M.Sc. Thesis Evaluation of Technical, Environmental and Financial Viability of Tri – Generation in Apparel Sector of Sri Lanka By Wasana Chinthaka Jagodaarachchi (830926 – P132) Anuruddha Ekanayake (850801 – P817) Master of Science Thesis KTH School of Industrial Engineering and Management Energy Technology EGI‐2013 SE‐100 44 STOCKHOLM
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ABSTRACTApparelindustryisthemainsourceofforeigncurrencyforSriLankaandistheonethatprovides most number of local employments. It has been severely affected by thecontinuousriseoffossilfuelprices.Industryisalsounderpressurebythegovernmentsandbuyers(majorretailchainsandglobalapparelbrandswhohastheirsupplychainemission reduction goals) tominimize the emissions aswell as to reduce the energyconsumption.Inviewofthat,thisstudywasfocusedontheviabilityofusingcombinedheating,coolingandpowergenerationortheTri‐Generation(TG)atfactorylevelwhichhasneverbeentriedintheapparelindustryinSriLanka.After the literature survey, local apparel sector was analyzed and then the factorieswere categorized in to fivemain groups out ofwhich themost affected groupby theenergycost,thefabricmanufacturing,wasselectedasthefocusgroup.Onefactoryfromthefocusgroup,TexturesJersey(TJ)wasselectedfortheinitialcasestudy.Afteradetailenergy audit at TJ, results were used to evaluate the environmental and economicalviability of two selected TG combinations. One with most favorable results wasoptimized and then studied in detail to see if it is environmentally, economically andtechnicallyviabletoTJ.ResultofthedetailanalysisoftheoptimalTGcombinationwasusedtocomeupwithgeneralguidelinestoimplementviableTGplantsforlocalapparelindustry.As per the results TJ can enjoy substantial benefits (15‐35% energy cost saving) byopting touseaTG, firedbyeithercoalorbiomass (sawdustbriquettesor firewood).Biomassispreferredovercoalduetolowpricesandreducedemissions.NotneedingofacomplicatedfuelpreparationandfeedingsystemasinacoalfiredTGsystemisalsoanadvantage of Bio‐mass. However biomass has relatively more supply chain issuescomparedtocoal.Auniversalsolutionthatcanbeusedbyanyapparelfactorycannotbearrived at, as economics of the TG is highly depended on local parameters. Howeverselecting the capacity of a TG based on the process heating demand of a factory isbeneficialifithasa24houroperation.IntermittentoperationofTGisnoteconomicalasfrequentstart‐upandshut‐downofaTGisnotpractical.Further,increasingelectricitygenerationinTGisnotveryattractiveowingtosubsidizedtariffs.
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ACKNOWLEDGMENTS
Firstofall,wearegratefultoourSupervisorsDr.MahinsasaNarayanaandDr.SadJarallfortheirguidanceandsupporttosuccessfullycompletethethesis.Wewouldalsoliketothank lecturers and staff of International College of Business & Technology, OpenuniversityofSriLankaandRoyalInstituteoftechnology,Swedenforthesupporttheyextendedbyfacilitatingandcoordinatingourthesisrelatedactivities.
Wetakethisopportunitytoacknowledgewithmuchappreciationthecrucialsupportbythemanagementand thestaffof theTextures Jersey forgivingpermission toconductthe energy audit and providing access to technical data and financial data for theanalysis. A special thank goes to tri generation plant equipment suppliers andcontractors for providing technical information and other literature relevant for thethesiswork.
CONTENTABSTRACT ................................................................................................................................................. i
ACKNOWLEDGMENTS ............................................................................................................................. ii
Table 5.3:Electricity Generation by Practical Turbine Capacities Calculated for Section 4.4 Design ... 42
Table 5.4: Electricity Use by Plant Equipment for Coal TG Plant .......................................................... 43
Table 5.5: Electricity Use by Plant Equipment for Biomass TG ............................................................. 43
Table 5.6: Fuel Consumption for Coal & Biomass Fired Systems .......................................................... 45
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ListofFigures Figure 1: Main Steps of the Analysis ....................................................................................................... 4
Figure 2 ‐ Energy Flow within Textured Jersey ..................................................................................... 12
Figure 3 ‐ Contribution of Each Energy Source to the Total in Textured Jersey ................................... 12
Figure 4 ‐ Variation of Fuel Oil Cost at Textured Jersey ........................................................................ 13
Figure 5‐ GHG (CO2e) Emission by Source in Textured Jersey ............................................................. 15
Figure 6 ‐ Percentage Energy Consumption by End‐use in Textured Jersey ......................................... 15
Figure 7‐ Daily Electricity Demand Variation in Textured Jersey .......................................................... 16
Figure 8‐ Monthly Cost and Consumption of Electricity in Textured Jersey ......................................... 16
Figure 9‐ Furnace Oil Consumption and Cost Variation in Textured Jersey ......................................... 19
Figure 10 ‐ Possible Electricity Generation Options.............................................................................. 21
Figure 11 ‐ Possible Heating Options .................................................................................................... 21
1 INTRODUCTIONIncreasingdemandforfossilfuelandtheconflictsinthemajoroilproducingcountrieshas ledfossil fuelpriceto increaseuptoa levelwhich isalmostunbearabletotheSriLankan industry. Among all, apparel manufacturing is one of the severely affectedindustriesbythesuddenfuelpricehikes.Asaresultoftheglobaltrendofsustainabledevelopment, pressure tominimize theemissionsby reducing theuseof fossil fuel&electricityconsumption,isanothermajorchallengefacedbythelocalapparelindustry.
ApparelindustryhaslongbeenthemainsourceofforeigncurrencyforSriLankaandisthe industry thatprovidesmostnumberof localemployments.Despite thesignificantgrowth of 13.8% in apparel manufacturing industry during 2011, overall productioncosthasbeenaffectedbyincreaseof furnaceoilpriceby80%,electricitycostby15%andsalaries&wagesby20%during2012.Amongallabove,thehighestandunexpected80% increase of furnace oil price has severely affected mainly to the knitting andweavingindustrywherefurnaceoilboilersareheavilyusedforsteamproduction.
Furthermore, the lower production cost associated with the apparel manufacturingindustries inneighboringcountries likeBangladesh,VietnamandthecountrieswithamassiveindustrialsectorlikeChina,hasmadeitmoredifficulttoSriLankatosustainitsmarket share in the internationalmarket. Hence, local manufactures are desperatelyseeking methods to reduce manufacturing cost, to keep their business runningsuccessfully. Since the lack of controllability over the production related costs likematerialcost,machinerycost,costoflabourandetc,themostviableoptionistoreducecost of energy incurred inprovidingutilities, such as air conditioning, lighting, steamgenerationandcompressedairgeneration.
Implementation of various energy efficiency methods and use of energy efficientequipmenthavebeenthetoppriorityactivitiestoreducetheenergyconsumption.ThisstudyisfocusingontheviabilityofusingTri‐GenerationatfactorylevelwhichhasneverbeentriedinSriLankanapparelmanufacturingindustry.
1.1 ProblemStatementandMethodology
A typical Sri Lankan apparel manufacturing factory requires electricity to run itsmachineries,airconditioning&Ventilationsystem,lightingsandutilityequipmentlikecompressors and pumps. Fossil fuels like Diesel and furnace oil are used to fulfillthermal energy requirements and to operate boilers to generate required steam formanufacturingprocess.Mainobjectiveofthisstudyistoanalyzingtheviabilityofself‐generation of required electricity while fulfilling the steam and cooling demand byimplementingacombineheating,coolingandpower(CCHP)plantwhichiscommonly
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knownasTri‐Generationintheindustry.TheTri‐Generationarrangementthathasbeenanalyzed in below chapters includes a high pressure steamboiler, a steam turbine, awasteheatrecoverysystemandabsorptionchillers.
