Descon Presentation on Co-Generation 13-07-2010

8/6/2019 Descon Presentation on Co-Generation 13-07-2010

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DESCONEngineeringLimited

SeminaratJuly2010

1


2/46

Cogenerationis:

Ahighlyefficientmeans

ofgeneratingheatandelectric

Atthesametime

Fromthesameenergysource.

Productionofheatandelectricseparated

2


3/46

en ra owergenera on

Simplecycleplant Combined

cycle

plantwithdieselengines Combined

cycle

plantwithgasturbines

E E E

E E

c ency c ency c ency

60%ofheat

dum ed in

condenser3


4/46

Co

generation

Combinedc cle lant Combinedc cle lant

withdieselengines withgasturbines

EProcess

steam

E

E

E

E

Process

steam

Process

steam

Cond.return Cond.return Cond.return

Byi.e.extracting 50%process

steam30%ofheatwillbe

4


5/46

Co

generation

without

condensing

Efficiencyofsystemcanbeincreasedinfarextendbydeletionof

.

Highheatlossesincondenserareeliminated

Process

steam

Process

steamE E Process

steam

Cond.return Cond.return Cond.return

Efficiencyofpowergeneration85till93%5


6/46

Inco enerations stems withcombinedc cles

EfficiencycanbeincreasedfurtherbyadditionalfiringinHRSG

E E

fuel fuel

Process

steam

E E Process

steam

Cond.return Cond.return

Efficiencyofpowergeneratedbyadditionalfiringis100

till120%

6


7/46

Effectofcogenerationonplantefficiency

How

Moreprocesssteamrequiredinrelationtoelectric

powerresultinhigherplantefficiency 7


8/46

Cogenerationsystemswithoutsteamturbine

Process Process

10barE E

10

bar

Con .return Con .return

Howeverhighefficiencyis

notalwayseconomic.

Inco enerations stems

deletionofsteamturbine

andalowpressureboiler

.

specialinsmallerunits 8


9/46

Impactofboilerpressure

on

power

output

in

co

generation

plants100bar/539

37%more

120

E 100t/h,

power

80

100

Processsteam

2barg,143C

30%more

power60Pressure

(Bar)Cond.Returnwith125C

45bar/430C

ar

17%more

power40

fuel

00 2000 4000 6000

E Process

steam

100t/h,2barg,143C

AdditionalPower(KW)withefficiencyofapprox86%

forbiomass/coaland94%forgasfiredCond.

Return

125

C 9


10/46

Sameappliesalsowhenmoreandmorepowerisgeneratedin

combinationofbackpressureandcondensingsteamturbine

EE E

E

E50t/h 50t/h

Process 50t/h, Process 50t/h,

s eamCond.Return50t h arg, s eamCond.Return50t h arg,

10


11/46

4300 Power(Kw)Incombinedcycleswithonlypowergenerationitisdifferent.

4239

4253

4228

4250

Additional

Power(KW)

45 Bar/66 Bar/

449C500C

41604150

30 Bar/

400C

428C 85 Bar/449C

E

4053

4050

4100

4000

0 20 40 60 80 100Pressure (Bar)

ar

WhenGTexhausttem erature500Cthena ressurebetween

30and45barwouldbeoptimal.

Howlowerthistemperaturehowlowerthepressure.

.

Forlargegasturbinesdoubleortriplepressuresaremore

economic. 11


12/46

Impactofsteamtemperature

insimplecyclecogenerationplants

EEThisprocesssteamshould

10t/h.

Shouldbe10Coverheated.

Process

steamCond.Return

100t/h,

2barg,143C

ThereforetakeHPsteam

temperaturehighenough.

. .

At45barmin.430C

At66barmin.486C

t arm n.

At100barmin.539C 12


13/46

HigherHPsteamtemperaturewillgivemoreoutput

. .

resultin0,8% morepoweroutput(byfiringadditionalfuelwith

efficiencyof86%).

W en u con ensingresu tin2% y iringa itiona ue wit

efficiencyof30till35%).

EEHoweverhighertemperatures10t hmeans

Selectionofhigheralloy/more

Process

steamCond.Return

100t/h,

2barg,143C

Isthiseconomic?

13


14/46

Feedwaterpreheating

Whenonl

rocess

steam

su l

:HowmuchmoreEpowerincaseofpreheating

with addingadditionalfuel:

E2estage:

At100bar4,7%more

Processsteam

2barg,143C

At65 ar 2,9 more

Withefficiencyofapprox45%onfuelinput.

