浸出過程的控制步驟

Controlstepsoftheleachingprocess課程導入

Courseguide礦物浸出反應是屬于水溶液與固體物質之間的多相反應體系，在多相體系中，反應是在相界面上發(fā)生的。Mineralleachingreactionisaheterogeneousreactionsystembetweenaqueoussolutionandsolidmatter.

Intheheterogeneoussystem,thereactionoccursatthephaseinterface.+

林忠

Lin

Zhong

主講教師

Lecturer課程導入

Courseguide結晶

——

化學反應過程Crystallization-chemicalreactionprocess擴散過程Diffusionprocess溶劑向相界面遷移Solventmigrationtowardphaseinterface反應產物由相界面排開Thereactionproductsaredisplacedbythephaseinterface反應過程

Reactionprocess浸出過程的控制步驟

Controlstepsoftheleachingprocess課程導入

Courseguide浸出反應總速度取決于步驟中最慢的一個過程。Theoverallrateoftheleachingreactiondependsontheslowestoneofthesteps.浸出過程的控制步驟

Controlstepsoftheleachingprocess課程導入

Courseguide浸出過程的控制步驟

Controlstepsoftheleachingprocess固

Solid液

Liquid白鎢礦的鹽酸浸出

Hydrochloricacidleachingofscheelite固

Solid液

Liquid閃鋅礦的高壓氧浸

Hyperbaricoxygenleachingofsphalerite氣

Gas課程導入

Courseguide浸出過程的控制步驟

Controlstepsoftheleachingprocess固

Solid液

Liquid白鎢礦的鹽酸浸出

Hydrochloricacidleachingofscheelite固

Solid液

Liquid閃鋅礦的高壓氧浸

Hyperbaricoxygenleachingofsphalerite氣

Gas浸出槽

Leachingtank浸出過程控制

Leachingprocesscontrol浸出過程的控制步驟

Controlstepsoftheleachingprocess化學反應控制

Chemicalreactioncontrol

外擴散控制

Externaldiffusioncontrol內擴散控制

Internaldiffusioncontrol混合控制

Hybridcontrol化學反應控制

Chemicalreactioncontrol主要研究浸出過程為化學反應控制的浸出分數(shù)與時間的關系。

Therelationshipbetweenleachingfractionandtimeoftheleachingprocesscontrolledbychemicalreactionwasprimarilystudied.UO2粉末在碳酸鈉中溶解的動力學曲線

KineticcurvesofUO2powderdissolutioninsodiumcarbonate浸出過程的控制步驟

Controlstepsoftheleachingprocess設有一浸出過程，若通過擴散層及固體膜的擴散阻力很小，以至反應速度受化學反應控制，則：Assumingaleachingprocess,ifthediffusionresistancethroughthediffusionlayerandthesolidfilmissosmallthatthereactionspeediscontrolledbychemicalreaction:對粒度均勻、致密，且浸出劑濃度可視為不變的過程而言，當其受化學反應控制時，浸出分數(shù)值與浸出時間成直線關系并過原點；Fortheprocesswithuniformanddenseparticlesize,andtheconcentrationofleachingagentcanberegardedasconstant,whenitiscontrolledbychemicalreaction,theleachingfractionvaluehasalinearrelationship

withtheleachingtimeandpassesthroughtheorigin;浸出過程的速度或浸出率隨溫度的升高而迅速增加；Thespeedorleachingrateoftheleachingprocessincreasesrapidlywiththeincreaseoftemperature;反應速度與浸出劑濃度的n次方成比例；Thereactionrateisproportionaltothenthpoweroftheconcentrationoftheleachingagent;攪拌過程對浸出速度無明顯影響。Thestirringprocesshasnoobviouseffect

ontheleachingspeed.CaCO3+2HCl(kg)=CaCl2(og)+H2O+CO2(g)(1-2)浸出過程的控制步驟

Controlstepsoftheleachingprocess化學反應控制

Chemicalreactioncontrol設有一浸出過程，若通過擴散層及固體膜的擴散阻力很小，以至反應速度受化學反應控制，則：Assumingaleachingprocess,ifthediffusionresistancethroughthediffusionlayerandthesolidfilmissosmallthatthereactionspeediscontrolledbychemicalreaction:對粒度均勻、致密，且浸出劑濃度可視為不變的過程而言，當其受化學反應控制時，浸出分數(shù)值與浸出時間成直線關系并過原點；Fortheprocesswithuniformanddenseparticlesize,andtheconcentrationofleachingagentcanberegardedasconstant,whenitiscontrolledbychemicalreaction,theleachingfractionvaluehasalinearrelationship

withtheleachingtimeandpassesthroughtheorigin;浸出過程的速度或浸出率隨溫度的升高而迅速增加；Thespeedorleachingrateoftheleachingprocessincreasesrapidlywiththeincreaseoftemperature;反應速度與浸出劑濃度的n次方成比例；Thereactionrateisproportionaltothenthpoweroftheconcentrationoftheleachingagent;攪拌過程對浸出速度無明顯影響。Thestirringprocesshasnoobviouseffect

