A blast furnace is a structure used to extract iron from its ore. It is a large, cylindrical furnace made of steel and lined with heat-resistant materials. Inside the furnace, iron ore, coke, and limestone are heated to high temperatures. The coke provides the heat and chemical reaction necessary for the extraction of iron from the ore. The limestone helps remove impurities from the iron ore. As a result, molten iron is produced and collected at the bottom of the furnace. This process is crucial in the production of iron and steel.