In the present study, the viscosity of the CaO–SiO2–FeO–Al2O3–MgO slag system was measured for the recovery of FeO in the electric arc furnace (EAF) process using Al dross. Considering the MgO-saturated operational condition of the EAF, the viscosity was measured in the MgO-saturated composition at 1823 K with varying FeO and Al2O3 concentrations. An increase in the slag viscosity with decreasing temperature was observed. The activation energy was evaluated, and the change in the thermodynamically equilibrated phase was considered. The changes in the aluminate structure with varying FeO and Al2O3 concentrations were investigated by Fourier-transform infrared spectroscopy, which revealed an increase in the [AlO4] tetrahedral structure with increasing Al2O3 concentration. Depolymerization of the aluminate structure was observed at higher FeO concentrations. The Raman spectra showed the polymerization of the silicate network structure at higher Al2O3 concentrations. By associations between the silicate and aluminate structures, a more highly polymerized slag structure was achieved in the present system by increasing the Al2O3 concentration.

The measurement and evaluation of MgO solubility in the molten fluoride system is of significant importance in the recently proposed magnesium electrolysis reduction process. In the present study, an in-situ quantitative method of evaluating the concentration of dissolved MgO in molten fluoride is proposed. The MgO solubility in the 32.8MgF2–67.2LiF system was measured at 1083 and 1123 K using a combustion analyzer. MgO saturation was achieved in under 2 h, and higher solubilities were observed as the temperature increased. Thermodynamic assessment was carried out in order to ascertain the applicability of the electrochemical oxygen sensor, which indicated that the logarithm of oxygen concentration in molten fluoride has a linear relationship with the measured electromotive force (EMF) potential. The EMF potential of the controlled MgO concentration was measured, and a straight calibration line was obtained, describing the relationship between the measured EMF and the logarithm of MgO concentration. From the obtained calibration line, MgO concentration in the 0.4 wt% MgO was calculated. The calculated value was 0.44 wt% that was in excellent accordance with the controlled MgO concentration of 0.4 wt%, verifying the practical applicability of electrochemical oxygen for the in-situ monitoring and evaluation of MgO solubility in the electrolysis magnesium reduction process.

The aim of this study was to develop a physical treatment method for obtaining iron concentrate with a grade higher than 60% from slag generated in the Waelz Kiln (WK) process. The size of the WK slag used in this work was several millimeters, with T-Fe and ZnO contents of 40.24% and 1.03%, respectively. The slag samples were pulverized in a laboratory rod mill for various grinding times, followed by a magnetic separation test under a low magnetic intensity of 0.05 T initially. The results showed that the highest iron grade was obtained from samples with a grinding time of 10 min. Additionally, for a grinding time of 20 min, the highest grade and recovery ratios were achieved at a magnetic intensity of 0.8 T. Based on these findings, the optimal physical treatment process proposed in this study resulted in iron concentrates with a grade of 61.34% and an enrichment ratio of 1.52.

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