Experimental Determination of the MnO Activity Coefficient in High-Manganese Slags Using the Chemical Equilibrium Method
Abstract
:1. Introduction
2. Materials and Methods
2.1. Principles of MnO Activity Measurement
2.2. Apparatus and Experiment
3. Results
Equilibrium between Ag and the MnO-SiO2-Al2O3 Slag
4. Discussion
Thermodynamic Assessment of aMnO and γMnO
5. Conclusions
- The MnO activity values measured at 1673 K range from 0.05 to 0.10 and rise with the increasing MnO concentration from 25 to 48%.
- Both the MnO activity and activity coefficients rise with the increasing MnO/SiO2 ratio at all temperatures in the experiments.
- The MnO activity coefficient exhibits a tendency to decrease with temperature in all slag compositions. Based on the derived results, it was shown that the temperature dependence of the MnO activity coefficient differs depending on the slag composition. For each MnO/SiO2 ratio, that is, 0.4, 0.6, and 1, the temperature relation was derived and presented graphically.
- For the MnO equilibrium distribution ratio between silver and the slag phase, the derived temperature dependence was found to be influenced by the slag composition to a great extent.
- The results show that both the temperature and the slag composition are important parameters that influenced the results.
- The thermodynamic assessment of the MnO activities and activity coefficients was carried out by applying the RSM and FactSage TM. Comparing the experimental results with the RSM, the values deviate from those calculated at 1623 K the most. The slags with the highest MnO activity, particularly higher than 0.15, showed the largest scattering in activity coefficients from the model calculations. At 1673 K, the contrast was the lowest.
- The deviation between the measured and calculated values may be due to high slag acidity with respect to the applied conversion factor, corresponding to more basic slags. In this case, the correction of a conversion factor may be needed.
- The MnO activity and activity coefficient values were plotted on the MnO-SiO2-Al2O3 ternary diagram at 1673 K and compared with those calculated using FactSageTM 7.3. At 1673 K the values generally agree, while at 1623 K, the deviation is the greatest. The scattering between the experimental values and FactSage TM calculations follows the same trend as in the case of the RSM application. The calculated by RSM and FactSage TM values are in good agreement.
- The findings derived in this work contribute to a better understanding of thermodynamic properties of manganese in the MnO-SiO2-Al2O3 slag and provide better process control in the metallurgical processes involving slags containing high MnO.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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Slag | MnO | SiO2 | Al2O3 |
---|---|---|---|
1 | 46 | 51 | 3 |
2 | 33 | 58 | 9 |
3 | 26 | 59 | 15 |
4 | 49 | 46 | 5 |
5 | 36 | 53 | 11 |
6 | 25 | 61 | 14 |
Sample | Mn in Ag, ppm | ||
---|---|---|---|
1673 K | 1723 K | 1623 K | |
Slag 1 | 720.61 | 1193.85 | 1896.13 |
Slag 2 | 584.77 | 465.21 | 609.52 |
Slag 3 | 343.27 | 350.48 | 116.77 |
Slag 4 | 1150 | - | - |
Slag 5 | 850 | - | - |
Slag 6 | 350 | - | - |
Slag No | T, K | CO2/CO Flow Ratio | Mn in Ag Mass % | Slag Composition, EPMA, Mass % | Experiment | RSM | FactSageTM | |||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
MnO | SiO2 | Al2O3 | aMnO | γMnO | aMnO | γMnO | aMnO | γMnO | ||||
1-a | 1673 | 0.021 | 0.072 | 48.62 | 48.00 | 3.38 | 0.105 | 0.25 | 0.161 | 0.356 | 0.130 | 0.28 |
2-a | 0.021 | 0.058 | 34.10 | 56.30 | 9.60 | 0.085 | 0.26 | 0.071 | 0.222 | 0.080 | 0.25 | |
3-a | 0.021 | 0.034 | 25.03 | 59.33 | 15.64 | 0.050 | 0.20 | 0.040 | 0.157 | 0.040 | 0.17 | |
1-b | 1723 | 0.012 | 0.119 | 49.42 | 47.46 | 3.12 | 0.075 | 0.18 | 0.169 | 0.400 | 0.14 | 0.30 |
2-b | 0.012 | 0.047 | 33.93 | 56.91 | 9.16 | 0.029 | 0.09 | 0.081 | 0.253 | 0.087 | 0.25 | |
3-b | 0.012 | 0.035 | 24.14 | 61.61 | 14.25 | 0.022 | 0.09 | 0.045 | 0.180 | 0.040 | 0.17 | |
1-c | 1623 | 0.039 | 0.191 | 49.70 | 47.30 | 3.00 | 0.666 | 1.57 | 0.133 | 0.314 | 0.13 | 0.31 |
2-c | 0.039 | 0.061 | 34.70 | 55.80 | 9.50 | 0.214 | 0.67 | 0.062 | 0.193 | 0.08 | 0.24 | |
3-c | 0.039 | 0.012 | 25.50 | 60.00 | 14.50 | 0.041 | 0.17 | 0.034 | 0.145 | 0.02 | 0.08 | |
4-a | 1673 | 0.021 | 0.115 | 49.00 | 47.90 | 3.10 | 0.167 | 0.37 | 0.196 | 0.431 | 0.14 | 0.31 |
5-a | 0.021 | 0.085 | 38.90 | 51.50 | 9.60 | 0.123 | 0.34 | 0.121 | 0.331 | 0.10 | 0.33 | |
6-a | 0.021 | 0.033 | 29.30 | 54.10 | 16.60 | 0.050 | 0.17 | 0.029 | 0.107 | 0.03 | 0.10 |
Ion-ion | Mn2+ | Si4+ | Al3+ |
---|---|---|---|
Mn2+ | - | −75,310 | −83,680 |
Si4+ | −75,310 | - | −127,610 |
Al3+ | −83,680 | −127,610 | - |
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Cheremisina, E.; Gao, X.; Ueda, S.; Kitamura, S.-y.; Yamashina, R.; Schenk, J. Experimental Determination of the MnO Activity Coefficient in High-Manganese Slags Using the Chemical Equilibrium Method. Metals 2021, 11, 1190. https://doi.org/10.3390/met11081190
Cheremisina E, Gao X, Ueda S, Kitamura S-y, Yamashina R, Schenk J. Experimental Determination of the MnO Activity Coefficient in High-Manganese Slags Using the Chemical Equilibrium Method. Metals. 2021; 11(8):1190. https://doi.org/10.3390/met11081190
Chicago/Turabian StyleCheremisina, Elizaveta, Xu Gao, Shigeru Ueda, Shin-ya Kitamura, Ryo Yamashina, and Johannes Schenk. 2021. "Experimental Determination of the MnO Activity Coefficient in High-Manganese Slags Using the Chemical Equilibrium Method" Metals 11, no. 8: 1190. https://doi.org/10.3390/met11081190