ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Thermodynamic Properties of Manganese Oxide in BOF Slags
Sung-Mo JungChang-Hee RheeDong-Joon Min
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2002 Volume 42 Issue 1 Pages 63-70


It is necessary to understand the thermodynamic properties of MnO in steelmaking slags for the smelting reduction of Mn ore in BOF process. Studies of the manganese distribution between CaO–SiO2–FetO–MnO slags and liquid silver in equilibrium with solid Fe in the temperature range of 1623 to 1723 K were carried out under a CO/CO2 atmosphere.
The FetO content in (32.436.3)%CaO–(31.644.0)%SiO2–(9.924.1)%FeO–(0.42.6)%Fe2O3–(8.910.8)%MnO slags was found to have a linear relationship with oxygen partial pressure. The values of Fe3+/Fe2+ in the same slag system increase by increasing the FetO content. The Mn distribution ratio between slag and metal, (%MnO)/[%Mn]Fe–Csat, increases with FeO content in a linear relationship over the measured FeO concentration range (6.7–24.1 mass%). The Mn distribution ratio decreases with increasing CaF2, which is believed to have the effect of increasing the activities of MnO and FeO.
Temperature dependence of equilibrium manganese distribution at pO2 = 6.6×10-12 atm in the temperature range of 1623 to 1723 K can be expressed as follows:

log{(MnO)/[%Mn]Fe–Csat} = 14270/T = −6.55

The relative partial heat of solution of MnO into (32.739.1)%CaO–(32.738.8)%SiO2–(10.220.78)%FeO–(1.02.4)%Fe2O3–(9.410.8)%–MnO slags was estimated to be 198 kJ/mol.

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