View
220
Download
3
Category
Tags:
Preview:
Citation preview
Chemistry
Metallurgy – SESSION II
Session Opener
What is sterling silver?
Solid solution of Cu in Ag
Session Objectives
Session objectives
Methods of purification of metals
Metallurgy of Fe, Cu, Ag, Zn, Al
Refining of crude metal
1. Liquation process
Do you know?
Infusible impurity left over during liquationis called as:
Dross
Refining of crude metal
• Based on difference in the boiling point of the impurities and the metal.
• Volatile metals form the vapour first and separated by condensing in a receiver.
2. Distillation:
Refining of crude metal
compressed crude metal
Metal under reduced pressurein electric furnace
Volatile impuritiesMolten metal (chilled to obtain puremetal)
3. Vacuum sublimation method
Refining of crude metal
Oxides are removed from impure metal
Re verbaratory furnace2 2 2 3Cu O Cu SO As O
Melted the metal
4. Furnace refining or poling
Reverbaratory furnace
Refining of crude metal
(5) Zone refining
Direction of trave l
a
ofheater, m olten zone
nd im purities
I m pure germ anium rod
Molten zone(containing im purities)
Recrystallized pure germ anium
Circular heater
Refining of crude metal
250ºC4
Ti taniumtetraiodide
Ti 2l2 Til
1400ºC4 2
Tungstenfilament
Til Ti 2 l
6. Van Arkel method (or Vapour phase refining)
Refining of crude metal
4Impure PureNickelnickel Nickletetracarbonyl
Ni 4CO Ni(CO) Ni 4CO
7. Thermal decomposition method (Carbonyl method, Mond Process)
Refining of crude metal
• Used for purification of silver containing impurity of lead.
• Based on selective oxidation of lead over silver.
• The impure silver is smelted in cupel (dish made of bone ash) in blast of air in reverberatory furnace.
• Lead is oxidised to lead oxide (PbO) and blown away by blast of air.
• The remaining part melts and is absorbed by the bone ash cupel. At the end cupel is covered by silver.
8. Cupellation
Refining of crude metal
9. Electrolytic refining
Electrolytic refining
10. Chromatographic method:
• Based on the difference in the adsorbability of the metal and
the impurities.
• Adsorbent–alumina (Al2O3).
• Eleuent
• Specifically useful for the separation of the elementsavailable in very small amounts.
Ellingham diagram
Metallurgy of Iron
(i) Ore – Haematite (Fe2O3)
(ii) Concentration of ore – by magnetic separation
(iii) Roasting – Moisture, sands are removed as oxide.
(iv)Smelting – Done in blast furnace. Roasted ore, limestone and coke are added in blast furnace for smelting.
Metallurgy of Iron
2 2
2
C O CO 415 kJ
CO C 2CO 162.3 kJ
3 2
2 3Flux Impurity Slag
CaCO CaO CO
CaO SiO CaSiO
Fe O + C + C aC O2 3 3
W asteG ases
S tee l sh e ll
H ot air b lastthrou gh thyeres
Zone of redu ction
C en tra l Zon e
Zone of fus ion
Zone of com bu stion
575 - 975 K
1175 - 1475 K
1475 - 1575 K
1775 - 1800 K
S lagM o lten iron
2 3 2
3 4 2
2
Fe O +CO 2FeO+CO
Fe O +CO 3FeO+CO
FeO+CO Fe+CO
Heat treatment of steel
1. Quenching or hardening
• Process of heating steelto red hot followed by sudden cooling by plunging to oil or water.
• Makes steel hard and brittle due to formation of iron carbide (Fe3C).
2. Annealing
• Process of heating steel to red hot then cooling slowly.
• Annealing makes steel soft and ductile.
Heat treatment of steel
3. Tempering
• Process of heating steel the quenched steel to temperature much below redness followed by slow cooling.
• Tempering retains the hardness but brittleness disappears.
4. Nitriding
• Process of producing hard coating or iron nitride on surface of steel.