Cond.Returnwith125C

Economic?

es age:At100bar5,8%more

At65bar 5,4%more

Withefficiencyofapprox52%onfuelinput. 14


15/46

Whennoprocesssteamsupply/onlycondensing:

without addingadditionalfuel:

E2estage:

At65bar 0,6% more

Economic?

1estage:

At100bar2%more

At65bar1 7%more

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Effectcogenerationonsteamturbineselection

Backpressurecontrolfor

controllingLPsteampressure

HPsteampressurecontrol

bysteamturbine

E

ofapprox10%ofdesignflow.

NOTE:

Steamturbinesshouldbeselected

ver accurate.

Process

steamCond.Return

100t/h,

2barg,143C

Thenormalandmaximumsteam

flowshouldnotdeviatemuch.

turbine.

Speciallyforcondensingpart. 16


17/46

Eachsystemisuniqueinsteamandelectric

requirement.

forthemosteconomic solution.

1. Whatarethemaximum,normalandminimum

steamandpowerrequirements.

2. Whataretheo eratin times3. Whatshouldbetheavailability

4. Donotusesteamturbinedrivenequipment

thenwiththepowergeneratingequipment.

5. Useelectricdrivenequipment.

6. Forlargepowerconsumersusevariablespeed

controldrives. 17


18/46

Boilerwaterandsteam requirements

Availabilityoftheplantdependshowthewaterandsteam

conditionsaremaintained.

It

is

recommended

to

use

demi

water

as

make

up

and

to

polish

thereturncondensatewhenits qualityisnotguaranteed.

Thedosingofchemicalsinthefeedanddrumwatershouldbe

controlledautomaticallytoensurecompliance.In ineinstrumentationisrequire tomaintaint erequire

qualitieswithinacertainband.

Maintenanceofsystemisessential.

ALabisneededtocollectdailyasamplestochecktheaccuracyof

.

Thechemicalsshouldbesuppliedbyreliablesuppliers. 18


19/46

BiomassFuelsinPakistan

1. Bagasse

2. SugarcaneTrashAllthosefuelshavecommon:

HighVolatilecontent. ornco s

4. Ricehusks5. CottonStalks

NettHeatingvalue onbasisofashand

waterfreeallapproxthesame(17,8till

19MJ k6. Wheatstraw

7. WheatriceNOTE: Thecompositioncanvaryper

seasonandperarea.

Fuelsaredifferentin:

moisturecontent

Ashcontent

foranalysis

Thefuelscanbefiredondifferent

Alkalicontentinash Sulfur

sto ertypesan n u ze e

system.

density19


20/46

Localcoal

KnownanalysisofminesinMakarwal Areaonly

ItisahighvolatileBbituminouscoal

Moisturecontent5till10%

Thesulfurcontentisveryhigh7,1wt%ondry.

s con en var es rom

Theinitialdeformationtemperatureisunknown(firstmeltingpoint

ofelementsinash .

Softeningtemperatureis1020C

Thequalityofcoalisnotconsistent

Thecoalsuppliedneedstobeanalyzedbeforefiringit. Duetohighersulfurcontentandexpectedvariationinashcontent

.

Tohandlethevarietyincompositionwerecommendabubblingfluidizedbed

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22


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Im rt c al

Hi h ualit coalissu liedfromIndonesia SouthAfricaand

China ItisahighvolatileAbituminouscoal

Moisturecontent10till 20%

ashcontent5till15%

w u u , ,

Highinitialdeformationtemperature,above1200C.

.

23


24/46

Characteristicsofbiomassandcoal

52

50.0

.

30

25 29

18 18.5 1620.0

30.0

.

8.4 811

5.71011

13

712

4.4

11.7

2 2.5

8 7.0

0.0

10.0

MoistureContent% LHV(MJ/Kg) Ash

24


25/46

Pric f i ma an l cal c al r k an r MJ

Pricesaremostl relatedtowei ht

Howevermorerealisticistorelatetoenergyonlowerheatingvalue(LHV).

Thepropertiesofbiomassfuelcandifferperareaandyear.It

isimportanttoverifythepropertiesofbiomassbyaproper

test rocedure.

Thesameappliesforlocalcoal

25


26/46

PricesofBiomass&Coal

r ce s g0.37

0.300.35

0.40

r ce s

5.36.0

8.0

10.0

.

0.21 0.19

.

0.15

0.200.25

.

