Unit operationsUnit operationsof metals productionof metals production

ContentsContents

Unit operations of Mining and enrichmentUnit operations of Mining and enrichment

Pyrometallurgical unit operationsPyrometallurgical unit operations Hydrometallurgical unit operationsHydrometallurgical unit operations Electrochemical unit operationsElectrochemical unit operations

Casting processesCasting processes Thermo-mechanical treatment of metalsThermo-mechanical treatment of metals Metal product manufactureMetal product manufacture

Not includedin this presentation

Water

Hydrometallurgicalmetal production

Materialsciences

Mining &Enrichment

Metallurgy:introduction

Electro-metallurgy

Extractivemetallurgy

OresMining

EnrichmentCrushingScreeningMechanicalseparation

(...)

Properties ofmetals

Physicalmetallurgy

Hot and coldrolling

(...)

Hydrometallurgy

Pyrometallurgy

e.g.zinc

nickel

Electrowinning

Cementation

Ionexchange

Chemicalprecipitation

Solventextraction

Similarmethods

Reactionkinetics

Thermo-dynamics

Theory

Metalrecovery

Impurityremoval

Fluiddynamics

Heattransfer

Masstransfer

Transportphenomena

Methods

Leaching

Iron andsteel

Sulphide-ores (e.g. Cu)

e.g. Roasting

Pyrometall.pretreatment

Pyrometallurgicalmetal production

e.g.iron/steelcopper

Sintering

Coking

Blastfurnace

Sulphurremoval

Ladletreatments

Converters(LD/AOD/...)

Casting

Flashsmelting

Converters(PS)

Electricfurnaces

(...)

AcidicBasic

Organic

Solvents

How to choose a process?How to choose a process?

Pyromet. unit operationsPyromet. unit operationsHydromet. unit operationsHydromet. unit operations

Electro-chem. unit operationsElectro-chem. unit operations

Production chainProduction chain ProductsProductsRaw materialsRaw materials

ResiduesResidues

$$MarketsMarketsTransportTransport

EnergyEnergy

Water neededWater needed

PyrometallurgicalPyrometallurgicalunit operationsunit operations

Raw Raw materialmaterial

pre-pre-treatmentstreatments

MetalMetalrefiningrefining

MetalMetalextractionextraction

Production of metalsProduction of metalsRaw materialsRaw materials ProductsProducts

ReductionReductionand and

oxidizingoxidizing

Thermal Thermal pre-pre-

treatmenttreatment

Metal Metal raffinationraffination

MatteMatteproductionproduction

ReductionReductionof oxidesof oxides

CompositionCompositioncontrolcontrol

Impurity removalImpurity removal

TemperatureTemperaturecontrolcontrol

SinteringSintering

DryingDrying

CalcinationCalcinationCokingCoking RoastingRoastingPelletizingPelletizing

DryingDrying Dangerous to charge wet materials to the Dangerous to charge wet materials to the

high temperature processeshigh temperature processes– The moisture that is allowed depends on the The moisture that is allowed depends on the

further processingfurther processing Mechanical moisture removal preferedMechanical moisture removal prefered

– Thermal drying requires a lot of energyThermal drying requires a lot of energy Counter-current drum-driers are common in Counter-current drum-driers are common in

the drying of metallurgical raw materialsthe drying of metallurgical raw materials Utilisation of the process waste heat Utilisation of the process waste heat

streamsstreams

SinteringSintering Problems in processing fine materialsProblems in processing fine materials

– Gas permeabilityGas permeability– DustingDusting

Thermal agglomerationThermal agglomeration– Partial meltingPartial melting– Minimisation of the surface energyMinimisation of the surface energy

as a driving force for agglomerationas a driving force for agglomeration Chemical and mineralogical changes in Chemical and mineralogical changes in

materialmaterial Drum-, batch- or belt-sinteringDrum-, batch- or belt-sintering

– Pretreatment: MicropelletisingPretreatment: Micropelletising

PelletizingPelletizing Feeding of concentrates, binding materials Feeding of concentrates, binding materials

and water into the rotating and sloped and water into the rotating and sloped pelletising drum or platepelletising drum or plate