ontheleachingspeed.CaCO3+2HCl(kg)=CaCl2(og)+H2O+CO2(g)(1-2)浸出過程的控制步驟

Controlstepsoftheleachingprocess化學反應控制

Chemicalreactioncontrol對化學反應控制的浸出過程而言，提高其浸出分數(shù)R（或稱精礦分解過程的分解率）的途徑主要為：Forchemicalreactioncontrolledleachingprocesses,waystoincreasetheleachingfractionR(ordecompositionrateofconcentratedecompositionprocess)Mainly:提高溫度TIncreasethetemperatureT提高浸出劑濃度CoIncreasetheconcentrationofleachingagentCo

降低顆粒的原始半徑Reducetheoriginalradiusoftheparticle浸出過程的控制步驟

Controlstepsoftheleachingprocess化學反應控制

Chemicalreactioncontrol反應物氣流邊界層的外擴散速度

Externaldiffusionvelocityofreactantgasflowboundarylayer反應總速度

Totalreactionspeed當不存在固體膜時，浸出率與時間成正比。與化學反應控制相似，因此僅根據(jù)動力學方程式（J=-DCxJ）不足以判斷控制步驟為外擴散步驟還是化學反應步驟。Whennosolidmembraneispresent,theleachingrateisproportionaltotime.Similartochemicalreactioncontrol,itisnotsufficienttojudgewhetherthecontrolstepisanexternaldiffusionsteporachemicalreactionstepbasedonthekineticequation(J=-DCxJ)alone.其表觀活化能較小，約為4~12kJ/mol。Itsapparentactivationenergyissmall,about4-12kJ/mol.加快攪拌速度和提高浸出劑濃度能迅速提高浸出速度。Speedingupthestirringspeedandincreasingtheconcentrationofleachingagentcanrapidlyincreasetheleachingspeed.主要特征

Keyfeatures浸出過程的控制步驟

Controlstepsoftheleachingprocess外擴散控制

Externaldiffusioncontrol加強攪拌

Intensifystirring加快溶液與固體顆粒表面的相對擴散速度

Acceleratetherelativediffusionvelocitybetweensolutionandsolidparticlesurface減小擴散層的厚度

Reducethethicknessofthediffusionlayer加快溶液與固體顆粒間的傳質速度

Acceleratemasstransferbetweensolutionandsolidparticles根據(jù)計算，強烈攪拌下浸出劑擴散層的有效厚度可減小為靜止時間的1/50~1/5。Accordingtothecalculation,theeffectivethicknessoftheleachingagentdiffusionlayercanbereducedto1/50-1/5oftheresttimeunderstrongstirring.提高浸出劑濃度Co。IncreasetheconcentrationCoofleachingagent.加強攪拌，減小擴散層厚度。Strengthenstirringandreducethethicknessofdiffusionlayer.提高浸出率的途徑

WaystoImproveLeachingRate浸出過程的控制步驟

Controlstepsoftheleachingprocess外擴散控制

Externaldiffusioncontrol提高溫度Raisethetemperature內擴散是指絕大多數(shù)反應物分子要沿著孔道向顆粒內部擴散。Internaldiffusionmeansthatmostreactantmoleculesdiffusealongtheporestotheinterioroftheparticle.其浸出分數(shù)與時間的關系浸出率與時間成正比。Therelationshipbetweenleachingfractionandtimetheleachingrateisdirectlyproportionaltotime.表觀活化能小，一般僅為

4~12kJ/mol;Theapparentactivationenergyissmall,generallyonly4-12kJ/mol;原礦粒度對浸出率有明顯影響;Theparticlesizeofraworehasobviousinfluenceonleachingrate;攪拌強度對浸出率幾乎沒有影響。Theagitationintensityhadlittleeffectontheleachingrate.主要特征

Keyfeatures浸出過程的控制步驟

Controlstepsoftheleachingprocess內擴散控制

Internaldiffusioncontrol礦粒的粒度Particlesizeoforeparticles降低原料粒度利于縮短時間或加快速度Reducingtheparticlesizeofrawmaterialsisbeneficialtoshortenthetimeorspeedup.固體膜厚度Solidfilmthickness影響浸出率的因素

Factorsaffectingleachingrate浸出過程的控制步驟

Controlstepsoftheleachingprocess內擴散控制

Internaldiffusioncontrol浸出過程的控制步驟

Controlstepsoftheleachingprocess兩個步驟的阻力

Two-stepresistance大體相同

Roughlyidentical遠大于其他步驟

Muchlargerthanothersteps兩者混合控制

Hybridcontrolofboth中間過渡控制

Intermediatetransitioncontrol化學反應速度外擴散速度數(shù)量級相同Thechemicalreactionvelocityandtheexternaldiffusionvelocityarethesameorderofmag