Autogenous roasting of iron ore
OwnerPatrick E. Cavanaghinventor
Life of this patent
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Abstract
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.
Claims11
A process for the thermal conversion of iron ore to magnetic gamma hemitite, which comprises the steps of:
- (a) preheating an iron ore concentrate feed to effect oxidation of magnetite therein to hematite,
- (b) reducing hematite contained in the oxidized concentrate to magnetite,
- (c) cooling the reduced concentrate to a lower temperature,
- (d) oxidizing magnetite in the cooled charge to magnetic gamma hematite, and
- (e) employing exothermic heat from said cooling and magnetite oxidation steps in said preheating step (a),
- whereby, after being brought up to operating temperature and steady operating conditions, said thermal conversion is effected in an autogenous closed cycle of thermal energy which is self-sustaining.
In a process for forming pelletized iron ore concentrate for feed to a blast furnace wherein finely-divided iron ore concentrate is pelletized, the improvement which comprises:
- providing a first iron ore concentrate containing hematite and magnetite and having an iron content of at least about 60 wt. % and a silica content of at least about 3 wt. %,
- subjecting a portion of said first iron ore concentrate to a roasting operation to convert hematite and magnetite to magnetic gamma hematite wherein iron ore particles shatter and free occluded minerals including silica,
- magnetically concentrating said magnetic gamma hematite to form a second iron ore concentrate having an iron oxide content greater than 99% and containing less than 0.5 wt. % silica, and
- blending the remainder of said first iron ore concentrate with said second iron ore concentrate to form a blended iron ore concentrate as pelletizer feed.
Dependencies are inferred from the claim text.