Mechanism of microwave assisted suspension magnetization roasting of oolitic hematite ore

Abstract

Oolitic hematite is an iron ore resource with rich reserves, complex composition, low grade, fine disseminated particle sizes, and a unique oolitic structure. In this study, a microwave-assisted suspension magnetization roasting technology was proposed to recover and utilize the ore. The results showed that under the conditions of microwave pretreatment temperature of 1050 °C for 2 min, a magnetic concentrate with an iron grade of 58.72% at a recovery of 89.32% was obtained by microwave suspension magnetization roasting and magnetic separation. Moreover, compared with the no microwave pretreatment case, the iron grade and recovery increased by 3.17% and 1.58%, respectively. Microwave pretreatment increased the saturation magnetization of the roasted products from 24.974 to 39.236 (A·m²)/kg and the saturation susceptibility from 0.179×10⁻³ m³/kg to 0.283×10⁻³ m³/kg. Microcracks were formed between the iron and gangue minerals, and they gradually extended to the core of oolite with the increase in the pretreatment time. The reducing gas diffused from outside to inside along the microcracks, which promoted the selective transformation of the weak magnetic hematite into the strong magnetic magnetite.

Keywords

oolitic hematite / microwave / suspension magnetization roasting / phase and magnetic transformation / microstructure evolution

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