Sulfur partitions between carbon-saturated iron melt and Na2O-SiO2 slags.

Abstract

The sulfur partitions between carbon-saturated iron melt and Na2O-SiO2 slags with the Na2O/SiO2 molar ratio of 3/2, 1/1, 2/3 and 1/3 have been measured at 1 250 and 1 350°C. The sulfide capacities C'S [=(wt%S)•(aO/aS)] calculated from the sulfur partitions were found to be in the range 10-2 to 10-4 and their temperature dependence was not observed. These values were lower than the previous measurements obtained from the gas-slag equilibrium studies above Na2O/SiO2=0.5-0.7, but were higher than the previous measurements at the slag composition below this ratio. The sulfur partitions between carbon-saturated iron melt and Na2O-CaO-SiO2 melts at the constant silica content were also measured at 1 250°C. The effect of lime on the sulfur distribution was compared with that of Na2O in the plot of log (S)/[S] vs. (Na2O+mCaO)/SiO2 ratio, thus resulting m=0.3. The significant amount of iron was observed in the slag phase after equilibration and the ratio of sulfur as FeS against total sulfur in slag was found to be maximum at the composition with the Na2O/SiO2 molar ratio of 0.9. Desulfurization and dephosphorization of the carbon-saturated iron melts (0.1% P, 0.05% S) by the sodium vapor produced by the reaction of NaCl with CaC2 investigated at 1 300°C. Desulfurization was found to occur, but no dephosphorization was found.