Kinetics of the Carbothermic Reduction of Manganese Oxide from Slag

Experiments were performed using a range of test conditions to elucidate the rate controlling step during the reaction of liquid iron-carbon droplets and slags containing manganese oxide. Four conditions were tested in the system: initial MnO content in the slag (5, 10, and 15 wt pct), initial carbon content of the metal (1, 2.5, 4.3 wt pct), initial droplet mass (0.5, 1.0, and 1.5 g), and reaction temperature (1823 K [1550 °C], 1873 K [1600 °C], and 1923 K [1650 °C]). Data were collected using the Constant Volume Pressure Increase (CVPI) technique which tracked the continuous pressure increase in the sealed furnace over time. Samples were quenched at the end of each experiment and chemistry was checked using LECO Carbon Analysis and ICP (Inductively Coupled Plasma) for manganese. The rate of reaction can be broken into a faster initial period related to internal CO formation, and a slower second reaction controlled by a complex mechanism involving transport of oxygen from slag to metal via CO₂ and decomposition of the CO₂ at the gas–metal interface.