生物分离工程过滤省公开课一等奖全国示范课微课金奖PPT课件.pptx

Chapter2Filtration第二章过滤Keyknowledgepoints(知识点)Filtrationseparatessolidfromaliquidbyforcingtheliquidthroughasolidsupportorfiltermedium.Thisisastraightforwardprocedureforwelldefinedcrystals.过滤是将料液经过固体支持或者过滤介质时，使得固体物质从溶液中分离，对于好定形晶体，这是一个最直接步骤。under6/55Howeverthesmallsizeofmicroorganismsmakefiltrationoffermentationbeersorotherbiologicalsolutionsconsiderablymorecomplicated.但对微小而形状多变微生物细胞，发酵液和其它生物溶液过滤就变得复杂了。Generally,fermentationbeersandotherbiologicalsolutionsarenotoriouslyhardtofilter.Theyareoftenhardtofilterbecauseofhighnon-Newtonianviscosityorhighlycompressiblecakes.Thatistosay,wemustmodifytheseproceduresforbio-separations.普通，因为料液通常都是高非牛顿粘度流体或者是高度可压缩滤饼，发酵液和其它生物溶液是极其难以过滤，也就是说，我们必须对这些生物分离程序进行修改。APretreatment预处理1、Heating加热2、Coagulationandflocculation凝聚和絮凝Simpleelectrolytesactbyscreeningtheelectrostaticrepulsionwhichcommonlyexistsbetweencolloidalparticles.Whenthiselectrostaticrepulsionisreduced,attractiveLondon-vanderwaalsforcespredominate.Thecolloidscanthencoagulateaslarger,denseparticleswhicharemoreeasilyfiltered.简单电解质降低了胶体粒子间排斥电位，从而使得范德华引力起主导作用，聚合成较大胶粒，粒子密度越大，越易分离。Simpleacidsandbases（简单酸或碱）Alum（明矾）Ferricchloridecrystals（三氯化铁）Syntheticpolyelectrolytesaddedaspretreatmentscanbothreduceelectrostaticrepulsionandadsorbonadjacentparticles,formingbridgesbetweenthem.Asaresult,thecolloidalparticlesflocculateaslarge,lessdenseaggregateswhicharemoreeasilyfiltered.Thesepolyelectrolytescanbeanionic,cationicornonionic.预处理时加入合成聚合电解质既能降低排斥电位，又吸附了周围微粒，形成桥架作用，促使胶粒形成粗大，密度低絮凝团。这些絮凝团很轻易被过滤得到。（1）、Diatomaceousearths硅藻土Diatomaceousearthsaretheskeletalremainsofthetinyaquaticplantsdepositedcenturiesago.硅藻土是百年前水生植物沉淀下来遗骸。（2）、Perlites珍珠岩Theperlitesarevolcanicrockprocessedtoyieldanexpandedform.珍珠岩是处理过膨胀火山岩。GradeB.GeneralTheoryforFiltrationDarcy方程－－fluidmechanicsforfiltrationDarcy’slaw：1、forincompressiblecake,simplestcase适合用于不可压缩和简单可压缩滤饼2、forcompressiblecake,commonforbio-separations适合用于可压缩滤饼，普遍使用于生物分离过程Darcy’slaw（达西定律）visthevelocityoftheliquidv–流体流速k：proportionalityconstant,usuallycalledtheDarcy’slawp