Capillar forces caused by moisture as cohesive Capillar forces caused by moisture as cohesive forceforce

Aftertreatments in order to achieve wanted Aftertreatments in order to achieve wanted propertiesproperties– SinteringSintering– Shaft furnaceShaft furnace

Small pellets are fed backSmall pellets are fed backto the processto the process

CalcinationCalcination Thermal disintegration of a compound (which Thermal disintegration of a compound (which

leads into a formation of gaseous product)leads into a formation of gaseous product)– Thermal conductivity (endothermic reactions)Thermal conductivity (endothermic reactions)– Removal of gas from the reaction surfaceRemoval of gas from the reaction surface

e.g. calcination of limestone to produce e.g. calcination of limestone to produce burned limeburned lime

Use of lime in iron and steelmaking slagsUse of lime in iron and steelmaking slags– CaCOCaCO33 = CaO + CO = CaO + CO22 HHRR >> 0 >> 0

– Counter-current shaft furnace or rotating drumCounter-current shaft furnace or rotating drum Other examplesOther examples

– Disintegration of CaMg(CODisintegration of CaMg(CO22))22 or Al(OH) or Al(OH)22

CokingCoking Pyrolysis of coal in order to modify it to be Pyrolysis of coal in order to modify it to be

more suitable for metallurgical processesmore suitable for metallurgical processes– Removal of water and volatile componentsRemoval of water and volatile components– Agglomeration of coal particlesAgglomeration of coal particles– Porous coke as a resultPorous coke as a result

Dry or wet quenchingDry or wet quenching Several by-productsSeveral by-products

– Reducing gas (HReducing gas (H22, CO), CO)

– Raw materials for chem. industryRaw materials for chem. industry

RoastingRoasting A process in which an anion of a solid A process in which an anion of a solid

compound is changed without changing the compound is changed without changing the valency of the cationvalency of the cation

High temperature processing of the sulphide High temperature processing of the sulphide ores without agglomerationores without agglomeration– Often used as a pretreatment for the Often used as a pretreatment for the

hydrometallurgical processeshydrometallurgical processes ExamplesExamples

– Oxidising roastingOxidising roasting– Sulphating roastingSulphating roasting– Chlorine/Fluor/Alkalines/...Chlorine/Fluor/Alkalines/...

Oxidising roastingOxidising roasting Difficulties to reduce sulphide ores using carbonDifficulties to reduce sulphide ores using carbon

– e.g. 2 ZnS + C = 2 Zn + CSe.g. 2 ZnS + C = 2 Zn + CS22 or ZnS + CO = Zn + COS or ZnS + CO = Zn + COS

– Equilibrium is strongly on the reactants’ sideEquilibrium is strongly on the reactants’ side Roasting of sulphides into the oxidesRoasting of sulphides into the oxides

– MeS + 3/2 OMeS + 3/2 O22 = MeO + SO = MeO + SO22

– Used e.g. in the production of lead, copper, zinc, cobalt, Used e.g. in the production of lead, copper, zinc, cobalt, nickel and iron when using sulphide ores as raw nickel and iron when using sulphide ores as raw materialsmaterials

– SOSO22 SO SO33 H H22SOSO44

Fluidized bed, sintering or shaft furnace roastingFluidized bed, sintering or shaft furnace roasting– Products are either fine material or porous Products are either fine material or porous

agglomeratesagglomerates

Sulphating roastingSulphating roasting Used in separation of metals from complex Used in separation of metals from complex

materialsmaterials– Some metals react to sulphates that are soluble to waterSome metals react to sulphates that are soluble to water

MeS + 3/2 OMeS + 3/2 O22 = MeO + SO = MeO + SO22

SOSO22 + 1/2 O + 1/2 O22 = SO = SO33

MeO + SOMeO + SO33 = MeSO = MeSO44

– Some are left as oxides (non-soluble)Some are left as oxides (non-soluble) A pretreatment for hydrometallurgical processesA pretreatment for hydrometallurgical processes Usually fluidized bed roastingUsually fluidized bed roasting Often used to remove iron from more valuable Often used to remove iron from more valuable

metals (Cu, Ni, Zn, Co)metals (Cu, Ni, Zn, Co)– When T > 600 When T > 600 C C Ferrisulphate is not stable Ferrisulphate is not stable

