燃烧学的理论方法及应用(船舶排放).ppt

REGULATIONS ThereareanumberofnationalandinternationalregulatoryorganizationsthatproposelimitationsonNOxaswellasotherharmfulemissions TheInternationalMaritimeOrganization IMO throughtheInternationalConventionforthePreventionofPollutionfromShips MARPOL AnnexVI regulatesthisonagloballevel Theyhavedevelopedanapproachtoreducinggreenhousegas GHG emissions includingNOx MembercountriesoftheIMOmustthereforeadheretotheregulationsthattheyhaveputforth However someorganizationshavecommittedtoadoptingregulationsthataremorestringent TheEnvironmentalProtectionAgency EPA oftheUnitedStatesandtheEuropeanUnion EU aretwosuchexamples TheseregulatorybodieshaveusedtheIMOcriteriaasastartingpointforGHGemissionsreductionbutaredevelopingcertainaspectsofthepolicythatarestricterthanthatoftheIMO InternationalMaritimeOrganization IMO isanagencyoftheUnitedNationswhichhasbeenformedtopromotemaritimesafety IMOshippollutionrulesarecontainedinthe InternationalConventiononthePreventionofPollutionfromShips knownasMARPOL73 78 On27September1997 theMARPOLConventionhasbeenamendedbythe 1997Protocol AnnexIRegulationsforthePreventionofPollutionbyOilAnnexIIRegulationsfortheControlofPollutionbyNoxiousLiquidSubstancesinBulkAnnexIIIPreventionofPollutionbyHarmfulSubstancesCarriedbySeainPackagedFormAnnexIVPreventionofPollutionbySewagefromShipsAnnexVPreventionofPollutionbyGarbagefromShipsAnnexVIPreventionofAirPollutionfromShipsMARPOLAnnexVIsetslimitsonNOxandSOxemissionsfromshipexhausts andprohibitsdeliberateemissionsofozonedepletingsubstances wasadoptedSeptember1997andenteredintoforceon19May2005 国际海事组织IMO批准了修订的船舶废气排放规则 IMO第57届海洋环境保护委员会于2008年3月31日 4月4日在伦敦召开 会上批准了对MARPOL附则VI修正案 以减少船舶有害气体的排放 硫氧化物 SOx 主要的变化是逐步减少船舶硫氧化物 SOx 的排放 燃油含硫量从当前4 50 减少到3 50 从2012年1月1日生效 然后减少至0 50 从2020年1月1日起生效 并最晚不迟于2018年完成可行性评估计 硫排放控制区 SulphurEmissionControlArea SECA 的适用标准将减少到1 00 当前为1 50 从2010年1月1日起生效 并进一步减少的0 10 于2015年1月1日起生效 目前的附则VI 指定了两个硫排放控制 SECA 也就是波罗地海 theBalticSea 和北海 theNorthSea 也包括英吉利海峡 theEnglishChannel 逐步减少发动机氮氧化物 NOx 排放的建议获得通过 TierI适用于2000年1月1日后2011年1月1日前安装在船上的发动机 即氮氧化物的排放量为17g kWh 已在现在的附则VI中有规定 TierII将氮氧化物的排放量减少到14 4g kWh 适用于2011年1月1日后建造或装船的发动机 TierIII将氮氧化物的排放量减少到3 4g kWh 适用于2016年1月1日安装在船上的发动机 但仅在排放控制区 EmissioncontrolArea 适用 在非排放控制区 等级II仍然适用 对1990年1月1日后2000年1月1日前安装的输出功率为5000kW 单缸排量为90L或超过90L的柴油发动机 海洋保护环境委员会 MEPC 同意用17 0g kWh的氮氧化物排放标准 海洋环境保护委员会 MEPC 批准了氮氧化物技术规则修订草案 并在2008年出台修订的氮氧化物技术规则 新的技术规则包括新的第7章 对2000年前发动机氮氧化物排放进行了规定 此外还包括对现有发动机的直接测量和进行监测的方法以及发证程序 以及对适用等级II和等级III的发动机的测试 氮氧化物 NOx 废气清洗系统 ExhaustGasCleaningSystems 本次会议同意将对废气清洗系统中间冲洗水的排放标准纳入到修订的废气清洗系统的导则中 挥发性有机物 VOCs 本次会议批准了 VolatileOrganicCompounds 挥发性有机物管理计划导则的草案 挥发性有机物管理计划的目的是为了确保适用于附则VI第15条的液货船 能防止或者将挥发性有机物的排放减少到可能的程度 附则VI第15条要求缔约国向IMO递交一个通报 该通报应包括所控制的液货舱尺寸 液货所需蒸汽控制系统及所采取得控制措施生效的日期等信息 海洋环境保护委员会通知IMO秘书处邀请国际化标准组织 ISO 考虑燃油标准的制订 重在强调空气质量 船舶安全 发动机性能以及船员健康并推荐给IMO考虑 温室气体 GHG 本次会议批准了秘书长关于加快温室气体排放工作的建议 特别是二氧化碳CO2排放指数方案的制订以及二氧化碳CO2排放基线调查的开展 温室气体排放工作组编写了下一步实际工作计划包括控制CO2排放的短期及长期措施 该计划获得了海环会批准 短期措施包括建议建立全球航运燃油税征收方案 globallevyscheme 以减少温室气体排放 根据该计划 