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| Metallurgy of Iron |
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| Iron is quite reactive, so it is not found in free state in nature. In the combined state, iron is found in the form of oxide, carbonate and sulphide. Iron occurs in the form of its sulphide in iron pyrites. It is not used commercially for the extraction because of its high sulphur content. |
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| In India iron ores are found mainly in Bihar, West Bengal and Karnataka. The main iron and steel plants for the extraction of iron are located in Bhilai, Durgapur, Rourkela, Jamshedpur,Asansol and Bhadravathi. |
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| Most of the metal is produced from the iron (III) oxide ore called hematite Fe2O3. The ore contains silicon di oxide as impurity. Hence to obtain the metal from the ore, |
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 a reducing agent that can reduce hematite to metal is needed. The reducing agent used in blast furnace is carbon monoxide which is obtained by burning coke. |
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A suitable flux to remove sand is also required. Sand is removed by using calcium oxide obtained by heating lime stone. |
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| Dressing and Concentration of Ore |
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| The iron ore is split into 2cm pieces and washed in water to remove sand, clay etc. |
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| Calcination |
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| The washed ore is strongly heated in the absence of air to expel water sticking to it. The calcinations converts the carbonate ore into oxide. |
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| Reduction |
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| The washed and dried hematite is mixed with measured quantities of coke and lime stone and fed into the blast furnace. |
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| Blast furnace is a cylindrical furnace made by refractory bricks surrounded by a steel shell. |
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| Blast Furnace |
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| Height of the furnace: 60-100ft |
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| Base of the furnace: 30-35 ft |
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| Double cup and cone arrangement |
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It allows the entry of charge into furnace but does not allow any gas to escape through it |
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The gases escape through the outlets at the top of the furnace and are later burnt |
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| Tuyeres |
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Circular pipes at the base of the furnace for the entry of hot compressed air |
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The air is blown from the sides and the molten iron below into the hearth, is not oxidised by air. |
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| Outlets |
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Outlet for slag |
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Outlet for molten iron |
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Roasted haemetite - 8 parts |
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Coke - 4 parts |
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| Charge Added to the Blast Furnace |
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Calcium carbonate - 1 part |
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| Combustion Zone |
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| Reaction : Combustion of coke |
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| Temperature of the region: 20000C |
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| Fusion Zone |
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| Reaction: Reduction of carbon dioxide to carbon monoxide |
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| Temperature of the region: 1300º C |
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| Decomposition of Limestone |
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| The lime stone (CaCO3) decomposes to give carbon dioxide and quicklime (CaO) |
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| The above reaction is endothermic and the temperature in the region falls to about 800-1000ºC. |
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| Formation of Slag |
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| The quicklime reacts with acidic impurities such as silica (SiO2) and forms a slag which melts and collects above the iron at the bottom of the furnace. Slag is an easily fusible mass having a low melting point. |
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| Reduction Zone |
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| Reduction of haemetite to molten iron takes place here. |
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| Temperature of the region: 500-700º C |
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| In the upper region of the furnace, the CO reduces the haemetite to molten iron and oxidizes it self to CO2. |
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The molten iron produced is collected, poured into moulds and solidified to give pig iron. |
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Pig iron contains carbon, sulphur, phosphorus, silicon and manganese as impurities |
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