Reduction of oxidesReduction of oxides

MeO + R = Me + MeO + R = Me + RORO– Me is a metalMe is a metal– R is a reducing R is a reducing

component (an component (an element or a element or a compound which compound which forms an oxide forms an oxide which is more stable which is more stable than MeO in the than MeO in the considered considered temperature)temperature)

Reduction of oxidesReduction of oxides Carbo-thermal reductionCarbo-thermal reduction

– MeO + C = Me + COMeO + C = Me + CO– In practice:In practice:

MeO + CO = Me + COMeO + CO = Me + CO22

C + COC + CO22 = 2 CO (= Boudouard reaction) = 2 CO (= Boudouard reaction)

Metallothermal reductionMetallothermal reduction– MeO + M = Me + MOMeO + M = Me + MO

Gas reductionGas reduction– Usually HUsually H22 and CO (separately or as a mixture) and CO (separately or as a mixture)

MeO + HMeO + H22 = Me + H = Me + H22OO MeO + CO = Me + COMeO + CO = Me + CO22

Reduction of oxidesReduction of oxides

The largest industrial CO2-emissionsin Finland and Sweden (Mt)

Specific and total CO2-emissionsof the Finnish steel industry

Matte productionMatte production Separation of metals from the sulphidesSeparation of metals from the sulphides

– ””Worthless” metal is oxidised Worthless” metal is oxidised Oxidic slag Oxidic slag– Wanted metal is still as a sulphide Wanted metal is still as a sulphide Matte Matte

Matte is further refined Matte is further refined Metal Metal Used e.g. in the production of copper, nickel Used e.g. in the production of copper, nickel

and leadand lead– 2 CuS + O2 CuS + O22 = Cu = Cu22S + SOS + SO22

– FeSFeS22 + O + O22 = FeS + SO = FeS + SO22

– 2 FeS + 3 O2 FeS + 3 O22 + SiO + SiO22 = Fe = Fe22SiOSiO44 + 2 SO + 2 SO22

Removal of impuritiesRemoval of impurities(from iron/steel)(from iron/steel)

Carbon removal (hot metal Carbon removal (hot metal crude steel) crude steel)– To achieve wanted propertiesTo achieve wanted properties– Decarburization in BOF-convertersDecarburization in BOF-converters

Removal of other oxidising impurities/elements (Si, Mn, Removal of other oxidising impurities/elements (Si, Mn, P)P)

Oxygen blowing Oxygen blowing Oxide formation Oxide formation Slag/Gases Slag/Gases Temperature is increasedTemperature is increased

– Scrap meltingScrap melting

– Vacuum treatmentVacuum treatment Burning of carbon is more efficientBurning of carbon is more efficient

in lowered pressurein lowered pressure Partial pressure of CO can also bePartial pressure of CO can also be

lowered using inert gaseslowered using inert gases

Removal of impuritiesRemoval of impurities(from iron/steel)(from iron/steel)

Deoksidation / Oxygen removalDeoksidation / Oxygen removal– Solubility of oxygen in steel melt is appr. 0,2 % (T > 1500 Solubility of oxygen in steel melt is appr. 0,2 % (T > 1500

C)C)– Solubility decreases when temperature is decreasedSolubility decreases when temperature is decreased

Causes CO formation, oxidation of alloying elements, etc.Causes CO formation, oxidation of alloying elements, etc.

– Alloying, diffusion or vacuum deoxidationAlloying, diffusion or vacuum deoxidation Gas removalGas removal

– Solubilities of gases decrease when T is decreased (cf. O)Solubilities of gases decrease when T is decreased (cf. O)– Gas removal is based on decreasing the partial pressure of Gas removal is based on decreasing the partial pressure of

the concerned element in the gas phase (vacuum, inert gas)the concerned element in the gas phase (vacuum, inert gas) Sulphur removalSulphur removal

– Formation of CaS Formation of CaS Into the slag Into the slag

Composition controlComposition control(Steel)(Steel)

Alloying of steel is made mainly in the BOF-Alloying of steel is made mainly in the BOF-converters after the blowingconverters after the blowing

