Manganese Equilibrium between BaO-BaF₂-MnO Fluxes and Ferro-manganese Melts

Abstract

The equilibrium distribution ratio of manganese between BaO-BaF₂-MnO slag and Mn(62-73%)-Fe-C_sat melt has been determined at 1573-1673 K. The effects of slag composition, oxygen partial pressure and temperature on the manganese distribution ratio have been investigated.
The equilibrium manganese distribution ratio was found to increase with oxygen partial pressure and BaO content in the slags. Addition of BaF₂ to BaO-MnO slag provided a beneficial condition to cut down the losses of manganese and enabled to dephosphorize ferro-manganese at a relatively high oxygen partial pressure. At a certain oxygen partial pressure, the molar fraction ratio of BaO to MnO decreased with the increased BaO content in a slag equilibrated with carbon-saturated ferro-manganese.
A high temperature resulted in a low manganese distribution ratio. For a BaO (50%)-BaF₂(47%)-MnO(3%) slag, the effect of temperature on the manganese capacity can be expressed as:
log C_Mn²⁺ = 21670/T−3.73
The heat of reaction
Mn(1)+1/2O₂=(MnO)
in the investigated temperature interval was estimated to be –415 kJ/mol.