Why coke and lime stone is used in furnaces/foundries?
Iron ore is a mineral called hematite which consists mainly of Fe2O3, but also has other impurities like quartz, which is silicon dioxide, SiO2. The limestone (CaCO3) reacts with the silica (SiO2) to make calcium silicate (CaSiO3) and carbon dioxide. The calcium silicate, which floats on top of the molten iron can be skimmed off and ends up as a waste product called slag. The coke, which is essentially pure carbon, reacts with the iron (III) oxide to reduce the iron to iron metal. The carbon in the coke is oxidized to carbon dioxide.
