Abstract: Through roasting-magnetic separation technology to treat flotation middling containing siderite at 700 ℃, an iron concentrate with Fe grade of 60.43% and Fe recovery of 83.59% was obtained.The study mainly focused on transforming mechanism of iron minerals in reductive roasting process by XRD and scanning electron microscopy.The results showed that with the roasting temperature changed, the roasting process went through three stages like the decomposition of siderite, the reduction of hematite and iron mineral reduction reaction, where the roasting temperature at reduction stage of hematite was just at 700 ℃.At this time, the iron minerals in calcined products are mainly magnetite, which is the most conducive to low intensity magnetic separation.

Key words: Siderite, Hematite, Flotation middling, Reduction roasting mechanism