Investigation of microwave reduction of low-grade banded iron ores

The present work investigated microwave carbothermic reduction of three low-grade banded iron ores (Fe similar to 34%). The iron ores were size reduced and subjected to microwave reduction with charcoal. Ferrite formation was observed within 10 min at <= 8 wt% charcoal dosage at a microwave power of 900 W. It was found that a small fraction of the irradiated ore-charcoal mixture rapidly melted to produce ferrite balls. Wustite, ferrite, cristobalite and fayalite formed at >= 7 wt% charcoal. During microwave treatment, the paramagnetic hematite phase converted to a ferromagnetic magnetite phase, leading to enhanced magnetic susceptibility. Optical micrograph of the ferrite clearly revealed the presence of retained austenitic and martensitic iron phases. Significant amounts of ferrite balls were formed at MW 900 W for 10 min with 12 wt% charcoal.