Thermodynamics of Phosphorus for the CaO-BaO-CaF2-SiO2 and CaO-Al2O3 Systems

The effect of BaO addition to the CaO-CaF2-SiO2 melts on the phosphorus partition ratio between CaO-CaF2-SiO2 melts doubly saturated with CaO and 3CaO·SiO2 and Fe-Csatd. melts was investigated at 1300°C by using a chemical equilibration technique. The partition ratio increases with increasing the BaO content. The addition of 26%BaO enhances the partition ratio six times.The phosphorus partition ratio between CaO-Al2O3 fluxes and Fe-Csatd. melts was measured at 1500°C. The phosphorus partition increases with increasing CaO content and its phosphate capacity ranges from 1019 to 1021.The activity coefficient of PO2.5 was also calculated.Furthermore, in order to calculate the above mentioned phosphate capacities, the activity coefficient of phosphorus in carbon saturated iron, fP, at hot metal temperature was determined by measuring the partition of phosphorus between CaO-CaF2-SiO2 fluxes and Fe-Csatd. melts and that between the same fluxes and silver at different oxygen partial pressures. The activity coefficient of phosphorus in carbon saturated iron is expressed as follows:logfP = -386/T + 0.891The relationship between phosphate capacity and sulfide capacity is also discussed for various fluxes.