1

49



In ;#E# eneration ivision (.!.".#.) @0/ design made of 7<4 '0 turbines is

used.

Wor6ing Princi8es9*

!he blades are attached to the turbine rotor. !he rapidly moving particles of

steam issuing from the noDDle enter the blade. ,s the blades are curved the

direction of motion of these particles of steam is changed.

;lades are designed in such a +ay that steam is made to glide upon and do

not get bombarded on the blade. ,s steam moves over the blades direction

is continuously changing and centrifugal pressure is exerted on the blade.

!he total motive force acting on the blades is the resultant of all the

centrifugal forces plus the change of momentum. !his causes the

rotational motion of blades.

&tea3 Tur#ine9*

!he turbine is condensing tandem compounded horiDontal reheat type single

shaft machine. It has separate high pressure ($") intermediate pressure (I") and

lo+ pressure (L") parts. !he $" and I" parts are single flo+ cylinder and L" part is

double flo+ cylinder. ue to steam turbine rotates and its energy is given to the

50



generator +hich produces electricity. !he turbine rotors are rigidly coupled +ith

each other and +ith generator rotor.

a. High Pressure Tur#ine /HPT19*

45 impulse stage

5C Reaction #tages

%uter casing is barrel

Inner casing axially split

#ingle flo+

,fter the super heater steam comes in to $"! here the steam expands and

steam does the +ork. ,fter this the temperature and pressure of steam

decreases. !hen it goes to the reheater to increase the pressure and temperature

through the cold reheat line (R$). !he R$ is provided +ith a non return

valve to prevent the back flo+ steam.

Para3eters 9*

5. Inlet pressure 53<-5<4 kgFcm7

7. Inlet temperature <34%

51



A. %utlet pressure 34kgFcm7

3. %utlet temperature A34%

#. Inter3ediate Pressure Tur#ine /IPT1 9

#ingle flo+ type

5> reaction stages

ouble casing ;oth ,xially #plit

Inner casing is axially split and carries guide blades

#team comes from the reheater +here the pressure and temperature are

increased. $ear the steam is allo+ed to expand and heat energy is converted into

mechanical energy. 8rom here the steam is lead to the L"! from the I"! exhaust

duct.

Para3eters 9*

+. Inlet pressure AC-A kgFcm7

0. Inlet temperature <34%

>. %utlet pressure >->.< kgFcm7

,. %utlet temperature A34%

52



c. Lo4 Pressure Tur#ine /LPT19

ouble flo+ type.

C reaction stages per flo+

asings2 - three casings. ,ll are axially split.

Inner casing carries five guide blades.

'iddle casing carries other three guide blades

Last three stages of L" rotor have t+isted blades. ,bove blade design

features reduces the relative velocity bet+een the droplets and the leading edges of

the moving blades resulting into less +ear and tear. 8irst five blades +ork in

superheated region and rest three in +et region. $o+ever the leading edges of the

final stage rotor blades are flame hardened to give protection against erosion.

BLA)E& O7 T$RBINE9

+. I38use T!8e9

In impulse turbine steam is expanded (i.e. pressure is reduced) in fixed

noDDles In impulse type of turbine pressure drop occurs in noDDles only not in

moving blades.

53



0 I38uses * Reaction T!8e9

In reaction type of turbine pressure is reduced in both fixed and moving

blades. !hey act like noDDles and are of same shape .0ork is done by the impulse

effect due to the reversal of direction of the high velocity steam plus a reaction

effect due to the expansion of steam through the moving blades

In ;#E# one impulse and other reaction blades turbine are used.

T$RBINE COMPONENT&9 *

!he various turbine components are

+1 Casing

01 Rotors

>1 Bading

,1 Turning gear

;1 Bearings

+. Casing9*

54



asing is a pressure vessel +hich must be capable of +ith- standing

maximum +orking pressure and temp. enerally casing is of ;,RREL type of

casing single F double.

!he +orking pressure aspects demand thicker and thicker casing and the

temperature aspects demands thinner and thinner casing. #o turbine casings are so

designed to take care of both pressure and temperature. #o three types of turbine

casing are there --

5. #ingle shell casing.

7. ouble (multiple) shell casing

A. ;arrel type of casing.

01 Rotors9*

Rotors are Bust like a shaft of machine. !he rotor used in .!.".# is Integral rotor

INTER"RAL T'PE O7 ROTOR9*

In this type of rotor in +hich +heels and shaft formed from one solid forging.

!he +hole rotor being one complete piece of metal

>1 Bades9-

!hese are most important components of the turbine. !hese are responsible

for main function of turbine.

55



, blade has A main parts

5. ,erofoil - It is +orking part of the blade.

