Metal Extraction 1

8/3/2019 Metal Extraction 1

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METALS AND METALLURGYEXTRACTION OF SODIUM(DOWN'S PROCESS)

NaCl

33.3% NaCl + 66.7% CaCl2

Electrolyte

Molten mixtureTemperature

6000C

NaCl = Na+ + Cl-

Cathode reaction : Na+ Na

Anode reaction : Cl

-

ClCl + Cl Cl

2

+e

-e

Electrodes :Graphite anodeIron cathode

Collection: Sodium is removed from time to time with the help of proforated ladles made by Niand kept under kerosene

By product

Cl2 gas


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METALS AND METALLURGYEXTRACTION OF SODIUM(CASTNER PROCESS)

NaOHElectrolyte

Collection: Sodium is removed from time to time with the help of proforated ladles made by Niand kept under kerosene

NaOH at 3180C

Molten

Electrode reaction

NaOH = Na+ + OH-

cathode : Na+ + e = Na

Anode : OH- -e = OH4OH = 2H2O + O2

Electrodescathode : steelanode : Nickel

cylinder

Water produced at anode is again electrolysed and H2 at cathode and O2 at anode

evolves.

By products:

H2 at cathode

O2

at anode


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METALS AND METALLURGYEXTRACTION OF CALCIUM BY ELECTROLYSIS

CaCl2

CaCl2 + CaF2 (6:1 ratio)

Electrolyte

Molten mixtureTemperature

7000C

Electrodes :cathode: Fe rod

anode : graphite

Calcium can not extracted by carbon reduction method because at higher temperature

calcium reacts with carbon to form calcium carbide(CaC 2)

Electrode Recation :

CaCl2

= Ca+2 + 2Cl-

Cathode : Ca+2 + 2e = Ca

Anode : 2Cl- = Cl2

By product :

Cl2

gas


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METALS AND METALLURGY

PREPARATION OF PURE ALUMINA(BAEYER'S PROCESS)

Finely powdered bauxite

containing Fe2O

3,TiO

2,SiO

2as impurities

FeO if anyCalcined(FeO Fe

2O

3)

organic matters areremoved

Calcined ore

Digested with 45% NaOH solnat 1500C under 80lb pressure

filtered

Filtrate

NaAlO2

+ Na2SiO

3

Residue

Fe2O

3,TiO

2

filtered

Filtrate

diluted with water and cooled to 25-300C,

Stirred with freshly preparedaluminium hydroxide(seeding agent)

Precipitate

Al(OH)3

wash withwater

heat

10000

C

Pure alumina

Al2O

3

Al2O

3+2NaOH = 2NaAlO

3+ H

2O

SiO2

+ 2NaOH = Na2SiO

2+ H

2O

NaAlO2

+ 2H2O = Al(OH)

3 + NaOH

2Al(OH)3 Al2O3 + 3H2O


5/12

METALS AND METALLURGYEXTRACTION OF ALUMINIUM(ELECTROLYSIS PROCESS)

pure alumina

Electrolyte

oxygen liberated at anode attacks anode.In order to prevent that, some coke is added to

electrolytic mixture.This coke reacts with O2 to form CO2

Molten

Electrode reaction

AlF3.3NaF = AlF3 + 3NaF

AlF3

= Al+3 + 3F-

cathode : Al+3 + 3e = Al

Anode : 3F- -3e = 3F

Al2O3 + 6F = 2AlF3 + 3[O]

6[O] = 3O2

Electrodescathode :carbonlined steel

anode : graphite

Pure alumina + fused cryolite + fluorsper

20:60:20


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METALS AND METALLURGYPURIFICATION OF ALUMINIUM(HOOP'S PROCESS)

electrolytic cell iron tank lined with carbon

Fitted with three liquidsdiffering in specific gravity

Upper layer is pure fused Alacts as cathode

Central layer is the moltenmixture of the fluorides ofAl,Ba and Na--- used as

electrolyte

Bottom layer is impure metalin fused state acts as anode

on passing current pure Al goes to the top layer from the central layer and an

equivalent amount of metal from the bottom layer passes into central layer


7/12

METALS AND METALLURGYEXTRACTION OF COPPER(FROM COPPER PYRITES)

Copper pyrites, contains

(3% Cu)- Cu2S, Fe

2S

3, silica

sulphur, arsenic

concentration by oilfloatation process

Concentrated ore, (25-30% Cu)

Cu2S,Fe

2S

3,SiO

2

Roastingin reverberatoryfurnace

Roasted ore, Cu2S,FeS

FeO,SiO2,little Cu

2O

Cu2S,Fe2S3 + O2 = Cu2S + 2FeS + SO2Cu

2S,Fe

2S

3+ 4O

2= Cu

2S + 2FeO + 3SO

2

2Cu2S + 3O

2= 2Cu

2O + 2SO

2

Cu2O + FeS = Cu

2S + FeO

Blast

Furnace

Matte : Cu2S + small amt of

FeS SO2

2FeS + 3O2

= 2FeO + 2SO2

FeO + SiO2 = FeSiO3CaO + SiO

2= CaSiO

3

Cu2O + FeS = Cu

2S + FeO

Smelting : roasted ore + coke

+ silica + lime stone

self reduction:Bessemer converter

Blister Copper98% pure

2Cu2S + 3O

2= 2Cu

2O + 2SO

2

2Cu2O + Cu

2S = 6Cu + SO

2

Cu2S + 2O2 = Cu2SO4Cu

2S + Cu

2SO

4= 4Cu + SO

2

By products :

