Magnesium-containing pellet regulating blast furnace ferrous burden interaction: softening–melting behavior and mechanism

MgO participates in all stages of sintering, pelletizing, and blast furnace ironmaking, and synergistically optimizing the distribution of MgO in ferrous burden can effectively enhance the interaction within the ferrous burdens and optimize the softening–melting properties of the mixed burden. Magnesium-containing pellets mixed with low-MgO sinter or mixed with high-MgO sinter in the blast furnace ferrous burden structure have opposite softening–melting performance laws. When the structure of the ferrous burden is magnesium-containing pellets mixed with low-MgO sinter, the magnesium-containing pellets can enhance the interaction of the ferrous burden in the process of softening–melting, which can optimize the composition of the slag phase and improve the slag liquidity. When the structure of the ferrous burden is magnesium-containing pellets mixed with high-MgO sinter, the magnesium-containing pellets weaken the interaction of the ferrous burden in the process of softening–melting, increase the content of the high melting point solid-phase particles in the slag, lead to an increase in the viscosity of the slag and difficult separation of the slag and iron, and decrease the permeability of the charge layer. Therefore, to ensure good permeability of the mixed burden, the following measures are suggested: optimizing the MgO distribution of the ferrous burden, reducing the MgO content of the sinter to 1.96 wt.%, increasing the MgO content of the pellets to 1.03–1.30 wt.%, controlling the MgO/Al₂O₃ ratio of the mixed burden within 1.15–1.32, narrowing the position of the cohesive zone, and maintaining an S value (permeability index) of approximately 150 kPa °C.