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Lecture23:ReductionSmelting

ContentsPreamble

Salientfeaturesofleadreductionsmelting

Materialbalanceinleadsmelting

Keywords:Ironmaking,imperialsmeltingprocess,smelting,metalextraction

PreambleReductionandsmeltingaretwoindependentunitprocessesemployedinmentalextractionthrough

pyromettallurgicalroute.Reductioniscarriedmostlybycarbon.Forexamplereductionof

FeO, ZnOand PbO.Whereassmeltingconsistsinheatingtheproductstoatemperatureabovethe

meltingpointtoseparateliquidmetalfromliquidslag.Bothunitprocessescanbecarriedout

simultaneouslyinonereactororintwoindependentinterconnectedreactors.

Typicallylead,zincandhotmetalareproducedinasinglereactorcalledblastfurnace.InKorexprocess

twoindependentinterconnectedreactorsareusedtoproducehotmetal. Shaftfurnaceisconnected

withasmeltergasifiesunit.

SalientfeaturesofleadreductionsmeltingInthefollowinglecturewewilldealwithproductionoflead.Asalientfeatureofleadblastfurnacewill

begivenandthelectureisfollowedbymaterialbalance.Adetaileddescriptioncanbefoundinthe

referencesgivenattheendofthislecture.

Pbisproducedbycarbonreductionofthesintercontainingleadoxideinaleadblastfurnace.SinterconsistsofPbS, PbO, PbSO,SiO, AlO etc

Heightofblastfurnace8m,topdia3m,crucibledepth. andstackheight5m. Temperatureatbosh1200 . Airisblowninthrough15tuyeres(1520)aroundtheboshtooxidizeCchargedwithsinterwhich

producesrequiredheat.

Attopoffurnacebaghousesareprovidedtocollectleadfurnacesfromoutgoinggases. Limestoneandquartzareaddedtomakeaslag.

Scrapironischarged.Thefollowingreactionsoccur.

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PbSiO Fe FeSiO Pb.

Pb.

Theproductsofsmeltingareliquidlead,matte,speiss,slagandgases.Leadhasdensity11g/cm3,matte

containingcopperhasdensity5g/cm3,whereasspeisshasdensity6g/cm3

MaterialbalanceinleadsmeltingA)Leadoreconcentrateofcomposition60%PbS,4% FeS2, 3% AlO, 2% CO and 31% SiOis

roastedbyusing300%theoreticalair.Duringroastedall FeS2, 90%PbSisoxidized.Determinefor

1000kgconcentrate.1) Volumeofairat1atmand273K2) Amountandcompositionofroastedproduct3) Amountandcompositionoffluegas

B)The

roasted

product

determined

above

is

smelted

in

blast

furnace

using

flux

as FeO,and CCOto

produceslaghavingaratioSiO: FeO: CaOequalto35:50:15.Theamountofcokeis16%ofweightof

concentrate.Thecokecontains85% C and 15% SiO. Find

4)Amountofeachflux

5)AmountofslagSolution:MolecularweightPb 239, Fe 56, Al 27, Ca 40, Si 28

Roastingreactionsare

PbS 1.5O PbO SO

FeS 2.5O 2FeO 2SO

Volumeofair=(theoreticalamount)x3

Theoreticalaircanbecalculatedfromthestoichiometricequation.

Volumeofair=135

RoastedproductconsistsofPbS, PbO, FeO,AlO,CaO and SiO. Wehavedoneearliermaterialsbalance

(Referlectures17,18,19,21,).

Amountofroastedproduct=948kg

Amountoffluegas=59kgmoles

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SmeltingofroastproductconstitutespartB.FluxusedislimestoneandFeO,Amount of CaCOdetermined from CaO 220 Kg.

Amount of FeO, 503 Kg

Amount of slag 984.3 kgy

Doyourself

2)ThechargeforPbblastfurnaceconsistsof

RoastedOre PbO 31% , PbS 19% , SiO 40% and feO 10%

(1000Kg)

Pyritecinder

FeO, 88%, CuS 5 %,SiO 7 %

(600Kg)

CokeC 89 %, SiO11%

(180Kg)

FluxCCO 100%

(220Kg)

Mattecontains

all

ofCu, S and 2% Pb.

No

Pb

is

lost

in

slag

or

gases.

ThegasescontainCO:CO 1: 1 byvolume

Calculate:

a) Chargebalanceoffurnaceb) Proximatecompositionofmatteandslagc) Volumeofblastused(at1atmand273K)Answers:

d) Amountoflead 443kge) Amountofmatte 106.54Kgf) Amountofslag 1106Kgg) Volumeofblast = 543m3

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Referencesforlectures23to30

1.H.SRay,RSridharandK.P.Abraham:

2.Rosenquist:Principlesofextractivemetallurgy

3.Butts:Metallurgical

problem

4.Coudrier;l,HupkinsD.WandIWilkomirnky:Fundamentalsofmetallurgicalprocesses.

5.Y.KRao:Strichiometricalcalculationinmettalurgical;processes.