所有从事国际航运的船舶将需缴纳基于每吨定值的燃油税 GHG工作组确认的长期的措施获得了海环会的批准并需进一步研究 这些措施包括 船舶设计的技术措施 使用替代燃料 新船的CO2 设计指数 CO2运行指数的外部查验 统一的CO2运行指数限制以及对不符合的惩罚 排放交易机制 EmissionsTradingScheme ETS 和 或清洁发展机制 CDM 以及港口基建费征收中的CO2排放因素 NOxEmissionStandards NOxemissionlimitsaresetfordieselenginesdependingontheenginemaximumoperatingspeed n rpm asshowninTable1andpresentedgraphicallyinFigure1 TierIandTierIIlimitsareglobal whiletheTierIIIstandardsapplyonlyinNOxEmissionControlAreas Figure1 MARPOLAnnexVINOxEmissionLimits EmissionControlAreas TwosetsofemissionandfuelqualityrequirementsaredefinedbyAnnexVI 1 globalrequirements and 2 morestringentrequirementsapplicabletoshipsinEmissionControlAreas ECA AnEmissionControlAreacanbedesignatedforSOxandPM orNOx orallthreetypesofemissionsfromships subjecttoaproposalfromaPartytoAnnexVI ExistingSOxEmissionControlAreasincludetheBalticSea adopted 1997 enteredintoforce 2005 andtheNorthSea 2005 2006 FutureEmissionControlAreascouldalsoincludezonesaroundpollutionsensitiveports TierIIstandardsareexpectedtobemetbycombustionprocessoptimization Theparametersexaminedbyenginemanufacturersincludefuelinjectiontiming pressure andrate rateshaping fuelnozzleflowarea exhaustvalvetiming andcylindercompressionvolume TierIIIstandardsareexpectedtorequirededicatedNOxemissioncontroltechnologiessuchasvariousformsofwaterinductionintothecombustionprocess withfuel scavengingair orin cylinder exhaustgasrecirculation orselectivecatalyticreduction Pre 2000Engines Underthe2008AnnexVIamendments TierIstandardsbecomeapplicabletoexistingenginesinstalledonshipsbuiltbetween1stJanuary1990to31stDecember1999 withadisplacement 90literspercylinderandratedoutput 5000kW subjecttoavailabilityofapprovedengineupgradekit Testing EngineemissionsaretestedonvariousISO8178cycles E2 E3cyclesforvarioustypesofpropulsionengines D2forconstantspeedauxiliaryengines C1forvariablespeedandloadauxiliaryengines Additionofnot to exceed NTE testingrequirementstotheTierIIIstandardsisbeingdebated NTElimitswithamultiplierof1 5wouldbeapplicabletoNOxemissionsatanyindividualloadpointintheE2 E3cycle Enginesaretestedusingdistillatedieselfuels eventhoughresidualfuelsareusuallyusedinreallifeoperation FurthertechnicaldetailspertainingtoNOxemissions suchasemissioncontrolmethods areincludedinthemandatory NOxTechnicalCode whichhasbeenadoptedunderthecoverof Resolution2 SulfurContentofFuelAnnexVIregulationsincludecapsonsulfurcontentoffueloilasameasuretocontrolSOxemissionsand indirectly PMemissions therearenoexplicitPMemissionlimits SpecialfuelqualityprovisionsexistforSOxEmissionControlAreas SOxECAorSECA ThesulfurlimitsandimplementationdatesarelistedinTable2andillustratedinFigure2 Heavyfueloil HFO isallowedprovideditmeetstheapplicablesulfurlimit i e thereisnomandatetousedistillatefuels Alternativemeasuresarealsoallowed intheSOxECAsandglobally toreducesulfuremissions suchasthroughtheuseofscrubbers Forexample inlieuofusingthe1 5 SfuelinSOxECAs shipscanfitanexhaustgascleaningsystemoruseanyothertechnologicalmethodtolimitSOxemissionsto 6g kWh asSO2 Figure2 