A process for the manufacture of magnetic gamma hematite by thermal conversion of iron ore

摘要

Iron ore concentrate is converted to magnetic gamma hematite in an autogenous roasting operation which is self-sustaining. The iron ore concentrate is preheated and contained magnetite is oxidized to hematite. Hematite is reduced to magnetite using carbon monoxide. After cooling, the magnetite is oxidatively exothermically converted to magnetic gamma hematite. The thermal energy resulting from the latter step is recycled to the preheating and reduction steps while thermal energy resulting from the cooling step also is recycled to those steps. The magnetic gamma hematite may be subjected to magnetic separation to produce a very low silica high purity iron oxide concentrate, which may be blended with high silica concentrate to provide a pellet feed for making blast furnace feed pellets.