34

2

0.0

2.0

4.0

0.00

0.05

0.10

Price(Rs/Kg) Price(Rs/MJ)

Thelocalcoalisver com etitiveinrelationtobiomassfuels.

Asbiomassfuelsareenvironmentfriendly theyneedmorestimulation.

i.e.carboncredits,positiveeffectontaxes,etc. 26


27/46

Eff ct f f l n l i tic

Com aredtocoalbiomasshaslowerdensit .

Morevolumetohandleintransport,storageandfeedingsystem.

Biomassisnotphysicallyhomogeneousandfreeflowing.

Difficultiesintransportation,metering,storageandfeeding

.

easiestonestodecompose.ItcanreducetohalfitLHVvalue

withinoneyearofstorage.

27


28/46

Effectonfuelhandlingforsolidfuels

20,336

23,780

20,000

25,000

LHV(MJ/M)

10,000

15,000

2,3091,302

2,5991,526

2,9541,615 2,098

0

5,000

28


29/46

Effectoffuelonashhandling

16.00

18.00

s con en g )

12.00

14.00

6.00

8.00

10.00

2.00

4.00

0.00

29


30/46

Envir nm nt BiomassisarenewableenergywhichdoesnotincreasetheCO2level. CO2

creditswillgiveacostsaving

Duetohighvolatilecontent theNOx levelswithbiomassfiringarelow

.

Sulfuremissionsarenil.Localcoalhashighsulfurcontentandrequirefluidized

bedcombustionwithlimestoneinjectiontokeepSoxemissionlow.

Sulfurdioxideemissionrequirementforfossilfiredboilersisunclear.

For

oca

coa

imestone

as

to

e

injecte

in

e

or

in ing

t e

su ur.

Norma y

80%ofsulfurisbondedwithlimestoneThiswillincreasethetotalashcontentwithapprox 60%.

Therequirementoflimestonemakesthelocalcoalapprox15%higherinprice.

30


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Fuelsaredifferentin:

A. moisturecontentWhatarethe

effectsonselection.

C. Sulfur

D. Chloride

offiringandboiler

system?

31


32/46

A.Moisturecontent

Highmoisturemeansthatthewaterhavetobeevaporatedfirst.

Thisrequirespreheatedairsupply.Thisrequiresanairpreheateratoutletof

boiler.

i.e.Bagasse of52%moisturecontentrequires220till260Cairtemperature.

Incaseoflowmoisturecontenttheairpreheatingshouldbelimitedinorderto

avoid

overheating

of

stoker

system.

Howhigherthemoisturecontenthow lowertheboilerefficiency

causesmoreerosion.

LowermoisturecontentinBa asse from50to40%resultsina rox1,8%hi her

efficiencyand15%lessfluegasvelocities.

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33/46

B.Ashcontent

Whenlowashcontentof2till4%andhighvolatilebiomass

fuelsareusedthenastationarystokertypecanbeused.Also

Steamnozzlesforcleaningthe

grate

Castironelements

attachedandcooledbythe

Watercooledtubesas

tubes

partofboilersystem

33


34/46

Dumpinggrateisnotrecommendedasitwillgive:

an nterrupt on nsteamsupp y ur ngc ean ng muchhigher unburnedlosses

moreinterruptionsduetooverheatingofgratebars

Inothercaseswithashcontentsupto20%atravellinggrateis

recommended.

34


35/46

Howhighertheashcontenthowmoreerosionintheboiler.

pec a yw ens cacontent svery g .

Howhighertheashcontenthowlargertheboilerwillbe.

Ricehuskshasextremely highsilicacontent of96%andsuffer

banks.

The

allowable

velocities

are

more

then

50%

less

then

for

other

omass ue san coa . sresu s namuc arger o er en

normallyseenforotherkindoffuels.

Furtheratravellinggratewillhavealsoahighwearandteardue

tothisash.

35


36/46

Asthericehuskwillbefiredmainlyin

furnacemainlyasflyashawatercooled

inclinedgrate systemisverysuitable.

Thegrateisthenprotectedfromoverfiring

bythewatercooledgratesystem.This rateisnormall usedforaver wide

rangeoffuelsandlowashcontents.

Theashofricehusksistransformingfromamorphousstateto

crystallinestatewhenitisexposedtotemperaturesabove850

. .

Theashcanthenbeeasilyusedinsteelmillsandother

applications.

t a u ze e systemt ewearan earpro em s

minimized.36


37/46

travellingorvibratinggrate.

emax mumamoun o coa s oweverres r c e .