Metallurgy of copper
1. Ore – Copper pyrite CuFeS2
2. Concentration — Froth floatation process.
3. Roasting —
2 2 2 2
2 2 2 2
2 2
2CuFeS O Cu S 2FeS SO
2Cu S 3O 2Cu O 2SO (Partly)
2FeS 3O 2FeO 2SO (Partly)
Metallurgy of copper
2 3Slag
FeO SiO FeSiO
Since iron has more affinity for oxygen, therefore FeO is formed first.
2 2Cu O FeS Cu S FeO
Slag is removed from upper layer. Molten mass containing Cu2S and Fe is called copper malte.
Smelting
Metallurgy of copper
Molten matter is mixed with sand (SiO2) and heated in Basemer converter.
2 2
2 3Slag
2FeS 3O 2FeO 2SO
FeO SiO FeSiO
2 2 2 2
2 2 2
2Cu S 3O 2Cu O 2SO
2Cu O Cu S 6Cu SO
Blister copper.
Basemerisation
Refining of copper
By poling of electrolytic refining.
What is matte?
(a) CuO + FeS
(b) CuS + FeO
(c) Cu2S + FeS
(d) None of the above
Metallurgy of Silver
1. Ore — Argentite AgS
2. Concentration — By froth flotation process.
3. Extraction — By Mac Arthur Forrest Process.
2 2 2Sodiumargentocyanide(water so lub le)
2 2 4
Ag S 4NaCN 2Na Ag(CN) Na S
2Na Ag(CN) Zn Na Zn(CN) 2Ag
4. Refining — By electrolytic method.
Illustrative example
Name the metals which areconsumed in elemental form?
Metals consumed in elemental form are Ag and Au.
Metallurgy of Zinc
1. Ore – Zinc blende (ZnS)
2. Concentration of ore — By froth flotation process.
3. Roasting—
2 22ZnS 3O 2ZnO 2SO
4. Conversion of ZnO to Zn
distillationZnO C Zn CO
Vapours of Zn of are collected after distillation.
Illustrative example
Spelter is
(a) 98% Zinc
(b) Pure Zinc
(c) 98% Al
(d) Impure Fe
Metallurgy of Aluminium
1. Ore — Bauxite Al2O3
2. Concentration of bauxite —The method of concentration of bauxite depends on nature of impurity present in it.
Baeyer’s process
Used when impurity is of ferrous oxide.
Baeyer’s process
2 3 2 2Al O 2NaOH 2NaAlO H O
2 2 3(White ppt)
NaAlO 2H O Al(OH) NaOH
3 2 3 2(Pure)
2Al(OH) Al O 3H O
Serpeck’s process
— Used when silica is the chief impurity in bauxite.
Al(OH)3
ImpureBauxite
+ C + N2
DAlN + Silicone (volatile)Aluminiumnitride
+ H2OD
(ppt)
D
Pure Al2O3
Serpeck’s process
2 3 2Aluminiumnitride
Al O 3C N 2AlN 3CO
3 2 3 2(Pure)
2Al(OH) Al O 3H O
2 3 3(Pr ecipitate)
AlN 3H O Al(OH) NH
Hall’s Process
Used when no specific type of impurity is present.
Al(OH)3
Na2CO3
NaOH
ImpureBauxite D
H2O and filtered
D
D
Pure Al2O3
Insoluble impurities (Fe2O3 and others)
Soluble sodium meta-aluminate
Precipitate Solution
Filtered
Hopp’s process
– +
Pure alum inium (cathode)
Cryolyte + BaF (electrolyte)2
Impure Al (Anode)
Impure a lum inium
Iron tank havinglining of graphite
Hopp's process
Electrolysis of pure alumina (Al2O3)
3 6 33
3
Na AlF 3NaF AlF
AlF Al 3F
3
2 3 3 2
At cathode 2Al 6e 2Al
3At anode Al O 6F 2AlF O 6e
2
Question
Thank you
Recommended