Extraction and phase transformation of iron in fine-grained complex hematite ore by suspension magnetizing roasting and magnetic separation

Suspension magnetizing roasting-magnetic separation technology was used to extract iron from fine-grained complex hematite ore. The effect of roasting conditions on the magnetizing roasting-magnetic separation process was studied. In summary, a concentrate with TFe grade of 69.96% and Fe recovery of 79.02% could be obtained under conditions of a roasting temperature of 500 degrees C, roasting time was 12 min, reductant concentration of 30%, and total gas flow of 200 mL/min, while TFe grade of final tailings was 5.66%. The phase composition and X-ray photoelectron spectroscopy analysis showed that hematite in the sample was transformed into magnetite during suspension magnetization roasting. After roasting, the proportion of Fe content in the phase of the magnetite increased from 5.91% in roasting feed to 97.96% in the roasting product. Transmission electron microscopy results also confirmed that hematite was transformed into magnetite with spinel structure, and the newly formed magnetite had good crystallinity. Scanning electron microscopy and BET analysis showed that roasting could increase the specific surface area, total pore volume, and porosity of the roasted product, which would strengthen the internal diffusion of CO and CO2 in the particles, to improve the reduction rate of hematite. The loose internal structure of roasted particles led to the decrease of mechanical properties, which was conducive to improving the subsequent grinding efficiency.

Automated summary

By using suspension magnetizing roasting - magnetic separation technology, iron was successfully extracted from fine-grained complex hematite ore. The optimized conditions were a roasting temperature of 500 degrees Celsius, roasting time of 12 minutes, reductant concentration of 30%, and total gas flow of 200 mL/min. Analysis showed that hematite was transformed into magnetite during roasting, improving the porous structure of the product and enhancing internal gas diffusion and reduction rate.