MARPOLAnnexVIFuelSulfurLimits EUStandardsforNon RoadEngines April2004 StageIII IVlimitsareharmonizedwiththeEPATier3 4standards TheEnvironmentalProtectionAgencyoftheUnitedStateshasbeenprotectinghumanhealthandtheenvironmentsince1970 LiketheEU theEPAhasadoptedtheregulationsissuedbytheIMObuthasuseditasafoundationforamorestringentpolicyformarineemissions fornon roadengines TheEPAregulationsystemisdividedintothreetiersthataremeanttoprogressivelyloweremissions Tier1standardsareequivalenttotheMARPOLAnnexVINOxlimitsandwerevoluntarywhenfirstimplementedbutmandatoryby2004 TheTier2standardsforallenginesizes whicharemorerestrictivethanTier1 aretobeinplaceby2007 Tier3standardsforenginesratedover37kW 50hp willphase infrom2006to2008 TheTier4standardsthatcurrentlyexistdonotapplytomarinedieselengines However Tier4criteriawereissuedalongwithan AdvanceNoticeofProposedRulemaking whichoutlinedtheintendedfutureemissionstandardsformarinedieselengines EnvironmentalProtectionAgency EPA EPATier2MarineEmissionStandard OveralltheEPAregulations likethoseoftheEU aremorerestrictivethanIMOMARPOLAnnexVI TheEPApolicyformarineenginesrequiresbetterenginecooling electroniccontrolsandotherdesignmodifications Also aswiththeStagesoftheEUsystem thestandardsoutlinedintheTiersystemlistspecificrestrictionsforanumberofairpollutants e g PM HC COandNOx whileIMOdoesnot CombustioninHighSpeedDieselEngines ASI AftertheStartofInjection ConceptualdieselSprayCombustionModel FromSAEpaper1997 970873 SocietyofAutomotiveEngineers Inc 1 柴油 约350K 喷入气缸内后 热空气 约950K 卷入并加热燃油 油束破裂 当燃油被热空气加热至约650K时 在浓混合气区 燃空当量比约4 0 当地温度约825K 出现预混合火焰 生成大量富油燃烧产物 CO 未燃HC PM 当地温度升高到约1600K 此时的放热量约为总放热量的10 15 2 在油束外围出现扩散火焰层 富油燃烧产物不断进入扩散火焰层进行扩散燃烧 产生约2700K的高温 使PM氧化 并生成CO2和水蒸汽 同时 扩散火焰层的高温使空气中的N2和O2反应 生成大量NOX 扩散燃烧放热量占总放热量的85 90 ThereareanumberofdifferentformationmechanismsresponsibleforNOxincombustionprocesses Therelativeimportanceofthesedifferentmechanismsisstronglyaffectedbythetemperature pressure flameconditions residencetimeandconcentrationsofkeyreactingspecies ThereactingspeciescanpotentiallyproceedthroughanumberofdifferentchemicalmechanismsresultingintheformationofNOx Atthetemperaturesgreaterthan2000Koxygencombineswithnitrogentoformoxidesofnitrogen Initially NOisformed thenduringthegasexpansionprocessinthecylinderaportionoftheNOconvertstoformnitrousoxide N2O andnitrogendioxide NO2 ThecombinationofNO NO2andN2OisknownasNOx NOxFormation 生成NO主要化学反应链见下图 该反应链已得到大多数研究人员的认可 在燃烧过程中生成的氮氧化物主要源于燃烧空气中的氮气 N2 和燃料中的有机氮 在燃料中如有机氮的重量含量大于1 NO的最终排放通常会增加10 30 在燃油的雾化过程中 这些有机氮会从燃料中释放出来 并快速生成氢氰化物 HCN 和氨气 NH3 ThermalNO Thethermalmechanism alsoknownisthe extendedZeldovichmechanism isresponsibleforthemajorityofNOxemissionsfromdieselengineswhenpeakcombustiontemperaturesexceed2000K Sincetemperaturesofthismagnitudearedesirabletomaximizeengineefficiency thismechanismhasbeenstudiedextensivelyandisfairlywellunderstood Thethreechemicalreactionsthatareimportantinthismechanismare O N2 NO N 1 N O2 NO O 2 N OH NO H 3 Theoverallreactionrateforthismechanismisslowanditisverytemperaturesensitive