DN1200氨吸收塔设计

页共62页madein1962thatstillformthebasisofmoderncodes:Pressurevesselsshouldbefullystressrelieved.Extremecareshouldbeusedtoeliminateoxygenfromammoniasystems.Ammoniashouldcontainatleast0.2%watertoinhibitSCC.LoginowreportedthatadoptionoftheserecommendationspracticallyeliminatedSCCincarbonsteelvesselsintheagricultureindustry.However,inarecentWesternCanadiansurveySCCwasfoundin100of117fieldstoragevesselsinspectedbywetfluorescentmagneticparticletesting(WFMT)(3).DespitetheabovemeasuresSCCcontinuedtooccurinroadtransporttanksconstructedfromhighstrengthsteels,inrefrigeratedstoragevesselsandinvesselswhichhadbeenweldrepairedbutnotsubsequentlystressrelieved.AnadditionalrecommendationtolimitsteeltensileoryieldstrengthwasembodiedintheU.S.andBritishammoniastoragecodes,respectively(4,5).ANSIK61.1—Nominaltensilenogreaterthan70,000psi(580MPa)U.K.Code—Minimumspecifiedyieldstrengthshallnotexceed350MPa(51,000psi).PRACTICALCONSIDERATIONSThisarticleisconcernedmainlywithpracticalconsiderationsimportanttopulpandpapermillsalreadypossessinganhydrousammoniastoragevesselsorplanningtofabricatesuchvessels.Inviewoftheindustry’sexperiencewithSCCincontinuousdigestersthegoverningobjectivesshouldbetocontrolfabricationandinspectiontoprevent,oratleastminimize,in-serviceproblemsincludingover-reactiontorelativelyminorcrackindications.Guidanceisavailableinthepublishedcodesanddetailedinformationisavailablefromsomeammoniasuppliers.FabricationThetwomainobjectivesinfabricationshouldbetoprovidethemostcrackresistantvesselpossibleatreasonablecostandtoensurethatanadequateinspectionbaselineisavailableforinterpretationofsubsequentin-serviceinspections.ASMESectionVIIIDivision1doesnotrequirestressreliefforanhydrousammoniastoragepressurevesselsunlesstheownerspecifiesalethalservicedesignation.Thelethalservicedesignationrequiresradiographictesting(RT)ofallbuttweldedjointspluspostweldheattreatment.ANSIK-61.1-1989,“AmericanNationalStandardSafetyRequirementsfortheStorageandHandlingofAnhydrousAmmonia,”addsseveralrequirements:FabricationtoASMESectionVIIIDivision1TableUW12atajointefficiencylessthan80%isnotallowed.InspectionandtestingunderUG-90(c)(2)(multiple,duplicatepressurevesselfabrication)isnotallowed.Steelusedforpressurecontainingpartsshallhaveanominaltensilestrengthnogreaterthan580MPa(70,000psi).Theminimumdesignpressureforambienttemperaturestorageshallbe16bar(250psig).Postweldheattreatmentismandatoryandafurnaceofsufficientsizetoaccommodatetheentirevesselisrecommended.Weldedattachmentsmaybemadetopadsafterpostweldheattreatment.Horizontalvesselsshallbemountedonsaddleswhichextendoveratleastonethirdoftheshell’scircumference.Thermalexpansionandcontractionshallbeallowedforandmeansprovidedtopreventcorrosionbetweentheshellandthesaddles.The1986BritishCode“StorageofAnhydrousAmmoniaunderPressureintheUnitedKingdom”requires:Steelmusthavespecifiedminimumyieldstrengthlessthan350MPa(51,000psi).Weldfillermusthaveminimalstrengthovermatchcomparedwiththebaseplate.100%magneticparticleinspectionofallinternalweldsinordertoprovidearecordagainstwhichallfutureinspectionsofthevesselcanbeassessed.Noweldingispermittedafterstressreliefwithoutsubsequentlocalstressrelief.Concretesaddlesareprohibited.Supportmustbeoncontinuouslyweldedsteelsaddlesattachedbeforestressrelief.AlthoughtheBritishCodedoesnotstatethatmagnetiparticleinspectionshouldbebyWFMTitisgenerallyagreedthatWFMTisthemostsensitivetechniqueandshouldbeusedforinspectionofammoniastoragevessels.Allinspectionshouldbeperformedbyqualifiedtechnicians.SNT-TC-1ALevelIIisarecommendedminimum.Onepulpandpapercompanyhasaddedthefollowingrequirementsforfabricationofsuchvessels:Incorporationofa“corrosionallowance”ofatleast1.6mm(1/16in.)topermitminordefectchasingduringin-serviceinspectionsandtoprovideamarginagainstpittingwhichmayoccurifwaterisallowedtoenteranoutofservicevessel.Allweldtoesprofiledbygrindingpriortowetfluorescentmagneticparticletesting(WFMT).AllWFMTindicationsgreaterthan1.6mm(1/16in.)toberemovedbygrindingbeforepostweldheattreatment.Shearwaveultrasonictesting(UT)ofnozzle-to-shellweldspermittedifRTisjudgedimpractical.WFMTtoberepeatedafterfinalhydrotesttestofthevesselandthereportretainedbytheowner.Vesseltobedriedcompletelyafterhydrotesttestandnitrogenpaddeduntilfilledwithammonia.Valves,piping,andfittingsBoththeANSIandU.K.codesaddresspiping,valves,andfittings.Adetailedsummaryisbeyondthescopeofthisarticle,butsomepointsareworthnoting.ANSIK61.1requiresallnonrefrigeratedammoniapipingtomeettherequirementsofANSI/ASMEB31.3“ChemicalPlantandPetroleumRefineryPiping.”TheU.K.Codestatescopperandcopperbearingalloysshallnotbeused.ANSI/ASMEB31.3requiresaminimumof5%ofpipingweldsberadiographicallytested.Valvesandotherapparatusshouldberatedforammoniaserviceandshouldnotcontaincopperorcopperalloycomponents.Inonecase,anickelrupturedisccorrodedtofailureatitsperipheryduetoformationofanammoniasolutionatagasketedjointexposedtotheweather.In-serviceinspectionVesselentryLiquidorgaseousammoniaishazardousandinsomejurisdictionsreleaseofammoniavaportotheatmosphereisprohibitedbylaw.Vesselsmustbeproperlypurgedbywaterand/orsteam.Detailedproceduresforvesselpurgingandentryareavailablefromammoniasuppliers(6).InspectionproceduresTheANSIstandarddoesnotaddressin-serviceinspectionbutdoesstateweldrepairoralterationmustconformtothecurrenteditionoftheNationalBoardInspectionCode(NBIC).The1992editionoftheNBICincludesnonmandatoryguidelinesforinspectionofliquidammoniavessels(7).Theseguidelinesrecommend:PowerbuffingorlightsandblastingassurfacepreparationforinspectionAllinteriorweldsbeexaminedbyWFMT.CracksshouldberemovedbygrindingwithoutencroachingontheminimumthicknessrequiredbyASMESectionVIIIandtheoriginaldesign.Weldrepairs,regardlessofsize,shouldbepostweldheattreatedwhereverpossible.LightgrindingdoesincreasethesensitivityofWFMTcomparedtosandblastingorpowerbuffing(8).ForexampletheNBICmandatesgrindingassurfacepreparationfordeaeratorinspection.Theomissionofgrindingintheguidelinesforammoniavesselin-serviceinspectionmaybeduetoconcernthatroughgrindingmayproduceresidualstresssufficienttoinitiateSCCinanhydrousammoniaservice.IfweldshavebeenproperlyprofiledforWFMToninitialfabrication,thengrindingforin-serviceinspectionshouldnotbeneeded.TheNBICguidelinesalsostatethatotherinspectionmethodssuchasacousticemissionorultrasonicsmaybeusedandthatfracturemechanicsmaybeusedtoassesstheintegrityofvesselswherecompleteremovalofcracksisnotpractical.Normallytheonlycorrosionthatoccursinanhydrousammoniavesselsisduetowateringressduringoutofserviceperiods.Shallowpitting,however,hasbeenfoundinthebottomofsomevesselsbeneathoilydeposits.Thesourceofoilispresumedtobefromcompressorsusedtohandletheammonia.Inviewofconcernsoveraircontaminationduetovesselentryandresidualstressimpartedbygrindingnonintrusiveinspection,techniqueslikeacousticemissionandUTcouldbeconsideredbyvesselowners.TheBritishCodedoesnotmentionnonintrusiveinspectionofambienttemperaturepressurevesselsbutdoesstatethat,ifacousticemissionistobeusedforsphericalstoragevessels,areferencebaseshouldbetakenduringinitialhydrotesting.Nonintrusiveinspectionisbeingusedinotherindustries(9).VesselrefillingSafetyproceduresshouldbeestablishedforrefillingavesselthathasbeenemptiedforinspection.ItisalsoveryimportanttopurgethevesselofairtopreventtheoccurrenceofSCC.Detailedinstructionsareavailablefromammoniasuppliers(10).Ifavesselisnottobereturnedtoserviceimmediatelyafterinspection,thencareshouldbetakentodryitandpossiblynitrogen-paditdependingonthetimeitwillremainoutofservice.InspectionfrequencyNeithertheANSIdocumentnortheNBICdealswithinspectionfrequency.TheBritishCoderecommendsthefollowing:WFMTinspectionof100%ofallinternalbuttweldswithinthefirstthreeyearsofserviceWFMTre-inspectionwithin2yearsifsignificantdefectsarefoundSubsequenttonosignificantdefectsbeingfound,anysubsequentinspectionshouldincludeWFMTofallTeejunctionsand10%ofthetotallengthofbuttweldsInnocaseshouldthesubsequentexaminationintervalexceed6years.Itisapparentfromtheabovethatlatitudecanexistforin-serviceinspectiontechniquesandfrequencies.Eachownershoulddetermineinspectionfrequencyinconjunctionwiththeappropriateauthority