7. Root - It is the portion of blade +hich is fixed +ith rotor of casing.

A. #hroud - It is riveted to main blade (but blade may be +ithout #hroud

,1 Turning "ear /Barring "ear19*

!urning gear is provided to rotate turbine shafts slo+ly during the pre run up

operation and after shutdo+n to prevent uneven heating or cooling of the shafts.

!his uneven cooling or heating +ill lead to bending and misalignment of the shaft.

/se of turning gear during starting eliminates of admitting suddenly a large

flo+ of steam to rotate turbine from rest. !o give lubrication to bearing and to

provide circulation of air +ithin the casing (L"!) after shutdo+n. #peed of !.. is

+ell chosen.

;1 Bearing of tur#ine shafts9*

56



!hese are seven bearings used in turbine. !he $" rotor is supported by t+o

bearings a double +edge Bournal bearing of the front end of the turbine and thrust

bearing directly adBacent to the coupling +ith the I.".rotor.

!he combined Bournal and thrust bearing incorporate a self adBusting

double +edge Bournal bearing and a thrust bearing +hich takes up residual thrust

from both directions. !he I.". & L.". rotors have a Bournal bearing each at end of

the shaft. !he Bournal bearing of I" & L" rotors are measured by thermocouple in

the lo+er shell directly under the +hite metal lining. !he temperature of the thrust

bearing is measured in t+o thrust pads on each side.

!he axial position of I" cylinder is also liked at the casing guide on rear end

of $" I" pedestals. !he expansion of I" cylinder takes place from $" & I" pedestal

to+ards generator.

T$RBINE "O%ERNIN" &'&TEM9

"o+er #tation !urbines are constant speed machines. In our country these

are supposed to rotate al+ays at a speed or A444 revolutions per minute (+ith in a

small band of fluctuations on either side) to enable the coupled generator to

produce electricity at <4$D fre*uency.

!he main purpose of governor is to maintain this desired speed of turbine

during fluctuation of load on the generator by varying steam input to the turbine.

57



!he governing system in addition to ensuring the falling load--speed

haracteristic of the turbine (i.e. a characteristic of falling output po+er +ith

raising shaft speed above nominal value) also ensures the follo+ing functions2

!he run of the turbine from rest to rated speed and synchroniDing +ith the

grid.

'eeting the system load variation in a predetermined manner +hen running

in parallel +ith other machines.

"rotecting the machines by reducing the load or shutting of completely in

abnormal and emergency situations.

T$RBINE A$?ILIARIE&2

!o facilitate proper functioning of turbine the auxiliaries are arranged at

different locations keeping in vie+ the easy installation proper operation and

maintenance and technical re*uirements.

A1 Condenser9

!he condensers used in !"# are surface condensers. In this type of

condensers condensation takes place on the outer surface of the tubes +hich are

cooled by sea+ater flo+ing through them.

58



!he function of condenser is2

ondenser condenses the steam exhaust from L" turbine by producing

vacuum in the condenser in order to increase the heat drop and increase the

efficiency of turbine by re-using the condensate.

!he cooling agent is sea +ater +hich is pumped by ooling 0ater "umps.

!he sea +ater is cleaned in debris filter and then it is taken to condenser through

t+o passes. $ence the condenser in !"# is a double pass single flo+ condenser.

!he pipes in the condenser are !itanium cladded. !hese tubes are half degree

inclined for self draining during tripping of ooling 0ater "umps. !he tubes are

expanded in main tube plates and are supported by support tube plates at

intermittent points to prevent sagging and to curb flo+ induced vibrations. !he

condenser is supported on springs to take the load variations +hen the condenser is

full and +hen the condenser is empty. !he 1acuum "ump creates vacuum in

ondenser and extracts all non-condensable gases to increase the steam inlet

in condenser.

&8ecifications9

5. 'ake ;$EL $ard+are

7. !ype #urface type

A. esign inlet temp AA

59



3. .0. flo+ per pass 5444tonesFhr

<. .0. temperature rise >.5

6. !ube material !itanium

>. o of passes 7

C. #urface area 5363Am7

. o of tubes 5>AAC

54. #iDe of tubes 77.77< x 4.>557 x 57744mm

B1 Condensate Etraction Pu389

ondensate extraction pump are five stages vertical double entry (at first

stage) centrifugal pumps. !hey are generally re*uired to operate on minimum et

"ositive #uction $ead ("#$). , vent line connects the hot +ell from +here the

E" takes the suction +ith condenser. !here should not be any temperature rise

here

&8ecifications9

5. 'ake ;$EL $yderabad7. o per unit 7

A. o of stages <

3. 8lo+ >>4mAFhr

<. Efficiency C7?

