Selectivity of Microwave Energy Consumption in the Reduction of Fe3O4 with Carbon Black in Mixed Powder

Abstract

In the present work, mixtures of magnetite and carbon black powers were irradiated by a constant microwave power supply of 2.8 kW at 2.45 GHz. The temperature was measured as a function of the irradiation time from 220°C. The progress of the reduction was examined by XRD analyses of reaction products at various temperatures in the range 400–1200°C. Under the present experimental conditions magnetite selectively absorbs microwave energy below approximately 650°C; meanwhile carbon black absorbs it in the whole temperature range. The reduction of magnetite to wustite was observed to occur from at least a measured temperature of 400°C but did not occur homogenously inside the mixture. At 800°C, the reduction of wustite to iron started and occurred almost homogeneously inside the reacting mixture mass.A general conclusion of this work is that microwaves are absorbed and used in their path within the irradiated mass by the material of highest absorbing microwave power.