《湿法冶金过程及设备培训》课件-浸出过程的控制步骤

浸出过程的控制步骤

Controlstepsoftheleachingprocess课程导入

Courseguide矿物浸出反应是属于水溶液与固体物质之间的多相反应体系，在多相体系中，反应是在相界面上发生的。Mineralleachingreactionisaheterogeneousreactionsystembetweenaqueoussolutionandsolidmatter.

Intheheterogeneoussystem,thereactionoccursatthephaseinterface.+

林忠

Lin

Zhong

主讲教师

Lecturer课程导入

Courseguide结晶

——

化学反应过程Crystallization-chemicalreactionprocess扩散过程Diffusionprocess溶剂向相界面迁移Solventmigrationtowardphaseinterface反应产物由相界面排开Thereactionproductsaredisplacedbythephaseinterface反应过程

Reactionprocess浸出过程的控制步骤

Controlstepsoftheleachingprocess课程导入

Courseguide浸出反应总速度取决于步骤中最慢的一个过程。Theoverallrateoftheleachingreactiondependsontheslowestoneofthesteps.浸出过程的控制步骤

Controlstepsoftheleachingprocess课程导入

Courseguide浸出过程的控制步骤

Controlstepsoftheleachingprocess固

Solid液

Liquid白钨矿的盐酸浸出

Hydrochloricacidleachingofscheelite固

Solid液

Liquid闪锌矿的高压氧浸

Hyperbaricoxygenleachingofsphalerite气

Gas课程导入

Courseguide浸出过程的控制步骤

Controlstepsoftheleachingprocess固

Solid液

Liquid白钨矿的盐酸浸出

Hydrochloricacidleachingofscheelite固

Solid液

Liquid闪锌矿的高压氧浸

Hyperbaricoxygenleachingofsphalerite气

Gas浸出槽

Leachingtank浸出过程控制

Leachingprocesscontrol浸出过程的控制步骤

Controlstepsoftheleachingprocess化学反应控制

Chemicalreactioncontrol

外扩散控制

Externaldiffusioncontrol内扩散控制

Internaldiffusioncontrol混合控制

Hybridcontrol化学反应控制

Chemicalreactioncontrol主要研究浸出过程为化学反应控制的浸出分数与时间的关系。

Therelationshipbetweenleachingfractionandtimeoftheleachingprocesscontrolledbychemicalreactionwasprimarilystudied.UO2粉末在碳酸钠中溶解的动力学曲线

KineticcurvesofUO2powderdissolutioninsodiumcarbonate浸出过程的控制步骤

Controlstepsoftheleachingprocess设有一浸出过程，若通过扩散层及固体膜的扩散阻力很小，以至反应速度受化学反应控制，则：Assumingaleachingprocess,ifthediffusionresistancethroughthediffusionlayerandthesolidfilmissosmallthatthereactionspeediscontrolledbychemicalreaction:对粒度均匀、致密，且浸出剂浓度可视为不变的过程而言，当其受化学反应控制时，浸出分数值与浸出时间成直线关系并过原点；Fortheprocesswithuniformanddenseparticlesize,andtheconcentrationofleachingagentcanberegardedasconstant,whenitiscontrolledbychemicalreaction,theleachingfractionvaluehasalinearrelationship

withtheleachingtimeandpassesthroughtheorigin;浸出过程的速度或浸出率随温度的升高而迅速增加；Thespeedorleachingrateoftheleachingprocessincreasesrapidlywiththeincreaseoftemperature;反应速度与浸出剂浓度的n次方成比例；Thereactionrateisproportionaltothenthpoweroftheconcentrationoftheleachingagent;搅拌过程对浸出速度无明显影响。Thestirringprocesshasnoobviouseffect

ontheleachingspeed.CaCO3+2HCl(kg)=CaCl2(og)+H2O+CO2(g)(1-2)浸出过程的控制步骤

Controlstepsoftheleachingprocess化学反应控制

Chemicalreactioncontrol设有一浸出过程，若通过扩散层及固体膜的扩散阻力很小，以至反应速度受化学反应控制，则：Assumingaleachingprocess,ifthediffusionresistancethroughthediffusionlayerandthesolidfilmissosmallthatthereactionspeediscontrolledbychemicalreaction:对粒度均匀、致密，且浸出剂浓度可视为不变的过程而言，当其受化学反应控制时，浸出分数值与浸出时间成直线关系并过原点；Fortheprocesswithuniformanddenseparticlesize,andtheconcentrationofleachingagentcanberegardedasconstant,whenitiscontrolledbychemicalreaction,theleachingfractionvaluehasalinearrelationship

withtheleachingtimeandpassesthroughtheorigin;浸出过程的速度或浸出率随温度的升高而迅速增加；Thespeedorleachingrateoftheleachingprocessincreasesrapidlywiththeincreaseoftemperature;反应速度与浸出剂浓度的n次方成比例；Thereactionrateisproportionaltothenthpoweroftheconcentrationoftheleachingagent;搅拌过程对浸出速度无明显影响。Thestirringprocesshasnoobviouseffect