60



6. 'otor etails

>. Rating 6<4 k0

C. #peed 53C< rpm

. Rated current >5.7 amp

C1 Lo4 Pressure Heaters9

!he type of L" heaters used in !"# is of horiDontal /-tube surface type of

feed +ater heater +hich are three in no +hich t+o passes per heater.

;affles are provided to ensure that the steam is directed across the tubes.

!he upper section of the *uadrant of the tube nest +hich carries the condensate in

its last pass through the heater is totally enclosed by vertical baffles so forming a

flashed-steam drain cooler section of the heater.

!he three L" heaters L"$-5 L"$-7 L"$-A extractions are taken from the

L" turbine and hence this type of system is called regenerative feed heating

system.

8or L"$-5 bleed steam is taken from L" turbine stage >.L"$-7 receives

steam from L" turbine stage <. L"$-A receives steam from L" turbine stage

A.

!he drain outlet of L"$-A enters drain inlet of L"$-7. !he drain outlet of

L"$7 is given to drain inlet of L"$-5. L"$-5 is located at the neck of the

61



condenser to reduce floor space. ,ir vents are provided through +hich non-

condensable gases pass out to the condenser +here these gases are sucked

by the 1acuum "ump.

!hus the main purpose of L" heaters to preheat the condensate before

entering the boiler thereby is increasing the efficiency of the plant

)1 %acuu3 Pu389

!here are t+o vacuum pumps per unit. !he function of the vacuum is to absorb

the gases and air bubbles and to create vacuum in condenser

&8ecifications9

5. umber of pumps2 7

7. #tages2 7

A. #peed2 <44 rpm

3. ischarge "ressure2 5.44A kgFs*uare cm

E1 )eaerator9

62



!he pressure of certain gases like oxygen carbon dioxide and ammonia

dissolved in +ater is harmful because of their corrosive attacks on metals

particularly at elevated temperatures. !hus to prevent internal corrosion the feed

+ater should be free as far as possible of all dissolved gases especially oxygen.

7eed Water &!ste39

!he main e*uipments coming under this system are2

a1 Boier 7eed Pu38 &et9

;oiler feed pump (;8") is a multi stage pump provided for pumping

8eed +ater to economiDer. In !"# t+o ;8" pumps are provided for one unit.

Inlet of ;8" comes from deaerator +hich is located at re*uired head. !he pumped

+ater then goes to high pressure heater ($"$) and from there it goes to boiler

drum.

!hese pumps are barrel casing three stage cartridge pumps. !he cartridge (pump-

barrel) includes all pump internals +ith shaft impellers diffusers shaft seals

bearing housings and pumps half coupling.

The 3ain ee3ents of B7P set are9

63



+. Booster Pu38.

0. Boier 7eed Pu38.

>. H!drauic Cou8ing

+. Booster Pu389

)escri8tion9*

!he booster pump is a single stage horiDontal axially split casing type having

double suction and single discharge. !he pump shaft is sealed at driving rotor

assembly is supported by plain +hite metal Bournal bearing and

axially located by double thrust bearing. !he casing is made of cast steel.

Importance2

!he main function of booster pump is to aid the safe +orking of ;8". It

maintains the re*uired "#$ and thus the lo+er deaerator height. ;y the use of

booster pump in the main pump suction line the positive suction pressure can be

achieved +hich removes the possibility of cavitations.

NP&H is an acronym for Net Positi=e &uction Head. It sho+s the difference in

any cross-section of a generic hydraulic circuit bet+een the pressure and the li*uid

vapor pressure in that section.

64

http://en.wikipedia.org/wiki/Acronym

http://en.wikipedia.org/wiki/Hydraulic

http://en.wikipedia.org/wiki/Vapor_pressure

http://en.wikipedia.org/wiki/Acronym

http://en.wikipedia.org/wiki/Hydraulic

http://en.wikipedia.org/wiki/Vapor_pressure



"#$ is an important parameter to be taken into account +hen designing a

circuit 2 +henever the li*uid stagnation pressure drops belo+ the vapor pressure

li*uid boiling occurs and the final effect +ill be cavitation2 vapor bubbles may

reduce or stop the li*uid flo+. entrifugal pumps are particularly vulnerable

+hereas positive displacement pumps are less affected by cavitations as they are

better able to pump t+o-phase flo+ (the mixture of gas and li*uid) ho+ever the

resultant flo+ rate of the pump +ill be diminished because of the gas

volumetrically displacing a disproportion of li*uid.

&8ecification9*

!ype fa 5b ><

#uction >.> kgFcm7

ischarge pressure 7<.3 kgFcm7

"o+er re*uired 6>4 k0

0. Boier 7eed Pu389

!he feed +ater +ith the given operating temperature flo+s to the pump under

a certain "#$. !he +ater then passes through the suction branch into the intake

spiral and from here it is directed to the first impeller. ,fter leaving through the

impeller it passes through the distributing passages of the diffuser +here it gets

certain pressure rise and flo+s over to guide vanes to the inlet of the next impeller.

