#ExtractionOfIron

#Chemistry

#MetalsAndAlloys

Introduction

• Iron is extracted in a large container called a blast furnace from its ore, hematite 

• Modern blast furnaces produce approximately 10,000 tonnes of iron per day 

The blast furnace

• The raw materials: iron ore (hematite), coke (an impure form of carbon), and limestone are added into the top of the blast furnace

• Hot air is blown into the bottom

Zone 1

• Coke burns in the hot air forming carbon dioxide 

• The reaction is exothermic so it gives off heat, heating the furnace

carbon + oxygen → carbon dioxide

Zone 2

• At the high temperatures in the furnace, more coke reacts with carbon dioxide forming carbon monoxide

• Carbon dioxide has been reduced to carbon monoxide

carbon + carbon dioxide → carbon monoxide

Zone 3

• Carbon monoxide reduces the iron(III) oxide in the iron ore to form iron 

• This will melt and collect at the bottom of the furnace, where it is tapped off

iron(III) oxide + carbon monoxide  →  iron + carbon dioxide

• Limestone (calcium carbonate) is added to the furnace to remove impurities in the ore

  • The calcium carbonate in the limestone thermally decomposes to form calcium oxide

calcium carbonate → calcium oxide + carbon dioxide

• The calcium oxide formed reacts with the silicon dioxide, which is an impurity in the iron ore, to form calcium silicate

• This melts and collects as a molten slag floating on top of the molten iron, which is tapped off separately

calcium oxide + silicon dioxide →  calcium silicate

Zone 1

• The burning of carbon (coke) to provide heat and produce carbon dioxide:

C (s)  +  O2 (g)  →  CO2 (g)

Zone 2

• The reduction of carbon dioxide to carbon monoxide:

CO2 (g)  +  C (s)  →  2CO (g)

Zone 3

• The reduction of iron(III) oxide by carbon monoxide:

Fe2O3 (s)  +  3CO (g)  →  2Fe (I)  +  3CO2 (g)

• The thermal decomposition of calcium carbonate (limestone) to produce calcium oxide:

CaCO3 (s)  →  CaO (s)  +  CO2 (g)

• The formation of slag:

CaO (s)  +  SiO2 (s)  →  CaSiO3 (l)