SO2,Ferrous silicate,anode slime


8/12

METALS AND METALLURGYPURIFICATION OF COPPER(POLING PROCESS)

Blister Copper + 2-3% Fe,sulphur, arsenic

reverberatory furnace linedwith silicaAir is passed

Blister copper is meltedFe and S oxidised to FeO and

SO2, and As to volatile oxide

FeO combined with silica

Ferrous silicate floates onmolten copper containing

some Cu2O

Cu2O removal : powdered coke is sprinkled

on molten mass and then it is stirred withgreenwood poles

Green poles of wood produces reducing gases

which reduce the cuprous oxide to metallic copper99.5% pureCopper


9/12


EXTRACTION OF ZINC (FROM ZINC BLENDE)

Zinc blendeZnS + gangue

Crushing and grinding

PowderedZinc blende

Concentration by oil f loatationmethod : water+ pyne oil + sod.xanthate + acid-blowing air

Concentrated

ore

Roasting-(i) controlled current of air

(ii) Temp : 850-9000C

Roasted ore(ZnO) + nonvolatile matters

Roasting reactions

2ZnS + 3O2

= 2ZnO + 2SO2

ZnS + 2O2

= ZnSO4

2ZnSO4

= 2ZnO + 2SO2

+ O2

Carbon reductionRoasted ore + excess of coke

temp : 1400

0

C

ZnO + C = Zn + CO

ZnO + CO = Zn + CO2

Spelter Znimpurites-Pb,Cd, Fe

thermal refining

temp : 9200C

distillateZn + Cd

Fractional dist

7670C

Pure Zn(99.9%)

Electro refining

Pure Zn


10/12


EXTRACTION OF CAST IRON(FLOW CHART)

Iron ores

(i)Magnetite(Fe3O4)

(ii)Haematite(Fe2O3)

(iii)Brown Haematite (Fe2

O3

.3H2

O)

(iv)Siderite(FeCO3)

Broken into pieces,screened and washedwith water to remove silicious materials

Roastng : Coke is mixed with ores andthe mixture is heated in excess of air

S+ O2

= SO2

4As + 3O2

= 2As2O

3

FeCO3

= FeO + CO2

Fe2O

3.3H

2O = Fe

2O

3+ 3H

2O

Fe3O

4= FeO + Fe

2O

3

4FeO + O2

= 2Fe2O

3

Roasted ore contains

Fe2O

3and SiO

2

Smelting of charge in blustfurnace at high temperatureCharge is:

Fe2O

3: Coke : lime stone

8 : 4 : 1

Smelting : in the blust furnace

Fe2O3 is reduced by coke andCO and slag is formed by theaction of lime on silica

slag cast iron

At 12000C :

C+ O2

= CO2

CO2+ C = 2CO

At 6000C -9000C :

Fe2O

3+ 3CO = 2Fe + 3CO

2

At 9000C :

CaCO3

= CaO + CO2

CO2 + C = 2COAt 10000C-13000C :

2CO = C + CO2

Fe2O3 + 3C = 2Fe + 3CO

CaO + SiO2 = CaSiO3(slag)

At 15000C :

MnO2 + 2C = Mn + 2CO

Ca3(PO

4)2

+ 3SiO2=3CaSiO

3+ P

2O

5

2P2O

5+ 10C = P

4+ 10CO

SiO2

+ C = Si + 2CO

reactions

reactnBy products :slag: calcium and aluminiumsilicateBlust furnace gas :

N2

,CO,CO2

,H2

, hydrocarbon,

C2N2


11/12

METALS AND METALLURGYEXTRACTION OF STEEL FROM CAST IRON ACID BESSEMER PROCESS

Cast iron containingMn,Si,MnO,S,C

molten iron is fed into conveter and hot air (7000C)

under high pressure passed into molten iron

Mn and Si oxidised to give MnO2 andsilica which combine together toform manganous silicate

+S oxidised to SO2 ,Fe to Fe2O3 which

reduced by C to form Fe, C to CO

calculated amt of spiegeleisen(alloy of Fe,Mn and C) is added

Mn and C removes dissolvedoxygen and reduce FeO to Fe

2Mn + O2 = 2MnO2

Si + O2 = SiO2

MnO + SiO2 = MnSiO3

S+O2 = SO2

4Fe + 3O2 = 2Fe2O3

Fe2O

3+ C = Fe + 3CO

2C + O2 = 2CO

FeO + Mn = MnO + FeFeO + C = Fe + CO


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METALS AND METALLURGYEXTRACTION OF STEEL FROM CAST IRON

BASIC BESSEMER PROCESS

Cast iron containingSi,P,S etc

molten iron is fed into conveter which is linedinside with manesia (MgO) or lime(CaO)

Mn and Si oxidised to give MnO2 and

silica which combine together toform manganous silicate

+S oxidised to SO

2,C to CO, P to

P2O5

Mn and C removes dissolvedoxygen and reduce FeO to Fe

2Mn + O2

= 2MnO2

Si + O2

= SiO2

MnO + SiO2

= MnSiO3

S+O2

= SO2

2C + O2

= 2CO

4P + 5O2 = 2P2O5

4CaO + P2O

5= Ca

3(PO

4)2.CaO

FeO + Mn = MnO + FeFeO + C = Fe + CO

Molten cast iron + some CaOhot air uner pressure ispassed

thomas slag

calculated amt of spiegeleisen is addedto molten iron

Metal Extraction 1

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