燃煤锅炉的燃烧进程控制毕业设计外文翻译.docx
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燃煤锅炉的燃烧进程控制毕业设计外文翻译.docx
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燃煤锅炉的燃烧进程控制毕业设计外文翻译
ControllingtheFurnaceProcessinCoal-FiredBoilers
Theunstabletrendsthatexistinthemarketoffuelsuppliedtothermalpowerplantsandthesituationsinwhichtheparametersoftheiroperationneedtobechanged(orpreserved),aswellasthetendencytowardtheeconomicalandenvironmentalrequirementsplacedonthembecomingmorestringent,arefactorsthatmaketheproblemofcontrollingthecombustionandheattransferprocessesinfurnacedevicesveryurgent.Thesolutiontothisproblemhastwoaspects.Thefirstinvolvesdevelopmentofacombustiontechnologyand,accordingly,thedesignofafurnacedevicewhennewinstallationsaredesigned.Thesecondinvolvesmodernizationofalreadyexistingequipment.Inbothcases,thetechnicalsolutionsbeingadoptedmustbeproperlysubstantiatedwiththeuseofbothexperimentalandcalculationstudies.
TheexperienceCentralBoiler-TurbineInstituteResearchandProductionAssociation(TsKTI)andZiOspecialistsgainedfromoperationofboilersandexperimentalinvestigationstheycarriedoutonmodelsallowedthemtoproposeseveralnewdesignsofmultifuelandmaneuverable—inotherwords,controllable—furnacedevicesthathadbeenputinoperationatpowerstationsforseveralyears.Alongwiththis,anapproximatezero-one-dimensional,zonewisecalculationmodelofthefurnaceprocessinboilershadbeendevelopedattheTsKTI,whichallowedTsKTIspecialiststocarryoutengineeringcalculationsofthemainparametersofthisprocessandcalculatestudiesoffurnacesemployingdifferenttechnologiesoffiringandcombustionmodes.
Naturally,furnaceprocessadjustmentmethodslikechangingtheairexcessfactor,stackgasrecirculationfraction,anddistributionoffuelandairamongthetiersofburners,aswellasotheroperationswrittenintheboileroperationalchart,areusedduringboileroperation.However,theeffecttheyhaveontheprocessislimitedinnature.Ontheotherhand,controlofthefurnaceprocessinaboilerimpliesthepossibilityofmakingsubstantialchangesintheconditionsunderwhichthecombustionandheattransferproceedinordertoconsiderablyexpandtherangeofloads,minimizeheatlosses,reducetheextenttowhichthefurnaceiscontaminatedwithslag,decreasetheemissionsofharmfulsubstances,andshifttoanotherfuel.Suchacontrolcanbeobtainedbymakinguseofthefollowingthreemainfactors:
(i)theflowsofoxidizerandgasesbeingsettomoveintheflameinadesiredaerodynamicmanner;
(ii)themethodusedtosupplyfuelintothefurnaceandtheplaceatwhichitisadmittedthereto;
(iii)thefinenesstowhichthefuelismilled.
Thelattercaseimpliesthataflame-bedmethodisusedalongwiththeflamemethodforcombustingfuel.Thebedcombustionmethodcanbeimplementedinthreedesignversions:
mechanicalgrateswithadensebed,fluidized-bedfurnaces,andspouted-bedfurnaces.
Aswillbeshownbelow,thefirstfactorcanbemadetoworkbysettingupbulkyvorticestransferringlargevolumesofairandcombustionproductsacrossandalongthefurnacedevice.Iffuelisfiredinaflame,theoptimalmethodoffeedingittothefurnaceistoadmitittothezonesnearthecentersofcirculatingvortices,asituationespeciallytypicalofhighlyintensefurnacedevices.Thecombustionprocessinthesezonesfeaturesalowairexcessfactor(α<1)andalonglocaltimeforwhichthecomponentsdwellinthem,factorsthathelpmakethecombustionprocessmorestableandreducetheemissionofnitrogenoxides.
Alsoimportantforthecontrolofafurnaceprocesswhensolidfuelisfiredisthefinenesstowhichitismilled;ifwewishtominimizeincompletecombustion,thedegreetowhichfuelismilledshouldbeharmonizedwiththelocationatwhichthefuelisadmittedintothefurnaceandthemethodforsupplyingitthere,fortheoccurrenceofunburnedcarbonmaybeduenotonlytoincompletecombustionoflarge-sizefuelfractions,butalsoduetofineonesfailingtoignite(especiallywhenthecontentofvolatilesVdaf<20%).
Owingtothepossibilityofpictoriallydemonstratingthemotionofflows,furnaceaerodynamicsisattractingagreatdealofattentionofresearchersanddesignerswhodevelopandimprovefurnacedevices.Atthesametime,furnaceaerodynamicsliesattheheartofmixing(masstransfer),aprocessthequantitativeparametersofwhichcanbeestimatedonlyindirectlyorbyspecialmeasurements.Thequalitywithwhichcomponentsaremixedinthefurnacechamberproperdependsonthenumber,layout,andmomentaofthejetsflowingoutfromindividualburnersornozzles,aswellasontheirinteractionwiththeflowoffluegases,withoneanother,orwiththewall.
Itwassuggestedthatthegas-jetthrowdistancebeusedasaparameterdeterminingthedegreetowhichfuelismixedwithairinthegasburnerchannel.Such
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- 关 键 词:
- 燃煤 锅炉 燃烧 进程 控制 毕业设计 外文 翻译
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