!his process is caused by the centrifugal action of +ater. !his process repeats from

one stage to the other fill if passes through the last impeller and the end diffuser.

65

http://en.wikipedia.org/wiki/Boiling

http://en.wikipedia.org/wiki/Cavitation

http://en.wikipedia.org/wiki/Centrifugal_pump

http://en.wikipedia.org/wiki/Pump#Positive_displacement_pumps

http://en.wikipedia.org/wiki/Boiling

http://en.wikipedia.org/wiki/Cavitation

http://en.wikipedia.org/wiki/Centrifugal_pump

http://en.wikipedia.org/wiki/Pump#Positive_displacement_pumps



from the speed difference bet+een impeller and runner. !his speed difference is

called slip.

!he +orking compartment is charged continuously by a pump +hich delivers

oil from the sump belo+ coupling. !he oil level in the +orking compartment

determines the speed of the runner +heel and the oil level depends upon the radial

position of scoop tube located in scoop chamber.

71 High Pressure Heaters9

$igh "ressure $eaters are of horiDontal /-tube surface type. !here are t+o

$"$ $"$-< and $"$-6. $igh pressure heaters receive condensate from the

;oiler 8eed "ump.

$" $eaters consist of tubes made up of stainless steel. !hese tubes expand

into the main tube plates and are supported by support tube plates at intermittent

points to prevent any sagging of tubes.

$"$-< receives steam from I.". turbine 54th stage and $"$-6 receives

steam from cold reheat line. $" $eaters consist of air vents through +hich non-

condensable bases are passed to the flash tank. 8rom there these gases go to the

67



condenser +here the 1acuum "ump sucks them thus creating a clear path for

steam. !he drain outlet of $"$-6 is given to $"$-<.

"1 Tur#ine Lu#rication Oi &!ste39

!his system fulfils the follo+ing important functions2

a) "rovides a supply of oil to Bournal bearings to give an oil +edge as the shaft

rotates.

b) 'aintains the temperature of turbine bearings constant at the re*uired level.

c) "rovides a medium for hydraulically operating the governor gear and controlling

the steam admission valves.

d) "rovides for hydrogen cooled generators a sealing medium to prevent hydrogen

leaking out along the shaft.

H1 Centrifuge9

!he purifier is used for purification of turbine oil. It dra+s oil from the

turbine oil tank (or dirty oil tank located outside turbine building) through a oil

pump. ,fter removing any +ater and entrained solid matter the clean oil is

returned to the oil tank (or pure oil tank).

!he entrifuge can perform the follo+ing t+o 8unctions2

68



5. Carification2 , li*uid (oil) - #ludge separation in +hich the machine is used

for separating of particles normally solids.

7. Purification 2 Li*uid (oil) - li*uid (+ater) separation in +hich the machine is

used for separating t+o intermixed li*uids +hich are insoluble in each other and

have different specific gravities solids +ith specific gravities higher than those of

the li*uids that can be separated off at the same time.

Princi8e of o8eration9

!he mixer of dirty oil +ater and solids impurities flo+ through the inlet

connection of the centrifuge hood and through the ports in the +alls of the inlet

pipe into the space bet+een the hub of the bo+l and the bore of the distributor. !he

mixer flo+s through holes in the conical base of the distributor and the discs to the

inner spaces bet+een the revolving disc +here the +ater and the solids are thro+n

out+ards by the centrifugal force and so are separated from the oil.

I1 )e#ris 7iter9

ebris such as shells sticks stones and plastic are a common cause of

failure in condenser. Improvements in primary screening +ould only lead to a

partial solution. It +ould only solve the problem of debris such from 0 pump

house. #econdary screening as close as possible to inlet +ater box is fulfilled by

ebris 8ilter.

69



!he internal construction and design is based on cooling +ater flo+ cooling

+ater inlet pressure siDe type and *uantity of debris. !he debris in cooling +ater

is collected at inner surface of 1-shaped screen housed inside the filter. ,

ifferential "ressure 'easuring #ystem ("'#) indicates the level of debris

fouling on filter screen across the screen +hen it reaches the preset limit the "'#

initiates the debris removal operation.

!he debris accumulated on the inside surface is removed by extraction

assembly +hich guides the debris along the basket into the debris discharge pipe

connected to main cooling +ater outlet pipe. !he filter incorporates a high-pressure

+ater-inBecting arm +hich is run by the 8lushing "ump.

O77&ITE A$?ILLIAR' $NIT& ARE9

70



+. Ash handing 8u38 house.