AlthoughfossilfuelsuchasDieselandFurnaceoilarenoteconomicallyviableoptioninSri Lanka due to high price, same are commonly used in the apparel sector as it isreadily available and easy to use. Coal and biomass are the two identified candidatefuelsandthechallenges(economical,technicalandenvironmental)ofusingthosefuelsfor thecombinedcooling,heatingandpowerplantneedtobeanalyzed.Basedon theresults,plantequipmenthastobeselectedeithertypeoffuels.
Next is to study the viable options to supply of low pressure steam for themanufacturing process while maintaining the high pressure steam to the turbine.Directly taping thehighpressure steamanduseofpressure reductionmethodologiescan be identified as one option whereas the tapping steam from various workingpressure from the turbine is another option. Above two options and possible othermethodsneedbestudied to identify technicalcomplexitiesandeconomical feasibility.Installation of water treatment plant to meet boiler feed water standards andappropriate emission reduction methodologies to meet with country and board ofinvestment (BOI) environmental regulations also has to be evaluated. Suitable fuelstoragecapacityandfuelfeedingmechanismhastobechosentoensureuninterruptedfuelsupplytoboiler.
Feasibilityofrunninganabsorptionrefrigerationcyclechillerwhichutilizesthewasteheat of steam turbine need be evaluated, against running of a vapor compressionrefrigeration cycle chiller fromelectricity. In a typical apparel factory air conditionedload accounts for about 40 to 50% of the total electricity consumption. Use of anabsorption refrigeration cycle chiller that runswithwaste heat substantially reducesthe above electricity demand and it downsizes the required steam turbine capacity.Smallerturbineresultsinalessamountofwasteheatthatwouldnotbesufficienttorunthe absorption refrigeration cycle chiller of the required capacity. Therefore it isrequiredtostudytheoptimumcapacitiesofallplantequipment.Beingonlyself‐sustainwiththeelectricityandfeedingthegridwiththeexcesselectricityarealsotwooptionsthatneedtobestudied.
Toanalyzetheabovesaidvariousoption,bothmanualandcomputerbasedcalculationmethodsareused.EngineeringEquationSolver(EES)andMicrosoftExcelspreadSheetsare the main software used for the evaluations. EES and MS Excel are manuallyprogrammedforthecalculations.Resultisthenusedtosimulatethebuildingoperationsand energy consumption patterns to calculate the optimal economical andenvironmentalbenefits.
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Therearemanyoperatingtri‐generationfacilitiesintheworldandalsolotofresearchhasbeencarriedoutbyvariouspartiesaboutthetechnology.Howeverashighlightedinthe previous sections, main issues to be addressed in this research is the lack ofknowhowinlocalindustry,meetingprocessrelatedrequirementsotherthantheenergyrequirementsandevaluationofsustainabilityoftri‐generationinthelocalcontext.
A literature survey was carried out in order to find out the current status of Tri‐generationplantsofthesimilarcapacityandapplication.Widerangeofkeywordsandvarioustoolswereusedtocarryoutthesurveytoensurethatthemostrelevantpapers,articles and case studies about this topic are referred. Two main component of theproject, namely the combined heat & power component and the cooling component(boththermallydrivenandelectricallydriven)ofsamecapacityrange,werefocusedinthesearch.Furtherliteraturereviewswerecarriedoutastheresearchprogresstoplantdesign stage, to find out the technical data of the various products required for thefunctioningoftheplant.
SummaryofrelevanttheoreticalanalysisofTri‐Generation,availabletechnologiesandthe developments and the results case studies of similar plants listed below in thereport.
2.1 TheoryandTechnology
Generation of electricity, useful heat and cooling using fuel combustion or by othermean of heat source is commonly known as combined heating, cooling and powergenerationorTri‐generation.InatypicalTri‐Generationplant,gasorsteamturbineisruntogeneratetheelectricityusing high temperature / high pressure source and this result in relatively lowtemperature waste heat. This waste heat is then used for heating and to generatecooling by an absorption chiller. Advantage of this kind of system is the ability ofattaininghigheroverallefficiencycompared toother typeof traditionalpowerplants.Efficiencyofatri‐generationplantiscalculatedasshownbelow.
“Tri‐generationinfoodretail:anenergetic,economicandenvironmentalevaluationforasupermarketapplication”bySugiarthaetal[5],discusses theresultsofanevaluationofeconomic and environmental performance of a Tri‐Generation plant for supermarketapplications. Analysis is based on factors such as fraction of the heat output used todrivetheabsorptionchillers,thechillerCOPandthedifferencebetweenelectricityandgas prices. As per this analysis of Sugiartha et al, three is obvious economical andenvironmental benefits compared to the conventional system. Further, both theeconomical and environmental benefits are optimized by operating the plant at fullelectricityoutputratherthanfollowingtheheat load.Economicsof theplant ishighlydependsoncostofelectricity,costofgasandtheCOPofthecoolingsystem.Main difference between this system and the proposed system to be studied is thenatural gas turbine. Proposed systemhas a steam turbine and theNatural gas is notconsideredasanoptionasitisnotavailable.Smallgenerationcapacity(80kW)andtheapplication (supermarket) are also differing much from an industrial application.HowevertheeconomicalmodelusedfortheanalysisprovidegoodbasicframeworktodevelopamodeltoTri‐GenerationinapparelindustryinSriLanka.
Andrea Costa et al[1], discusses about an industrial application in their paper“Economics of tri‐generation in a Kraft pulp mill for enhanced energy efficiency andreduced GHG emissions”. The most important thing in this paper is the similaritycomparedtothecaseofanapparelfactory. Thepulpmillthathasbeenstudiedhasarequirement for cooling and steam at different pressure levels. Cooling ismet by anabsorptionchiller.AndreaCostaetalpropose threeoptionand theyconclude thatallthree have economical benefits. However results show that system without powergeneration(withonly theabsorptionchiller)has thehighestsimplepaybackwhereastheoptionwithtri‐generationhashighnetpresentvalues.
Unlike the caseof anapparel factory, “Economicalanalysisoftri‐generationsystem”bySüleyman Hakan et al[8], present results of a research carried out on tri‐generationapplicationinauniversitycampuswhereheatingisutilizedforbuildingheating(notforprocess heating). However one important objective of this paper is to come upwithmodeltodetermineoptimumcapacityofatri‐generationsystem.Moreoverit isaboutthe economics of embedding a tri‐generation system to existing systemwhich is thecaseinsystembeingstudied.
Thoughhavingahighenoughcapacitytosupplyallenergydemandsofthebuildingisthe requirement of the Tri‐Generation, research result indicates that meeting totalenergydemand could increase the investment thereby resultinghigherpayback time.Main reason behind this scenario is the non existence of the peak demand for longperiods. However the situation could be different in industrial facility located in atropicalclimate.
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Lozan et al present in their paper, “ThermoeconomicAnalysisofSimpleTri‐generationSystems”, a much generalized economical analysis of a simple tri‐generation system.UnlikemanypapersonTri‐generation,thisstudyisnotlimitedtoaspecificapplication.Thesystemisconnectedwith themainelectricitysupplygridallowingsystemsupplyexcesselectricitytogridandtoreceivetheshortage. Paperismoreorientedtowardstheeconomicsratherthanthetechnicalaspects.Lozanetal[4]haveusedalinearprogrammingmodeltoobtainthemodewiththelowestvariable cost, out of series of options available to meet a given demand of a user.Analysisusesthreedifferentapproachestocalculatethecostoffinalproductandeachapproach results in different costs. Thismeans that a universal approach cannot beusedforeconomicalevaluationofTri‐generationandtheviabilityiswidelydependsonthespecificapplication.
Fromthedatacollectedduring literaturereview, it isevident that this technologyhasbeenusedinapplicationwherethereisasubstantialdemandinelectricity,coolingandheating (process or comfort heating). Further themost of the applications hasmuchhigherdemandforall threeformofenergythanatypicalapparel factory inSriLankaand the demand has more of distributed form (Similar to district systems, militarycampsandcampuses)thanamediumscalemanufacturingfacility(SimilartotypicalSriLankanapparelfactory).Itisclearthatthesetwofactors,thedistributeddemandandthe substantially higher demand are key factors that affect the economics and thesustainabilityofaTri‐generationfacility[6],whichisnotthecaseofanapparelfactory.