Asaconsequence thermalNOonlyappearsinsignificantquantitiesinthepostcombustion Also theactualNOconcentrationfromthismechanismdeviatessignificantlyfromequilibriumconcentrations Thisgivesthismechanismaverystrongtimedependencethatisimportantforlowspeedengines ThermalNO Theforwardrateofreaction 1 andthereverseratesofreactions 2 and 3 havestrongtemperaturedependencies Therefore thismechanismisveryimportantathighertemperatureandatair fuelmixturesthatareclosetostoichiometric ItscontributiontoNOxemissionsisalmostinsignificantattemperaturesbelow1700K butisstronglyacceleratedastemperatureincreasesabove2000K Thetemperaturesensitivityofthismechanismalsomeansthatasthetemperatureinthecombustionchamberdropsduringtheexpansionstroke theNOconcentrationfreezesshortlyaftertopdeadcentre PostcombustionequilibriumconcentrationsofOandOHareveryimportantforthismechanism FactorsthatincreaseordecreasetheconcentrationsoftheseradicalscanhaveasignificantimpactonNOfromthismechanism PromptNO ThepromptNOmechanism alsoknownasthe Fenimoremechanism isveryrapidandresultsinNOformationinthecombustionzone ThemostimportantpathwayforpromptNOisinitiatedbytherapidreactionofhydrocarbonradicalsfromthefuelwithmolecularnitrogen leadingtotheformationofaminesorcyanocompoundsthatsubsequentlyreacttoformNO ThemostimportantinitiationreactionforpromptNOis CH N2 HCN N 4 SubsequentrapidconversiontoNOisstronglyaffectedbyOandOH PromptNOismostsignificantwhencombustionoccursatfuelconcentrationshigherthanstoichiometrywherethereisahighconcentrationofhydrocarbonradicalstoformHCNandtheconcentrationsofOandOHarestillhighenoughtocausetheHCNtoproceedtoNOthroughthefollowingreactionsequence HCN O NCO H 5 NCO H NH CO 6 NH H N H2 7 N OH NO H 8 Theratesofthesereactionsarenotverysensitivetotemperature ReactionsarerapidandthesequenceresultsinNOformationintheflamezone HightemperaturesdonotaffectedpromptNOtothesameextentasthermalNO PromptNO Zeldovichmechanism反应链ThermalNO对于反应温度是非常敏感的 通过计算流体动力学的仿真模拟计算和燃烧实验发现 当温度低于1700K时 NO的生成速率比较缓慢 温度上升 特别当温度大于2000K NO的生成度 并在高温时尽可能地减少供氧量 可以有效地降低NO的生成和排放 然而Fenimoremechanism反应链PromptNO对于反应温度是非常不敏感 燃料中如有机氮在燃油雾化过程中将从燃料中释放出来 会快速生成氢氰化物 HCN 并在较低的温度下 小于1100K 反映生成NO N2OPathwayAnotherNOformationmechanismimportantincombustionistheN2Opathway Theinitialreactionforthispathwayisthethreebodyreaction O N2 M N2O M 9 WhileN2OgenerallyrevertsbacktoN2 thisisnotalwaysthecase Underconditionswheretheairfuelratioislean NOcanformthrougheitherofthefollowingtworeactions N2O O NO NO 10 H N2O NO NH 11 ThisNOformationrouteisfuelandpressuredependent Athigherpressuresandlowertemperature thethree bodyinitiationbecomescompetitivewiththeO N2reactioninthethermalmechanism FuelNitrogenManyheavyfueloilscontainorganicnitrogenboundtothefuelmolecule ThisnitrogencanreacttoformadditionalNO TheextentoftheconversionoffuelnitrogentoNOisnearlyindependentoftheidentityofthemodelcompound butisstronglydependentonthelocaltemperatureandstoichiometryandontheinitiallevelofnitrogencompoundinthefuel airmixture