低浓度悬浮液电场膜过滤临界场强的研究

低浓度悬浮液电场膜过滤临界场强的研究＊刘姝红　赵宗艾　邓　玲(,　300072)　　探讨了操作压差、主体流速、料浆浓度等因素对电场膜过滤中临界场强的影响.实验结果表明:操作压差对临界场强的影响较大,而主体流速和料浆浓度的影响较小.从理论上推导出临界场强的计算式,并得到了较好的实验验证,从而解决了电膜滤过程中的一个难题.　低浓度　电场膜过滤　临界场强　TQ028.8　　,、.,,..,,,.,,,;,.,,,.,———[1],.1　临界场强的基本概念,1.1,E,,,;,1　:μE;E;w;μE·E·w;D;dw/dx;D·dw/dx;J;J·w;wb;ws;δ;x,,,,Ec.,,,,.,.,.:1998-07-16;:1998-09-17:,26,＊(No.2979271-2)19　2　　　　　Vo1.19　No.219994MEMBRANESCIENCEANDTECHNOLOGYApr.1999DOI:10.16159/j.cnki.issn1007-8924.1999.02.0072　临界场强的计算模型2.1　,EEc,2,1—2—3—4,1,.,,:J·w=UE·w+J·wp-D·dw/dx(1)　J———,m/s;w———;wp———;D———,m2/s;UE———,m/s,UE=μE·E,μE(m2/V·s);E(V/m).2　,Ec,,,dw/dx=0,w=wb,(1):J·wb=μE·E·wb+J·wp(2)J=wbwb-wpμE·Ec(3)(3),J、wb、wp、μE,Ec.wb、wp、μE,J.2.2　J,d,L.E,,=0.3.,.[2],,.,.,,.,,,,.,(ζ),δ′.,,0.3　Navier-Stokes[3]:ρDυDt=-p+μ2υ+ρFg(4)　ρ———,kg/m3;υ———,m/s;t———,s;———;p=p/x+p/y+p/z=gradp,Pa/m;p———,p=pd+ps,pd,ps,Pa;μ———,Pa·s;2———;2υ=(2υ/x2+2υ/y2+2υ/z2);Fg———,N/kg.Navier-Stokes　·34　　　·　　　　　19　.,,(4):ρDυDt=-p+μ2υ+ρg+η(E+Ei)(5)　Ei———,V/m;η———,C/m3.,(5),(z):　υzt+υrυzr+υrυzθ+υzυzz=μρ1rr(rυzr)+1r22υzθ2+2υzz2+　g-1ρpz+ηρ(E+Ei)z(6)　z、r、θ———、、(3);υz、υr、υθ———、、.(6),υz,:(1)、(z).(2)Ei(r).(3),,z,zE.(4),ε.,:υzt=0,υr=0,υθ=0,υzz=0,pz=dpdzυzθ=0,　2υzz2=0,　(E+Ei)z=E,[4]:g=1ρdpsdz(7)(6):-dpddz+μ1rddr(rdυzdr)+ηE=0(8)　dpd/dzz.3,:r=0,dυz/dr=0r=d/2-δ′,υz=0(8),:υz=ε(-ζ)Eμ-(d-2δ′)2-(2r)216μ·dpddz(9)(9):υz=∫d-2δ′20υz·2πr·drπ·(d-2δ′2)2=(d-2δ′)232μ(ηE-dpddz)(10)(10)qT,qT=υz·ε′·A(11)　qT———,m3/s;ε′———;A———,m2.,(),:J=qTA(12)dδ,(10)～(12),JE:J=qTA=d232μ·η·ε′·E-d232μ·ε′·dpddz(13),,JE.,(13):J=KmE+J0(14)　Km=d232μ·η·ε′;　　J0=-d232μ·ε′·dpddz,,(14)Km,J0.2.3　EcEc,(3)(14):Ec=J0wbwb-wpμE-Km(15),,KmJ0,μE,(15),Ec.3　各操作参数对临界场强的影响及临界场强模型的验证3.1　:Δp=0.07MPa,2:·35　　　·　wb=0.05%,u=0.039m/s.4.4　4,,66.67V/cm(1080L/m2·h)(301L/m2·h)3.6.,,.,4,a.a,,,.,.,.,,,,.a,,,,..[5],.,a,.,a.,—.3.2　3.2.1　5.5,5　.,,,,,,,,,.3.2.2　(0.023～0.139m/s,0.025%～0.2%),,,.3.3　,3,,1.表1　电场膜过滤的3组实验数据　　Henry[1][5]SiO2SiO2wb/%0.030.050.05Δp/MPa0.070.120.07J0×108/m·s-13.07.23.3μE×108/m2·s-1·V-14.93.42.64Km×108/m2·s-1·V-13.802.041.83　　1,(15)Ec,2.2,(15),.,,0.,-,-.　·36　　　·　　　　　19　表2　临界场强计算值与实验值的比较Ec/V·cm-1Ec/V·cm-1/%Henry27.325.0+8.353.150.5+5.240.738.0+7.14　结论1)———,3.、.2),,..1　HenryJD.Asolid/liquidseparationprocessbasedoncrossflowandelectrofiltration.AIChEJ,1977,23:5472　,..:,1990.170～1713　,　..:,1987.474　.:.:,1992.65　.:[].:,1995Astudyoncriticalelectricfieldstrengthofelectro-membranefiltrationforlowconcentrationsuspensionLiuShuhong,ZhaoZong'ai,DengLing(DepartmentofChemicalEngineering,TianjinUniversity,Tianjin　300072)Abstract　Theeffectofoperationpressure,bulkflowvelocityandfeedconcentrationontheelectro-membranecriticalfieldstrengthhavebeeninvestigated.Thetheoreticalformulaisdeducedforcalculatingthecriticalfieldstrengthandverifiedthroughexperiments.Keywords　lowconcentration　electro-membranefiltration　criticalfieldstrength(26)InvestigationofthefactorsinfluencingtheCA/CTAasymmetricalnanofiltrationmembraneintheprocessofmembranepreparationZhouJinsheng,ChenGuanwen(InstituteofChemistry,TheChineseAcademyofSciences,Beijing　100080)Abstract　TheCA/CTAasymmetricalnanofiltrationmembranewaspreparedbyphaseseparationtechnique.Theparametersaffectingtheperformanceofpreparedmembraneintheprocessofmembranepreparationwereinvestigated,forexample,theratioofCA(CA/(CA+CTA)),solvent,theamountofadditivesinthecastingsolution,concentrationofpolymerincastingsolution,andsomeothermanufacturevariables(includingevapora-tiontime,coagulationbath,coagulationtemperature,post-treatingtimeetc.).Theseparametersaffectthepreparedmembraneperformancebychangingthesizeandamountofaggregationporesandnetworkporesintheseparatinglayerofasymmetricnanofiltrationmembrane.Keywords　celluloseacetate(CA)　cellulosetriacetate(CTA)　nanofiltrationmembrane2:·37　　　·