Influence of sintering conditions on the reducibility of iron ore sinter analogues

During iron ore sintering the green granulated sinter bed undergoes significant changes in its structure and mineralogy due to the formation of liquid in the flame front. These changes influence the sinter reducibility, which is an important parameter influencing the productivity and fuel efficiency of the blast furnace. Bulk measurement of sinter product from sinter pots and sinter strands reflect the average conditions experienced by the sinter, however, significant variation in the temperature, partial pressure of oxygen and local chemistry occur due to the heterogeneity of the green bed and the change in the flame front width as it descends through the bed. To understand the relative importance of the pore structure and mineralogy on sinter reducibility, a series of low variability iron ore sinter analogues was created under a range of sintering conditions. Fine hematite ore (<1 mm) was fluxed to a basicity of 2.0 with chemical reagents, then sintered varying the maximum temperature, holding time and cooling rate under a controlled atmosphere in an infra-red rapid heating furnace. The reducibility of 1.5 g analogues was measured in a TGA at 900 C in a 30% CO, 70% N₂ atmosphere. Reducibility was found to be correlated with the pre-reduction porosity of the analogues. Firing analogues for longer times at temperatures below 1320 ℃ increased their reducibility, however, firing at 1320 ℃ resulted in over-sintering and a decrease in reducibility. In contrast to previous work, no correlation was found between the SFCA-I content and reducibility.