Activation of the carbothermic reduction of manganese ore

The effect of extended milling on the carbonthermic reduction of a manganese ore has been examined using a combination of thermal analysis and X-ray diffraction (XRD). Thermodynamic modelling indicated that reduction of MnO₂ to MnO was possible at 25 °C, although no reaction was found to occur during milling of the ore with graphite for up to 10 h. For a physical mixture, cryptomelane, KMn₈O₁₆, reduced at 500 °C and braunite, Mn₇SiO₁₂, at 700 °C after 10 h milling these temperatures were reduced by 200 °C. The initial product was Mn₃O₄, although in the 10-h-milled powder, the reduction of braunite may have been directly to MnO. Reduction at 600 °C only formed Mn₃O₄ in the unmilled powder but the major product in the 10-h-milled powder was MnO. The increased extent of reaction after premilling may allow current processing plants to expand their throughput without increasing the size of reduction kiln.