Sulfide Capacity of the CaO–SiO2–MnO Slag at 1873 K

Abstract

The sulfide capacity of the CaO-SiO2-MnO slag through the entire composition range was measured at 1 873 K using a gas-slag equilibration method and the effect of basicity and the activity coefficient of sulfide on the sulfide capacity of molten slag was investigated. Furthermore, the relationship between the sulfide capacity and the optical basicity of MnO-containing slags was evaluated in view of industrial applications. Sulfide capacity of the slag linearly increased by increasing the content of MnO not only at a given silica content but also at a fixed Vee ratio (=CaO/SiO2). The capacity and the modified Vee ratio (=(CaO+MnO)/SiO2) showed a good linear relationship. Assuming that the basicity and the stability of sulfide ion in the slag are proportional to the activity of MnO (aMnO) and the activity coefficient of MnS (γMnS), respectively, the composition dependency of sulfide capacity was well described by the changes in the ratio of aMnO to γMnS. The iso-sulfide capacity of the CaO-SiO2-MnO slag at 1 873 K was constructed in the present study. The capacity contours seemed to rotate clock-wisely from the CaO-SiO2 binary side to the MnO-corner. The sulfide capacity increased with increasing ratio of MnO to CaO at relatively acidic region in which silica content greater than about 40 mass%, while the substitution of CaO by MnO does not significantly affect the capacity in the low silica region. The sulfide capacity generally increased with increasing content of MnO regardless of changes in the content of other constituents in multicomponent MnO-containing slags. It is necessary to take different values for the theoretical optical basicity of MnO in order to estimate the sulfide capacity of MnO-containing slags depending on the content of silica.

Activity Measurement of the CaS–MnS Sulfide Solid Solution and Thermodynamic Modeling of the CaO–MnO–Al2O3–CaS–MnS–Al2S3 System

“…), replacing CaO by MnO does not increase CS. Although no experimental work was carried out in this particular system, Park et al 42) observed similar a clock-wise rotation of sulfide capacity in the CaO-MnO-SiO2 slags by experiment, and the mechanism was reasonably well explained by one of the present authors using the MQM in the quadruplet approximation. 31) As the similar modeling approach has been used in the present study for the S dissolution in CaOMnO-Al2O3 slag, it is expected that the predicted clockwise rotation of the iso-CS lines is likely to reflect the reality.…”

Effect of Atmosphere and Slag Composition on the Evolution of PH3 Gas during Cooling of Reducing Dephosphorization Slags

“…However, the distribution ratio of phosphorous remained constant at CaO content greater than about 20 mass%, where the flux is saturated by solid lime from the CaO-CaF2 binary phase diagram, 20) indicating that the activity of free O 2-ions is approximately constant, assuming that is proportional to aCaO in the flux. [21][22][23][24][25][26][27][28] …”

Sulfide Capacity and Excess Free Energy of CaO^|^ndash;SiO2^|^ndash;MnO Slag Derived from Structural Analysis of Raman Spectra

“…Hence, the log will be directly proportional to the log , if the second term in Eq. (3) would not be significantly changed by silicate composition at a fixed temperature.The sulfide capacity of the CaO-SiO 2 -MnO slag measured by Abraham et al 4) and Park et al 5,6) is shown in Fig. 1 as a function of the concentration of free oxygen ions obtained in previous study.…”

“…The sulfide capacity of the CaO-SiO 2 -MnO slag measured by Abraham et al 4) and Park et al 5,6) is shown in Fig. 1 as a function of the concentration of free oxygen ions obtained in previous study.…”

“…basicity but also the effect of structural modification behaviour on the stability of oxygen and sulfide ions in silicate melts. 5,6,8) In previous works of the present author, 1,5,6,8) it was found that, in the relatively acidic region of which silica content is greater than about 30(±5) mass%, the large amounts of Ca 2+ ions are consumed to modify the silica networks due to a large ionic potential, resulting in a stabilization of S by Ca 2+ ions due to an interaction between Ca 2+ and S 2-ionic pair which is stronger than Mn 2+ and S 2-pair. The more details on this discussion are available in Refs.…”