0. Coa handing unit.

>. C.W Pu38 house.

,. Water 8retreat3ent 8ant.

;. Water de3ineraiation 8ant.

A&H HAN)LIN" P$MP HO$&E

!he ash handling system of !"# is of +et and dry type. !he +et ash

handling system consists of bottom ash evacuation. ,sh disposal piping and pump

house. !he bottom ash collected in bottom ash hopper and evacuated once in shift.

!he bottom ash is crushed in clinker grinder and conveyed to the main slurry sump

by means of hydro-eBector. !he bottom ash evacuated at the rate of 574mtFhrs.

!he fly ash is collected in ,"$ /! E#" E%%'I#ER hoppers. !heash is evacuated by feeder eBector and conveyed to the intermediate sump by sluice

+ay trenches. !he ash from intermediate sump is pumped to the main slurry pump.

!he fly ash is evacuated at the rate of 564mtFhrs.

!he ash from main slurry sump is further disposed in ash pond by 3 streams

of slurry pumps +hich are connected to t+o no of basalt disposal pipe lines of

7@m each.

COAR&E A&H &'&TEM

71



,sh collected in 57 no=s of EconomiDers FuctF,"$ hoppers +ill be

removed once in a shift. !he changeover of hopper group is affected through either

timers or lo+ level s+itches +hichever events are earlier. Each coarse ash hopper

is provided +ith one number manually operated hopper isolation valve

pneumatically operated valve expansion Boint and feeder eBector. !he pressuriDed

+ater feed to the feeder eBector mixes +ith the free falling ash and the resultant

slurry +ill be conveyed into slurry trench connected to intermediate 8E slurry

sump.

7L' A&H HAN)LIN" &'&TEM

8orty-eight electrostatic precipitator hoppers four E#" hoppers constitute one

group. !hus there are 57 groups of fly ash hoppers. Each group of fly ash hoppers

is operated one by one in se*uence. ,ll the hoppers of one group openFclose

simultaneously. !he changeover of hopper group is affected through either timers

or lo+ level s+itches +hichever event is earlier.

Each fly ash hopper is provided +ith one no manually operated hopper

isolation valve pneumatically operated fly ash valve expansion Boint and feeder

eBector. !he feeder eBector +hen feed +ith pressuriDed +ater serves to mix the free

falling fly ash +ith +ater and discharge the resultant slurry into the slopping trench

provided underneath +hich is connected to main slurry trench. !he fly ash slurry

extracted from various hoppers flo+s do+n through main slurry trench. !he fly ash

slurry extracted from various hoppers flo+s do+n through main slurry trench

aided by high-pressure +ater Bets to the intermediate fly ash slurry sump. 8rom

there the slurry +ill be transported to the main slurry sump by means of one 8ly

ash slurry pump in unit-I and t+o fly ash pump in unit-II. Intermediate slurry sump

72



of both units +as interconnected by common trench. Each group of hopper has one

pneumatically operated valve in feeder eBector +ater line.

A&H )I&PO&AL &'&TEM

!he bottom ash coarse ash & 8ly ,sh led to common slurry pump sets &

disposal lines. 8our no=s of identical streams connected to t+o no=s of slurry

disposal lines. %ut of four streams provided single stream run continuously for

both units & the remaining three streams serve as standby. 'ake valve & line

flushing are provided in each compartment to enable the slurry disposal pumps to

run & flush the disposal pipelines. 1arious level s+itches provided in each of the

sump initiates highFlo+ level alarm protects the sump from dangerously lo+ level

& also controls the makeup valves.

,sh slurry sump +hich is common for both units is a R tank +ith four

compartment one for each of the pump stream. ,gitating noDDles provided in the

sumps keeps the solids in slurry in floating state. "neumatically operated suction &

discharge valve for each stream of pumps helps in isolation of the stream. isposal

piping has special E:9 coupling Boints to ensure ease in periodical rotation of the

pipes for uniform +ear.

R9 ,#$ #9#!E'

• !he fly ash collected at the E#" hoppers are gravity fed into individual

transmitter vessels provided belo+ each hopper • %n initiation of dry fly ash collection system the inlet valve opens and

allo+s the fly ash to be fed into the transmitter vessel for pre-determined

time after +hich the inlet valve closes.

73



• ,fter+ards the compressed air is allo+ed to flo+ into the transmitter vessel

by opening the air inlet valve.

•%nce the desired conveying pressure is reached inside the vessel the fly ashstorage silo through transport piping.

• !he conveying air is vented through the bag filters mounted on top of the

silo in order to limit the dust concentration in the vented air.

COAL HAN)LIN" $NIT

COAL

oal may be defined as that part of the Earth=s crust +hich has been formed as a

result of the accumulation of decayed plant remains million of years ago and its

subse*uent consolidation over the years by a complex series of chemical and

physical changes. oal is essentially carbon and is mainly used as a combustion

fuel.

