METALLURGY OF IRON
- Symbol : Fe
- Colour : Greyish white
- Atomic mass : 55.9
- Atomic number: 26
- Valency : 2 & 3
- Electronic
- configuration : 2,
8, 14, 2
Occurrence:
Iron is the second most abundant metal after aluminium. It
occurs in nature
as oxides, sulphides and carbonates.
Ores of iron Formula
- Haematite Fe2O3
- Magnetite Fe3O4
- Iron pyrites FeS2
Extraction
of Iron from haematite ore (Fe2O3)
Concentration by gravity
separation
The powdered ore is
washed with stream of water. As a result, the lighter
sand particles and other impurities are washed away and heavier
ore particles
settle down.
Roasting and calcination
The concentrated ore
is strongly heated in a limited supply of air in a reverberatory furnace. As a
result, moisture is driven out and sulphur, arsenic, phosphorus impurities are
oxidised off.
Smelting (in Blast furnace)
The charge consisting of roasted ore, coke and limestone in the ratio
8 : 4 : 1 is smelted
in a blast furnace by introducing
it through the cup and
cone arrangement at the top. There are three important regions in the
furnance.
The lower
region(combustion zone)- temperature is at 1500° C. In this
region, coke burns with oxygen to form
CO2 when the charge comes in contact
with the hot blast of air.
C + O2→ CO2 + heat
It is an exothermic
reaction since heat is liberated.
The middle
region (fusion zone)-The temperature prevails at 10000C.In this
region CO2 is reduced to CO.
CO2 + C → 2CO
Limestone decomposes to calcium oxide and CO2.
▲
CaCO3→ CaO + CO2
These two reactions are endothermic due to the absorption of heat.
Calcium oxide combines with silica to form calcium silicate
slag.
CaO + SiO2 → CaSiO3
The upper
region (reduction zone)- temperature prevails at 4000C. In
this region carbon monoxide reduces
ferric oxide to form a fairly pure spongy
iron.
400°C
Fe2O3 + 3CO → 3Fe + 3CO2
The molten iron is collected at the bottom of
the furnace after removing the slag.
Physical
properties
• It is a heavy metal of specific gravity 7.9
• It is a lustrous metal and greyish white in colour.
• It has high tensility, malleability and ductility.
• It is a good conductor of heat andelectricity.
Chemical properties
Reaction with air or oxygen:
Only on heating in air, iron forms magnetic oxide.
3Fe + 2O2 → Fe3O4 (black)
Reaction with moist air:
When iron is exposed to moist air, it forms a layer of brown hydrated ferric oxide on its surface. This compound is known as rust and the phenomenon of forming this rust is known
as rusting.
4Fe + 3O2 + 3H2O → 2Fe2O3.3H2O(Rust)
Reaction with steam:
When steam is passed over red hot iron,magnetic oxide
of iron is formed.
3Fe + 4H2O(steam) → Fe3O4 + 4H2↑
Reaction with chlorine:
Iron combines with chlorine to form ferric chloride.
2Fe + 3Cl2 → 2FeCl3(ferric chloride)
Reaction with acids:
- With dilute HCl and dilute H2SO4 it evolves H2 gas.
Fe + 2HCl → FeCl2 + H2↑
Fe + H2SO4 → FeSO4 + H2↑
- With conc. H2SO4 it forms ferric sulphate
2Fe + 6H2SO4 → Fe2(SO4)3 + 3SO2 + 6H2O
- With dilute HNO3 in cold condition it gives ferrous nitrate
4Fe + 10HNO3 → 4Fe(NO3)2 + NH4NO3 + 3H2O
When iron is dipped in conc. HNO3 it becomes chemically inert or passive due to the formation of a layer of iron oxide (Fe3O4) on its surface.
Uses of iron
- Pig iron is used in making stoves, radiators, railings, man hole covers and drain pipes.
- Steel is used in the construction of buildings, machinery, transmission and T.V towers and in making alloys.
- Wrought iron is used in making springs, anchors and electromagnets
An electric motor is an mechanical device that converts electrical energy into mechanical energy.
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Conversion of Bauxite into Alumina by Baeyer’s Process
