应用化学专业文献原文及翻译Word文件下载.docx
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应用化学专业文献原文及翻译Word文件下载.docx
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Abstract:
Theinfluencingfactors,abnoimalphenomenonandrectificationprocesswereanalyzedtodirectactualoperation
Keywords:
rectificationtower,recification,reboiler,operation
Distillationcolumnisamulti-stagepartialvaporizationandpartialcondensationaccordingtothedifferentcomponentsinthemixturevolatilityineachfloortowerboardtoachievetheseparationofamixtureofvariouscomponentsofthetowergas-liquidcontactdevice,alsoknownasdistillation.Aplatecolumnandpackedcolumntypes.Accordingtomodeofoperationaredividedintocontinuousdistillationandbatchdistillation.Steamfromthebottomofthecolumnentry,andthedeclineinliquidcountercurrentcontactwiththetwoincontact,thedropinthevolatileliquid(lowboilingpoint)componentsiscontinuouslytransferredtothesteam.Thedifficultyofsteamvolatile(highboiling)componentcontinuedtodeclineinthetransferofliquid,steamthecloserthetopofthetower,thehighertheconcentrationofitsvolatilecomponents,whilethedeclineintheclosertowerbottomliquid,itshardtobemorevolatilecomponentsrichset,toachievecomponentseparation.Steamrisingfromthetopofthetowerintothecondenser,theliquidpartofthecondensateasrefluxliquidtoreturnintothedistillationtower,therestisremovedasdistillate.Towerbottomoutflowofliquid,someofwhichintothereboiler,thermalevaporation,thesteambacktotower,andtheotherpartoftheliquidasresiduarelease.
Comparedwithotherchemicalunitoperations,distillationunit,althoughrelativelysimple,singleproductionrunthatoftenappearinavarietyofproblemsaffectingtheoperationofthedistillationunit,leadingtotowertoporbottomofproductfailure,severeconstraintsofproductionequipmenttheoperationresultinginproductloss.
1.Regularchangesinprocessconditionsofdistillationcolumn
1.1Reboilertemperature
Underthesameoperatingpressure,raisingthetemperatureofthereboiler,thevolatilecomponentsinthetowerliquidtoreduce,atthesametime,therisingvaporvelocityincreases,andhelptoimprovetheefficiencyofmasstransfer.Ifproductsfromthetopofthetower,thetowerreactordischargeofdifficultvolatilesvolatilecomponentstoreduceandreducelosses.Ifthetowerreactoreffluentsfortheproduct,itcanimproveproductqualitytowerdischargeofvolatilecomponentsentraineddifficultnolatilecomponentsincreased,therebyincreasingthelosses.Inbalancedoperation,thereactortemperatureissuddenlyincreased,andittoolatetoadjustthepressureandtemperaturewillinevitablyleadtothereboilerfluidissteam-air,thepressureincreased.Atthistime,thetowergas,liquidcompositionchanges,therestructuringwerelikelytobesteamedtothetopofthetower,sothatthefailureoftopproduct.
1.2Operatingpressure
Inthecaseofcertainoperatingtemperature,increasingtheoperatingpressurecanincreasetheproductivecapacityofthetower,sothatstableoperation,butthecontentofvolatilegroupinthetowerreactorproducts.Indistillation,oftenprovidesfortheadjustmentrangeoftheoperatingpressure.Whenthefalloutoftheoperatingpressurebyextmrnalfactors,weredestroyed,thenormaloperationofthetowerwillbecompletelydestroyed.
1.3Feedingtemperature
1.3.1Condensatefeed,thefeedtemperatureislowerthanthetemperatureofthefeedingboard,andaddedifallthematerialintothestrippersegment,strippingsegmentloadincreases,thereboilerconsumptionincreaseintheamountofsteam,andthetopofthetowerisdifficultvolatilegroupwerelower.
1.3.2Saturatedsteamfeed,thefeedmaterialtemperatureishigherthanthetemperatureoffeedboard,allthematerialofthefeedintotherectifyingsectionandstrippingsectionoftheloadreduction,andincreasedloadoftherectifyingsection,makethetopproductqualityreduce.
1.4Feedingquantityandcompositionchanges
Changesinthefeedstockofadirectimpactonthechangeoftheamountofsteam,thelatterincreasewillproduceentrained,evenflooding.Thefeedstockistoolow,theoperationisnotgoodtomaintainthebalanceofthetower,thesteamvelocitydecreases,theplateispronetoleakage,therectificationefficiencyislow.Inthelow-loadoperation,maybeappropriatetoincreasetherefluxratio,thetoweroperatinginaloadlowerlimitabovenormalandstableoperationinordertomaintainthetower.Feedingcomponentofthechangesdirectlyaffecttheproductquality.Increasedrestructuringconcentrationincreaseintherectifyingsectionloadseparationisnotgood,theresultsofrestructuringwerebroughttothetopoftower,causingthetopofthetowerofinferiorquality.Productfromthereboiler,thetopofthetowerlossesincrease.Iftheconcentrationofthevolatilegroupinthefeedinggroupwereincreased,andthestrippingsectionoftheloadincreases,maybepoorduetotheseparationcausedbythetowerreactorproductsofinferiorquality,whichentrainedvolatilecomponentsincreased.Feedingrestructuringconcentrationincreased,thefeedingmouthmovedownandviceversa,thenmoveup.Thesametime,operatingtemperature,backflowandoperatingpressuremustbeadjustedaccordinglyinordertoensurethestabilityofthedistillationoperation.