More accurate alloying in the steel ladleMore accurate alloying in the steel ladle– LumpsLumps– Powder injectionPowder injection– Wire injectionWire injection

StirringStirring– InductiveInductive– Using an inert gasUsing an inert gas

Temperature controlTemperature control Increased significance due to continuous Increased significance due to continuous

castingcasting Optimisation of a tap temperatureOptimisation of a tap temperature Inductive heatingInductive heating Use of fuelsUse of fuels Plasma heatersPlasma heaters Chemical heating (Al, Si)Chemical heating (Al, Si) Electric arcsElectric arcs InsulationInsulation Scrap coolingScrap cooling StirringStirring

HydrometallurgicalHydrometallurgicalunit operationsunit operations

ActivatioActivationn

Raw materialRaw material

PoorPoorrawrawmaterialsmaterials

ImpureImpurerawrawmaterialsmaterials

WastesWastesBy-By-productsproducts

LeachingLeaching

Impurity Impurity removalremoval

Metal Metal recoveryrecovery

ChemicalChemicalElectro-Electro-chemicalchemical

ProductProduct

WasteWastetreatmentreatmen

tt

WasteWaste

By-productBy-product

Cleaning / Cleaning / regeneration regeneration

of the of the solventsolvent

Pyro-Pyro-metallurgicalmetallurgical

Hydro-Hydro-metallurgicalmetallurgical

LeachingLeaching Grinding, enrichment and activation as pre-Grinding, enrichment and activation as pre-

treatmentstreatments

SolventsSolvents– WaterWater

For sulphates and chloridesFor sulphates and chlorides

– AcidsAcids Sulphuric acid most commonly usedSulphuric acid most commonly used Nitric and hydrochloric acidsNitric and hydrochloric acids

– more expensive and corrodingmore expensive and corroding

– BasesBases Ammonia waterAmmonia water

– Organic solventsOrganic solvents

LeachingLeaching Direct leachingDirect leaching

– For poor ores and residuesFor poor ores and residues Tank leaching (in atmospheric pressure)Tank leaching (in atmospheric pressure)

– For rich ores and concentratesFor rich ores and concentrates– Smaller reactors and faster processesSmaller reactors and faster processes– StirringStirring

Autoclave leachingAutoclave leaching– Tank leaching in which reaction kinetics are enhanced Tank leaching in which reaction kinetics are enhanced

by increasing temperature over the boiling point of by increasing temperature over the boiling point of the solution (in increased pressure)the solution (in increased pressure)

Metal recoveryMetal recovery CrystallizationCrystallization

– Separation of solid crystal from a homogenic solutionSeparation of solid crystal from a homogenic solution– Pure products (impurities only on the surfaces)Pure products (impurities only on the surfaces)– Saturated solutionSaturated solution– Kinetics?Kinetics?

Chemical precipitation (as sulphides or as metals)Chemical precipitation (as sulphides or as metals)– Addition of anions or cations in order to form a Addition of anions or cations in order to form a

compound with a low solubilitycompound with a low solubility– SelectivitySelectivity– Gases (HGases (H22S, HS, H22, SO, SO22, CO) are efficient additives, CO) are efficient additives

ElectrowinningElectrowinning

Impurity removalImpurity removal Procedures between leaching and metal Procedures between leaching and metal

recoveryrecovery Physical removal of solid materialsPhysical removal of solid materials

– ThickeningThickening– FilteringFiltering

Removal of impurities from the solutionRemoval of impurities from the solution– Similar methods as in metal recoverySimilar methods as in metal recovery– Ion exchangeIon exchange– Liquid-liquid-extractionLiquid-liquid-extraction

Ion exchangeIon exchange To remove small amounts of impurities from To remove small amounts of impurities from

large amounts of solutionslarge amounts of solutions– Best with dilute solutions (< 10 ppm)Best with dilute solutions (< 10 ppm)

Possibility to achieve very low impurity levelsPossibility to achieve very low impurity levels Resin to which metal ions are tranfered from Resin to which metal ions are tranfered from

solutionsolution– SelectivitySelectivity

Saturated resin is recovered with other Saturated resin is recovered with other solutions to which the metal ions are solutions to which the metal ions are transferedtransfered– Saturation of metals as chlorides, sulphates, etc.Saturation of metals as chlorides, sulphates, etc.

