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Explain smelting process. |
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Answer» Solution :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. (a) The Lower Region (Combustion ZONE): The temperature is at `1500^(@)C`. In this region, coke burns with oxygen to form `CO_(2)`when the charge comes in contact with a hot blast of air. `C + O_(2) underset(Delta)overset(1500^(@)C)to CO_(2)` + Heat It is an exothermic REACTION since heat is liberated. (b) The Middle Region (Fusion Zone) The temperatureprevails at `100^(@)C`. In this region, `CO_(2)` `CO_(2) + C underset(Delta)(overset(1000^(@)C)to 2CO -` Heat Limesteon decomposes to calcium oxide and `CO_(2)` `CaCO_(3) underset(Delta)to CaO + CO_(2)` - Heat These two reactions are enodthermic due to absorption of heat. Calcium oxide combines CaO + `SiO_(2) to CaSiO_(3)` (c ) 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. `Fe_(2)O_(3) + 3CO overset(400^(@)C)/(to 2Fe + 3CO_(2)` The molten iron is collected at the bottom of hte furnance after removing the slag. The iron thus formed is called pig iron. It is remelted and cast into different moulds. This iron is called cast iron. 
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