Howevertheavailable literatureandthecasestudiessuggestthatthis technologycanbe used in applicationswhich do not exhibit above characteristics, depending on thestatusoftheotherparameters.Followingcanbeidentifiedastheparametersthatwillaffect the economical viability and the overall sustainability of a tri‐generationapplicationinanapparelfactory.
a) Cost,qualityandtheaccesstoavailableenergyb) Scaleofthefacilityandtheoperationhoursc) Environmentalconstrainsandtargets
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3 ResultsofEnergyAuditConductedinSelectedFactoryFirststepofthisstudywastoidentifyanapparelfactorywhereallthreeformofenergyuses namely; electricity, process steam (Heating) and air conditioning are used andconductadetailedenergyaudittoidentifytheconsumptionpatternoftheeachform.
In identifyinga facility, themanufacturingprocessesofvariousapparel factorieswerestudied and it was noted that those can be categorized in to several different typesbased on theirmanufacturingprocesses. Following are themain categories identifiedduringthestudy.
Table 3.1: Comparison of Identified Factories of Different Categories
From above categories, a fabric manufacturing facility (Textured Jersey Lanka,Avissawella) was selected for initial energy audit after studying factors that arepotentiallybeneficialforTri‐generationplant.Table3.1indicatesasummaryofenergyconsumptionandcoolingrequirementsofeachoftheindentifiedfacilities.
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3.1 FactorsConsideredinSelectingtheFacilityFromtheinformationfoundduringtheliteraturereviewsandthebackgroundsearch,itwas learned that there are many factors that would affect the viability of a tri‐generation plant. Based on that knowledge, severalmain factorswere identified andconsideredinselectingtheabovefacilitytoconductanenergyaudit,resultofwhichwillsubsequentlybeusedtoevaluateviabilityofthetri‐generation.Factorsconsideredarelistedbelow,
ImpactbytheEnergyCostIf a cheap source of energy is available, none of the activities such as self‐generation, use of renewable energy sources and investing on energy savingmethodmaynot paid back inmonetary terms. Therefore itwas considered toselectafacilitywherethecostofenergyisveryhighcomparedtootherswhichwill induce a higher possibility of economical attractiveness for the Tri‐Generation.
ExtensiveSteamUsageAsexplainedabove,tri‐generationplantsproduceelectricity,coolingandheatingsimultaneously.Therefore,forsuchaplanttobeviableitisessentialtohaveenduse that require above three form of energy. The only usewhere heat can beutilizedistheprocessrelatedapplications,sinceSriLankaisatropicalcountrywherespaceheatingorservicehotwaterisnotarequirement.Fabricmanufacturing factories require thermal energy fordyingmachines andStentormachines,whereasmostoftheothertypesuseonlyforironingpurpose(Generally this is based on steam generation). Since a substantial amount ofsteamisgoingtobeavailableafterthepowergenerationinsteamturbineitwasdecidedtoselectafacilitywithsubstantialsteamconsumption.
EnvironmentalTargetsAnother importantchallenge facedbytheapparelmanufactures inSriLanka ismeeting the environmental targets such as reduction of carbon foot print,enforcedbytheirinternationalbuyersandvariousregulatorybodies.Therehadbeenmanyinstancesintheindustrywheremanagementinvestingonmeasureswhichareeconomicallynotviable,tomeettheenvironmentaltargets.Therefore,it was assumed that a facility with environmental targets such as emissionreductionshouldbeconsideredfortheenergyaudithopingthatcertainmeasureof Tri‐Generation will be environmentally viable even if those are noteconomicallyattractive.
for subsequentuses[2].Therefore itwasassumed thataplantwithcomparablyhighenergyconsumptionhastobeselectedforthestudy.
SubstantialAirConditioningLoadOneoutcomeofTri‐generationisthewasteheatthatcanbeusedtooperateairconditioning systems, which operate with the absorption cycle. If the airconditioningloadisverysmallsuchwasteheatwouldnotbeadequatelyutilized.
ResourceAvailabilityforCogenerationPlantTri‐generation isnot viable if other required resource suchas space, access towater,transportationandetcatsitearenotavailable,regardlessofthestatusofthefactorsmentionedpreviously.
3.2 OverviewoftheSelectedFacility
3.2.1 GeneralOverviewTexturedJerseyisoneofSriLanka'smostsophisticatedfacilities,manufacturingknittedfabricsfortheintimateapparel(lingerie)andsportswearindustries.Specializedinthemanufacturing of high quality weft‐knitted and dyed stretch fabrics, it is a majorsuppliertoapparelmanufacturersthroughoutAsiaandend‐chainretailers.Amongstitsbuyers,thelargestareMarks&SpencerandVictoria'sSecret.Textured JerseywasawardedtheprestigiousOeko‐TexStandard100Certification,aninternationally recognized test forharmful substancespresent in textilemanufacture,which is now the benchmark for quality and safety amongst the textile industry inEurope.
TexturedJerseysuppliesitsproductstothetwolargestGroupcompaniesproducingitscore products, specializing in stretch fabrics. Infrastructure at the facility enables acapacity to knit, dye and finish up to 2.5millionmeters of fabrics amonth.With thecontribution of the annual turnover, TJ can be called as a backbone of Sri Lanka’sapparel sector. Textured Jersey’s contribution to the total annual turnover in wholeapparelsectorwas2.6%inlastfinancialyear.
Manufacturing process of the facility is of three‐steps which take place across threemajorproductionunits:
3.2.2 EnergySources&ConsumptionsTexturedJerseyobtainsitenergydemandfromthreemainenergysourcesasshowninTable3.2andthecostincurredinyear2011&2012toobtaineachofthesourcesaregiven in the table3.2.Financial statementofTextured Jersey for theyearending31stMarch2012isgiveninfollowingTable3.4.
Table 3.4 : Financial Statement for Year 2011/2012 of Textured Jersey
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FlowofenergytoendusegiveninTable3.2fromthreeenergysourceisshowninbelowFigure 2. Out of three sources furnance oil contribute to the highest amoutwhich isabout~80%of the total as shown in Figure 3. Electricty consumption contributes torestofthe20%.Dieselinonlyusedasstandbyenergysourcehencethecontributionbythesameismearly1%.
Figure 3 ‐ Contribution of Each Energy Source to the Total in Textured Jersey
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3.3 ImpactofEnergyconsumption
3.3.1 EconomicalImpactTherecentamendmentof furnaceoilprice shown inFigure4 (fromLKR50 toLKR90perliter)hasseverelyaffectedtheoperationalcostwithanincreaseof55%.Accordingto the global fuel market, more hikes are anticipated in the future, rather thanmomentaryreductions.Hence,maintainingtheproductioncost isbecomingmoreandmorechallenging.
Figure 4 ‐ Variation of Fuel Oil Cost at Textured Jersey
Table 3.5 : Expected Cost Increase of Furnace Oil in Sri Lanka
Note: Years are financial years from April to March
As per the Table 3.5, increase of furnace oil price has resulted in extra cost of LKR386,750,000 annually. Table 3.6 is a comparison of the financial figures, if the sameamount of sales, same amount of fuel consumption and no change in other cost areassumedforyearstocome.
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10.0
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Table 3.6 : Expected Financial Statement for Year 2012/2013 with the FO Price Hike in Textured Jersey
Manufacturingfacilitycanadversely impacttheenvironmentbyvariousmeans.GreenHouseGas(GHG)emissionduetoenergyconsumption,landfillduetowastegeneration,use/pollutionofwaterresourcesandheatislandeffectaresomeofthemostcommonscenarios that adversely affect the surrounding of any factory or a manufacturingfacility.Onlytheenvironmentalimpactduetoenergyconsumptionisstudiedunderthissince a setting‐up of tri‐generation facility will only contribute to change in GHGemissionrelatedtoenergyconsumption.
Currently ‘Textured Jersey’ is using three energy sources; namely electricity,combustion of Furnace Oil to run Boilers / Oil heaters and Diesel for stand bygenerators. Another indirect contributor (related to energy consumption) isrefrigerantsusedinairconditioningsystem.
As per the records kept by the maintenance department of the facility, annualconsumptionofeachsourceofenergyisgivenintheTable3.7.
Figure 6 ‐ Percentage Energy Consumption by End‐use in Textured Jersey
Figure 5‐ GHG (CO2e) Emission by Source in Textured Jersey
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3.4.1 ElectricalSystem
The facility comprises of 6000 kVA transformer capacity and average maximumdemand is around 3400 kVA. As per the logged data, the demand for electricitythroughout the day is not fluctuating significantly, except the small drop during thenighttime.Figure7indicatestheaveragedailyvariationoftheelectricaldemandofthefacility. Since there are no seasonal variations this can be assumed as the averagethroughouttheyear.
Figure 7‐ Daily Electricity Demand Variation in Textured Jersey
3.4.2 AirConditioningSystemTheairconditioningsystemismainlytomaintain the thermalcomfort inofficeareas.Sincethecurrentsystemistobereplacedwithheatdrivencoolingsystem,itisessentialstudytheenergyconsumptionpatternofthecoolingsystem.ThereforeconsumptionofthemajorcomponentoftheACwasloggedusingdataloggersandconsumptionoftherest of the equipment was calculated using spot readings. Component of the totalinstalledairconditioningunitsareasgiveninTable3.10.
Operatinghours 7Daysperweek 12hrsperdayTable 3.10 : Summary of AC Equipment in Textured Jersey
3.4.3 BoilerandSteamSystemCurrently the facility operates three furnace oil boilers and three furnace oil firedthermic oil heaters. Specification of boilers and thermic oil heaters are as shown inTable3.11&Table3.12.
Table 3.12 : Specifications of Thermic Oil Heaters in Textured Jersey
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Outoftotalfurnaceoilconsumption,60%isconsumedforsteamboilersand40%isforthermic oil heaters. No significant fluctuation of process heating demand has beendetectedthroughouttheday.Table3.13indicatesthedetailsofsteamrequirement.
Figure 9‐ Furnace Oil Consumption and Cost Variation in Textured Jersey
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4 PossibleCombinationsforTri‐GenerationPlantBased on the result of the energy audit and historical data analysis of the “TexturesJersey”, it isobviousthatmeetingtheprocessheatingdemandof theFacilitybymoreeconomical mean is the most important aspect to increase the profitability of thefactories. Since this study is investigating viability of the Tri‐Generation, all possiblecombinationsforasuchplantwasstudiedtoidentifytheprospectiveoptionsthatwillbebotheconomicalandenvironmentalfriendly.Followingflowcharts(figure–10andFigure11)listallpossibleoptionofTri‐GenerationsuitableforTexuresJersey.
Figure 10 shown below indicates posible combinations available for electricitygeneration.Thethreemainoptionsforelectricitygenerationaretogeneratepartoftheexisting electricity demand, generate electricity to satisfy existing demand, andgeneratingelectricityinexcessofexistingdemand.
Capacity requirementof the firstelectricitygenerationoption is arrivedby sizing theplant to meet the existing process heating demand of the facility. In this option, thesteam requirements and the qualities will be considered to back calculate the boilercapcacity and threby the turbine capcity. Another possible sub option to be studiedsubsequentlyunderthisistoseeifthereisacapacitylessthantheabovewhichcangivemoreoptimumresults.
Viabilityoftwodifferentelectricitygenerationcapacitiesneedstobestudiedunderthesecondoptions.Onecapacitywillbecalculatedassumingtheplanttobeaco‐generationfacilityratherthanTri‐generation.Underthis,itisassumedthattheproposedplantwillmeet the existing electricity demand (including energy requirement by vaporcompression chillers). Next option is to size the steam turbine to meet the existingelectricity demand excluding the energy requirement by vapor compression chillers.Important thing to study under this option is to see if heating requirement of theAbsorption cycle chillers can be met economically with the reduced capacity of thesteamturbine.
Third electricity generating option as per figure 10 is to generate excess energycompared to the existing electricity demand. Two possibilities identified under thiscategoryistogenerateenoughelectricitytofeedthegridortogeneratetheelectrictyrequiredforoilheatinginThermicoilheaters.
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ProcessHeatingEnergyRequirement
SteamGeneration
HighPressureSteam
LowPressureSteam
FromHighPressureBolier
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calculatedBasedonProcessheating
GenerateCurrentDemand
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FeedtheGrid
Figure 11 ‐ Possible Heating Options
Figure 10 ‐ Possible Electricity Generation Options
EndUsesofHeatEnergy
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As shown in the figure 11 the process heating requirement of the facility is of threeforms; namely steam formanufacturing process, oil heating for Thermic heaters andheat for absorption cycle chillers, if installed. Steam for manufacturing process isrequiredintwosubformsnamely;lowpressuresteamat6barandhighpressuresteamat10bar.
Thereare twopossiblecommonmethodsbywhich thesteamcanbeobtained for themanufacturingfacility.Oneistoobtainedsteamdirectlyfromthehighpressuresteamboiler (a high pressure boiler anyway has to be operated for a TG) and uses it formanufacturing process by reducing the pressure to suitable levels using a pressurereducing valves. Second commonmethod is to tap the steam turbineat suitable leveland obtain steam for the processes. In addition to these two commonmethods, lowpressuresteamcanbeobtainedbyusingthesteamexitingtheturbine.
4.1 BaselineOptionsforPlantArchitectureWhenfigure10andfigure11areconsidereditisobviousthattherearemanyoptionsforthearchitectureofTri‐generationplant.Sinceevaluationofalloptionsinfigure10and figure 11 is not practical (some options are not worth evaluation for obviousreasons)twobaselinesystemarchitectureswereidentifiedtowhichothercombinationwouldbecompared.
Since it is unknown as to which combination would have the best viability at initialstage,several factorswereconsideredinarrivingatbaselinesystemarchitecture.Oneofthemainfactorsconsideredistheeconomicsoftheplantsthathavebeenevaluatedbyvariousauthorsinpreviousstudies.Manyofthosepaperssuggeststohaveabestnetpresent value it is necessary to include cooling (absorption cycle) to the chiller andmaximize electricity generation while meeting the heating requirement withoutgenerating excess heat. Plant architectures give in related case studies; heatingrequirementsandthequalityof therequiredheataretheotherparametersthatwereconsideredindesigningthetwobaselinecases.
Asshowninfigure12andfigure13bothbaselinecasesincludehighpressureboilers,steamturbineandanabsorptioncyclechiller.Thosetwodifferfromeachotherbyonlyoneaspect; thepointatwhich thehighpressuresteam isobtained. Inoption01highpressure steam is obtained directly from the boiler whereas in option 02 same isobtainedbytappingthesteamturbineatasuitableintermediatepressure.
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E
Cooling tower
To Production
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High Pressure Steam
for production
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Figure 13‐ Baseline Option 02 Schematic Diagram
Figure 12‐ Baseline Option 01 Schematic Diagram
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When heating requirement and the required quality of the heat is considered, it isobviousthattheabsorptioncyclechillerrequiredthelowestqualityheat.Inviewthat,absorptionchillerswerearrangedinbothaboveoptiontoreceivethesteamexistingtheturbineassumingthatitwouldhavethehighestviabilityoutofmanyoptions.Similarlylowpressuresteam(6bar)hasassumedtobeobtainedfroma intermediatepressurelevel from thegas turbine inbothoptions. Thisarrangement for lowpressure steamwasselectedassumingthatitismoreviabletoallowsteamfromtheboilertoreduceitpressure through the turbine rather than drastically reduce pressure directly from apressurereducingvalve.
Following section includes the theoretical calculations that have been preformed toevaluateabovetwooptions,resultofwhichhasbeenusedtoevaluatetheaccuracyofassumptionsmadeand to identify furtheroptions, if any, tobestudied fromtheoneslistedinfigure10and11.