.Somejurisdictionsrequirea3-yearinspectionfrequency.SUMMARYTheuseofcarbonsteelpressurevesselsforstorageofanhydrousammoniainthepulpandpaperindustrycouldbeanon-eventordeteriorateintoacycleofinspectionandrepair.ThisarticlehashighlightedmajorconcernsrelatedtoSCC.ThereisawealthofadditionalinformationavailableonallconsiderationsrelatedtothesevesselsfromtheANSIandBritishCodes,theNACEdocument,ammoniasuppliers,andthecurrenttechnicalliterature.TheAmericanInstituteofChemicalEngineers(AIChE)holdstheannualAIChEAmmoniaSafetySymposiumaimedatfindingwaystosafelymanufacture,transport,andstoreammoniaandrelatedchemicals.TheproceedingsofthesesymposiaarepublishedbyAIChE.Itisrecommendedthatanyownerofsuchvesselskeepawareofcurrentexpertise.ReidismaterialsandcorrosionsectionheadwithMacMillanBloedelResearch,4225KincaidSt.,Burnaby,BC,CanadaV5G4P5.Taskgroupmembers:CraigReid;R.S.Charlton,LeveltonAssociatesConsultingEngrs.;R.C.Faloon,MQSInspectionsInc.;andW.E.Boudreau,BelleTestingInc.LiteraturecitedLoginow,A.W.,MaterialsPerformance25(12):18(1986).NACETechnicalCommitteereport5A192,IntegrityofEquipmentinAnhydrousAmmoniaStorageandHandling,Houston,NACEStorageTank,Spokane,1992.Stephens,J.D.andVidalin,F.,1994AIChEAmmoniaSymposiumNotes,AmericanInstituteofChemicalEngineers,NewYork,p.9.CompressedGasAssociationInc.,AmericanNationalStandardSafetyRequirementsfortheStorageandHandlingofAnhydrousAmmoniaANSIK61.1-1989,Arlington,VA,1989(CGAPamphletG-2.1-1989).StorageofAnhydrousAmmoniaUnderPressureintheUnitedKingdom,London,HerMajesty’sStationeryOffice,1986.(HealthandSafetyBookletHS/G30)ComincoFertilizers(U.S.)Inc.,DecommissioninganAmmoniaStorageTank,Spokane,1992.TheNationalBoardofBoilerandPressureVesselInspectors,NationalBoardInspectionCode:AManualforBoilerandPressureVesselInspectors,Columbus,OH,1992,p.197.Reid,J.C.andReid,C.,TAPPI1992EngineeringConferenceProceedings,TAPPIPRESS,Atlanta,BookI,p.163.Conley,M.J.,Sture,A.,andWilliams,D.,“AmmoniaVesselIntegrityProgram:AModernApproach,1990AIChEAmmoniaSymposiumNotes,NewYork,AIChE,1990.ComincoFertilizers(U.S.)Inc.,“CommissioninganAmmoniaStorageTank”,Spokane,1992.附录二外文翻译：纸浆和造纸行业中的无水氨压力容器本文的目的是为了确保纸浆和纸张经营公司，他们的工程顾问，承建商了解在脱水氨设备中的应力腐蚀开裂现象。这篇资料是由美国纸浆与造纸工业技术协会无损检测工程部和质量控制小组委员会共同编写。细菌生存在一些活性污泥污水处理系统中需要充足的食物。在某些情况下，这种食品是氨和磷酸的储存现场。氨通常以无水液氨的形式贮存在室温和1.6MPa(250磅)的压力的碳钢容器中。这些容器可能会受到应力腐蚀开裂(SCC)。应力腐蚀开裂可能导致氨泄露，这是一种危险化学品。用于无水氨设备的碳钢容器中的SCC是有点类似于连续蒸煮罐的经验。例如，减少压力的引入在生产和在役检查过程都是很常见的。本文关注在常温下的卧式压力容器，像这类型容器通常用于纸浆和造纸的应用。大型冷藏储罐在化工行业一般是常压储存。SCC在氨储罐的历史在碳钢氨储存容器的历史是由（）审查通过也是在简要回顾了技术委员会报告题为“完整的设备在无水氨的储存和处理”（2）。在20世纪50年代，液氨作为肥料直接注入土壤。碳钢贮存容器由于应力腐蚀开裂而导致的故障开始出现。这些故障是意外，因为液氨已用于在制冷，化工多年，金属热处理行业没有报告的问题。调查结果证应力腐蚀是开裂的原因。1962年提出了三条建议构成了现代条例的基础：压力容器应充分消除应力。要特别小心是消除氨系统中的氧气。