T!8es of Coa9*

0e use the term TcoalT to describe a variety of fossiliDed plant materials but no

t+o coals are exactly alike. $eating value ash melting temperature sulfur and

other impurities mechanical strength and many other chemical and physical

properties must be considered +hen matching specific coals to a particular

application.

!he carbon content of coal supplies most of its heating value but other factors

also influence the amount of energy it contains per unit of +eight.

74



!here are four main types of coal and are arranged in increasing order of their

carbon content on moving do+n+ards2

Lignite

#ub- ;ituminous

;ituminous

,nthracite

COAL 7OR THERMAL POWER &TATION9

India is blessed +ith a very good reserve of non-coking coal. on coking

;ituminous or #ub ;ituminous oal is normally the basic fuel used for thermal

po+er generation. !o achieve economy of individual plant and also to ascertain the

efficiency of the generating e*uipments representative coal sampling is of prime

interest. 8urther coal prices are fixed as per the *uality of coal hence if the proper

vigilance is not given for the *uality of coal +hich are received then consumer

may suffer a substantial loss. $ence continuous monitoring of coal *uality is

essential.

ationalisation of collieries and introduction of modern e*uipments for coal

mining and loading has resulted into variation of coal *ualities even from singlemine.

COAL $&E) AT )AHAN$ THERMAL POWER &TATION

,) Indian oal

75



I) Ra+ oal

II) 0ashed oal (lean coal)

;) Imported oal

Coa testing is di=ided into > 8arts

I) #ampling

II) Reduction & preparation

III) ,nalysis

I1 &AMPLIN" O7 COAL9 I# -3A6 J "art I J #ec- I2 563 Reaffirmed 7445

ra+ing of Indian oal samples at .!.".#. is carried out at t+o locations J

i) #ampling from running onveyor ;elt

ii) #ampling from Loaded 0agons

)ra4ing of I38orted Coa sa38es at ).T.P.&. is carried out at

Jett!.

i1 &a38ing fro3 Running Con=e!or Bet9 *

ollection of coal samples are carried out from onveyor ;elt 5, F 5; after

!ippler.

i) !he *uantity of coal to be dra+n approx. A44 to 344 kg per rake.

76



ii) #ample collection to be done +ith the help of a suitable scoop.

iii) !he increment shall be dra+n +ith the help of a scoop at regular intervals.

iv) Each increment shall be of A @g (approx.).

v) !he increments shall be collected from the center and left and right sides of the

belt along the same +idth.

vi) !he scoop shall s+eep the bottom of the conveyor.

vii) !he material collected from all the increments shall be mixed together and

shall constitute a gross sample.

viii) !his gross sample shall be used for *uality analysis.

ix) #eparate unexposed sample shall be dra+n for the determination of !otal

'oisture.

x) !he *uantity of the above sample shall be <4 @g (approx.)

ii1 &a38ing fro3 Loaded Wagons9*

oal rake contains <> to <C nos. of +agons.

i) !he *uantity of coal to be dra+n approx. A44 to 344 kg per rake.

ii) , minimum of 7< ? of the +agons shall be selected at random basis for

collection of coal sample.

iii) %ne point shall be located at random on the coal surface of each of the selected

+agons.

77



vii) !his gross sample shall be used for *uality analysis.

viii) #eparate unexposed sample shall be dra+n for the determination of !otal

'oisture.

ix) !he *uantity of the above sample shall be <4 @g (approx.)

II1 RE)$CTION PREPARATION9

!he gross sample (A44-344 @g) for *uality analysis shall be crushed to 57.< mm

and then to A.A< mm siDe by Lab. Ha+ rusher. 8urther reduction of *uantity up to

7.4 @g by using the techni*ue coning & *uartering after air drying. rind the

above material to pass 757 neither micro nor >7 mesh siDes by Lab. "ulveriser.

!his sample shall be used for S"roximate ,nalysisU.

!he gross sample (<4 @g) for !otal 'oisture analysis shall be crushed to57.< mm

by Lab. Ha+ rusher. 8urther around 5.4 kg sample shall be collected from abovesample & kept for air drying for 73 hrs for determination of surface moisture (O).

8urther this sample is crushed to 7.C4 mm siDe & heated at 54C V < eg. in Lab.

%ven for A $rs. 0eight loss isrecorded as W9=.

!otal moisture (?) O X 9 (5 J OF544)

!he coal +hich has been exposed to contact +ith +ater in the seam or in a

+ashery or coal +etted by rain may carry free or visible +ater. !his +ater plus the

moisture +ithin the material is referred to as !otal moisture.

