简介:Electricalcapacitancetomography(ECT)wasappliedinmeasuringxolidsdistributioninsquarecirculatingfluidizedbeda.Thefluidizationconditionsvariedfrombubblingfluidizedbedtocirculatingfluidizedbed.Inthewholerangeoffluidizationconditions,ECTwasabletoinstantaneouslyprovidethesolidsconcentrationandvoidsdistributionsinthefluidizedbeds.AccordingtotheacquireddatafromECTandreconstructedimage,differentfluidizationregimescanalsobeidentified.
简介:Amathematicalmodelforatmosphericstagedcirculatingfluidizedbedcombustion,whichtakesfluiddynamics,combustion,heattransfer,pollutantsformationandretention,intoaccountwasdevelopedintheinstituteofEngineeringThermophysics(IET)recently.Themodelofgassolidflowatthebottomofthecombustorwastreatedbythetwo-phasetheoryoffluidizedbedandintheupperregionasacore-annulusflowstructure.ThechemicalspeciesCO,CO2,H2,H2O,CH4,O2andN2wereconsideredinthereactionprocess.Themathematicalmodelconsistedofsub-modelesoffluidnamics,coalheterogeneousandgashomogeneouschemicalreactions.heattransfer,particlefragmentationandattrition,massandenergybalancetec.Thedevelopedcodewasappliedtosimulateanoperatingstagedcirculatingfluidizedbedcombustionboilerofearlydesignandtheresultswereingoodagreementwiththeoperatingdata.Themainsubmodelsandsimulationresultsaregiveninthispaoper.
简介:Anexperimentalinstallationofcoldmodelsimulationwassetuptostudythebedpressuredropindifferentregionsoffixedfluidizedbedreactorduringtopfeedingandbottomfeeding,respectively,atvariousgasvelocitieswiththefluidizationimageofsolidparticlesmonitoredatthesametime.Bycomparingthechangesinbeddensityandoperatinggasvelocityindifferentregionsoffixedfluidizedbedreactor,theinfluenceoftopfeedingandbottomfeedingpatternsonfluidizationbehaviorcouldbeinvestigated.Theresultsshowedthatthebeddensityintopfeedingreactorrespondedmorestablytothechangeingasvelocityalongwiththeadvantageofworkinginawiderrangeofoperatinggasvelocities.Basedonthisstudy,itisconcludedthatexistingbottomfeedingreactorconfigurationscannotmeetthefluidizationrequirements;andoptimizationofbottomfeedingreactorwillbeneeded.
简介:Theprocessesoffineironorereducedinfluidizedbedhavebeenreviewedinthispaper,thesuperioritiesandlimitationsoftheprocessesofdirectreduction,pre-reductioninfluidizedbedhavealsobeencomprehensivelyanalysed,whichmatcheswithbathsmeltingfurnaceorcokebedtypefurnace.Theanalysishasalsobeenmadeonseveralcontroversialtopics,andthegasuseratiohasbeenpointouttobethekeyofthecompetitionofthereductionprocessinfluidizedbed.Thesuitabilitywithfinalreductionfurnaceisalsoimportanttotheenergysavinginthewholesmeltingreductionprocess.
简介:Thispaperpresentsanewapproachtostudytheprocessofcoalgasification.Non-linearprogrammingtechniquesareusedtodeterminethevalueofthemodelparametersthatdependsoncoalspeciesandexperimentalconditionsandthusminimizethedifferencebetweenexperimentalresultsandmodelpredictions.Modelpredictionsbeingingoodagreementwiththeexperimentalresultsshowthatthismethodofcombiningmodelwithexperimentiseffectiveformodelingcomplexprocesses.
简介:Thefluidized-bedpolymerizationprocesshasbeeninusefordecades.Fromthemanufacturer'sperspectiveitisdesirabletoimprovetechnologywithoutmajormodificationofthereactorsystem.Therefore,inordertomeetthedemandfornewproductsormoreefficientreactoroperation,manufacturersprefertoimprovethecatalystsysteminthemostcosteffectivemanner.Usingpolypropyleneproductionasanexample,somerecentadvancesinfluidized-bedpolymerizationtechnologyarepresented.
简介:Mathematicalmodelsforpulsedfluidizationaresystematicallydiscussed.SeveralundeterminedconstitutiverelationshipsareincludedintheGeneralTwo-FluidModel(GTFM),theadjustableparametersofwhicharealwayschosenatwilltosomeextent.AlthoughtherearenoadjustableparametersintheBasicTwo-FluidModel(BTFM),itseigenvaluesarecomplexnumbersanditisill-posedforinitial-valueproblems.TheLocalEquilibriumModel(LEM),afurthersimplificationofBTFM,isdiscussedatlength.Althoughthemodelisverysimple,itishighlycapableofsimulatingcomplexprocessesinpulsedfluidizationoverabroadrangeofoperatingparameters,anditsnumericalresultswellfitexperimentalresultsinboththevariationofbedheightandthedistributionofparticleconcentrationasfluidizingvelocityvaries.
