Influence and Mechanism on the Preparation of Pellets Using Phosphate Ore Powder

Abstract

This study investigates the reduction mechanisms of pellets fabricated from phosphate ore powders under varying operational parameters (temperature, time, coal-to-ore ratio, and silica-to-lime molar ratio). Analytical techniques, including ash fusion temperature analysis, x-ray diffraction, and scanning electron microscopy, were employed. The results indicate that an optimal coal addition range of 20–24% and maintaining the silica-to-lime ratio of the concentrated ore powder at 1.0 yield superior pellet reduction performance. At lower reduction temperatures, silica reacts preferentially with fluorapatite to form Ca₃(PO₄)₂. It subsequently reduces with carbon to form CaO, which reacts with SiO₂, generating new silicate phases. As the temperature increases, the reduction rate of pellets rises, and solid particles transition into a molten state, facilitating the formation of a vitreous phase. The highest reduction rate of 93.72% was achieved at 1400 °C using raw phosphate ore powder pellets. At 1450 °C, reduction rates for pellets made from concentrated phosphate ore and mixed ore types reached 89.1% and 91.33%, respectively. It was demonstrated that pellets formulated from a blend of high-grade concentrated ore powder and low-grade raw ore powder could substantially lower the reduction temperature and reduce energy consumption, all while maintaining a high reduction rate.