How can iron be extracted from haematite ore?
How can iron be extracted from haematite ore?
Extraction of Iron from Haematite Ore (Fe2O3)
1. Concentration by Gravity Separation
The powdered ore is washed with a stream of water. As a result, the lighter sand particles and other impurities are washed away and the heavier ore particles settle down.
2. 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 and phosphorus impurities are oxidized off.
3. Smelting (in a 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 furnace.
i). The Lower Region (Combustion Zone)-The temperature is maintained at 1500∘C. In this region, coke burns with oxygen to form CO2 when the charge comes in contact with a hot blast of air.
C+O2→CO2+heat
It is an exothermic reaction since heat is liberated.
ii). The Middle Region (Fusion Zone)-The temperature prevails at 1000∘C. In this region, CO2 is reduced to CO.
CO2+C→2CO−heat
Limestone present decomposes to calcium oxide and CO2.
CaCO3→CaO+CO2−heat
These two reactions are endothermic due to the absorption of heat. Calcium oxide combines with silica to form calcium silicate slag.
iii). The Upper Region (Reduction Zone)- The temperature prevails at 400∘C. In this region, carbon monoxide reduces ferric oxide to form a fairly pure spongy iron.
Fe2O3+3CO→2Fe+3CO2
The molten iron is collected at the bottom of the furnace after removing the slag. The iron thus formed is called pig iron. It is melted again and cast into different moulds. This iron is called cast iron.
Extraction of Iron from Haematite Ore (Fe2O3)
1. Concentration by Gravity Separation
The powdered ore is washed with a stream of water. As a result, the lighter sand particles and other impurities are washed away and the heavier ore particles settle down.
2. 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 and phosphorus impurities are oxidized off.
3. Smelting (in a 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 furnace.
i). The Lower Region (Combustion Zone)-The temperature is maintained at 1500∘C. In this region, coke burns with oxygen to form CO2 when the charge comes in contact with a hot blast of air.
C+O2→CO2+heat
It is an exothermic reaction since heat is liberated.
ii). The Middle Region (Fusion Zone)-The temperature prevails at 1000∘C. In this region, CO2 is reduced to CO.
CO2+C→2CO−heat
Limestone present decomposes to calcium oxide and CO2.
CaCO3→CaO+CO2−heat
These two reactions are endothermic due to the absorption of heat. Calcium oxide combines with silica to form calcium silicate slag.
iii). The Upper Region (Reduction Zone)- The temperature prevails at 400∘C. In this region, carbon monoxide reduces ferric oxide to form a fairly pure spongy iron.
Fe2O3+3CO→2Fe+3CO2
The molten iron is collected at the bottom of the furnace after removing the slag. The iron thus formed is called pig iron. It is melted again and cast into different moulds. This iron is called cast iron.