ThepathwaythatfuelnitrogenfollowstoformNOdependsonwhetherthenitrogenisboundtoanaromaticringoranamine Ifthefuelnitrogenisboundtoanaromaticring thenitrogeninthefuelformshydrogencyanide HCN Intheflame equilibriumexistsforthereactionHCN H CN H2andthenitrogenwouldformNOthroughamechanismthatisessentiallythatofpromptNO Ifhoweverthefuelnitrogenisboundtoanamine ammonia NH3 wouldformquicklyintheflamezone Inlargeradicalpools theNHcompoundsareinequilibrium NH3 NH2 NH N 12 TheimportantreactionsforformingNOfromthisradicalpoolare NH2 O NHO H 13 NH2 O2 NHO OH 14 HNO X NO XH 15 HNO M NO H M 16 NOxinDieselFlamesThecriticalflamezoneinDieselcombustionforNOformationisthediffusionflamethatsurroundsthejet InnormalDieselcombustion thefuelhydrocarbonradicalsarebrokendownintofuelfragments H2andCOinthepartiallypremixedzonethecoreofthefueljet WhileNOcanforminpartiallypremixedflames thetemperatureofthiszoneinDieselenginesisgenerallytoolowtoresultinsignificantNOformation Thefuelfragments H2andCOfromthecoreofthejetarethefuelthatfeedstheouterdiffusionflame NOxinDieselFlamesUnderdiffusionflameconditionsfedwithhydrocarbonfragments H2andCO theNOformationmechanismsmentionedcanallplayanimportantrole ThermalNOisespeciallyimportantwhenpeaktemperaturesinconditionsexceed2000K PromptNOwillalmostcertainlybeproducedfromhydrocarbonfuelfragmentsanditsrelativerolewouldtendtoincreaseasmeasuressuchaschangesincombustionphasingaretakentolowercombustiontemperaturestoreducethermalNO TheimportanceoftheN2OmechanismunderDieselengineconditionshasalsobeenrecognized Itsrelativeimportanceisincreasedunderconditionsofincreasedturbulence ItisespeciallyimportanttoconsidertheNOformedfromorganicfuelnitrogeninenginesburningheavyfuels Mostofthesefuelscontainsignificantamountsofnitrogen TherelativeimportanceoffuelnitrogenwouldincreaseasothermeasuresaretakentoreduceNOxformedbyothermechanisms NOxREDUCTION GENERALOVERVIEW MethodstoreduceNOxemissionsmaybecategorizedaseitherPrimaryorSecondary PrimarymethodsreduceNOxformationatthesourceintheengineandincludemethodssuchasenginetuning modificationsandwaterbasedtechnologies SecondarymethodsreduceNOxintheexhaustgasbydownstreamtreatment reductionofNOxafterformationintheexhaust Althoughsomesecondarymethodsareveryeffective forexample SelectiveCatalyticReduction SCR hasareductioncapabilityofupto95 overallcostsaretypicallyhigher Primarymethodstypicallyhavehigherinitialcosts usuallyassociatedwiththemodificationstotheengine buttheoverallexpenseisconsiderablyless TheeffectivenessofdifferentNOxreductionmethodsvariesconsiderably Dataisoften manufacturerclaimed andeffectivenesscanbedependentonthespecificengine installationandloadconditions NOxReductionMethods 1 Intakeairhumidification waterinjection2 Stratifiedfuelwaterinjection3 Directwaterinjection DWI witha two needletype fuelandwaterinjectionnozzle4 DWIwitha separatewaterinjectionnozzle 5 Fuel wateremulsion Water BasedEmissionControlTechnologies TheeffectsofthisDWIatbothanearliertiming EDWI andalatertiming LDWI oncombustionwereclarifiedmainlybyhighspeedvisualstudiesofburningsprays