Whenthiswouldbetoohighthelocalfiringtemperaturesget

toohighandtheashofthebagasse wouldclinkerandcause

problemsonthegrateandfoulinginfurnaceandheating

Withtheotherfuelmixturessimilarlimitationsarethere.

37


38/46

C.Chlorine,sulfurandashcharacteristics

Theashcharacteristicsoffuelsareimportant.

Speciallyimportantare:

thealkalimetals(Ca,Na,K)areimportant.

Further

the

sulfur

and

Chlorine

content

in

the

fuel

is

an

important actor

Thosecontentsneedstobeverifiedinthelabbeforedeciding

thebestcombustionandboilersystem.

38

El i bi & l i ll


39/46

Elementsinbiomass&coalpotentially

.7.1

7.00

8.00

4.005.00

6.00

0.60

0.20.02 0.1 0.03

0.3 0.2

0.80.50 0.4

0.2 0.1 0.01

0.70.5

1.47 1.47

0.73

0.32 0.18

2.442.22

0.12 0.09

0.00

1.00

2.00

.

Sulphur(S)%

K+Na%

39


40/46

Thoseelementsdeterminetheclinkering,slagging

andfoulingandalsotheerosionandcorrosion

potentialsofthefuels.

Arangeofindicesareavailabletoassistinpredicting

thosepotentials.

Alsotestarerequiredtodeterminethefollowing

conditions inthelab oftheashathightemperatures:

initialdeformationtemperature

sinterin tem erature

hemisphericaltemperature Flowtemperature

Thosetestswillalsoassistinpredictingthe

clinkering,slagging andfoulingpotentialofthefuels 40


41/46

Thepotasium (K)salts(KCl andKOH)becomevolatileabove

650Canddepositiondownstreamcancauseserious

corrosionandfouling.

For that reason the flue asses will be cooled down in water

cooledcavitiestill650C whentheindicesindicatesthis

potentialproblem.

Werecommendtofirefuelswithhigh(Ca,Na,K)contentsin

afluidizedbedsystemasthecombustiontemperatureinthebedandfreeboardarelowandcanbecontrolledmore.

Thebiomassfuelsare:

cottonstalks

sugarcanetrash corncobs

Thosecanbefiredincombinationwiththelocalcoal. 41


42/46

Theratioof sulfurtochlorineindicatesifcorrosioncanbe

expectedinthesuperheaters.IfChlorineismuchhigherin

contentthenthesuperheater tubemetaltemperature

needs to be ke t low maximum 450 C .

Orinconel tubesshouldbeusedwhenhighersteam

temperaturesarerequired.

Thesulfurcontentisalsoanindicationforthesulfur

dewpoint ofthefluegasses.Thewaterinlettemperatureofeconomiser andalsothetubemetaltemperatureoftheair

preheatershouldbekeptabovethistemperatureinorder

toavoidsulfurcorrosion.

42


43/46

Inordertooptimizethefiringprocess

furnacecorrectly.

mpor an ac orsare:

furnaceliberationrate

ExcessairAmountofundergrateandoverfiring

airamounts

Correctinstallationofoverfiring

system

es ence me

Furnacefluegasoutlettemperature43


44/46

44


45/46

Allthosefactorswilldeterminetheunburnedcontentat

.

Theflyashshouldnotbesticky atoutletoffurnaceinorder

toavoid heavyfoulingofthesuperheaterarea

Thetubesintheboilerconvectionsectionwillbearran ed

inlineandinbetweenthetubessufficientdistance willbe

keptinordertominimizethefouling.

Byadequatesteamsootblowingthesurfaceswillbekept

clean.

Thedustcollectedinthehoppersandcyclones'willbere

injectedinthefurnaceonseveralpointsjustabovethe

grateintothefurnacetolowertheunburnedto50%.

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So,beaware:

Fordesigningthemostappropriatefiringandboiler

systemtherangeoffuelshavetobedeterminedin

advanceandlabtestshouldbemadeavailable.

Thenwecansu l as stemwhichwillbein

compliancewithyourrequirementsinsteamand

powersupply,availabilityandreliabilityofthesystem.

Forensuringhighefficiencies,reliabilityandthe

capabilitytofirealargerangeofbiomassandcoalfor

its

life

time

we

recommend

abubblingfluidizedbed

system.

ThankYouForYourAttention

46

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Descon Presentation on Co-Generation 13-07-2010

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