Liquid-liquid-extractionLiquid-liquid-extraction Recovery of metal ions from the water Recovery of metal ions from the water

solution using an organic extraction agentsolution using an organic extraction agent– Two immiscible liquidsTwo immiscible liquids

Reaction area is increased using efficient stirringReaction area is increased using efficient stirring

– Formation of complex compoundsFormation of complex compounds– Settling in order to separate two liquid phasesSettling in order to separate two liquid phases– Recovery of valued metals from the complex Recovery of valued metals from the complex

compoundscompounds SelectivitySelectivity

CementationCementation Substitution of a metal ion (MSubstitution of a metal ion (M++) with a less ) with a less

noble metal (Me)noble metal (Me)– Me(s) + MMe(s) + M++(aq) = Me(aq) = Me++(aq) + M(s)(aq) + M(s)

Efficiency depends on the difference of the Efficiency depends on the difference of the ”nobilities” of the metals”nobilities” of the metals

Electro-chemicalElectro-chemicalunit operationsunit operations

Electrolysis = reduction/oxidation that is Electrolysis = reduction/oxidation that is controlled with the electricitycontrolled with the electricity– Electrolyte that contains ionsElectrolyte that contains ions– Anions (-) are transfered to the anode (+) Anions (-) are transfered to the anode (+) Oxidation Oxidation– Cations (+) are transfered to the cathode (-) Cations (+) are transfered to the cathode (-)

ReductionReduction Can be hydrometallurgical ...Can be hydrometallurgical ...

– ElectrowinningElectrowinning– Electrolytical refiningElectrolytical refining

... or pyrometallurgical... or pyrometallurgical– Molten salt -electrolysisMolten salt -electrolysis

ElectrowinningElectrowinning

Anodes are not dissolved (e.g. Pb)Anodes are not dissolved (e.g. Pb)– Formation of oxygen as a main reactionFormation of oxygen as a main reaction– Formation of hydrogen occurs with less noble metalsFormation of hydrogen occurs with less noble metals– The amount of HThe amount of H++-ions is increased in the electrolyte-ions is increased in the electrolyte

Metal-ions from the solution are precipitated in Metal-ions from the solution are precipitated in the cathodethe cathode– The amount of metal ions is decreased in the The amount of metal ions is decreased in the

electrolyteelectrolyte– Metal-poor electrolyte is recycled back to the Metal-poor electrolyte is recycled back to the

leaching processleaching process Used in the production of nickel and zincUsed in the production of nickel and zinc

Electrolytical refiningElectrolytical refining

Anodes are dissolving (impure metal to be refined)Anodes are dissolving (impure metal to be refined)– Wanted metal is dissolved to the electrolyteWanted metal is dissolved to the electrolyte– All the less noble metals are also dissolvedAll the less noble metals are also dissolved– More noble metals don’t dissolve More noble metals don’t dissolve an anode sludge is an anode sludge is

formedformed CathodesCathodes

– Precipitation of a wanted metalPrecipitation of a wanted metal– Less noble metals are left in the electrolyte from which Less noble metals are left in the electrolyte from which

they can be recoveredthey can be recovered Refining of pyrometallurgically produced metalsRefining of pyrometallurgically produced metals

– Especially copperEspecially copper

Electrolysis using Electrolysis using molten salts as molten salts as

electrolyteselectrolytes Halide melts as electrolytesHalide melts as electrolytes The principle is same as in hydro-The principle is same as in hydro-

metallurgical electrolysesmetallurgical electrolyses Higher temperaturesHigher temperatures

– Refractoriness of the reactors etc.Refractoriness of the reactors etc. Used in the production of aluminium, Used in the production of aluminium,

magnesium, beryllium, cerium, lithium, magnesium, beryllium, cerium, lithium, potassium and calciumpotassium and calcium– i.e. metals that are produced from the raw materials i.e. metals that are produced from the raw materials

with high melting temperatureswith high melting temperatures