ontheleachingspeed.CaCO3+2HCl(kg)=CaCl2(og)+H2O+CO2(g)(1-2)浸出过程的控制步骤

Controlstepsoftheleachingprocess化学反应控制

Chemicalreactioncontrol对化学反应控制的浸出过程而言，提高其浸出分数R（或称精矿分解过程的分解率）的途径主要为：Forchemicalreactioncontrolledleachingprocesses,waystoincreasetheleachingfractionR(ordecompositionrateofconcentratedecompositionprocess)Mainly:提高温度TIncreasethetemperatureT提高浸出剂浓度CoIncreasetheconcentrationofleachingagentCo

降低颗粒的原始半径Reducetheoriginalradiusoftheparticle浸出过程的控制步骤

Controlstepsoftheleachingprocess化学反应控制

Chemicalreactioncontrol反应物气流边界层的外扩散速度

Externaldiffusionvelocityofreactantgasflowboundarylayer反应总速度

Totalreactionspeed当不存在固体膜时，浸出率与时间成正比。与化学反应控制相似，因此仅根据动力学方程式（J=-DCxJ）不足以判断控制步骤为外扩散步骤还是化学反应步骤。Whennosolidmembraneispresent,theleachingrateisproportionaltotime.Similartochemicalreactioncontrol,itisnotsufficienttojudgewhetherthecontrolstepisanexternaldiffusionsteporachemicalreactionstepbasedonthekineticequation(J=-DCxJ)alone.其表观活化能较小，约为4~12kJ/mol。Itsapparentactivationenergyissmall,about4-12kJ/mol.加快搅拌速度和提高浸出剂浓度能迅速提高浸出速度。Speedingupthestirringspeedandincreasingtheconcentrationofleachingagentcanrapidlyincreasetheleachingspeed.主要特征

Keyfeatures浸出过程的控制步骤

Controlstepsoftheleachingprocess外扩散控制

Externaldiffusioncontrol加强搅拌

Intensifystirring加快溶液与固体颗粒表面的相对扩散速度

Acceleratetherelativediffusionvelocitybetweensolutionandsolidparticlesurface减小扩散层的厚度

Reducethethicknessofthediffusionlayer加快溶液与固体颗粒间的传质速度

Acceleratemasstransferbetweensolutionandsolidparticles根据计算，强烈搅拌下浸出剂扩散层的有效厚度可减小为静止时间的1/50~1/5。Accordingtothecalculation,theeffectivethicknessoftheleachingagentdiffusionlayercanbereducedto1/50-1/5oftheresttimeunderstrongstirring.提高浸出剂浓度Co。IncreasetheconcentrationCoofleachingagent.加强搅拌，减小扩散层厚度。Strengthenstirringandreducethethicknessofdiffusionlayer.提高浸出率的途径

WaystoImproveLeachingRate浸出过程的控制步骤

Controlstepsoftheleachingprocess外扩散控制

Externaldiffusioncontrol提高温度Raisethetemperature内扩散是指绝大多数反应物分子要沿着孔道向颗粒内部扩散。Internaldiffusionmeansthatmostreactantmoleculesdiffusealongtheporestotheinterioroftheparticle.其浸出分数与时间的关系浸出率与时间成正比。Therelationshipbetweenleachingfractionandtimetheleachingrateisdirectlyproportionaltotime.表观活化能小，一般仅为

4~12kJ/mol;Theapparentactivationenergyissmall,generallyonly4-12kJ/mol;原矿粒度对浸出率有明显影响;Theparticlesizeofraworehasobviousinfluenceonleachingrate;搅拌强度对浸出率几乎没有影响。Theagitationintensityhadlittleeffectontheleachingrate.主要特征

Keyfeatures浸出过程的控制步骤

Controlstepsoftheleachingprocess内扩散控制

Internaldiffusioncontrol矿粒的粒度Particlesizeoforeparticles降低原料粒度利于缩短时间或加快速度Reducingtheparticlesizeofrawmaterialsisbeneficialtoshortenthetimeorspeedup.固体膜厚度Solidfilmthickness影响浸出率的因素

Factorsaffectingleachingrate浸出过程的控制步骤

Controlstepsoftheleachingprocess内扩散控制

Internaldiffusioncontrol浸出过程的控制步骤

Controlstepsoftheleachingprocess两个步骤的阻力

Two-stepresistance大体相同

Roughlyidentical远大于其他步骤

Muchlargerthanothersteps两者混合控制

Hybridcontrolofboth中间过渡控制

Intermediatetransitioncontrol化学反应速度外扩散速度数量级相同Thechemicalreactionvelocityandtheexternaldiffusionvelocityarethesameorderofmag