Mamdouh Omran

Dielectric properties and carbothermic reduction of zinc oxide and zinc ferrite by microwave heating

This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFe2O4) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFe2O4 were investigated. The results show that ZnFe2O4 has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFe2O4 are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFe2O4 completely decomposed to zincite and wustite in 3 min.

Treatment of blast furnace sludge (BFS) using a microwave heating technique

Recycling industrial waste saves landfill space, conserves resources and minimises its environmental impact. Recently, a great deal of attention has been paid to the microwave heating process as an alternative recycling method. The present study aims to investigate the use of microwave energy as a heat source for the treatment of blast furnace sludge (BFS). BFS is treated directly with microwaves, without the addition of a reducing agent. BFS contains carbon (its Fe/C ratio is approximately one), which functions as a self-reducing agent. The original BFS sample and the products of its carbothermic reduction by microwave heating are characterised using X-ray diffraction, scanning electron microscopy, thermogravimetry and differential scanning calorimeter, Fourier transform infrared and X-ray photoelectron spectroscopy. It is found that, after microwave treatment, the haematite is completely reduced to metallic iron with some wustite. The findings of this study indicate that microwave heating can be used to process and recycle BFS generated by iron-making processes.