describe the reaction that take place in blast furnace?

http://en.wikipedia.org/wiki/Blast_furnace

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In the Blast furnace, reduction of iron oxides takes place in different temperature ranges. Hot air is blown from the bottom of the furnace and coke is burnt to give temperature upto about 2200K in the lower portion itself. The burning of coke therefore supplies most of the heat required in the process. The CO and heat moves to upper part of the furnace. In upper part, the temperature is lower and the iron oxides (Fe2O3 and Fe3O4) coming from the top are reduced in steps to FeO. Thus, the reduction reactions taking place in the lower temperature range and in the higher temperature range, depend on the points of corresponding intersections in the ΔrG0 vs T plots. These reactions can be summarised as follows: At 500 – 800 K (lower temperature range in the blast furnace) :

3 Fe2O3 + CO → 2 Fe3O4 + CO2 Fe3O4 + 4 CO → 3Fe + 4 CO2 Fe2O3 + CO → 2FeO + CO2 At 900 – 1500 K (higher temperature range in the blast furnace): C + CO2 → 2 CO FeO + CO → Fe + CO2 Limestone is also decomposed to CaO which removes silicate impurity of the ore as slag. The slag is in molten state and separates out from iron. The iron obtained from Blast furnace contains about 4% carbon and many impurities in smaller amount (e.g., S, P, Si, Mn). This is known as pig iron and cast into variety of shapes. Cast iron is different from pig iron and is made by melting pig iron with scrap iron and coke using hot air blast. It has slightly lower carbon content (about 3%) and is extremely hard and brittle. Further Reductions Wrought iron or malleable iron is the purest form of commercial iron and is prepared from cast iron by oxidising impurities in a reverberatory furnace lined with haematite. This haematite oxidises carbon to carbon monoxide: Fe2O3 + 3 C → 2 Fe + 3 CO (6.33) Limestone is added as a flux and sulphur, silicon and phosphorus are oxidised and passed into the slag. The metal is removed and freed from the slag by passing through rollers.