Answer Usually, limestone (calcium carbonate, CaCO3) is calcined in a lime kiln, where it is heated to form lime (CaO) and CO2 gas. The lime is then used in both steelmaking furnaces to refine liquid iron into steel, and also on ladles as slag to The main role of limestone in extraction of iron is to decomposes in hot furnace and form the calcium oxide. Iron is extracted from its ore, haematite, in a blast furnace. The ore is fed into the top of the furnace along with coke and limestone. ... The limestone decomposes in the hot furnace, forming calcium oxide. Aug 13, 2020 In the extraction of iron, a basic flux limestone is used. Limestone decomposes to form CaO which reacts with silica gangue present in the iron ore is acidic in nature to form calcium silicate (slag).