Iron Ore Pelletization: A Comprehensive Overview with Real-Time Plant Insights

⇨  This Article presents real-time plant data and operational experience in iron ore pelletization. This real-time insight into iron ore pelletization provides a practical understanding of the process, key control parameters, and optimization strategies used in an actual plant. By continuously monitoring and adjusting these factors, pellet quality can be improved, leading to higher efficiency in steel production.

 Pellets: Iron ore pellets are small, spherical aggregates of iron ore concentrate, typically 8-16 mm in diameter, used as a raw material in steel production. They contain a high percentage of iron, generally between 63% and 72%, and other materials to adjust the chemical and metallurgical properties.

IRON ORE PELLET

Raw Materials : The primary raw material is filter cake, a slurry of ground iron ore collected from the beneficiation unit. Additives such as dolomite, coke, and bentonite are sourced from the grinding unit and stored in bins within the proportioning building. Iron ore fines from the Electrostatic Precipitator (ESP), coke from Pulverized Coal Injection (PCI), and lime and bentonite from silos are also used. All fine materials are transported using compressed air and conveyors using Belt conveyor for two different unit P1 and P2.

What is Iron Ore Filter Cake?

Iron ore filter cake is a semi-solid material obtained after the filtration of iron ore concentrate slurry in the beneficiation process. This material has high moisture content and requires further processing before use in pelletization. It typically undergoes mixing with additives like bentonite, dolomite, and coke before being sent to the pelletizing disc or drum.

Key Properties of Filter Cake & Their Significance

Factors	Value(Average)	Significance
Blaine No.	1800-2100 cm²/g	Indicates fineness; affects pellet strength, porosity, and sintering behavior.
Fe(T) (Total Fe)	58-62%	Determines iron content and influences final pellet quality.
LOI (Loss on Ignition)	3.5-5.5%	Represents moisture, combined water, and volatile loss; affects drying and induration processes.

Filter Cake Size Distribution
Particle Size	Percentage
+500	0.35
+212	5.86
+150	6.31
+75	17.19
+45	11.13
-45	59.20

Blaine Number (1800-2200 cm²/g) – The right fineness ensures proper bonding, pellet strength, and porosity. Too fine material can reduce permeability in the induration furnace.
Total Iron (Fe(T) ≥62%) – Higher iron content improves pellet quality and enhances reducibility in blast furnaces or DRI kilns.
Loss on Ignition (LOI 3.5-5.0%) – LOI represents moisture, volatile matter, and combined water loss. If too high, it increases energy consumption and can cause pellet cracking.
Moisture Content (8-10%) – Proper moisture is critical for green pellet formation. Too much moisture makes pellets weak, while too little affects balling.
Silica (SiO₂ ≤3%) – Lower silica content improves metallurgical properties and reduces slag formation in downstream processes.
Alumina (Al₂O₃ ≤2%) – Excess alumina leads to poor pellet strength and higher slag viscosity, negatively affecting furnace operations.
Fine Particle Distribution (-45µm: 65-80%) – Proper particle size distribution ensures uniform green pellet formation, better drying efficiency, and strong fired pellets.

Mixing and Blending: 

The ground material and additives are conveyed using conveyor belts to the mixing unit, where they are thoroughly blended to improve pellet quality. From the mixer unit, the ground material is moved to the mixer bin. Using a Disc feeder the mixed filter cake is fed into the balling discs.