III1 ANAL'&I& 9

oal samples can be analyDed by the follo+ing methods2-

79



,) "roximate ,nalysis I# -5A<4 J "art I J 5C3 Reaffirmed 7445

;) /ltimate ,nalysis I# -5A<4 J "art I1 J 5>3 Reaffirmed 7444

) ross alorific 1alue I# -5A<4 J "art II J2 5>4 Reaffirmed 7444

) $ard-rove rind ability Index ($I) I# -33AA 5> Reaffirmed 7444

A1 Proi3ate Ana!sis 9*

"roximate analysis is carried out on ,ir dry basis (,;)

"roximate analysis of coal means determination of -

i) Inherent 'oisture (I. '.)

ii) ,sh ontent

iii) 1olatile 'atter (1. '.)

iv) 8ixed arbon (8. .).

ANAL'&I& O7 COAL9

i1Inherent Moisture /I.M19

'oisture in the coal sample after it has attained approx. e*uilibrium +ith air to

+hich it is exposed or it is the moisture in coal +hich has been air J dried under

the laboratory atmospheric condition prior to analysis.

,pprox. 5.4 gm of pulverised laboratory sample Is dried in Lab. %ven at 54C V

< eg. for A $rs. Loss in +eight is reported as Inherent 'oisture.

80



ii1 Ash9

It is the residue of mineral matter obtained by incinerating coal under define

conditions. In simple term ash is incombustible matter present in the coal.

,pprox. 5.4 gm of Laboratory sample is heated at C5< V 5< deg. in Lab.

8urnace for 5.< to 7.4 $rs and the residue left behind is reported as ,sh content.

iii1 %oatie Matter /%. M.19

1olatile matters are the volatile products of thermal decomposition of coal.

,ctually it is the loss in +eight of moisture free coal.

,pprox. 5.4 gm of lab #ample is heated at 44 V 54 eg. in Lab. 8urnace for

>.4 mins. !he +eight loss minus inherent moisture is reported as 1olatile 'atter.

i=1 7ied Car#on /7. C.19

It is the residue of carbon left after deduction of 1. '. ,sh & 'oisture

8. . 544 J (,sh X 1. '. X I. '.)

B1 $ti3ate Ana!sis9*

;y ultimate analysis +e mean ultimate composition of coal in terms of percent

arbon $ydrogen itrogen #ulphur and %xygen.

arbon & $ydrogen2 arbon & hydrogen in coal directly contributes

to+ards the alorific 1alue of coal. $igher the percent of arbon &

$ydrogen better is the *uality of coal and higher is its calorific value.

itrogen2 It is present in small *uantity say nearly 5-7? and does not

contribute any /seful value to coal.

81



%xygen 2 !he lo+er the oxygen content the more is the maturity of the coal

and greater is its

alorific 1alue. If %7 content is more the capacity of coal to hold moisture

increases and the caking po+er increases.

/ltimate analysis is determined by using the formulae.

? 4.> 8. X 4.> (1.' J 4.5 ,) J 4.6 I.'

? $ 4.4A6 8. X 4.45 (1.' J 4.5 ,) J 4.4< I.'

? 7.5 - (4.457 x 1.')

? % 544 J (? X ? $ X ? X ? # X ? ,#$ X ? I.')

#ulphur2-#ulphur in coal is determined gravimetrically by the Eschka=s

'ethod.

!he sample of coal is heated in intimate contact +ith Eschka=s mixture in anoxidiDing atmosphere to remove combustible matter and to convert the sulphur to

sulphate. !his is then extracted and determined by gravimetric method by

precipitation as barium sulphate +ith barium chloride.

#ulphur present in coal contributes to heating value of coal but its combustion

products (#%7 & #%A ) have corrosive effects on e*uipments also harmful for

environment. !herefore coal +hich contains lo+ sulphur is preferred.

Esch6aFs 3iture* A 3iture of 3agnesiu3 and dried sodiu3 car#onateG used

as a reagent for deter3ining su8hur in coa or co6e.

82



C1 "ross Caorific %aue2

!he calorific value of a sample determined by burning the sample in a controlled

environment. !he heat released by combustion is proportional to the calorific value

of the substance. alorific value is measured by an instrument called S;%';

,L%RI'E!ERU is measured in @cal F@g or al F gm or ;tu F lb i.e. ;ritish

thermal unit per pound.

"ross caorific =aue is e38o!ed to find out(

5) !hermal efficiency of combustion.

7) oal consumption per @0$.

A) $eat value of coal.

