In the production of iron ore pellets, fluxes are essential additives that improve pellet quality by adjusting the chemical composition and enhancing metallurgical properties during the induration (heat hardening) process. The primary flux used is limestone (CaCO₃) or dolomite (CaCO₃·MgCO₃), which decomposes into lime (CaO) and magnesia (MgO) at high temperatures.
Key Fluxes Used in Iron Ore Pellet Production:
1. Limestone (CaCO₃)
– Decomposes to CaO (lime) during induration.
– Acts as a basic flux to neutralize silica (SiO₂) and form calcium silicates, improving pellet strength.
– Helps in slag formation during blast furnace smelting.
2. Dolomite (CaCO₃·MgCO₃)
– Provides both CaO and MgO, enhancing pellet reducibility and high-temperature stability.
– Improves softening-melting characteristics in blast furnaces.
3. Bentonite (as a binder, not strictly a flux but often used with fluxes)
– Acts as a binding agent for green pellet formation but does not contribute chemically like limestone or dolomite.
Role of Fluxes in Pelletization:
– Improve mechanical strength of pellets by forming slag phases during induration.
– Adjust the basicity ratio (CaO/SiO₂ or MgO/SiO₂) for better metallurgical performance.
– Reduce melting temperature in blast furnaces, aiding efficient ironmaking.
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Typical Composition Adjustments:
– Basic pellets: CaO/SiO₂ ratio of ~0.4–0.8.jpg)
– Acid pellets: Low CaO, relying on bentonite only (~0.1–0.2 basicity).
Process Impact:
– Excessive flux can reduce pellet porosity and reducibility; optimal dosing is critical.
Would you like details on specific pelletizing processes or alternative fluxes?