4.2 CapacityEstimationforProposedPlantArchitecturesAsnotedearlieratrigenerationplantcanbedesignedeithertomeetagivenamountofelectricitywhilemeetingpartorallheatingrequirement(electricitybaseddesign)oritcan be designed tomeet a given amount of heatwhilemeeting part or all electricityrequirement(heatingbaseddesign).Sincetheobjectiveofthisstudyistofindoutthemost economical mean, two basic calculation approaches that represent the twoextremeoperatingconditionsoftheabovetwodesignoptions(electricitybaseddesign/Heatingbaseddesign)wereidentifiedtocarryoutthetheoreticalcalculation.ThetwobaselineTGoptions represented in Figures 12&13were then evaluatedusing thesetwo calculation approaches. Graphical representation of the calculation process isshowninfigure14andthedetailsoftheseapproachesaregivenbelow.
Approach01:FirstapproachistoevaluatetheperformanceofaTGplantdesignedbasedonagivenelectricitydemand.As the theoretical extremecondition, itwasassumed thatplant issized to have an electricity generation capacity that will be sufficient to meet theexisting demand of entire facility (excluding vapor compression chillers). Under this,effects (on boiler capacity) of various inlet pressures and temperatures of the inletsteamofturbineareevaluated.Sincetheresultsofthisevaluationrepresentthestatusin an extreme design condition, same was used to identify whether electricitygenerationcapacityshouldbeincreasedordecreasedtoimprovetheplanteconomics.
Approach02:SecondapproachistoevaluatetheperformanceofaTGplantdesignedbasedonagivenheatingdemand.Asthetheoreticalextremecondition,itwasassumedthattheplantissized to have a heating energy generation capacity that is sufficient to meet the
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productionrelatedsteamdemandandtheheatdemandoftheabsorptioncyclechillers.Under this also, effects (on turbine capacity) of various inlet pressures andtemperatures of the inlet steam of turbine are evaluated. Since the results of thisevaluation represent the status in an extreme design condition, same was used toidentifywhetherheatingenergygenerationcapacityshouldbeincreasedordecreasedtoimprovetheplanteconomics.
4.2.1.1 CalculationBasedonOption01(HPSteamDirectlyfromBoiler)AcomputerprogramwrittenusingEngineeringEquationSolver(EES)hasbeenusedtocalculate the possible electricity generation capability for various standard boilercapacities and boiler operating conditions (Pressure and Temperature) when highpressure steam is directly taken from the boiler and low pressure steam is taken bytapping the turbine. EES Program and the calculation procedure are given in theAppendixB.
AssumptionsMadeforCalculation:Assumptions were made for calculation based on industry accepted norms, currentoperating conditions, values published is various papers and data provided byequipmentmanufactures.Followingarethelistofassumptionsmade.
SimilartoprevioussectionEngineeringEquationsolverhasbeenusedtocalculatethepossible electricity generation capability for various standard boiler capacities andboiler operating conditions (Pressure and Temperature) when both high pressuresteamandlowpressuresteamaretakenbytappingtheturbine.EESProgramandthecalculationprocedurehavebeengivenintheAppendixB.
AssumptionsMadeforCalculation:Assumptions are same as section 3.2.1.1 except the location of extraction of the highpressuresteamusedformanufacturingprocess.
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5 PlantOptimizationFollowing section describes the possible optimizations that would provide mostbenefits to the load pattern of the selected apparel factory. Optimization possibilitieshavebeenidentifiedbasedonthefindingoftheChapter‐04.
Oneofthemostimportantfindingisthedifferenceinenergycostsavingswhenhigh pressure steam is tapped off from the turbine compared to directlyobtaining steam from the steam boiler through a PRV. As per the abovecalculationsformercangenerate~20%moreelectricitywithoutadditionalfuelthanlaterwhichcontributestotheincreasedsavings.Inadditiontothatcapitalsavingcanbeachieved,asformerneedsasmallercapacityboilertogenerateagivenamountof electricity compared to the later. Thisobservationeliminatesthe requirement to analyze the further plant architectures (options base onfigure‐10and11)thatdirectlyobtainhighpressuresteamfromtheboileritself.
Each of the graphs that represent the calculation results indicates that theincreasedoperatingpressureandtemperatureofagivenboilercapacityresultsincreasedcostsavings.Furtherforagivenoperatingpressureandtemperaturelowest capacity boiler gives the highest savings, regardless of the higherelectricity generation by the higher capacity boiler. This is mainly due to theincreasedfuelcostingeneratingmoreelectricity.
Anotherprominentobservationissizingtheplanttomeettheelectricityresultsin lower energy cost saving than sizing the plant to meet process heatingdemand. This scenario is caused by the increased fuel cost as noted in thepreviouspoint.
If coal is used CO2 emissions are always higher than current emissions of thefactory,fortri‐genapplications.
One Option to avoid the energy waste would be to tap out steam at a suitableintermediatepressure levelwhich is justsufficient tomeet theenergyrequirementofthechillerwhileallowingexcesssteamtofurtherexpandthroughtheturbinebyusingacondensingtypesteamturbine.Howevertheveryhighcapitalcostofcondensingtypeturbines(canbe50%to70%higherthanbackpressuretype)negatestheeconomicalbenefitsofeliminatedenergywastage.Henceforthissortofapplicationsitisbesttouseabackpressuretypeturbinewithminimumenergywastage.
Theonlyway that excess energyavailable for absorption chiller canbe reduced, at abackpressuretypeturbinesteamexit, isbyreducingthesteammass flowrate(smallboiler). Even when the result of Chapter‐04 and the observation mentioned in theprevious section are considered, it is obvious that smallest possible boilers has to beoperated in the suitable pressure (Operating Pressure shall be decided based oneconomical result of the economical analysis) to obtain optimum economical andenvironmentalresults.
Further the generating steam at high pressure and using them at a lower pressurethroughapressurereducingvalveisalsoleadstounnecessaryenergyuse.ThereforeitisevidentthattheplantarchitectureproposedinFigure12(BaselineOption02)isthemostsuitableforthissortofapplication.Detailedplantarchitecturedevelopedbasedonfigure12systemispresentedandanalyzedintheSection4.4.
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5.3 TechnicalFeasibilityandOtherIssues
Ifrequiredknow‐howisnotavailableorothertechnicalbarriersarepersisting,wholeTGbecomes infeasibleregardlessofeconomicalandenvironmentalviability.SinceTGplantsarenotbeingusedinSriLankaasofnow,itisimportanttoidentifythepossibletechnicalissues,ifany,thatmayariseinimplementingthesame.Thisisawellestablishtechnology where hundreds of researches have been carried out to improve theefficiencyovercomeothertechnicalissues.Henceitisobviousthatimplementingsuchasystemwon’t be hindered by fundamental technical issues.However there are issuesuniquetolocalconditionsandtothesectorthatneedtobesortedout.
Though not used before locally, combine heat, power and cooling systems have beensuccessfully installed and commissioned in theneighboring countries like India. Also,therearelocalexperts,suppliersandconsultantswhohaveundertakendesign,supply,installationandcommissioningofindividualcomponentoftheTGplantssuchassteamturbinepowerplants,chilledwatersystems,highpressuresteamboilersandetc.Hencetransferringtechnologycanbedoneeasilymakingtheimplementationoftri‐Generationsystemstechnicallyfeasible.Howevercertainissuesneedtobeaddressedifsuchplanttobeimplemented.
CoalSupplyCoalhastobeimportedasitisnotminedlocally.Importingcoalinsmallandmediumquantitiesisnoteconomicalduetoshippingandhandlingrelatedissues.Hencecoalhastobeimportedinbulkorders.Thereisverylimitednumberoflocalindustriesthatusecoal. Stateownedutility company, theCeylonElectricityBoard (CEB)and thebiggestlocal cementmanufacture, theHolcimLankaPLC are theonlybulk importers of coal.ThereforeanyonewhowishestousecoalinmediumquantitieslikeforTGplantshastocollaboratewitheitherofaboveparties.SinceCEBisagovernmententity,itisdifficultfor private sector institutes (like apparel factories) to enter in to collaboration.ThereforecomingintoagreementwithHolcimcanbeseenasthebestoptions.
