奥托昆普哈加瓦尔塔镍加压浸出流程1.docx

奥托昆普哈加瓦尔塔镍加压浸出流程1.docx

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奥托昆普哈加瓦尔塔镍加压浸出流程1

NEWNICKELPROCESSINCREASINGPRODUCTIONATOUTOKUMPUHARJAVALTAMETALSOY,FINLAND

TABLEOFCONTENTS

1.0Introduction2

2.0NickelSmelter3

3.0Nicke!

Refinery5

4.0Conclusions18

Presentedat

ALTA1997Nickel/CobaltPressureLeaching&Hydrometallurgy

Forum,May19-20,1997,PerthAusffalia

1.0INTRODUCTION

OutokumpuOyhasproducednickelatHarjavaltaWorksinFinlandsince1960.Theproductionhasbeenbasedonflashsmeltingtechnologyandelectrowinningofnickel.Thecapacityoftheprocesshasbeenincreasedgraduallyto18000tpabyseveralsmallexpansionsandprocessimprovements.TheproductionreliedondomesticnickelconcentratesuntilthaAttheturnofthe1990sanewnickelstrategywasdevelopedandOutokumpustartednickelexplorationinAustraiiaandCanada.TheworksecuredlongtermdeliverycontractsofnickelconcentratesfromMt.KeithandstartingofminingoperationsatForrestaniaandSilverSwaninAustralia.

AtthesametimeOutokumpustudieddifferentalterativestoexpandthenickelandcopperproduction.n1993,adecisionwasmadetoinvestintheexpansionandmodernisationofHarjavaltaoperations.Outokumpudecidedtoincreasenickelproductionfrom18000tpato32000tpaandblistercopperproductionfrom100000tpato160000tpa.ThecopperrefineryinPoriwasexpandedfrom72000tpato125000tpa.Inaddition,theexpansionincludedanewoxygenplant,twohydrogenplantsandanewsulphuricacidplant.Theconstructionstartadin1993andtheHarjavaltaprojectwascompletedin1996.Duringtheconstructionthenickelproductionwasdecidedtoincreasefurtherto40000tpa.TherealisedcapitalexpenditureofthewholeexpansionprojectofHarjavaltawasFIM1600million（$US370million）.

Theexpansionofthenickelproductionhasmeantseveralprocesschangesinthanickelsmelterandrefinery.ThedecisiontoinvestinnickelwasprecededbyresearchanddevelopmentworkatOutokumpuHarjavaltaMatalsOyandatOutokumpuRasaarchOy.Theinvestigationprogramledtothefollowingimprovementsoftheprocess:

DevelopmentofdirectOutokumpuNickelSmelting（DON）Process.

Leachingprocessforhighironnickelmatte

UtilizationofOutokumpu-developedanddesignedreactorsforatmosphericandpressureleaching.

UtilizationofOutokumpu-developedsolventextractionprocessinthenickel/cobaltseparation

UtilizationoftheSherrittprocessforhydrogenreductionofnickalandcobalt.

Sulphuroutletasammoniumsulphate

Theprocessimprovementswereincorporatedintheexistingnickelflashsmelter,matterefineryandelectrowinningprocaiss.Thecapacityofthenickelrefineryis18000tpanickelcathodesand22000tpabriquettes.

2.0NICKELSMELTER

Intha1980sOutokumpustartedtodevelopaconverterlessdirectsmeltingprocesstopraduceahighgradenickelmatteforfurtherrefining.TheprocesswastestedonapilotscaleatOutokumpuResearchOyinPoriandfoundtobeviable.ThebenefitsofthisprocesswereinasimplifiedflowsheetandhighgradeS02gasflowtotheacidplant.TheprocesswasnamedthedirectOutokumpuNickelSmeltingProcessorDONProcess/1-3/.

Attumof1990sOutokumpucontinuedthedevelopmentworkontheDONProcessbasedonafeedwithhighnickelandmagnesiacontentandlowironcontent.AsaresultofthisworktheDONPrccesswasfurtherdevelopedtoproducetwomattes:

Lowironmatteintheflashsmaltingfumace（FSF）tobeleachadintheexistingleachingcircuitofHarjavalta.

Highironmatteintheelectricfurnace（EF）tobeIeachedinanewEFmatteleachingcircuit.

Byproducingtwomattesitwaspossibletoeliminatetheconverterswhichhasmeantasimpleprocesswithlowinvestment,maintenanceandoperatingcosts.Inaddition,itisnowpossiblatosmeltconcentrateswithahighmagnesiumcontent.TheferricresiduefromtheEFmatteleachingisaddedtothesmeltingchargetoincreasetheirontomagnesiumratioandtoreducesmeltingtemperatureoftheslag.Futher,thecobaltrecoveryoftheDONPracessishigherthanintheconventionalsmeltingprocess.

InHarjavalta'scase,itwasessentialthattheprocesscouldusetheexistingflashfurnaceandelectricfurnaceaswellastheexistingleachingplant.FigurelshowstheflowsheetoftheDONProcessatHarjavaltanickelsmelter.

Theprimaryfeedofthenickelsmelterisablendofvariousconcentrates.Alsonickelcontainingsecondarymaterialsareusedasafeed.Inadditiontothefluedustfromthewasteheatboilerandtheelectrostaticprecipitator,theironprecipitatefromtheEFmatteleachingiscirculatedbacktotheflashfurnace.Thismakesitpossibletoconvertleachresiduetodisposablefayaliteslag.Concentratesandsandaredriedinanoil-firedrotarydrum.Afterdrying,thefeedmixtureandoxygenenrichedairarefedthroughtheconcentrate'burnerintothereactionshartoftheflashsmeltingfumace.Duringtheoxidationprccesstheironcontentofthenickelmatteiscurrentlyreducedtofivepercent.Thenickeimatteisgranulateddirectlyintowaterdewateredandfedtotheleachingplant.

