1. Mining:
- Iron ore is extracted from mines through open-pit mining or underground mining techniques.
2. Beneficiation:
- To improve the quality of the ore, beneficiation processes may be applied to remove impurities like silica and waste materials. This can involve crushing, screening, and various separation techniques.
3. Sintering or Pelletizing:
- Iron ore fines or concentrates are agglomerated to improve their physical properties for efficient smelting.
- Sintering involves heating the ore particles with additives like limestone and coke in a sintering machine, forming porous, strong agglomerates called sinter.
- Alternatively, pelletizing involves transforming ore fines into small, spherical pellets by rolling them in a rotating drum.
4. Blast Furnace:
- The primary smelting process occurs in a blast furnace, which is a tall, cylindrical structure.
- Coke (produced from coal), as the primary fuel, and hot air are continuously blown into the furnace from the bottom.
- As the charge descends in the furnace, the coke reacts with the oxygen in the hot air to produce carbon monoxide gas (CO).
- The CO gas then rises through the layers of ore and reacts with iron oxides, reducing them to form molten iron and releasing carbon dioxide (CO2).
5. Slag Formation:
- Impurities in the ore react with fluxes such as limestone (calcium carbonate) and dolomite, forming slag.
- Slag floats on the surface of the molten iron due to its lower density and is then tapped off and discarded.
6. Iron Tapping:
- Molten iron accumulates at the bottom of the blast furnace. When a sufficient amount has collected, it is tapped (drained) periodically into a container called a "torpedo ladle" or a refractory-lined rail car.
The resultant product of the smelting process is molten iron, also known as pig iron. In this form, iron contains high levels of impurities (mainly carbon) and needs further refining to produce steel or other useful iron-based materials.
