8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Recently, reduction of CO₂ emission and also energy conservation in ironmaking process are serious concerns which persuaded the researchers to look for a cleaner and a more efficient method for iron production. Microwave heating has been considered as a new heating method for iron ore reduction which could decrease the required carbonaceous materials for iron production. However, it would be preferable for low carbon ironmaking if reduction reaction could be conducted by non-carbonaceous materials, such as H₂, during microwave heating. For this purpose, magnetite would be the best form of iron ore due to its high microwave susceptibility even at room temperature. In the present study, possibility of magnetite reduction by H₂ during microwave heating is investigated using a tablet shape magnetite sample and a microwave generator with a frequency of 2.45 GHz at the output power of 1050 W. The sample was heated to ca. 530°C in 6 minutes under N₂ atmosphere followed by changing the atmosphere from N₂ to H₂ and then heating for a certain time. Results of the weight change measurements showed that a reduction degree of 8, 17.6, 30, 32, 36, 51 and 65% could be achieved after a treatment under H₂ for 2.5, 7.5, 11, 15, 20, 30 and 60 minutes, respectively. Reduction of magnetite to FeO and Fe seems to cause some variations in microwave absorption capability of the sample due to the different magnetic and dielectric properties of the new-formed phases. Also, some changes were observed in the heating pattern of the sample after changing the atmosphere to H₂ confirming the effect of the above-mentioned phase transformations on microwave absorption capability. Furthermore, according to SEM observations of microwave heated sample, some cracks were formed which would be due to the rapid and selective heating characteristics of the microwaves irradiation causing a favorable porous structure for the reduction.