外文翻译(英文)能源审计和干法水泥回转窑系统

Energyauditingandrecoveryfordrytypecementrotarykilnsystems––AcasestudyTahsinEngin*,VedatAriDepartmentofMechanicalEngineering,UniversityofSakarya,EsentepeCampus,54187Sakarya,TurkeyReceived30January2004;accepted29April2004Availableonline2July2004AbstractCementproductionhasbeenoneofthemostenergyintensiveindustriesintheworld.Inordertoproduceclinker,rotarykilnsarewidelyusedincementplants.ThispaperdealswiththeenergyauditanalysisofadrytyperotarykilnsystemworkinginacementplantinTurkey.Thekilnhasacapacityof600ton-clinkerperday.Itwasfoundthatabout40%ofthetotalinputenergywasbeinglostthroughhotfluegas(19.15%),coolerstack(5.61%)andkilnshell(15.11%convectionplusradiation).Somepossiblewaystorecovertheheatlossesarealsointroducedanddiscussed.Findingsshowedthatapproximately15.6%ofthetotalinputenergy(4MW)couldberecovered.
2004ElsevierLtd.Allrightsreserved.Keywords:Cementplant;Rotarykiln;Energyaudit;Heatbalance;Heatrecovery1.IntroductionCementproductionisanenergyintensiveprocess,consumingabout4GJpertonofcementproduct.Theoretically,producingonetonofclinkerrequiresaminimum1.6GJheat[1].How-ever,infact,theaveragespecificenergyconsumptionisabout2.95GJpertonofcementproducedforwell-equippedadvancedkilns,whileinsomecountries,theconsumptionexceeds5GJ/ton.Forexample,Chinesekeyplantsproduceclinkeratanaverageenergyconsumptionof5.4GJ/ton[2].Theenergyaudithasemergedasoneofthemosteffectiveproceduresforasuccessfulenergymanagementprogram[3].ThemainaimofenergyauditsistoprovideanaccurateaccountofenergyconsumptionandenergyuseanalysisofdifferentcomponentsandtorevealthedetailedEnergyConversionandManagement46(2005)551–562*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail],[e-mail](T.Engin).0196-8904/$-seefrontmatter
2004ElsevierLtd.Allrightsreserved.doi:10.1016/j.enconman.2004.04.007informationneededfordeterminingthepossibleopportunitiesforenergyconservation.Wasteheatrecoveryfromhotgases[4]andhotkilnsurfaces[5]inakilnsystemareknownaspotentialwaystoimproveoverallkilnefficiency.However,itisstillfairlydifficulttofindadetailedthermalanalysisofrotarykilnsystemsintheopenliterature.Thispaperfocusesontheenergyauditofahorizontalrotarykilnsystem,whichhasbeenusingintheVanCementPlantinTurkey.Ade-tailedthermodynamicanalysisofthekilnsystemisfirstgiven,andthen,possibleapproachesofheatrecoveryfromsomemajorheatlosssourcesarediscussed.2.ProcessdescriptionanddatagatheringRotarykilnsarerefractorylinedtubeswithadiameterupto6m.Theyaregenerallyinclinedatanangleof3–3.5,andtheirrotationalspeedsliewithin1–2rpm.Cyclonetypepre-heatersarewidelyusedtopre-heattherawmaterialbeforeitentersthekilnintake.Inatypicaldryrotarykilnsystem,pre-calcinationgetsstartedinthepre-heaters,andapproximatelyonethirdoftherawmaterialwouldbepre-calcinedattheendofpre-heating.Thetemperatureofthepre-heatedmaterialwouldbeoftheorderof850C.Therawmaterialpassesthroughtherotarykilntowardstheflame.Inthecalcinationzone(700–900C),calcinations,aswellasaninitialcombinationofalumina,ferricoxideandsilicawithlime,takeplace.Between900and1200C,theclinkercomponent,2CaOÆSiO2,forms.Then,theothercomponent,3CaOÆSiO2,formsinasubsequentzoneinwhichthetemperaturerisesto1250C.Duringthecoolingstage,themoltenphase,3CaOÆAl2O3,forms,andifthecoolingisslow,alitemaydissolvebackintotheliquidphaseandappearassecondarybelite[6].Fastcoolingoftheproduct(clinker)enablesheatrecoveryfromtheclinkerandimprovestheproductquality.ThedatatakenfromtheVanCementPlanthavebeencollectedoveralongperiodoftimewhenthefirstauthorwasaprocessengineerinthatplant.Theplantusesadryprocesswithaseriesofcyclonetypepre-heatersandanincline-kiln.Thekilnis3.60mindiameterand50mlong.Theaveragedailyproductioncapacityis600tonofclinker,andthespecificenergyconsumptionhasbeenestimatedtobe3.68GJ/ton-clinker.Alargenumberofmeasurementshavebeentakenduring2yr,andaveragedvaluesareemployedinthispaper.TherawmaterialandclinkercompositionsaregiveninTable1.TherotarykilnsystemconsideredfortheenergyauditisschematicallyshowninFig.1.Thecontrolvolumeforthesystemincludesthepre-heatersgroup,rotarykilnandcooler.Thestreamstoandfromthecontrolvolumeandallmeasurementsareindicatedinthesamefigure.3.Energyauditingandheatrecovery3.1.MassbalanceTheaveragecompositionsfordriedcoalandpre-heaterexhaustgasareshowninFig.2.Basedonthecoalcomposition,thenetheatvaluehasbeenfoundtobe30,600kJ/kg-coal.Itisusuallymoreconvenienttodefinemass/energydataperkgclinkerproducedperunittime.ThemassbalanceofthekilnsystemissummarizedinFig.3.Allgasstreamsareassumedtobeidealgasesatthegiventemperatures.552T.Engin,V.Ari/EnergyConversionandManagement46(2005)551–5623.2.EnergybalanceInordertoanalyzethekilnsystemthermodynamically,thefollowingassumptionsaremade:1.Steadystateworkingconditions.2.Thechangeintheambienttemperatureisneglected.3.Coldairleakageintothesystemisnegligible.Rawmaterial,41.66t/h500CRotarykiln,Φ3.6m-50mCoal,2.875t/hCoolingair300CClinker,25t/h,1100CHotair2150CPre-heaterexhaust3150CSecondaryairPre-heatergroupDust,1.05t/h3150CDust,0.15t/h2150CC