Effect of mineralogy on reduction behaviour of iron ore pellets

Abstract

The present study deals with influence of gangue content (Al2O3, SiO2) in iron ores on reduction of its pellets for production of sponge iron. Iron ore pellets were reduced isothermally with noncoking coal fines in the range of 1123 - 1273 K with a time interval of 15, 30,45,60,90 and 120 min. As the temperature rose from 1123 to 1223 K, the rate of reduction of all iron ore pellets increased and then decreased at temperature 1273 K. All iron ore pellets shows complete reduction at temperatures of 1173 and 1223 K within 120 minutes. The reduction results clearly show that the reducibility of the pellets depends on the initial mineralogy of the ore. It was also observed that the reducibility decreased as gangue content (Al2O3 + SiO2) increases. The activation energy of the pellets decreased from 46.54 and 49.13 kJ/mol when the gangue content increased. The pellets were analyzed with X-ray diffraction and scanning electron microscopy before and after reduction to identify phase transformations. Examination of the SEM microphotographs revealed that Whisker shape of iron grains were formed during the reduction process and clear porous structure was observed.