PRODUCTION OF ALUMINUM
Bauxite (about 4 kg)
4 kg)
ƒ Gibbsite (Al2O2. H2O)
ƒ Diaspore (Al2O3. H2O)
Bayer Process
(ore‐dressing & calcination)
Alumina: 99.4% Al
(about 2 kg)
Hall‐Heroult Process
(reduction by electrolysis)
Electrolytic Al: 99.6% Al
(about 1 kg)
H
P
Hoopes
Process
(three‐layer electrolytic cell)
Pure Al: 99.99% Al
Al: 99 99% Al
BAYER PROCESS
HALL-HEROULT PROCESS
1. MIXING
ƒCrushing & grinding bauxite ore.
ƒMixing with caustic soda, lime,
sodium hydroxite,
hydroxite and hot water.
water
2. DIGESTION
ƒUnder high pressure & heat,
caustic soda dissolves alumina in
bauxite to form sodium aluminate.
aluminate
3. CLARIFICATION
ƒSodium aluminate remains liquid.
ƒIron oxides and other solid impurities
are pumpedd to
t disposal
di
l as red
d mud.
d
HOOPES PROCESS
4. PRECIPITATION
ƒSodium aluminate is seeded with aluminum
hydroxite, and converted to aluminum hydrate.
ƒAs cooling continues, aluminum hydrate settles
to bottom while sodium hydroxite rises to top.
5. CALCINATION
ƒAluminum hydrate is calcinated
(roasted) at 1100 °C to remove water,
and pure alumina (99.4%) is obtained.
Facts and Properties:
› Very ductile & malleable
› White or grey-white metal
› Better strength-to-weight ratio than steel
› Melting point of 660 °C
› Good thermal & electrical conductivity
PRODUCTION OF COPPER
air-oxygen
GRINDING
Refining
f
( l ) in Reverbatory
(Poling)
b
Furnace
Tough‐pitch Cu: 99% Cu
slag
anodes
slag
Matte Cu
ELECTROLYSIS
air
CONVERTING
FFLOTATION
Concentrated
Copper
+
–
slag
Bli t Cu
Blister
C (98%)
tailings
slime
cathodes
Electrolytic Cu
(99.95%)
air
Further refining by melting
under protective atmosphere
to remove residual oxygen
(0.03‐0.06%)
(0.03
0.06%)
Electrolysis to deposit Cu on cathodes
Electrolytic Cu: 99.95% Cu
air
Si flux
reagents
Blister Cu: 98% Cu
off-gas
off
gas
Matte Cu
(40-45%)
(40
45%)
Smelting in Reverbatory Furnace
Converting
Co
e t g in Bessemer
esse e Co
Converter
e te
heat
REFINING
water
Concentrated Cu
Matte Cu: 40‐45% Cu
silica flux
SMELTINNG
Ore‐Dressingg
ƒ Crushing in jaw crushers
ƒ Grinding in ball mills
ƒ Concentrating by froth floatation
Sulphide
O
Ores
CRUSHING
Sulphide Ores
ƒ Chalcocite
h l i (Cu
( 2S): 79.8% Cu
)
ƒ Chalcopyrite (CuFeS2): 34.5% Cu
Oxygen‐Free High‐Conductivity
(OFHC) Copper
Facts and Properties:
› Soft, heavy, reddish metal
› Melting point of 1083 °C
C
› High ductility
› Excellent thermal & electrical conductivity
PRODUCTION OF LEAD
Galena (PbS): 1‐10% Pb
(PbS): 1 10% Pb
Concentrating by floatation
Roasting with O2 (at 600‐700 °C)
2PbS + 3O2 Π2PbO + 2SO2
Smelting with coke (in blast furnace at 900 °C)
2PbO + C Π2Pb + CO2
Crude Pb: 60‐80% Pb
Refining by heating (in air
(in air at 400 °C)
at 400 °C)
Removing impurities
ƒ Cu (by adding sulphur)
ƒ Sb & As (by selective oxidation)
ƒ Zn (by distillation)
ƒ Ag (by electrolysis)
Facts and Properties:
› Heavy, greyish metal
› Melting point of 327 °C
C
› High malleability, low strength
Pure Pb: 99.9% Pb
› Good corrosion resistance
PRODUCTION OF MAGNESIUM
Seawater: 1300 ppm Mg
Seawater: 1300 ppm
Mixing with milk of lime
Magnesium Hydrate
Adding hydrogen chloride (HCl)
Magnesium Chloride (MgCl)
Electrolysis with carbon anodes & steel cathodes
using 60,000 A in an electrolyte (Ca + NaCl)
Pure Mg (deposited on cathodes)
Facts and Properties:
› Light,
Light soft,
soft silver
silver-white
white metal
› Melting point of 650 °C
› Chemically active metal
PRODUCTION OF NICKEL
PRODUCTION OF TIN
Penthandite [NiS.(FeS)2]
Cassiterite (SnO2): tin stone (1‐5% Sn)
Concentrating by floatation
Washing to remove impurities
Heavy tin oxide
Smelting in furnace
Matte Ni
(having Cu & iron sulphides)
Smelting in reverbatory furnace
(with powdered coal & lime at 1200 & lime at 1200 °C)
C)
Matte Sn
Refining by Mond Process:
ƒ Crushed & heated to drive off sulphur
ƒ Converted to NiO
ƒ Treated with sulphuric acid to remove Cu
ƒ Reduced with water gas (H + CO) at 300 °C
(
)
Refining in two stages:
ƒ Liquation (at low temp.) to remove Cu, Fe, As
ƒ Oxidation in open crucible (kettle) to remove Zn
Pure Sn: 99% Sn
Pure Ni: 99.8% Ni
Facts and Properties:
› Whitish metal
Further refining by electrolysis
Pure Sn: 99.9% Sn
› Melting point of 1452 °C
C
Facts and Properties:
› Low strength
› White coloured metal
› High malleability, low strength
› Resistance to corrosion & oxidation
› Melting point of 232 °C
› Good corrosion resistance
PRODUCTION OF ZINC
Sphalerite (ZnS): zincblende, ruby
(ZnS): zincblende ruby jack
Floatation to remove Pb, Cu, iron sulphides
Concentrated Zinc
Roasting Roasting with O2
Zinc Oxide
Purifying in two ways
Di till ti in
Distillation
i Zinc
Zi Retort:
R t t
ƒ Zinc oxide (with coke) is pressed into walls of briquettes, and
retorts are placed in furnace at 1200‐1400 °C.
ƒ Due to the reaction occurring in furnace at atmospheric
pressure, Pure Zn is produced in vapour form and then
condensed at 500 °C.
Roasting & Electrolysis
ƒ Zinc concentrate is roasted & leached (i.e. soluble particles are
removed) with a weak solution of sulphuric acid.
ƒ Oth
Other metals
t l are filtered
filt d outt and
d the
th solution
l ti (zinc
( i sulphate)
l h t ) is
i
pumped into electrolytic tanks.
ƒ Cathodes (pure Al) and anodes (Pb‐Ag alloy) are lowered into
tanks, electric current is passed through solution, and Pure Zn is
deposited.
ZnO + C ΠZn + CO
Facts and Properties:
p
› Bluish-white metal
› Melting point of 419 °C
› Low strength,
strength low ductility
› Easily formable & machinable
› Readily attacked by alkalis and acids