2013 Volume 53 Issue 8 Pages 1341-1349
The addition of MgO to iron ore pellets is known to beneficially influences many high temperature reduction properties such as reducibility and swelling. When the pellet is metallized, MgO dissolved in the wustite concentrates in the unmetallized part, which is why MgO-levels much higher than the average concentration could be expected locally. In this work the impact of the elevated MgO-content on the reduction at 1000–1300°C was studied by SEM-EDS. The MgO content in the pellet was also varied by additions of a), highly reactive olivine b) unreactive olivine c) combined addition of reactive olivine and fine quartzite and d) combined addition of unreactive olivine and fine quartzite. Two cases of metallization were observed 1) a gradual reduction front with only moderate magnesium levels and 2) a sharp reduction front with strongly elevated magnesium levels before the metal front. The samples with added quartzite reduced a little better at 1100°C, compared to those with only olivine, but apart from that, reduction was not affected much by the additives in the range 1000–1200°C. The greatest difference in reduction degree appeared at 1300°C where a metal skin formed in most samples, hindering further reduction. At this temperature, the sample with addition of only reactive olivine had superior reducibility due to a porous morphology of the iron being mantained throughout the experiment.