湿法冶金去除铁和铝

Removalofironandaluminumimpuritiesfrommetallurgicalgrade-siliconwithhydrometallurgicalrouteYUZhan-liang(于站良)1,2,MAWen-hui(马文会)1,2,DAIYong-nian(戴永年)1,2,YANGBin(杨斌)1,2,LIUDa-chun(刘大春)1,2,DAIWei-ping(戴卫平)3,WANGJin-xian(汪金仙)31.FacultyofMaterialsandMetallurgicalEngineering,KunmingUniversityofScienceandTechnology,Kunming650093,China;2.NationalEngineeringLaboratoryforVacuumMetallurgy,Kunming650093,China;3,KunmingDiBooTechnologyCo.,Ltd,Kunming650093,ChinaReceived15July2007;accepted10September2007Abstract：Anewmethodforproductionofsolargradesilicon(SoG-Si)atlowcostfrommetallurgicalgradesilicon(MG-Si)viavacuummetallurgicaltechniquewasproposed,whichisapromisingprocesstofeedstocksolarenergysiliconmaterialindependenceoftraditionalSiemensmethod.Inthisprocedure,pre-treatmentofMG-Siusinghydrometallurgicalroutestoremovethemetallicimpuritiessuchasironandaluminumtoreducetheproductioncostisanimportantprocess.Theinfluencesofacidagents,acidconcentration,reactiontimeandtemperatureandparticlesizeofrawmaterialgroundontheremovalefficiencyofironandaluminumimpuritieswereinvestigated,respectively.TheresultsshowthattheoptimumoperationconditionsforleachinginacidCare:acidconcentration6mol/L,temperature60℃,time4d,diameterforrawmaterial50µm.Theremovalefficienciesofimpuritiesironandaluminumareupto85%and75%,respectively.Keywords:solargradesilicon;metallurgicalgradesilicon;hydrometallurgy;purification1IntroductionSolarenergyisoneoftheidealrenewableenergyresourcesbecauseofthenon-pollution,non-moverparts,theuniversalityofresourceandnon-exhaustionforever,accordingtotheenvironmentalprotectionnowadaysandtherequirementofthesustainabledevelopment[1−2].Thecrystallinesiliconhasthemainstatusasthebasalmaterialofthesolarcellsinthefutureof20years,becauseoftheadvantageofthehigh-stabilizationefficiency,lowenvironmentalloading,permanenceofcapabilityandsoon[3].TheSiemensprocessandthedecompositionofthesilicanearetwomajorroutestomanufacturesiliconwithhighpurityatexpensivecostforbothphotovoltaicandelectronicindustries.Soitisveryimportanttoresearchnewprocedures,whichisindependenceofthetraditionalsiliconproduction.MostofthemetallicelementspresentedasimpuritiesinMG-Sihaveasmallsegregationcoefficientinsilicon,aslistedinTable1.Thus,inspiteofthehighsolubilityofimpuritiesinthemoltensilicon,theyhavesmallsolubilityinthesolidandresultinconcentratingatthegrainboundaries.UponpulverizingtheMG-Si,fractureoccursmainlyatgrainboundaries,exposingtheimpuritiesasactivereactioninterfacesinacidsolutions.ThemajoradvantageofacidleachingforMG-Sipurificationisthatitcouldberealizedatlowtemperaturewithlowenergyconsumptionandsimpleinstrumentstoreducecost,comparedwithotherrefiningprocesses[4].SomenewtechniquesinproductionofSoG-Siinresentyearshavebeenproposedandstudied[5−13].AnovelprocesswasproposedbytheauthorstoproducesolargradesiliconfromMG-Siviavacuummetallurgyatlowcost[14].Inthisprocedure,thepretreatmentofMG-Sitoremovesomemetallicimpuritiesisanimportantprocesstosimplifypurificationinthenextsteps.Foundationitem:Project(50674050)supportedbytheNationalNaturalScienceFoundationofChina;Project(2006BAE01B08)supportedbytheSustentationProjectofScienceandTechnologyofChina;Project(20060674004)supportedbyPhDProgramsFoundationofMinistryofEducationofChinaCorrespondingauthor:MAWen-hui;Professor;Tel:[phone];E-mail:[e-mail]-liang,etal/Trans.NonferrousMet.Soc.China17(2007)s1031Inthispaper,wereportedthemainresultsofremovaleffectforironandaluminumimpuritiesinthepurificationofMG-SiproducedbycarbothermicreductionofquartzinthefurnacefromacompanyinYunnanProvinceofChina(CCYP),byleachingofthegroundmaterialwithdifferentacidsolutionsasafunctionoftheirconcentration,leachingtemperatureandleachingtimeandparticlesizeofMG-Si,respectively.2Experimental2.1CharacterizationofMG-SiMG-SiproducedbyCCYPhasbeenanalyzedbyinductivelycoupledplasma-atomicemissionspectrometry(ICP-AES)andtheresultsarelistedinTable1.Themajormetallicimpuritiesareiron(0.15%),aluminum(0.054%)andcalcium(0.032%).Otherimpuritiesaretitanium,boron,vanadiumandphosphorus.Thenon-metallicimpuritiessuchasboron,carbonandphosphoruscouldnotbedirectlypurifiedbymeansofacidleaching,whichhasbeendiscussedinRefs.[15−16]Table1ChemicalcompositionandsegregationcoefficientsinMG-SifromCCYPElementConcentration/(mg·kg−1)Segregationcoefficient[7]Fe15006.4×10−6Ca3201.6×10−3P1120.35V104×10−6Al5402.8×10−3B180.8C10007×10−2Ti123.6×10−62.2MicrostructureThemicrostructuralanalysisofMG-Siwasinvestigatedusingscanningelectronmicroscopy-energydispersivespectrometer(SEM-EDS)thatenabledaqualitativeanalysisofmainelementspresented,showninFig.1.Theimpuritiesamongsilicongrainswereobserved.WhenthecastMG-Siispulverized,breakageoccursmostlyatthegrainboundaries.ThusifMG-Silumpsarepulverizedtoaparticlesizethatisequivalenttothesizeofthepolycrystallinegrains,amajorportionofthemetallicimpuritiespresentedonthesurfaceofthegrainsisexposed,whichenhancesthereactionofMG-Sipulverizedinacidsolution.Fig.1SEM/EDSimagesofMG-SifromcertaincompanyinYunnanProvince:(a),(b)SEMimages;(C)EDSimage2.3Leachi