Reactions taking place in the blast furnace.

Iron ore and coke are fed into the blast furnace. Limestone (CaCO3) is also added to impurities like silicon dioxide. Blasts of hot air are sent in at the bottom of the furnace.
First, coke burns in the presence of air to form carbon dioxide. (The heat produced helps to maintain the temperature of the furnace.)
Carbon dioxide rises up to the furnace and reacts with more coke to form carbon monoxide. Note: Carbon Monoxide is the reducing agent which reduces hematite to iron.
Hematite is reduced by carbon monoxide to form molten iron and carbon dioxide. The molten iron then sinks to the bottom of the furnace and tapped off at intervals.
Iron produced is impure and contains mainly sand (silicon dioxide) which is removed by the addition of limestone to the furnace. Limestone decomposes by heat to form calcium oxide and carbon dioxide.
Calcium oxide combines with the sand to form calcium silicate (slag).
Molten iron and molten slag sink to the bottom of the furnace with the slag floating on top. Slag and iron rapped off separately and allowed to solidify.

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Notiz am Extraction and Uses of Metals, erstellt von Davyd Tan am 18/04/2014.