Manufacture Of Iron By Blast Furnace Process.

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Manufacture Of Iron By Blast Furnace Process

Iron is a naturally occurring element in its ore form (Haematite), however for iron to be of any use the impurities must be removed. This is done by a process involving a blast furnace. Extremely high temperature in the range of 870°C are reached within the blast furnace and this heat causes reactions to occur within the blast furnace that remove some of the impurities from the iron ore. The materials placed in the blast furnace are iron ore, coke and limestone. Coke is the reducing agent [substance that causes the substance it is reacting with to be reduced and in turn is oxidised], when hot air is blasted into the furnace it reacts with the coke to form carbon monoxide, this carbon monoxide then goes on to react with the iron oxides which are present in the iron ore to reduce [removal of oxygen from a substance] the oxides to metallic iron. The limestone is simply present to react with the impurities removed from the ore forming calcium silicate. Without the limestone Iron Silicate would form therefore reducing the yield of metallic iron. The Calcium Silicate and other impurities sit on top of the molten metallic iron forming a layer known as slag. Therefore the metallic iron can be tapped off and removed for further refining.    

Below is a diagram of a blast furnace you can see at the top the reactants are fed into the blast furnace and at the bottom the molten iron is being tapped off and taken away in carriages.

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There is a lot of waste products in the layer of slag that is formed when the process of obtaining molten iron is carried out. The table below shows the usual composition of slag showing the different waste products created:

At 500°C and 850°C

Iron Oxide combines with the carbon monoxide formed when coked reacts with the hot air to create iron oxide and carbon dioxide removing some ...

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