the blast furnace

A blast furnace is a large, controlled vertical structure used to produce iron from iron ore. Iron ore, coke (a form of carbon), and limestone are added at the top. Hot air is blown into the bottom, causing the coke to burn fiercely, generating intense heat. This process separates the iron from impurities, forming molten iron called "pig iron" that collects at the bottom. The impurities combine with limestone to form slag, which floats on top and can be removed. The molten iron is then tapped out to be refined into steel or other products.