Investigation on the Consolidation Characteristics and Metallurgical Performances of Oxidized Pellets with Different Alumina Occurrence

Abstract

With the increasing consumption of high-grade magnetite concentrates, the contents of gangue minerals in concentrates are increasing, especially Al₂O₃. In this paper, four types of Al-containing additives, kaolinite, illite, gibbsite, and corundum, were adopted and the influence of alumina occurrence on the consolidation characteristics and metallurgical performance of oxidized pellets was revealed. Kaolinite is more beneficial for the properties of green pellets, followed by illite, gibbsite, and corundum in that order, which is mainly due to the different morphology characteristics of Al-containing additives. The adverse effect of Al₂O₃ on the recrystallization of Fe₂O₃ can be inhibited by the addition of kaolinite or illite due to the more formation of a liquid phase during roasting, especially the former. When alumina is in the form of different occurrence states, the pore structure and mineral compositions of fired pellets are also different, which leads to differences in metallurgical performance. Overall, kaolinite is the most ideal alumina occurrence state for the pelletizing process of magnetite concentrates, followed by illite, gibbsite, and corundum in that order. When the Al₂O₃ content rises to 2.0%, the compressive strength of fired pellets exceeds 3250 N Per⁻¹ with kaolinite or illite added, while it is below 3000 N Per⁻¹ with corundum or gibbsite added.