Theslagfromtheflashfumaceistappedintotheelectricfumaceforcleaning.Inthepurificattonprocess,coalisusedasareductantanddrynickelconcentrateasasulphidizingagenttoproduceadesiredqualityofmatteandslag.ThematteisgranulatedbyasimilarprocassasusedfortheFSFmatteandisfedtothenewEFmatteleachingplant.TheslagfromtheEFfumaceisalsogranulatedandfinailystoredinslagdumps.

Hotgasfromtheflashfurnaceiscooleddownto350℃inawasteheatboilerandbeforefeedingtotheacidplant,dustisremovedinanelectrostaticprecipitator.

Tablelgivesatypicalcompositionofthefeedmixture,flashfurnacematte,andelectricfurnacematteandslags/4/.

Thesmeltingcapacityofconcentratesis250000tpacorresponding40000tpaofnickelatthecurrentblendofconcentrates.

TablelCompositionoffeedmixture,flashsmeltingfurnacematte,electricfurnacematteandslags.

3.0NICKELREFINERY

AnoyerallflowsheetofthenickelproductionprocessatHarjavaltaisshowninFigure2.ThegranulatedmattesfromtheFSFandtheEFarethestartingmaterialsforthenickelrefinery,where,aftergnnding,themattesareleachedinseparatecircuits.Theproductsolutionfromtheleachingplantisledtoasolventextraction（SX）processforcobaltseparation.TheSXplanthasreplacedtheformercobaltremovalprocess/5,6/,wherecobaltwasprecipitatedasacobaltichydroxide.Therearetwofinalproducts;cathodenickelproducedinanelectrowinningstepandnickelbriquettesproducedinahydrogenreductionstep.Therearealsofacilitiesforhydrogenreductionofcobalt.

Thenickelrefinery,orinfacttheentireHarjavaltaplant,isautomatedusingtheVALMETDamaticXDprocesscontrolsystem.Inthenickelrefinery,OutokumpuMintecon-streamanalysersformanessentialpartoftheautomation,TheCourier30APanalysersmeasureliquidphaseconcentrationsofcopper,ironandarsenicusingX-rayfluorescencewhereasautomaticOTItitratorsareusedformeasuringsulphuricacidconcentration.

3.1LEACHINGPLANT

TheleachingplantatHarjavaltaisespeciallydesignedfortreatmentofthetwomattesfromtheDONProcess.ThechemistryoftheIeachingprocessisdescribedpreinsection3.1.1,whereastheactualcircuitatHarjavaltaanditsparametersaresentedinsection3.1.2.

3.1.1Outokumpunickelmatteleachingprocess

BasedonexperiencesfromtheHajavaltaleachingplantandresearchworkusingsmall-scaleequipment,OutokumpuhasdevelopeditsmethodforIeachingtwodifferentnickelmattes.AflowsheetoftheOutokumpunickelmatteIeachingprocessisshowninFigure3.

AccordingtotheOutokumpunickelmatteleachingconcept,theFSFmatteisleachedinthreestepsconnectedincounter-currentandtheEFmatteisIeachedintwostepsinseries.Mainleachingagentsareoxygenandsulphuricacid.

ThemainproductoftheIeachingplant,i.e.thesolutiongoingtocobaltandnickelseparation,isachievedfromthecopperremovalstep.ThecopperisobtainedascoppersulphideprecipitatefromthenickelIeachingautoclaveintheFSFpressureleachingstep.AnypreciousmetalsintheFSFmattearecollectedintotheresiduefromthetotalIeachingautoclave/7/.TheironisprecipitatedasgoethiteorhematiteintheEFIeachingcircuit.

a）Atmosphericcopperremoval

TheatmosphericcopperremovalintheFSFIeachingcircuitproducesaNi-andCo-sulphatesolutionwithimpuritiesatlevelslowenoughforsubsequentcobaltextractionandnickelreduction.ThemainmineralsinthematteareheazlewooditeNi3S2,coppersulphideCu2SandaNiCualloy.Theotherelementsoccurpartlyinseparatephasesbutalsomixedintothethreemainphases.ThemostreactivephaseisthemetallicalloyfollowedbyNi3S2andthenCu2S.

Importantreactionsaretheprecipitationofcopperandthesimultaneousleachingofnickel.Mostimportantnetreactionsareshowninthefollowing:

CuSO4+NiCu+0.5O2—Cu2O+NiSO4

（1）

2CuSO4+2Ni3S2+0.5O2—Cu2O+2NiSO4+4NiS

（2）

3CuSO4+2Ni3S2+O2+2H2O—Cu3SO4（OH）4+2NiSO4+4NiS（3）

2CuSO4+NiCu+O2+2H2O—Cu3SO4（OH）4+NiSO4（4）

lroninthesolutionsfedtothecopperremovalstepisvirtuallyasFe++,anditisoxidizedandprecipitatedasFeOOHaccordingto

FeSO4+Ni3S2+0.75O2+0.5H2O—FeOOH+NiSO4+2NiS（5）

butsomeFe（OH）3isalsoformed.

Arsenic,antimonyandbismutharemainlyprecipitatedtogetherwithironinpoorlysolubleferriccompoundssimilartoferricarsenate,FeAs04.Thus,theremovaloftheseelementsfromthesolutionisenhancedbyanincreasedironprecipitation.

b）Nickelatmosphericleach

Intheat