Abstract: Magnetization roasting and magnetic separation is one of the main methods for treating refractory iron ores at present.In order to explore the influence law of roasting process parameters on hematite magnetic conversion rate and magnetic separation index,magnetization roasting-magnetic separation test of hematite with natural pure hematite as the research object were systematically carried out,and the growth trend and phase transformation process of magnetite were explored by polarizing microscope and XRD.The test results showed that:aiming at the sample,the suitable roasting temperature of hematite is 550 ℃,the CO concentration is 20%,and the reduction time is 4 min.At this time,the magnetic separation recovery of the sample reaches 99.58%,and the magnetic conversion of hematite is 32.99%.In the roasting process of hematite,newborn magnetite is first formed on the mineral surface and cracks.With the increase of roasting time,newborn magnetite grows internally along the surface of ore particles.When the outer part of the particles is reduced to magnetite and the conversion rate of hematite reaches 32.99%,the whole particles can be recovered in the magnetic separation process,good magnetic separation indexes can be obtained without completely reducing hematite to magnetite.

Key words: hematite,magnetization roasting,recovery rate,polarizing microscope,VSM