耐火材料熔渣侵蚀定量方法

121Chair of Ceramics –University of LeobenAPPROACHESTOQUANTIFYREFRACTORYCORROSIONBYDISSOLUTIONINSLAGSHaraldHarmuth,SandraVollmann221H.Harmuth2014-Refractorycorrosionisinmostcasesadiffusioncontrolledprocess.--IttakesplacewithinNernst‘diffusiveboundarylayergovernedbyFick‘s1stlaw:-1.1Corrosionanderosion-Corrosionofthebondingphasesprepareslatererosionbyfluidmotion.-cgradDj⋅−=j..massfluxD..diffusivityc..concentration1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitemscS..solubilitylimitc1..concentrationatslag/refractoryinterface/c0..concentrationdistantfrominterfacej..massfluxD..diffusivityδ..Nernst‘boundarylayerthickness321H.Harmuth20141.2MasstransfercoefficientββcgradDj⋅−=Fick‘s1stlawdycDj∂⋅−=Foronedimension:δ0ccDjseff−⋅=Withsimplifiedapproximationofthederivative:()0ccjs−⋅=βAtechnicalsolutionδβeffD=1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems421H.Harmuth2014Dimensionlessnumbersareappliedtodescribeandquantifymasstransfer:νLuRe⋅=effDLSh⋅=βeffDScν=Sherwoodnumber;Lisaspecificdimensionoftheliningorthevessel.LReynoldsnumber;νisthekinematicviscosity.νSchmidtnumberiΓSeveralsimplicesandcomplexesResultscanberepresentedintheform:()i,ScRe,fShΓ=andoftensatisfiesapowerlaw:∏⋅⋅⋅=icibaiScReconstShΓwhichyieldsapowerlawforthemasstransfercoefficient:∏Γ⋅⋅⋅⋅⋅=−−−iciaaabbeffiLuDconst11νβ1.3Dimensionlessrepresentationofmasstransfer1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems521H.Harmuth2014()01ccLuconstDDjsiciaaabbeffeffi−⋅Γ⋅⋅⋅⋅⋅⋅=∏−−−νDeffImpactofdiffusion1/δImpactoffluiddynamics∆cImpactofthermochemistryQuantityDependencyDeterminationDeterminationofa,b,cibyCFDsimulationsa,b,ciThermochemicalsimulationforcS,chemicalanalysisforc0.cSc0Thermochemicalapproachforthermodyn.FactorImplicationpO2dependencemightbeimportantpO2dependencemightbeimportantMarangoniconvectioncouldoccur1.4Quantitiesimpactingmasstransferandpossibilitiesfortheirdetermination1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems621H.Harmuth2014ladleradiusRslagbathheightHslagviscositydiffusioncoefficientDeffinletvelocityofpurginggasuggasflowrateVgv,DVg,ugHRggeffeffguRVDHShDvScvHuReHR⋅=⋅==⋅==πΠβΓ2&Relevantdimensionlessnumbers:3410721074562964031052340412235−−⋅≤≤⋅≤≤≤≤≤≤..ScRe..ΠΓEstablishedequationformasstransfer:forgeometricallysimilarladleswithratioofladleradiustoclearanceheightof0,42andplugpositionedeccentricallyat0,242·Rand0.420.242()726017602952310252...ScRe.Sh⋅⋅⋅⋅⋅=−ΠΓ2.1EquationforcorrosivemasstransferintheslagbathareaofagaspurgedsteelladleVollmann2010[1]1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems721H.Harmuth20142.2ChallengesofCFDsimulationswithrespecttorefractorywearfortheexampleofasteelladleDoletschek2013[2]Modelingatthesteel/slaginterfaceIdentificationofsuitableturbulencemodels.Modelingofflowfieldevolution-Determinationofmasstransfersteel/slaginordernottodecreaseitwhenreducingthemasstransferrefractory/slag.-/-Calculationofpossibleslagentrainment.-1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems821H.Harmuth2014LES(LargeEddySimulation)k–SSTRANS(ReynoldsaveragedNavier-Stokes)SASRANS(scale-adaptivesimulation)LESandSASsimilarilypredictawavyandfluctuatingflowfield,whilethek–SSTshowsamorestationaryanduniformvelocityfield.k–SSTComparisonofdifferentturbulencemodels1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems921H.Harmuth20142.3Marangoniconvection1aMarangoniconvectionatthethreephaseboundarysteel-slag-refractory(usuallydecisive)--1bMarangoniconvectionattheslagsurface(usuallynotdecisive)2possibleadditionalforcedconvection(optional)σ1interfacetensionattheinterfacesteel/slagσ2interfacetensionattheinterfacesteel/slagclosetotherefractoryDrivingforce:Differenceinsurface/interfacetension∆σ=σ2-σ1/Reasonsforinterfacetensiongradient:-Dissolutionofrefractorycomponentsinslag-Gradientofoxygenconcentrationinsteelassociatedwithmagnesiacarbonrefractories1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems1021H.Harmuth2014IsMarangoniconvectionrelevantinthecaseofsimultaneousforcedconvection?Vollmann2013[3]AMarangoninumbertoquantifytheintensityofMarangoniconvection:effDMa⋅⋅∆=ηδσ∆σ…differenceininterfacetensionδ…Nernstboundarylayerthicknessη…dynamicviscosityDeff…effectivediffusioncoefficientByCFDsimulationthefollowingcriterionwasdereivedforthecaseofarotatingfingertest:175051031.Re.Ma⋅⋅=I.e.forMalowerorRehigherthanaccordingtoaboveequationMarangoniconvectionmaybeneglected.1Introduction2Masstransfercalculations3Thermochemicalconsiderations4Corrosionpre-paringerosion5Furtherre-searchitems1121H.Harmuth20143.1Twothermochemicalimpactsondiffusioni)SolubilitylimitcS()0