EXTRACTION OF IRON
 
 
 
INTRODUCTION
 
  Iron is extracted from its oxide ore called HAEMATITE (Fe2O3).
 
PRINCIPLE OF EXTRACTION
 
  Extraction of iron is based on the reduction of HAEMATITE (Fe2O3) with carbon..
 
DETAILS OF EXTRACTION
 
  The process of the extraction of iron is carried out by the following steps:
  Concentration of ore
Calcination or Roasting of ore
Reduction of ore
  Concentration of ore:
In this metallurgical operation, the ore is concentrated by removing impurities like soil etc. The
process involves the crushing and washing of ore.
  Calcination or Roasting of ore:
The concentrated ore is now heated in the presence of air. The process of roasting is performed to remove moisture, CO2, impurities of sulphur, arsenic. Ferrous oxide is also oxidized to ferric oxide.
 
Reduction of ore
 
  The process of reduction is carried out in a blast furnace.
Blast Furnace
 
The blast furnace is a cylindrical tower like structure about 25m to 35m high. It has an outer shell of steel. Inside of furnace is lined with fire bricks. The top of the furnace is closed by a cup-cone feeder.
 
The charge
 
 

The charge consists of :
roasted ore
Coke
Limestone

 
Details of reduction
 
  The charge is fed into the furnace from its top. A preheated blast of air at 1500OC, is blown into the furnace under pressure near to the bottom. The blast oxidizes carbon to CO2.
 
C + O2 CO2 + heat
Formation of CO2 is an exothermic reaction in which a huge amount of heat is liberated which rises the temperature to 1900OC in this region. As the CO2 passes upwards, it reacts more coke to form carbon monoxide.
CO2 + C 2CO + heat
Formation of CO is an endothermic reaction and the temperature in this region falls to 1100OC. CO
is the main reducing agent in the upper portion of blast furnace.
Reactions in blast furnace  
 
Fe2O3 + 3C 2Fe + 3CO
Fe3O4 + 4CO 3Fe + 4CO2

CO2 + C 2CO     
Overall reaction
 
Fe2O3 + 3CO 2Fe + 3CO2
The liquid iron runs downward to the bottom of the furnace and is withdrawn through tap hole.
Slag formation
 
Lime stone on heating decomposes to CaO and CO2.
CaCO3 CaO + CO2
CaO now reacts the impurities of ore called GANGUE to form slag. Slag is the mixture of CaSiO3
and Ca(AlO2)2. The slag floats over the top of molten iron. Slag is a useful byproduct. It is used
in road making, cement manufacturing a light weight building materials.
Flux + Gangue Slag           
CaO + SiO2 CaSiO3
    CaO + Al2O3 Ca(AlO2)2
 
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