Extraction of iron in the blast furnace Tamil revision mind map built as a vertical furnace cross-section with zone-matched side notes: the charge of iron ore coke and limestone loaded from the top with countercurrent hot air blast from the bottom, the roughly 500 kelvin zone where carbon dioxide is reduced by hot coke to carbon monoxide, the roughly 1100 kelvin zone where carbon monoxide progressively reduces iron oxide through magnetite and iron two oxide to molten iron in three sequential steps, the roughly 1500 kelvin zone where limestone decomposes and calcium oxide reacts with silica impurities to form slag that floats on the denser molten iron, and the roughly 2000 kelvin combustion zone at the base where coke burns in the hot air blast, with molten iron and slag tapped separately from the bottom.