氨应该包含至少0.2％的水，以抑制应力腐蚀开裂。Loginow报告说，采用这些建议能有效避免应力腐蚀发生在农业用碳钢容器中。然而，最近的加拿大西部的调查显示通过湿荧光磁粉探伤检查（WFMT）（3）发现117处农场的储罐中有100处发生了应力腐蚀开裂。尽管采用了上述措施，SCC仍然发生在由高强度钢建造的公路运输油罐、冷藏储存容器以及作了焊接修复却没后续的应力消除的容器。另外一条建议被纳入美国和英国的氨储存条例，以限制钢材的拉伸或屈服强度。ANSIK61.1-名义抗拉强度不超过70,000磅（580兆帕）英国条例指定的最低屈服强度不超过350兆帕（51,000磅）。实用的考虑本文主要关注是实际问题对于已拥有无水氨贮存容器的纸浆和造纸厂或计划制作这类容器的重要性。以连续蒸发罐中SCC的经验来看，执行目标应该是控制制造和检验，以避免或至少减少在运行中的问题，包括过度反应相对轻微裂缝的迹象。从一些氨的供应商提供公开条例和规范资料可以得到相关的指导。制造制作中的两个主要目标应是提为抗裂容器供合理的成本，并确保为后续在役检验的解释有适当的检验基线可用。ASME第1部第VIII节没有要求无水氨存储压力容器要应力消除，除非拥有者指定了一个致命的部件名称。指定的致命部件需要焊接接头的焊后热处理加所有对接射线检测（RT）。美国国家标准化组织（ANSI）K-61.1-1989,“美国国家标准无水氨的存储和处理安全要求”增加了几个要求：制造符合ASME第一部第VIII节UW12表的效率不能低于80%。基于UG-90（c）检查和测试是不允许的。用于压力容器部件的钢材的标称抗拉强度应当不低于580MPa（70,000psi）。室温储罐的最低设计压力应当为16bar（250psig）的。•必须进行焊后热处理，要求足够大的熔炉来适应整个容器。附件的焊接点可能要进行热处理卧式压力容器应当安装在鞍座超过至少有一个壳体的周长三分之一。应允许热膨胀和收缩和给出以防止壳体和鞍座之间腐蚀的方法。1986年英国章程“英国常压无水氨储存”要求：钢材的指定最低屈服强度必须小于350兆帕（51,000磅）。焊接填充物的最小强度必须高于于比母材强度。100%的内部焊缝磁粉探伤，对未来所有的容器检查提供可以评估的纪录。没有后续局部应力消除的应力消除后允许无焊接混凝土鞍座是禁止的。钢制鞍座连续焊接必须在应力释放之前。虽然英国规范并没有规定磁化粒子检查应当进行湿荧光磁粉实验，人们普遍认为，WFMT是最灵敏的技术，应该用于检验氨贮存容器。所有的检查应该由合格的技术人员来完成。SNT-TC-1AII级是建议的最低水平。其中纸浆和造纸公司已对这些容器的制造增加了下列要求：设立“腐蚀裕量”至少1.6毫米（1/16英寸），允许在役检验中出现的微小缺陷，并在容器停止服役期间浸水，对可能出现的腐蚀保持一定的裕度。，湿荧光磁粉探伤（WFMT）检验所有焊接接头前要进行磨削。在焊后热处理前，大于1.6毫米（1/16英寸）所有WFMT迹象要被磨削。如果射线探伤不符合实际，可以使用横波超声波检测（UT）。容器水压试验后重复进行WFMT,由业主保留的测试报告。容器水压试验后要完全干燥，并且进行充氮保护直至填充氨。阀门，管道及配件ANSI和英国压力容器规范都对管道，阀门和配件进行了论述。详细摘要已经超出了本文的范围，但有些要点是值得注意的。ANSIK61.1要求所有的非冷却氨管道要满足符合ANSI/ASMEB31.3的规定“化工厂和石油精炼厂管道。”•英国压力容器规范规定铜及铜合金轴承不得使用。ANSI/ASMEB31.3要求5%以上管道焊缝需要X线测试。阀门和其他设备应使用标准的的氨部件，并且不能含有铜或铜合金成分。在一个案例中，一个镀镍爆破片腐蚀失效原因在于衬垫上的氨溶液的形成在役检查容器引进。液态或气态氨是危险化学品的，而且某些司法管辖区的法律禁止氨蒸气释放到大气中。容器必须用水或蒸汽妥善清除。从氨供应商获取详细的清洗和引进说明（6）。检查程序。ANSI标准不涉及在役检查，但要求焊接修复或改装，必须符合现行版国家检测局规范（NBIC）。该NBIC1992年版包括液氨储罐非强制性的检查指导。这些指导原则建议：抛光或喷砂表面处理为检查做准备所有的内部焊缝进行WFMT检测。裂缝应磨削处理以符合ASME第八节规定的最小设计厚度。焊缝，不论尺寸，都应进行焊后热处理。轻微磨削相对喷砂处理和电学抛光可以增加WFMT灵敏性相（8）。例如，NBIC要求磨削作为除氧检测的表面处理的准备。在氨储罐的在役检查指导中磨削的遗漏可能是由于担心粗磨可能产生的残余应力以致产生应力腐蚀开裂。如果在初始制造过程中焊缝因WFMT产生了合适的变形，那么在在役检查中磨削就没有必要了。该NBIC准则还规定，如可能使用声发射或超声波等检查方法，断裂力学可用于评估那里的容器完整性裂缝彻底清除是不实际的。通常，腐蚀只发生在无水氨储罐，是因为在停止运行期间渗入水。浅点蚀已发现在有些容器底部的油性沉淀物。油源被假定为从用来处理氨的压缩机。针对由于容器引进而产生的空气污染问题和磨削无损检测产生残余应力的问题，采用如声发射技术和UT的技术可以由使用者考虑。英国规范并没有提及常温常压容器的无损检测，但指出了，如果声发射检测要用于球形储存容器，应当在初始水压试验采取相应的参考。无损检测应用于其他行业。储罐填充。应该为因检查而清空的容器填充建立一个安全规程。这对于净化容器空气防止发生应力腐蚀开裂是非常重要的。从氨供应商获取详细说明（10）。如果容器在检查后没有被立刻送回返修，然后应注意干燥，并有可能氮封它取决于停止服役的时间。检查频率。无论是ANSI文件或NBIC没有处理检验频率。英国规范建议如下：在首三年服役期WFMT100%检查所有内部的对接焊缝如果在两年内发现重大缺陷进行重新检查，继无发现明显缺陷后，后续的任何检查应对所有T型接头和的对接焊缝总长度的10%进行WFMT检测在任何情况下后续检查的时间间隔超过6年。从上述可以很明显看出在役检查技术和频率存在一定范围。每个使用者应与结合相关部门确定检查频率。有些管辖区需要3年的检查频率。总结对纸浆和造纸工业的碳钢无水氨储存压力容器的使用可能是一个非活动或进入检查和维修的恶性循环。本文重点关注的是应力腐蚀开裂。从ANSI和英国规范，NACE文件，氨储罐供应商和现行的技术文献可以获取的大量有关注意事项的信息。在美国化学工程师学会（AIChE）举行的年度合成氨安全研讨会旨在发现在安全生产，