Iron is extracted from different ores exist in the world. Hematite (Fe2O3) is reduced to iron metal in the blast furnace under several steps. Limestone and coke are used as other raw materials to generate heat and reducing agents. Iron extraction is one of the largest chemical industry in the world because iron is a very useful metal to manufacture lot of things in our daily life.
Iron is located in the middle part of the electrochemistry series. Therefore Ferric oxide and Ferrous oxide can be reduced to iron by reducing agents such as carbon monoxide or coke.
When a mineral is available for using a metal in useful way, it is defined as ore.
Following ores contain iron. But according to the amount of existing iron amount, ability of extraction is depend. If iron percentage is high, it is a good for extraction because it will give good yield. When other metals exist with those ores they make problems in iron extraction.
Iron is fairly reactive element. Because of that it does not exist as a free substance in the world (iron reacts with oxygen to form oxides).
SiO2, Al2O3 is mixed with hematite.
To produce heat and increase the temperature in burst furnace.
Fe2O3 reduction to iron is done step by step. Temperature variation along the blast furnace will help to occur these reactions. Now, we can study what are the reactions occurring inside the blast furnace at different temperatures.
Ferric oxide (Fe2O3) is reduced Fe3O4 by carbon monoxide. Fe3O4 contains FeO and Fe2O3.
Fe3O4 = FeO.Fe2O3
at 5000C - 6000C
CO is reduced to carbon and oxidized CO2.
FeO is reduced liquid Fe by CO. CO is oxidized to CO2.
Limestone decomposes to CaO and CO2.
FeO is again reduced to liquid Fe at this temperature. Also, CO2 combines with C to give CO.
Slag is produced at this temperature. It exists as a liquid. Mixture of liquid CaSiO3 and liquid Ca(AlO2)2 is the slag.
Melting pointof pure Iron is 10150C. But including impurities will reduce the melting point to 1015 0C.
CaO reacts with SiO2 and Al2O3. It produce slag which is CaSiO3 and Ca(AlO2)2. Slag exist in liquid state. Liquid slag floats on liquid iron bottom of the blast furnace. Therefore oxidization of iron is prevented by entering air.
Iron manufacturing process makes a lot of environmental pollution problems.
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