3) $ard rove rind ability Index ($I)2 I# 33AA2 5> (,mended in 7444)

$I indicates hardness property of coal. 0hich indicates its easiness to+ards

pulveriDation of coalY

It also reflects the life and efficiency of the pulveriDing e*uipments. Lo+er $I

means difficulty in pulveriDation. 1ery high $I is also not +anted as it +ill start

giving fines right from the mines. oal fines are very difficult in handling

particularly in rainy season as it forms a very sticky mass.

<4 grams of coal sample of the siDe 4.6 mm to 5.7 mm is grinded in $I

machine for 64 rotations. !he grinded material is passed through 744 ,#!'

mesh. !he +eight of material passed is taken as W0=

83



REPORTIN" O7 ANAL'&I& RE&$LT&

• In the actual prevailing conditions there may be variation in the moisture

ontent of coal +hich +ill affect the end *uality. It is advisable to procure and

analyse the coal on W,s Received ;asis =.

• !he analysis of coal is being carried out under laboratory condition. ,ll the

results obtained are on W,ir ried ;asis =.

• !he moisture correction is being applied for converting ,; results in to

,R;.

Pro#e3s Associated 4ith

+1 Moisture of coa

Loss of ;oiler Efficiency

Reduce pulveriDing capacity

8orms reducing atmosphere

($7% X $7 X % )

Reduce the temperature of primary air leading to mill clogging up.

8luctuating moisture tends to cause mill fire

01 Ash content

$igh ash reduce flame stability

#lag & clinkering problem

84



!ube deposit

ifficulty in ,sh handling and dumping

Reduce life of 'ill components

Erosion in boiler tubes and ash slurry pipes

>1 %oatie Matter

Lo+ 1' coal difficult to burn and less reactive

$igh 1' coal easy to burn and more reactive

$igh 1' coal catch fire in coal yard due to atmospheric temperature

,1 7ied Car#on

1 is dependent on 8 in oal

Lo+er the 8 lo+er is 1 higher is the coal consumption.

;1 &u8hur

8ormation of #%x

$ot corrosion on boiler tubes

85



COOLIN" WATER P$MP HO$&E

!he cooling +ater pump house is situated on the sea shore of ,rabian sea

+hich is about 7-Akm a+ay from the main plant and the sea +ater is used for the

cooling of steam in the condenser +hich is delivered to the main plant using the

pipe lines.

,s the sea +ater comprises of the living organisms as +ell so if +e deliver

this uncleaned +ater to the main plant then these living organisms could stack thedelivery pipe lines so to prevent this chlorination is done of this +ater to kill those

living organisms and chlorination is done only in that *uantity so that "$ of the

+ater could also be maintained through this addition of chlorination the living

organisms died and are separated from +ater in the primary stage of filtration

through +hich the pump sucks the +ater from the sea.

!his pump house comprises of 3 no of pumps. Each pump is concrete volute fitted

and are mixed flo+ +ith vertical suction.7 pumps are used for the supply of

cooling +ater for cooling a single unit of condenser of 7<4'0 by supplying

7Z7>444 mA Fhr (the capacity of each pump is 7>444mAFhr supply of +ater).

!his +ater cools the steam in the condenser +hich came there from turbine and

converts it in the li*uid form thus forming a recycle process and this converted

+ater is again used for steam formation and approximately 4? of the steam is

converted into li*uid.

86



P$MP &PECI7ICATION9*

Efficiency2 - 6.<?

Rating2 - 5764@0

R"'2 - 7>

#tarting method2 - irect on line (%L)

"o+er factor2 - 4.>>4

!emp rise2 - ><4c

'ade by2 - ;$EL ($ard+ar)

87



,fter sand filtration the +ater is stored at a certain place and by doing chlorination

to certain part of it +ater is supplied for the use of drinking +ashing etc to the

colony.

,fter that rest of the +ater it transferred to the emineraliDation plant for its

further treatment

IMP$RITIE& IN WATER

)isso=ed "ases &us8ended I38urities Tota )isso=ed &oids

)ust )e#ries Cooids Cations /1 Anions /*1

Tur#idit! /NT$1 Caciu3 /Ca1 Choride /C1

Magnesiu3 / Mg1 &u8hate /&O,1

&odiu3 /Na1 &iica /&iO01

Nitrate /NO>1

Car#onate /CO>1

Bicar#onate/ HCO>1

Conducti=it! /& c31

The 3ain O#5ecti=es of Water Treat3ent in Po4er Pant9

5) "revention of scaling in boiler

7) "revention of corrosion in boiler.

A) "revention of steam F +ater contamination.

89



Basic structure of 4ater 8re treat3ent 8o4er 8ant

90



7ig*+.interna of de3ineraiation 8ant

PLANT MAINTAINENCE

5.!he tanks are cleaned thoroughly during the maintenance time period of the

plant.

7 In case of failure of any of the tank due to any reason then there is the presence

report of thermal power plant

Documents