Investigations on the Barium-Bearing Magnetite Concentrate Roasted in Air

To expand the application of barium-bearing magnetite in pellets, the oxidation induration mechanism for barium-bearing magnetite concentrate pellets with the BaSO₄ contents from 0 to 8wt pct as an additive was investigated in this paper. The green pellets were preheated at 900 °C for 10min and roasted at 1200 °C for 20min.The XRD, SEM-EDS, and TG were used to systematically analyze the phase composition, microstructure, elemental distribution, and oxidation behavior of the pellets with the different contents of BaSO₄. The results indicated that BaSO₄ reacted with SiO₂ and Fe₂O₃ to form BaSiO₃ and BaFe₂O₄, respectively. When the content of BaSO₄ was less than 2 wt pct, the Ba-bearing silicate filled the hematite grains, which promoted the induration process of the pellets. With a further increase in the amount of BaSO₄, the growth of hematite grains was suppressed by the Ba-bearing silicate. In addition, the BaFe₂O₄ distributed along the hematite grains’ boundaries, and the SO₂ that decomposed from BaSO₄ separated out from the pellets, which led to a decrease of compressive strength. Thereby, the compressive strength decreased, the porosity increased. A schematic of the oxidation induration mechanism is also presented based on the experimental results, providing the theoretical and technical foundations for the use of Ba-bearing oxide minerals in pellets.