Coal imported by Holcim arrives in vessels to Trincomalee port which is located inNorth East coast of the Country. Transportation from there to the site has to bearrangedbycoveredtrucks.
Bio‐MassSupplyAs per “The Biomass Energy Sector in Sri Lanka, Successes and Constraints” byJayasinghe P., 2,873,880 MT of bio mass is produced per year by waste of variousindustriesandcommerciallygrowntrees[7].Howevermostof thesearewastedduetonon‐availabilityofproperdemandandsupplymechanism.MostofthecurrentBiomassfuelsupplierssupplywoodlogsthoughsameisavailableinmanyformssuchaspaddy
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husk,sawdustandbriquettes.Furtherwiththedrastichikeoffurnaceoilprice,manyindustrieshavestartedmovingtowardsbiomassboilerstoreducethefuelcost.Thus,anew demand for biomass suppliers and a significant shortage of supply can also beobserved.
Therefore establishing consistent supply of Biomass has to be addressed at the verybeginningof theproject.Failing todosowill fail the totaleffortput in to theTG. SriLankaBoardofInvestmenthasintroducedaregistrationsystemofauthorizedbiomasssuppliers.Sowhoeveriswillingtousebiomassasfuelinindustrialscalehavetohaveagreements signed with minimum of three authorized biomass suppliers afore thepermission.
5.3.2 IssuesRelatedtoFuelStorageLiquid fossil fuel has a higher calorific value compared to coal and biomass and thecountryhasawell‐establishedsupplychainforthesame.Thereforelargestoragesthatwouldlastforweeksarenotrequired.Howeversolidfuelslikecoalandbiomassneedbiggerstoragesandmoreattentionduetocertaintechnicalmatters.
CoalStorageThemain technical issues related to coal storage are the finding of adequate storagespace, possiblemoisture contamination and environmental pollutions. Therefore, nothavingasuitablestoragespacecanfailtheentireproject.Around60Mtofcoalisrequiredondailybasisfortheplantdesignsubjectedtostudy,whichrequireapproximatelya40–50m3areafordailystorage.Therefore,asthefirststepofimplementingTG,astoringareashouldbeidentifiedtobothtruckunloadingandboilerfeeding.ThenasuitableshelteroracoveringmechanismhastobeimplementedtopreventstockpiledcoalabsorbingmoisturefromrainwhichwillreducetheLHVoftheCoal. It isalsovery importantto takeactiontopreventcoalgettingwashedoffbyrainandblownoffbywindtoavoidcoalwaste,contaminationofnearbywaterbodies,contaminationofsoilandair.
CoalPreparationCoalhas tobe crusheddependingon the typeof combustorused in theboiler.Threemain combustionmethods have been studied for suitability. Coal crushing causes airpollutionaswellasnoisepollution.Hencethisprocessshouldbecarriedoutinenclosedenvironment,withspecialrespiratorsandheadphones.CoalcrushingsystemhastobedesignedtomeettherequirementsstipulatedbyBoardofInvestment.
BiomassPreparationIssuesrelatedtobiomasspreparationdependonthetypeoffuelused.Ifwoodlogs(firewood) are used as fuel it is very difficult to design an automatic or semi‐automaticfeedingsystemasfuelisfedaslogs.Theonlywayoutistousemanuallaborwhichcanbenotveryfeasibleforlargecapacityplants.
SelectionofCombustorSelectionofcombustorhastobedoneconsideringthetypeoffuelused.Movinggratetype,pulverizedandfluidizedbedcombustorarethethreemaintypestochoosefrom.MovingGrateCombustorMoving grate combustor is one of the oldest technologies which utilizegratefiringwherethecoal ismechanicallydistributedontoamovinggrateatthebottomofthe combustion chamber in partially crushed gravel like form. Air for combustion isblownupward through thegrate, so it carries the lighter ashandsmallerparticlesofunburnedcoalupwithit.Nospecificcrushingisneededforthistypeofcombustor,butsystemefficiencyislower.The main advantage of this technology is the ability to progressively move the fuelwithinthecombustionchamber. Itsabilitycombustwetfuels isadvantageousforbio‐massfiredTGplants.Asthefuelmovesforwardthoughamovinggrate,itgoesthroughdifferentstagesofcombustion.Atfirstthefuelentersthecombustionchamberandisimmediatelyexposedtotheheatofthecombustionchamber,atthisstagethewetfuelstartstodry.Thenthefuelsubjectscombustionandfinallyendsupinashpit.
PulverizedCoalCombustorPulverizedfuelboileristhemostcommonlyusedmethodinthermalpowerplants.Coalispulverized (ground) toa finepowderwith less than70–80µmparticle sizes.Thepulverizedcoalisblownwithpartofthecombustionairintotheboilerplantthrougha
seriesoSchema
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Result shown in theTable5.1abovehasbeenobtained for theplantdesignshown insection 5.4 by using the same calculation procedure used in Section 4.2.1.2. Theresultant gross electric power output indicates theoretical values that need to becorrectedforthecapacityofsteamturbinethatareavailableatthemarket(eg:1000kWturbine should be considered instead of theoretical value of 1015kW). In the caseswheretheoreticalgrosselectricpoweroutputhastoberoundedup(eg:11921200)operatingpressuretemperaturehastobeadjustedaccordingly.Highlightedcellsinthe
above table need to be adjusted suit the practical application. Table 5.2 indicates theactualturbinecapacities,adjustedtemperaturesandpressures.Case BoilerOperating
5.5.2.1 ElectricityGenerationSamecalculationprocedureusedinChapter04hasbeenusedwithamendmentforthecalculationof electricity generation. Practically available turbine capacitieshavebeenused for calculations instead of theoretical turbine capacities arrived in the samesectionforthecalculations.FurtherthreesetsofoperatingpressureandtemperatureshavebeenalteredtomeetthepracticallyavailableturbinecapacitiesasshowninTable5.1. In addition, two important factors have been considered in calculating total netelectricalenergygeneratedbyeachoftheturbinesidentifiedinTable5.2.
ElectricityRequirementof theTGPlant: As shown in the Schematic plantdesign, CCH plant comprises of various equipment such as blowers, fans,motors and pumps which are electric driven. Hence part of electricitygeneratedbytheplantwillbeoffsetbytheenergyconsumedbytheabovesaidequipment.
Total electricity generation by the turbines identified in Table 5.2, calculatedconsideringabovetwofactorsaregiveninTable5.3.
TotalEnergyConsumption 1,070,647Table 5.5: Electricity Use by Plant Equipment for Biomass TG
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5.5.2.3 OperationalandLaborCostsSimilar to any industrial plant equipment Tri‐Generation plant will also incur anadditional cost to the owner in terms of operations and labor. Operation cost willincludeCostofspares,costofchemicals,costofwaterandadministrativecost.Itisverydifficult toaccuratelyestimatethesecostasmostof thesearecasespecific.Thereforethecost figuresused in the industryby the leadingTGplantequipmentsuppliershasbeen used for the calculation. Following are the list of such figures obtained from aleadingsupplier.
Inadditiontoabovecostseveralstaffhasttobeemployedfortheoperationoftheplantwhichwill contribute to labor cost related to the TG plant. Since the plant has to beoperated24hours,foursupervisorylevelstaff,eighttechniciansandeightlaborerswillbe required at a minimum. Based on this manpower requirement following costcalculation has been done according to the current pay mechanism of the TexturesJersey
Above three economical parameters were calculated for the tri generation plantdesignedfortheTexturesJersey.Unlikemostoftheindustriesapparelindustryisveryvolatile and the future trends are highly unpredictable. Therefore apparel industrynormallydoesnotmake investmentsconsidering longperiods like20yrs.Consideringthisfactandthelifecycleofplantequipmentofthetri‐genplant,a10yearperiodwastakenfortheeconomicalanalysis.
