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1、Cryst.Res.Technol.38,No.1,34–41(2003)/DOI10.1002/crat.2003100042003Influenceofcrystallizationconditionsonthemechanismandrateofcrystalgrowthofpotassiumsulphate12W.Omar,J.Ulrich1Al-BalqaAppliedUniversity,TafilaUniversityCollege,DepartmentofNaturalResourcesandChemi
2、calEngineering,Tafila,Jordan2Martin-Luther-UniversitätHalle-Wittenberg,FBIngenieurwissenschaften,InstitutfürVerfahrenstechnik/ThermischeVerfahrenstechnik,06099Halle,GermanyReceived2December2002,accepted9December2002Publishedonline7January2003Keywordscrystallizat
3、ion,potassiumsulphate.Growthrateofpotassiumsulfatecrystalswasstudiedinafluidizedbedcrystallizer.Highergrowthrateswereobservedatlargerbedheights.Largercrystalsgrowfasterthansmallersizecrystalsduetothechangedfluiddynamics.Thegrowthratewasfoundtobeverysensitivetoth
4、epHvalueofthesolution.ThegrowthrateincreaseswithincreasingthepHvalueandtheincreaseofgrowthintheacidicmediumisfasterthaninthe3+basicmedium.ThepresenceofsmallamountsofCrionsreducesthegrowthrateofpotassiumsulfate3+dramatically.ThepresenceofCrionslowersthesaturation
5、temperatureandincreasesthewidthofthemetastablezone,i.e.shiftsthemetastabilityofthesolutiontobeatlowerlevelofsupersaturation.1IntroductionPotassiumsulfateisanimportantindustrialfertilizerproducedbycrystallizationfromitsaqueoussolution.Thequality(size,shapeandpuri
6、ty)oftheproductisaffectedbymanyparametersinfluencingthegrowthmechanismsuchashydrodynamicconditions,pHofthecrystallizingsolution,andthepresenceofadditivesandimpurities.Thedevelopmentofdesignandoperationofindustrialcrystallizationprocessesrequiresdataonthekinetics
7、ofcrystalgrowthandunderstandingtheeffectofoperatingconditionsonkineticsandrateofcrystalgrowth.ThecrystalgrowthprocessisdescribedbyNielsen[1,2,3]withseveralconsecutivestepsofmasstransfer(bydiffusionorconvection)ofsolutemoleculesfromthesolutiontothecrystalsurface,
8、adsorptionofthesoluteonthesurfaceofcrystalandtheintegrationofsoluteintothegrowthsite.Thegrowthratedependsonthelevelofsupersaturationwhichisthedrivingforce.Thecrystalg
