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.

[IMAGE]

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:

Name of Compound

Symbol of compound

Percentage Composition

Calcium oxide

CaO

38%

Silicon dioxide

SiO2

36%

Alumina

Al2O 3

12%

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