Distillation,increasingtherefluxratio,canimprovethequalityoftheproduct,buttherefluxratioistoolarge,theinnerloopofthetowerincreased,increasingenergyconsumption.Reductionoftherefluxratio,thetowergas-liquidcontactisnotgood,thebalancetodamagedandthereforethemasstransferefficiencydecreased.Thesametime,theoperatingpressuredrop,difficultvolatilecomponentseasilybroughttothetopofthetower,resultinginasubstandardproduct.
2Anomaliesinthedistillationcolumnduringoperation
2.1Platecapacity
Rectifyingsectiontraydowncomeroverflowliquidtransportation,however,thatthetowerupperpartofthebeginningofflooding,aphenomenonknownasdowncomerobstructionorliquidflooding.Itscausesistoblocktheliquidleavingthetowerboardlevelriseinthedowncomerplatebetweenmistentrainedexcessiveleavingthetrayefficiencytoreduceentrainmentofthisphenomenonisknownastheexcessivefogorsteamflooding,thereasonistherelativeinthegaswhilethetowerboardbubblingareaistoosmall.
2.2Platefouling
Sedimentcumulativetotheboardofboardofthetowerisanimportantissue,traysofdirtwilltowerprematurefloodingwillreducetheplateefficiency.Platescalingphenomenon:
(1)Therefluxratioisnothighonliquidpan;
(2)Thepressuredropincreasebetweenthetray;
(3)Increasetherefluxratioonthebottomofthecolumntemperature,floworreboilerloaddoesnothaveanyimpact,iftherefluxratiototheheatbalanceandmaterialbalanceof20%to30%,whilethetowerdidnotchangesignificantly,thenthetowermustbecompletelyfullofliquid.Theamountofreturningtowerdirectstreamgaspipelinethroughthetopofthetowerbacktotherefluxtank.
2.3Slugflowsintheriser
Slugflowintheriserisadistillationcolumnrunningunstable,maybecausedduetoanunstablegas-liquidmixtureflowintheverticalpipeline.Refluxtankiselevatedattheofthecondenserbythecondenserdischargelogisticsisthatpartofthepipelinebetweenthegas-liquidtwo-phasemixture,thecondenserandrefluxtankiscalledtheriser.Generatealiquidcolumnintheriserflowrateistoolowwillresultintwo-phaseseparation,thedistillationcolumntoproduceabackpressure,thisliquidcolumnintermittentlybeintroducedaftertheriser,backpressurewillweaken,thentherisergraduallybeingfilledwithliquid,suchslugflowwillcausethetowerpressureperiodicpulseofchange.
Abnormalfactorscausedistillationcolumnplatewaswashedaway,condensercorrosion,cloggedcaondenser,notcondensablegasinfluencecondenser.
3.Reboiler
Reboilerinthedistillationcolumnoccupiesaveryimportantposition,itusedtobebottomafterthevaporizationoftheliquidpartofthebacktothedistillationcolumn,twophasesofthetowergas-liquidcontactandmasstransfertoproceed.Whichusedtheverticalthermalsiphonreboiler,whichisaverticalplacementoftheshellandtubeheatexchanger.Partialvaporizationofliquidinthebottom-uptubepassesthroughtheheatexchanger,heatingtheheatcarrierintheshell.Verticalthermalsiphonreboilerfeatures:
(1)cycledrivingforce:
thedensityofthereactorliquidandtheheatexchangertubegas-liquidmixture;
(2)compact,smallfootprint,highheattransfercoefficient;
(3)oftheshellcannotbemechanicallycleaned,notsuitableforhightowerreactor,heattransfermediumviscosity,ordirty;
(4)providethespaceandbufferzonesofthegas-liquidseparator.
Factorsthatdeterminethedistillationcolumncapacityrestricted,findthereboilerfailureisthemostlaborious,thedistillationcolumnbysteamreboiler.
(1)gas-barrierdrainvalvefailure;
(2)steamcondensatecollectedindoorpressureistoolarge;
(3)thecondensateliquidsealfailure.
Hydrophobicfailurecausedbyhydrophobicfailurefactors:
3.1Thermosiphonrebilerfailure
Reboilerliquidinletpipeandoutletpipecoldliquidmixtureexistsbetweenthedensitydifferenceisthedensitydifferencedrivingtheprocessofprocessingliquidflowthroughthereboiler.Whentowerhumoralbitelevatedtothereboilerbacktotheliquidnozzleheight,siphoncirculationwillbeimpeded.Thecirculationratereductionwillresultinthereductionofheattransfer,thusthecoverbacktothefluidnozzleisclearlyanimportantreasonforfluctuationsinthereboilerduties.
3.2Non-condensablegasinthewatervapor
Steam
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