简介:Gas-solidtwo-phaseflowinacirculatingfluidizedbed(CFB)isaffectedbyoperatingconditions(e.g.,superficialgasvelocity,solidsinventory),materialpropertiesandgeometricfactors,suchastheentryandexitconfiguration.Inparticular,thesuspensionsection,whichislocatedbetweentheriserbottomandthesolidsrecycleinlet,affectsthehydrodynamicsintherisersignificantly.However,thesuspensionsectionhasreceivedlessattentioncomparedwithothergeometricfactors.Mostcomputationalfluiddynamics(CFD)simulations,especiallytwo-dimensionalsimulationsdonottakethisfactorintoaccount.Weperformedthree-dimensional,full-loopCFDsimulationswithadragcoefficientthatwasdeterminedbytheenergy-minimizationmulti-scalemodel,andinvestigatedtheflowbehavioroftwoCFBswithdifferentsuspension-sectionlengths.ThesimulationresuitsrevealedthattheaxialprofilesofvoidageintheriserwithalongersuspensionsectionaremorelikelyS-shaped,whereasthosewithshortersuspensionsectionsdecayexponentially.ThedependencesofsolidsfluxonsolidsinventorydifferinthetwoCFBs.Ashortersuspensionsectionmayresultinasmoothtransitionfromdilutetodensetransportwithoutintermediateaccumulativechoki-ng,whereasaIongersuspensionsectionmayleadtoachokingtransition.Thesesimulationresultsarequalitativelyconsistentwiththeflowbehaviorsdescribedinliterature.
简介:单个粒子的动态行为在在一张煤气的使流体化的床上的粒子混合物的混合/分离的过程期间被分析。分析基于从分离粒子模拟产生的结果,与轨道和对单个粒子起作用的力量的焦点。典型粒子被选择代表三种粒子运动:开始在床并且最后的底部部分的一个漂浮物粒子在床的最高的部分使流体化;开始在床并且最后的最高的部分的一个投弃货物粒子在底部呆在床的使流体化de的层;并且间歇地正在加入顶的一个投弃货物粒子使流体化并且底部使流体化de的层。一个粒子的运动在宏观或全球的规模是混乱的,但是能很好以它的相互作用在显微镜的规模被解释的结果表演与另外的粒子,particlefluid相互作用力量,和本地流动结构强迫,接触调节。他们也为建立一个合适的方法连接在不同时间和长度规模产生并且当模特儿的信息加亮需要。
简介:Withtherevisionofemissionstandards,deepdesulphurizationandDeNOXisneededincirculatingfluidizedbed(CFB)boilers.Theoperationofthefirstsetof300-MWCFBboilerpluslimestone/gypsumwetfluegasdesulphurization(FGD)systemintheworldshowsthatdeepdesulphurizationandDeNOXofCFBboilershashigherSO2removalefficiencyatalowerCa/Sratiocomparedwithtraditionalinnerdesulphurizationmode.Itcanmeettheincreasinglyrigidemissionstandards,andissuitableformorefuels.DeepdesulphurizationandDeNOXcanalsoachieveahighly-efficienthigh-temperatureCFBboilerthatcannotonlyachieveinnerdesulphurizationandlowNOXemission,butbenefitslow-grade,highsulfurcontentfuelsaswell.ResearchofdeepdesulphurizationandDeNOXwillbeadevelopingdirectionforCFBboilers.
简介:Inthepresentwork,artificialneuralnetworks(ANNs)wereproposedtomodelnonlineardynamicbehaviorsoflocalvoidagefluctuationsinducedbyhighlyturbulentinteractionsbetweenthegasandsolidphasesincirculatingfluidizedbeds.Thefluctuationsoflocalvoidageweremeasuredbyusinganopticaltransmittanceprobeatvariousaxialandradialpositionsinacirculatingfluidizedbedwithariserof0.10mininnerdiameterand10minheight.TheANNstrainedwithexperimentaltimeserieswereappliedtomakeshort-termandlong-termpredictionsofdynamiccharacteristicsinthecirculatingfluidizedbed.Anearlystopapproachwasadoptedtoenhancethelong-termpredictioncapabilityofANNs.TheperformanceofthetrainedANNwasevaluatedintermsoftime-averagedcharacteristics,powerspectra,cyclenumberandshort-termpredictabilityanalysisoftimeseriesmeasuredandpredictedbythemodel.
