In 1705 Abraham Darby showed that iron ore could be reduced using coke in a blast furnace. The temperature in the furnace rises to 2000 °C. Write an equation for the exothermic reaction that causes this high temperature.
The iron ore is reduced inside the blast furnace through a series of reactions:
1) 3 Fe2O3 + CO = CO2 + 2 Fe3O4 -Begins at 850° F
2) Fe3O4 + CO = CO2 + 3 FeO -Begins at 1100° F
3) FeO + CO = CO2 + Fe
FeO + C = CO + Fe - Begins at 1300° F
The heat required for creating and maintaining such high temperature is supplied by exothermic combustion of coke (carbon): C + O2 = CO2 + 394 KJ/Mole of Heat energy
Since the reaction takes place in the presence of excess carbon at a high temperature the carbon dioxide is reduced to carbon monoxide in an endothermic reaction as well:
CO2+ C = 2CO – Heat.
In essence, exothermicity of the combustion reaction far outweighs endothermicity of the latter reaction and a constant temperature, high enough to keep iron in molten state, is maintained inside the furnace.