HumidAirMotor HAM 4 Stroke DiagramofHAMprinciple 1 Seawaterinjectionintothechargeairbyanadd 2 HAMvesselbetweenTCandchargeairmanifold3 HT coolingwaterand orexhaustgasheatusedforwaterpreheating3 CACbypassed4 NOxreduction 65 withadditionalheat NOx Humidity Trend EngineDesign 1 OperationwithHAMshiftturbochargertosurginglimit TCrematchingandbypass2 CurrentchargeaircoolerbypassedEngineperformance 1 IncreasedboostpressureandTCspeed2 Exhaustgastemperatureandenginecomponentstemperaturesignificantlylower3 NoTCwashingrequired4 LimitedincreaseofSFOCabout1 nodeviationovertime5 Enginederatingnecessary 1 050kW cyl insteadof1 200kW cyl for48 60B EngineAdaptation ScavengeAirMoistening SAM System 2 Stroke 1 Firststageseawater followingstagesfreshwaterinjectionintochargeair2 InstalledinsidetheCACcasing3 Onlydesignedfor2 stroke stillunderdevelopment 4 NOxreduction 40 ScavengingAirMoistening SAM systemforNOxreduction SAMSystem8S60MC 100 Engineload SAMSystemInstallationofparts HumidifiedAirSystems HAM CASSandTDCSystems TheHAMprocessdesignedbyMuntersEuroformGmbHwasfirstbenchtestedonaMANB W3V40 50prototype4strokemediumspeeddieselengineintheresearchanddevelopmentfacilitiesofS E M T Pielstickin serviceverificationwascarriedoutinco operationwithVikingLineononeengine 12PC2 6 5 750kW onboardtheRoRoferry Mariella operatingintheBalticSea TheHAMsystemwasinstalledonmainengineNo 1inthesummerof1999 NOxreductionsof60 wereclaimedwithafinalcertificationvalueof4 4g kWhNOx Thehumidificationvesselis4mlong 1 4mindiameterandhas3humidifierstageswhichhumidifyandcooltheairfromapproximately160oCattheoutletofthecompressordowntoapproximately65 70oC Theairreachesabout98 relativehumiditywhichcorrespondstoanabsolutehumidityintherangeof60to80gwater kgdryair Seawaterisusedandre circulateduntilthesaltcontentincreasesbyabout6 Duringtheyear2000 Marioff adeveloperofwatermistsystemsforfiresuppression startedtodeveloptheCombustionAirSaturationSystem CASS Thekeytothissystemdevelopmentisthespraynozzleandcontrolsystem Airandwaterinvaryingratiosaresuppliedtothenozzleprovidingwaterdropletsizesaround50to200 mandW Fratiosfrom0 5to2 5 Theair waterratiosuppliedtothenozzleisvariedsothatthewaterdropletsizeisafunctionofengineloadwiththesmallestdropletsizesproducedwhentheengineloadislowandgoodevaporationismoredifficult Earlyin2001 apressreleasewasissuedthatstatedthatMarioffandW rtsil hadformedapartnership During2001andearly2002 full scaleenginetestswerecarriedoutatW rtsil inFinland ReductionofNOxtolessthan3g kWhwasclaimedatthetimeforstartingvaluesof10 15g kWh Currentclaimsare 50 NOxreductionatW F 2 0andsaturatedairat50 90oC PrototypeintakeairwaterinjectionsystemshavebeendevelopedbyM A TurboandtheTransportationDevelopmentCentre TDC ReadersaredirectedtoSection8ofthisreportfordetailsonthesesystemsandtestdatasets Bothsystemsareintendedforretrofittoexistingengines UnlikeHAMandCASSwhicharesophisticateddesignsintendedtoinputgaseouswater vapour intothecylinder theM A TurboandTDCsystemsintroduceatomizedliquidwa