Activity of Phosphorus Oxide in CaO–MnO–SiO2–PO2.5(–MgO, FetO) Slags

The CaO-MnO-SiO 2 -PO 2.5 (-MgO, Fe t O) slags were equilibrated with liquid copper alloys in a molybdenum crucible under a flowing CO 2 /H 2 atmosphere in the temperature range of 1 573 to 1 673 K. The activity coefficient of PO 2.5 , γPO 2.5 , and the phosphate capacity, C PO4 3-=(%PO 4 3-)/ρ 1 /2 P2 ρ 5/4 O2 of the slags were expressed as follows: log γPO 2.5 = -2.59{(%CaO) +0.33(%MnO)+0.55(%MgO) -0.90(%Fe t O) -0.77(%PO 2.5 )} /(%SiO 2 )+1 400/T-5.75 log C PO4 3-=2.60{(%CaO) +0.33(%MnO) +0.55(%MgO) -0.90(%Fe t O) -0.77(%PO 2.5 )}/ (%SiO 2 )+40 400/T-6.48 The phosphorus distributions between hot metal and the slag were examined, based on the thermodynamic data obtained in the present study. From comparison with the plant data, it was concluded that the thermodynamic data obtained in the present study are satisfactorily applicable to the thermodynamic assessment of hot metal pretreatment with high MnO slag.