Kinetics and mechanism of the reduction of Mamatwan manganese ore fines by solid carbon

[摘要] The kinetics of reduction of the manganese ore from theMamatwan mine has been studied by thermogravimetric(TGA) analysis, x-ray diffraction analysis (XRD),optical microscopy, and energy dispersive analysis ofx-rays (EDAX) between 1100 and 1350 degree celcius with puregraphite under argon atmosphere. It has been observedthat the rate and degree of reduction increased withincreasing temperature and decreasing particle size.The effect of the different reaction atmosphere hasalso been investigated by replacing argon atmospherewith carbonmonoxide (CO) and carbondioxide (C02)' Theresults clarified importance of some reactions in thereduction mechanism of the ore.In early stages of reduction, up to about 4 minutes ofreaction time, carbothermic reduction of higher oxidesof manqanase and iron (Mn203 and Fe2o3) to manganeousoxide (MnO) and metallic iron respectively was observedwhich was controlled by diffusional process across theboundary layer between the solid phases. Apparentactivation energy is calculated as 61.03 kJ for thisstage which corresponds to about 30 percent reduction.Metallization started as random nucleation of iron richcarbides around Mno grains inside the particle. After30 percentreduction the formation of a silicate phasewas observed. Up to 70 percent reduction at 1350oC,reduction rate was controlled by chemical reactionbetween oxide phase and gaseous phase with an apparent.activation energy of 153 32 kJ.

[发布机构] University of the Witwatersrand