Phase compositions of manganese ores and their change in the process of calcination

The phase compositions of Wessels, Groote Eylandt, CVRD and Gabonese manganese ores and their change in the process of calcinations in different gas atmospheres were studied. Wessels and Groote Eylandt manganese ores were examined at the University of New South Wales (Australia) using XRD, optical, SEM and EPMA analyses; CVRD and Gabonese ores were studied at SINTEF and NTNU (Norway) using quantitative XRD analysis. The manganese ores had significant differences in chemistry and mineralogy. Equilibrium phases in ores at temperatures of 800 °C, 1000 °C and 1200 °C in different gas atmospheres were examined using FACTSage software. The calculated phase composition was in agreement with quantitative XRD analysis.In the process of calcination of manganese ores in air, MnO2 was reduced to Mn2O3 and Mn3O4, while during calcination in a reducing atmosphere manganese oxides were reduced to MnO and iron oxides to metallic iron. Formation of a liquid slag in ores at equilibrium was predicted for Wessels, Groote Eylandt and Gabonese ores at 1200 °C in air and 1000–1200 °C in a reducing atmosphere. No liquid slag was predicted for equilibrium phases in CVRD ore.