Thermodynamic model for MnO-containing slags and gas-slag-metal equilibrium in ferromanganese smelting

The thermodynamics of MnO-containing slags was reviewed, and the properties of such slags were correlated by application of the cell model. This model, together with a previously developed unified interaction parameter model for the metal phase, was used to simulate the gas-slag-metal conditions in the hearth of a ferromanganese submerged arc furnace. The calculated slag and metal compositions and distribution of Mn, Si, and K between slag, metal, and fume were compared with plant data and satisfactory agreement was obtained. A steady recirculation of potassium inside the furnace was also predicted. For a potassium percentage in the raw materials of 0.63 pct, the amount of the recirculating potassium was about 160 kg per metric ton of ferromanganese. Due to the recirculation, the average potassium content in the solid mix coming down to the hearth could be as high as 7 pct.