Activation of the carbothermic reduction of manganese ore

The effect of extended milling on the carbothermic 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 degreesC, 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 degreesC and braunite, Mn7SiO12, at 700 degreesC after 10 h milling these temperatures were reduced by 200 degreesC. 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 umnilled 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. (C) 2002 Elsevier Science B.V. All rights reserved.