5.4 describe and explain the main reactions involved in the extraction of iron from iron ore (hematite), using one, limestone and air in a blast furnace

In order to extract iron from hematite (iron ore) you need a blast furnace, coke (for reducing the iron oxide to iron metal) and limestone (for taking away impurities). The process is as follows...



- Hot air is blasted into the furnace (hence name, blast furnace), this makes the coke burn much faster than normal, and also raises the temperature to around 1500ºC. The coke burns to produce carbon dioxide (C + O2 ---> CO2)
- The CO2 then reacts with unburnt/leftover coke, producing carbon monoxide (CO2 + C ---> 2CO)
- The carbon monoxide will then react with the iron ore, producing iron. (3CO + Fe2O3 ---> 3CO2+ 2Fe)
- The limestone removes the silicon dioxide (SiO2) that is the main impurity. This happens as the limestone is decomposed by the heat into calcium oxide and carbon dioxide (CaCO3 ---> CaO + CO2). The calcium oxide then reacts with the silicon dioxide forming calcium silicate, aka slag (CaO + SiO2---> CaSiO3).
- The iron and slag are both molten so sink to the bottom of the furnace. However, slag is less dense than iron so the slag sits into of the iron, they are both tapped off.

NOTE: although the slag is useless in this, the process is still sustainable as the slag is not wasted. It can be used in fertilisers and road building (bit random, i know)

NOTE NOTE: It is very important to understand that this is a reduction reaction (the iron is reduced as it loses oxygen)

image credit: BBC

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