Iron ore pellets are produced by combining fine iron ore concentrate with a binder and water, forming green pellets that are then dried and hardened through a heating process.
Here's a breakdown of the process:
1. Mixing and Pelletizing:
- Iron Ore Concentrate: The process begins with fine iron ore concentrate, which is the raw material extracted from iron ore deposits.
- Binder Addition: A binder, such as bentonite clay or organic binders, is added to the concentrate. This helps the fine particles adhere together.
- Water Addition: Water is added to create a moist mixture suitable for pelletizing.
- Pelletizing: The mixture is fed into a pelletizer, which is typically a rotating drum or disc. As the drum/disc rotates, the material rolls and forms small, spherical "green pellets." The size of the pellets is carefully controlled.
2. Drying:
- Green Pellet Drying: The green pellets are then dried at relatively low temperatures (around 105°C) to remove excess moisture. This prevents them from cracking or disintegrating during the subsequent heating stage.
3. Induration (Hardening):
- High-Temperature Heating: The dried pellets are then heated to very high temperatures (typically 1200–1300°C) in a process called induration. This process hardens the pellets and gives them the strength to withstand storage, handling, and transportation. The heating process can be done in different types of furnaces, such as grate-kiln systems or shaft furnaces.
- Chemical Changes: During induration, several chemical and physical changes occur, including oxidation, sintering, and crystallization, which contribute to the pellets' increased strength and durability.
In summary, iron ore pellets are created from fine concentrate through binding, shaping, drying, and high-temperature hardening to produce a consistent and durable product suitable for use in iron and steelmaking.
