Abstract
Fluidized bed processes for iron ore reduction (e.g. FIOR®, FINMET®, FINEX®) operate in a continuous multi-staged countercurrent mode. To optimize iron ore reduction, different operating conditions occur in each stage.
Significant influence of the first reduction stage on the final reduction degree was observed in industrial plant. The iron ore particles seem to “memorize” the precursor autoclave conditions.
To optimize iron ore reduction, as well as to develop new reduction processes, it is necessary to understand this phenomenon. Industrial plants operate on pressures up to 12 bar and temperatures up to 900°C. So a laboratory-scale pressurized fluidized bed reactor was built to perform experiments similar to industrial conditions.
Two-stage experiments with Mt. Newman hematite ore from Western Australia at variable operating conditions show significant influences of temperature and residence time of the pre-reduction stage on the final reduction degree. Microscopical analysis showed the influence of mineralogy and texture on the reduction behavior of original respectively partly reduced iron ore. Formed magnetite in the pre-reduction stage causes a degradation of final reduction degree. Additionally the amount of newly formed magnetite depends on pre-reduction temperature, composition of the reducing gas and residence time.
