Almalyk Branch of Tashkent State Technical University named after Islam Karimov, Almalyk, Uzbekistan

Sh. T. Khojiev, Cand. Eng., Associate Prof., Dept. оf Metallurgy, e-mail: hojiyevshohruh@yandex.ru
D. B. Kholikulov, Dr. Eng., Prof., Dept. of Metallurgy, e-mail: Kholikulov.d@tdtuof.uz
S. S. Mutalibkhonov, Senior Lecturer, Dept. of Metallurgy, e-mail: mutalibkhonov1990@gmail.com
I. I. Shaymanov, Doctoral Student, Dept. of Metallurgy, e-mail: ikromshaymanov5@gmail.com

Wuhan University of Science and Technology, Wuhan, China

G. Ma, Cand. Eng., Prof., Hubei International Science and Technology Cooperation Base of Low Carbon Metallurgy Technology, e-mail: gma@wust.edu.cn

This paper presents a thermodynamic analysis of the carbothermic reduction of fayalite — the main iron-containing component of silicate slags in black metallurgy — using calcium and sodium oxides as fluxing additives. It is demonstrated that the reaction involving Na₂O is exothermic and exhibits significantly higher energy efficiency compared to CaO. A comparative assessment of Gibbs free energy and equilibrium constants in the temperature range of 323–1873 K shows that the use of Na₂O enables spontaneous reduction of iron even at lower temperatures. The optimal temperature range was determined to be 1205–1300 °C, with peak efficiency observed at approximately 1250 °C. Within this zone, the process achieves thermodynamic stability and effective separation of molten pig iron and silicate slag. Moreover, reducing the Na₂O dosage to 1 mole improves the economic feasibility without compromising thermodynamic advantages. The findings offer practical value for the development of resource- and energy-efficient technologies for processing metallurgical slags to recover iron.

1. Kolesnikov Yu. A., Bigeev V. A., Sergeev D. S., Dudchuk I. A. Possibility of usage of siderite ore for smelting converter steel with increased cast iron share in metal charge. Chernye Metally. 2017. No. 6. pp. 40–44.
2. Kukkala V., Kumar A., Nirala R., Patel V. Beneficiation of low-grade hematite iron ore fines by magnetizing roasting and magnetic separation. ACS Omega. 2024. Vol. 9, Iss. 10. pp. 12765–12775.
3. Pelevin A. E. Improvement of concentrate quality by using fine screening in iron ore grinding stages. Chernye Metally. 2023. No. 10. pp. 4–9.
4. Pelevin A. E. Effect of magnetic flocculation on iron-bearing ore concentration. Obogashchenie Rud. 2021. No. 4. pp. 15–20.
5. Roshchin V. E. et. al. Role of a silicate phase in the reduction of iron and chromium and their oxidation with carbide formation during the manufacture of carbon ferrochrome. Russian Metallurgy (Metally). 2016. Vol. 2016, Iss. 11. pp. 1092–1099.
6. Khojiev S. T. Processing of copper slag using waste tires. Metallurgist. 2025. Vol. 68. pp. 1–10.
7. Hou Y., Yu J., Zheng D., Xu J., Ma G., Khojiev S., Kadirov N. Preparation and chromatic performance of black ceramic tiles from chromium slag, copper slag and silicon manganese slag. Journal of Ceramic Processing Research. 2025. Vol. 26, Iss. 1. pp. 139–147.
8. Yusupkhodzhaev A. A., Khozhiev Sh. T., Akramov U. A. Use of non-traditional reducing agents to expand the resource base of OJSC Uzmetkombinat. Chernye Metally. 2021. No. 4. pp. 4–8.
9. Klinger A., Altendorfer A., Bettinger D., Hughes G. D., Al-Husseini A. A., et al. A The new system for control and improvement of technological process at DRI units. Chernye Metally. 2017. No. 10. pp. 19–27.
10. Temnikov V. V., Kalimulina E. G., Tleugabulov B. S. Analysis of formation and processing of metallurgical wastes at “EVRAZ NTMK” JSC. Chernye Metally. 2018. No. 7. pp. 32–37.
11. Romenets V. A., Valavin V. S., Pokhvisnev Y. V. Technological assessment of the romelt process in the classic and two-zone variants. Metallurgist. 2014. Vol. 58. pp. 20–27.
12. Allen W. C., