Combustion Dynamics in Iron Ore Pellet Production Systems

Iron ore pellet production relies on the precise control of combustion within induration furnaces, most commonly grate-kiln and straight-grate systems. Combustion dynamics govern flame shape, temperature distribution, heat transfer to the pellet bed and formation of by-products such as deposits and nitrogen oxides. In grate-kiln processes, a layer of preheated “green” pellets advances into a rotary kiln where pulverised coal or alternative fuels drive high-temperature oxidation of residual carbon, inducing sintering and strength development. The interplay of gas-solid mixing, radiative and convective heat transfer, and chemical kinetics determines thermal efficiency, emission profiles and throughput. Key challenges include achieving uniform pellet temperature, suppressing ring- and deposit-forming liquid phases that impair kiln rotation, and minimising NOx generation under high flame temperatures. Advances in burner design, co-firing with hydrogen and real-time optical diagnostics have begun to reconcile productivity with decarbonisation targets, while computational models now link flame aerodynamics, particle transport and radiative heat transfer in three dimensions. The global significance of this field stems from its direct impact on iron-making energy intensity, greenhouse-gas emissions and raw-material yield in a market that supplies more than two-thirds of the world’s steel.

Research from Nature Portfolio

Recent studies have elucidated the mechanism of ring formation in magnesian flux pellets within rotary kilns, a phenomenon that restricts production yield and kiln longevity. Detailed microstructural analysis revealed that the addition of magnesium-bearing fluxes alters the bonding process of pellet powder, promoting the in-situ formation of low-melting ferrite and silicate liquid phases. These liquid phases enhance the diffusion and recrystallisation of hematite, increasing briquette compressive strength and encouraging ring growth. Investigation of pellet basicity (CaO/SiO₂ ratio) showed that higher basicity lowers the melting point of the liquid phase and intensifies ring formation, whereas maintaining kiln temperatures below 1 200 °C can limit initial ring stability. This work underlines the critical balance between flux chemistry, induration temperature and mechanical integrity in controlling unwanted solid deposits.

Combustion Dynamics in Iron Ore Pellet Production Systems publication trend

The graph below shows the total number of articles in combustion dynamics in iron ore pellet production systems across all publications each year (not limited to Nature Index journals).

Technical terms

Green pellet: Unfired agglomerates of iron ore concentrate and binder prior to thermal treatment.

Induration: Thermal hardening of green pellets in a furnace to develop mechanical strength.

Rotary kiln: A cylindrical, slightly inclined furnace that rotates to ensure uniform heating of material.

Grate-kiln process: A two-stage induration method combining a moving grate for preheating and a rotary kiln for final hardening.

Basicity: The ratio of calcium oxide to silicon dioxide in pellet or flux chemistry, influencing melting behaviour.

Radiative heat transfer: Thermal energy exchange by electromagnetic radiation, a dominant mode in high-temperature furnaces.

References

1. Cofiring of hydrogen and pulverized coal in rotary kilns using one integrated burner. International Journal of Hydrogen Energy (2024).
2. Research on the ring formation mechanism of magnesian flux pellets in rotary kiln. Scientific Reports (2023).
3. The Deposit Formation Mechanism in Coal-Fired Rotary Kiln for Iron Ore Pellet Production: A Review. Crystals (2021).
4. Heat Transfer Conditions in Hydrogen-Fired Rotary Kilns for Iron Ore Processing. Industrial & Engineering Chemistry Research (2023).