- Charging the Furnace: The process begins by loading raw materials into the blast furnace. These materials typically include iron ore (in the form of iron oxides such as hematite or magnetite), coke (a type of coal), and limestone. The materials are carefully layered in the furnace.
- Heating and Combustion: Once the materials are inside the furnace, a blast of hot air, enriched with oxygen, is blown into the bottom of the furnace. This air is heated to extremely high temperatures. The coke serves as the primary source of fuel and undergoes combustion, producing carbon monoxide (CO) and a tremendous amount of heat. The carbon monoxide then reacts with the iron ore, reducing the iron oxides to molten iron (Fe).
- Iron Formation: The intense heat causes the iron ore to melt, and the molten iron gradually accumulates at the bottom of the furnace due to its higher density. The impurities in the iron ore combine with the limestone to form slag, which floats on top of the molten iron.
- Tapping the Furnace: Periodically, the molten iron is tapped or drained from the bottom of the furnace through a hole. This process is carefully controlled to ensure the quality of the iron. The iron can then be further processed and cast into various shapes, such as pig iron or steel.
- Slag Removal: The slag, which is less dense than iron, remains on top and is also periodically removed from the furnace. Slag has various industrial applications, including as a construction material.
In summary, a blast furnace is a high-temperature reactor where iron ore, coke, and limestone are combined to produce molten iron. This process relies on the intense heat generated by the combustion of coke to extract the iron from its ore, with slag as a byproduct. Molten iron is then tapped from the furnace and further processed for various industrial uses.