Optimisation of thermal regime and consolidation properties of high-silica magnesium-containing pellets

An in-depth study on the preparation process of high-silica magnetite magnesium pellets based on a grate-rotary kiln process is of great significance for promoting the utilisation of low-grade magnetite resources. When the magnetic hematite ratio is 30% and the proportion of magnesia is 1.5%, the performance of green pellets is the best. The preparation of high-silica magnesium pellets requires two stages of grate preheating for additional heating, and the appropriate preheating system is 1150°C for 15 min. The suitable magnetic hematite mixture ratio of pellets should not exceed 30%, and the reasonable magnesia ratio should not exceed 1.5%. Otherwise, the preheating temperature should be further increased, or the preheating time should be extended. The suitable roasting temperature is low, only 1225°C for 15 min, and the pellet strength can reach more than 2365N. Magnetic hematite and added magnesium flux inhibited the continuous crystallisation consolidation property in the pellet. The high SiO₂ content in the gangue of high-silica magnetite impedes the recrystallisation consolidation of Fe₂O₃ particles in the pellet. At the same time, the primary Fe₂O₃ in the magnetic hematite mixed ore is less reactive than the new Fe₂O₃ in the magnetite oxidation. With the roasting process, the magnesium ferrite content in the pellet increases, and the recrystallisation consolidation is inhibited, so the grate-rotary kiln process to produce high-silica magnesium-containing pellets is suitable to use a higher preheating temperature to meet the requirements of grate-rotary kiln pellet strength.