Blast Furnace Reactions
The blast furnace process involves a number of reactions.

Carbon (coke) is burnt to carbon dioxide, producing heat. The carbon dioxide then undergoes a shift reaction with carbon to give two moles of carbon monoxide, the main reducing agent: CO reacts with iron oxide to give iron (which falls to the bottom) and CO2. (Some iron oxide is also directly reduced by carbon.)

Calcium carbonate loses CO2 to give CaO, which reacts with silica to give slag, calcium silicate.