5.5.3.1 EconomicAnalysisforCoalFiredSystemPositiveNPVover10yearperiod(Figure25),IRRhigherthanthecurrentdiscountrate(Figure26)andthepaybackintherangeof4years(Figure27)indicatesthatinvestingon a tri‐generation plant is economically highly favorable. Though none of thecalculatedparameters(NPV,IRR,SPB)exhibitauniformtrend,itisevidentthathighertemperature and pressure points results in better values for all three parameters.Howeverchangeineachparameterwithvariousoperatingconditionsisnotsubstantialfor a management to take decision on an optimum condition. Hence capital in handplaysahugeroll inselectinganoperationconditionashigherpressure/temperaturesrequirehigherinvestments.Othernon‐economicalparameterssuchasemissions,Ashdisposal, coal storage, supply chain issues, safety requirement also may consider inselectingtheoperatingconditions.
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5.5.3.2
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19,924 1 0.3 2447 0.3 13,2135 / Inadditiontoabovetheseverecontrastbetweenthepricesofthetwotypeofbiomasscontributestomajordifferencesineconomicparameters.AsshowninFigure28,inbriquettessystem,capitalrequirementforincreaseoperatingpressure and temperature steadily increase while NPV is maintained positive. Thisscenarioissameforthefirewoodboilers.NPVofbothcasesdoesnotindicatemuchofavariationwhereasNPVoffirewoodsystemveryhigh(~4timesthecapital)asshowninFigure29owingtothehighersavingresultedfromcheapfuelcost.
Simplepaybacksoftwosystemsalsodonotvarymuchwiththeoperatingpressureandtemperatures as shown in Figure 31. Here again the firewood system indicates paybacksassmallas1.6yrs(almosthalfofbriquettesandcoalsystems)duetoextremelylowfuelprices.AsshowninFigure30,IRRofbothBiomassfueltypesexhibitthesamepatterns.
Similar to coal powered systems economic parameters do not exhibit substantialvariation at different operating conditions. Therefore capital in hand should beconsidered in selecting a suitable operating condition. Other non‐economicalparameters also, such as Ash disposal, storage, supply chain issues and safetyrequirementhastobeconsideredinselectingtheoperatingconditions.
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Whencomparedtoeachotherpurelyoneconomicterms,biomassfiredtri‐generationplant is economically attractive than the coal fired plant. Threemain contributors totheseeconomicallyattractiveresultsarethelowerpriceofbiomass,lowercapitalcostofbiomasstri‐genplantandhigherelectricityconsumptionbytheauxiliaryequipmentofthecoalfiredplants.
GreenhouseGas(GHG)EmissionsOne of themain reasons for implementing TG plants is to harness themaximumamount of energy thereby reduces the GHG emissions. Sri Lankan apparel sectoralsoisundergreatpressurefromtheirinternationalbuyersandthegovernmenttoreduce theemissions. However,as indicated in thebelowFigure32, it isevidentthatuseofcoalwillfurtherincreasetheemissionwhencomparedwiththecurrentemissionquantities.Thishappensduetooffsetofemissionreductionachievedbygenerating electricity and eliminating electricity requirement for chillers by theexcessive coal combustion. Coal combustion release CO2, N2O and CH4 thatcontributesto theglobalwarmingandtheFigure32 indicatestheequivalentCO2emissionbyallgreenhousegases.
However,theGHGemissioncanbedrasticallyreducedasshowninfigure32byuseof biomass (both briquettes and firewood) if the CO2 emission by the same isassumedtobezero.
SO2EmissionsCoal has a certain percentage of Sulphur. Coal is imported from Indonesia forcurrentmajor localapplicationssuchas coalpowerplants runby the localutilitycompanies. Hence same coal will have to be used by the tri‐gen plants ifimplemented.TypicalIndonesiancoalhaslowerSulphurcontentanditisabout1%as a fraction of mass. Therefore, 400 to 470MTs of SO2 will be released to theenvironment ifcoal isusedfortheTGplant,dependingontheoperatingpressureandtemperature.
CombustionAshAnysolidfuelfiredboilergeneratesbottomashafterthecombustionprocess.Coalandbiomassarenodifference. Locallyusedcoalhasapproximateash contentofabout 6% (source: Holcim test report) whereas bio mass has approximate ashcontent of about 4.3% (source: ITI test report). ThereforeTGplant fired by both
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fuel typeswill result in1,200 to1,800MTsof solidwaste (ash) annually. Properdisposalmethods such reuse in cementmanufacturing has to be implemented toavoid
AirborneParticlesWhen solid fuel like biomass or coal is combusted certain percentage of ash getairborne and exist the chimneywith the flu gas. This airborne particles then getcarriedbythewindandcangetdepositedintheneighboringarea.Unlike biomass, coal can create more airborne particles in form of dust duringloading,unloading,storing,crushingandconveying.
WaterandLandContaminatingThishappens if coal isused.Normally coal is stored inoutdoorbefore it isbeingused.During such time, rain fallson to stored coal canwashaway solidparticlesandcancontaminatethelocalwaterbodiesandthesurroundingland.
TransportRelatedEmissionsProposedplant thatwas subjected to studywill require20,000 to40,000MTsofsolid fuel (coal or biomass) depending on the fuel type and operatingpressure/temperature. Handling of these quantities will require lot oftransportationwhichagaincontributesharmfulemissions.
IndirectDeforestationInthisanalysisithasbeenassumedthatbiomasswouldcomefromwoodwasteorfromtreescommerciallygrownforfirewood.Howevercurrentlythereisnopropermechanism to check the actual source of the biomass. There have been manyincidentsofdeforesting for firewood. If thathappens,wholepurposeofusingbiomasswillbelost
processheatingcanenjoyeconomicbenefitsbyshiftingtocoalorbiomassfiredTGplant. However NPV, IRR and the payback time will vary with the parametersuniquetotheplacewhereTGplantisimplemented.Thereforeitisadvisabletodoan economic analysis after doing a schematic design considering followingguidelines.
InfrastructureOnemustinvestigatewhetherthenecessaryinfrastructureisinplacetoimplementaTGPlant.First requirement is space.Normallymostof the localapparel factorybuildingsoccupiedmostof the landofthe locatedsite, leaving littlespaceforthiskind of projects. TG plants need adequate space for place the boilers, turbines,coolingtowers,watertreatmentplants,otherplantequipment,fuelstorageandetc.Eachof thesehas tobeplaceswithadequatemaintenanceaccessandwith safetyclearances.Furthertheavailabilityoftransportaccesstotransport&erecttheplantandtotransportfuelshouldalsobeconsidered.
PlantCapacityBoiler and the turbine are the twomain components in a TG plant, ofwhich thecapacityaffecttheeconomicsofthetotalplant.Restoftheplanthastobedesignedaccordingtothecapacitiesofthesetwocomponents.Itisalwaysimportanttosizethe plant considering the process heat requirement rather than considering theelectricitydemand,becausethereisnoalternativesourceforheating.Ontheotherhand,excesselectricitycanbe fedtothegrid, ifanyorelectricityshortagecanbeobtained from the grid, once the plant is sized tomeet process heating demand.Therefore,optimumboilercapacitycanbearrivedbyadditionofallprocesssteammassflowratesandthesteammassflowraterequiredbyabsorptionchillers(thisistheminimumboilercapacitypossible).Selectingaboilerwithhighercapacitythantheminimumsteamrequirementallowstheusertohaveabiggerturbineandtherebygeneratehigheramountofelectricity.Differencebetween costs of self‐generated kWhelectricity andpurchased kWh ismarginalasIndustrialelectricitypriceinSriLankaisheavilysubsidized.Thereforecost saving by increased self‐generations not substantial compared to the capitalcost incurred inpurchasinghighercapacityboilerand turbine.Howevereven thesubsidized grid electricity is not cheap enough to use for heatingpurposeswhencomparedwiththecostoffuelssuchasHFO,coalandbiomass.
