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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
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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
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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
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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
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METALS AND METALLURGY
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
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METALS AND METALLURGY
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
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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
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