简介:Inthispaper,multifractalanalysistogetherwithwavelettransformmodulusmaxima(WTMM)methodisusedtoanalyzethefluctuatingsignalsofcirculatingfluidizedbed(CFB).Singularityspectrumshowsthatthegas-particleflowinCFBhasmultifractalcharacter.Motionbehavioroftheparticle-fluidsystemofCFBcanbedescribedbysingularityspectrum.Intermittencyindexcanbeusedtodeterminethetransitionofflowregimefromfastfluidizationtopneumaticconveying.
简介:Experimentalfluidizationresultswerecomparedforthreegasdistributorswiththesameopeningratiobutdifferentorificeinclinations(30,45,and90).Hydrodynamicstudieswereconductedwithglassbeads(diameter154p.m)toevaluatetheimpactsoforificeinclinationandstaticbeddepthonpressuredrop,pressuredropfluctuations,bedexpansion,andminimumfluidizationvelocity.Solidsresidencetimedistributionsweredeterminedusingphosphorescenttracerparticles(meandiameter76pm),activatedbyultravioletlight.Thebedpressuredropwashigherwiththeinclined-holedistributorsandincreasedwithstaticbedheight.Inashallowbed,theinclined-holedistributorsgavelessexpansion;however,indeepbeds,theorificeanglehadnegligibleinfluenceonbedexpansion.Theminimumfluidizationvelocityvariedwithstaticbedheightfortheinclined-holedistributorsandwashigherforsteeperangles.Theturnovertimeestimatedusingbubbling-bedequationsmatchedtheexperimentalresultswellforverticalmixing.Probesandportsatthewallsofthefluidizationcolumnreducedthedense-phasedownwardvelocitybyupto40%.Thetangentialparticlevelocitywashighestforthe30-holedistributoranddecreasedwithincreasingorificeangle.Tangentialmixingwasdescribedbyadispersionmodel;thedispersioncoefficientfortheinclined-holedistributorswasapproximatelytwicethatforthe90-holedistributorinashallowbed.
简介:Measurementofbubblesizeandlocalaveragebubblerisevelocitywascarriedoutinaverticallysinusoidalvibro-fluidizedbed.GlassbeadsofGeldartgroupBparticleswerefluidizedatdifferentgasvelocities,whilethebedwasvibratedatdifferentfrequenciesandamplitudestostudytheireffectsonthebubblebehavior.Thisiscomparedwiththecaseofnovibrationinatwo-dimensionalbedanditisconcludedthatwithvibrationthelocalaveragebubblesize,dbav,decreasessignificantly,especiallyatminimumbubblingvelocity.Theaveragebubblesizeincreasesslightlywithincreasingvibrationfrequencyandamplitude.Thelocalaveragebubblerisevelocityishigherthanthatwithnovibration,thoughwithincreasingvibrationfrequencyandamplitude,itdoesnotchangesignificantly.
简介:Inthe'90sDEMsimulationresearchwassuccessfulinexploringitspotentialinthesimulationoffiuidizationphenomenaandinitsapplicationtothedesignoffluidized-bedprocesses.Nevertheless,notmuchprogresshasbeenmaderegardingtherealistictreatmentofcollisionprocessesthatarecriticalindeterminingmacroscopicmodeoffiuidization.Allthroughthesecondhalfofthe'90s,theauthorinvestigated/demonstratedtheissuebyintroducingdifferentsurfaceinteractionscausedbyformationofliquidand/orsolidbridges,vanderWaalsforceandtheexistenceofsurfaceroughness.Inthefirstpartofthepresentationthesearetobesummarizedandthetasksremainingarediscussed.Inthesecondpart,arepresentedtheresultsfromanewlydevelopedforce-deformationmetertodemonstratethesignificanceofthesurfaceroughnessanditselasto-plasticcharacteristics.
简介:Flocculationtimeisconventionallybelievedtobeproportionaltotheflocculationefficiencyofacylindricalfluidizedbedflocculator.However,inasingle-stagevelocitygradientsituation,theflocculationefficiencydecreaseswhentheoptimalflocculationtimeisexceeded.Amulti-stagevelocitygradientwasestablishedinacylindricalfluidizedbedflocculator,basedonthehydraulicclassificationtheory.Thismulti-stagevelocitygradientfluidizedbedflocculator(MGF)createdamoresuitableenvironmentforflocgrowthandprotection,whichwasconfirmedbythesizedistributionofflocsalongthebedheight.Correspondingly,theabatementefficienciesforKaolinslurryanddyedwastewatertreatmentintheMGFwereenhancedby5-10%,andby7-20%,respectively,comparedwiththoseinthesingle-stagevelocitygradientfluidizedbedflocculators(SGFs).TheinitialbedheightdistributionratioalongthevelocitygradientswasanimportantfactorforMGFoptimization.