PlantArchitecturePlant architecture depends mainly on how and at what point one is going toobtained process steam from the cycle.Main options are to directly obtain somesteamfromtheboilerthroughPRV,tappingtheboileratsuitablepressurelevelsorselecting the turbine to have an exit steam pressure at highest pressure levelrequired.Both firstandthirdoptionsreducetheelectricitygenerationcapacityofthe TG plant and require additional fuels as steam is obtained through PRVs.
OptimumOperatingconditionsAtaminimum,anyselectedoperatingpressureandtemperatureshouldbeabletoprovideenoughsteamatsuitablequalityattheturbineexit toruntheabsorptionchillers. Further, as shown in the calculations, operating at higher pressures andtemperatures gives better economical and environmental performance. Since theprocess heating requirement is anyway met, increased P & T will increase thesavings only by offsetting electricity drawn from the grid. Further this increaserequires additional capital. As explained earlier designing the plant consideringelectricity generation is not very profitable. Therefore one must decide theminimum operating P&T considering energy availability to the absorption chillerandwhethertoincreasethepressurethantheminimumcanbedecidedconsideringtheavailablecapital.
OperatinghoursTexturesJersey,whichwassubjectedtoanalysisoperate24hoursaday.Thelongeroperatinghourshavecontributeda lot to theshorterpaybacksof the investment,extremelyattractiveNPVandIRR.Hadtheplantranontypical12hour,10hoursor8hourshiftthepaybacktimesbecomesnonattractiveasthereisnochangeintheinvestment. Negative NPVs will be resulted for certain operating conditions.Moreover,startingandshuttingoffthiskindofaplanteverydayisnotadvisableasthese plant are meant to run continuously. Options available for factories withshortershiftaretoeithertohaveanotherturbine(withouttapings)torunduringthe off hours or to run the existing turbineby rejecting heat via a cooling tower.Both these options seriously affects the economics and therefore case by caseeconomicalanalysisisrequired.
FuelSelectionFirewood,Sawdustbriquettesandcoalarepreferredas the fueloverHFO in therespectiveorder.Biomassispreferredovercoalowingtotwomainreasons.Firstisthereducecapital requirementasTGplantbecome lesscomplicatedcomparedtothe coal fired systemas itdoesnot require complex fuelpreparationand feedingsystem. This makes the Bio mass system more economically attractive. It alsocreatesmuchlowernetCO2emissioncomparedtoacoalfiredsystem.Ineconomic terms, firewood ispreferredoversawdustbriquettesdue to~40%lowercostperMJandlowercapitalcost.CostperMJofbiomassisslightlyhigherthanthatofthecoal,yet it iseconomicallyattractiveduetopreviouslymentionedreasons. However the main advantages of coal are the availability and the wellestablish supply chain. Whether large quantities of bio mass can be sourcedcontinuouslythroughouttheyearisdoubtful.Thereforeonemustnotventureintobio‐massfiredTGplantuntilcontinuoussupplyisensured.
M.Sc. Thesis
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6 Conclusion
Increaseddemandforfossil fuelandtheconflicts inthemajoroilproducingcountrieshas ledfossil fuelpriceto increaseuptoa levelwhich isalmostunbearabletotheSriLankan industry. Among all, apparel manufacturing is one of the severely affectedindustriesbythesuddenfuelpricehikes.Asaresultoftheglobaltrendofsustainabledevelopment,pressure fromvarious institutes tominimize theemissionsby reducingtheenergyconsumption,isanothermajorchallengefacedbythelocalapparelindustry.A typical Sri Lankan apparel manufacturing factory requires electricity to run itsmachineries,airconditioning&Ventilationsystem,lightingsandutilityequipmentlikecompressorsandpumps.FossilfuelslikeDieselandfurnaceoilareusedtorunboilerstogenerate steamrequired formanufacturingprocess.Tri‐generationhasneverbeenusedbythelocalapparelindustryasasolutionfortheeverincreasingenergycost.Themainobjectiveofthisresearchwastoevaluatethefeasibilityoftri‐generationifusedinapparelindustryandtherebyprovidesetofgeneralizedguidelinestothelocalapparelsector to identify the economical, environmental and technical challenges and thebenefitsthattheywouldcomeacrossinimplementingaTri‐Generationplant.Aspertheresearch results it is evident that apparel factories that utilize HFO can enjoyeconomicalbenefitsbyimplementingaTGplantrunbycoalorbiomass.
After the local apparel sector was studied it was found out that all factories can becategorizedintofivemaintypes.OutofthatknittingandweavingwasidentifiedasthemostsuitabletypetoimplementaTGplant.TexturesJerseyswhichisaknittingfacilitywas selected for the pilot study. After conducting a detail energy audit the end usequantitieswere estimated. Simultaneously, the possible combinations for a TG plantswere also identified based on the energy flow in the facility. Out of numerouscombinations,twomostpracticalsolutionswereevaluatedusingEngineeringEquationSolver.Thentheresultswereusedtoarriveatoptimalsolution.AfterdesigningadetailschematicoftheplantNPV,IRR,Paybackenvironmentalimpactanalysiswasconductedassumingthefuelascoal,sawdustbriquettesandfirewood.GeneralguidelinesonTGforlocalapparelsectorwerethendevelopedbasedonanalysisresult.
ResultsoftheenergyauditconductedatthetexturesjerseyispresentedintheChapter‐03.Ithasapeakelectricitydemandofabout3400kWandusesofstaggering8.9millionlitersofheavyfueloilannually.Facilityneedabout6MTofsteamat10barand10MTofsteamat6bar.Recentfueloilpriceincreasehasresultedinmorethan50%reductionin its net profit, making the facility good candidate to implement a Tri‐generationsystem. In thenext sectionall possible combinations forTri‐Generation systemhavebeenidentified.WhentheseoptionswereanalyzedusingmanualcalculationsandEESseveralimportantfactswererevealedthatultimatelyleadtotheoptimalsolution.Someofthemostprominentfactsrevealedareasfollows.
Lower overall energy cost for Increased operating pressure and temperature of agivenboilercapacity
Lower overall energy cost achieved by lowest capacity boiler at a given operatingpressureandtemperature
Sizing the plant tomeet the electricity results in lower energy cost saving due toincreasedfuelcost
Steam exiting from the turbine has to be at, at least 1atm to be able to use forabsorption chiller. Availability of excess energy at exit indicates room foroptimization.
In a backpressure type turbine, Excess energy available for absorption chiller canonly be reduced by reducing the steammass flow rate. Hence, it is obvious that asmallest possible boiler has to be operated in the suitable pressure to obtainoptimumresults.
However boiler must have a capacity that at least is sufficient to meet the totalprocesssteamrequirementofthefactory.
Economical analysis conducted for the plant designed for Textures Jersey based onabove factors, exhibit veryattractive results for all three fuelsnamely; coal, sawdustbriquettes and firewood. Biomass fired systems indicates highly favorable GHGemissionreductionwhereascoalfiredsystemincreasestheoverallemissions.
AvoidPRVs SelectP&TconsideringcapitalandenergyavailabletoAbsorptionchillers Suitableonlyfor24hoperations Firewood, Saw dust briquettes and coal are preferred as the fuel over HFO in therespectiveorder
Oneofthemostprominentfactsintheresultsistheextremelyfavorableeconomicandenvironment result of the bio mass fired Tri‐Generation plants. Such systems aretechnicallyalsosimplecomparedtocoalsystems.Paddyhusk,hey,commerciallygrownfirewood,municipalsolidwaste,timbermillwastesarethemostcommontypesofbiomassavailable.Furtherresearchshouldbecarriedoutonhowtoimprovethebiomasssupplychain,howtoefficientlyutilizetheavailablebiomass,howtocreateamarketforbiomassandhowtoavoidharvestingnaturalforestsforbiomass.Anotherimportantarea to study is how to create a certificate system or special tariff for self‐generatedelectricity that would encourage the industry to implement tri‐generation. Study onimplementingmethodologiestoobtainbenefitsfromcarboncreditsisalsoimportant.
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