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

Abstract

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.