Effects of SiO₂ on the preparation and metallurgical properties of acid oxidized pellets

The effects of SiO₂ content on the preparation process and metallurgical properties of acid oxidized pellets, including compressive strength, reduction, and softening–melting behaviors, were systematically investigated. Mineralogical structures, elemental distribution, and pore size distribution were varied to analyze the mechanism of the effects. The results show that with an increase in SiO₂ content from 3.51wt% to 7.18wt%, compressive strength decreases from 3150 N/pellet to 2100 N/pellet and reducibility decreases from 76.5% to 71.4%. The microstructure showed that pellets with high SiO₂ content contained more magnetite in the mineralogical structures. Additionally, some liquid phases appeared, which hindered the continuous crystallization of hematite. Also, the softening–melting properties of the pellets clearly deteriorated as the SiO₂ content increased. With increasing SiO₂ content, the temperature range of the softening–melting zone decreased, and the maximum differential pressure and the comprehensive permeability index increased significantly. When acid oxidized pellets are used as the raw materials for blast furnace smelting, it should be combined with high basicity sinters to improve the softening–melting behaviors of the comprehensive charge.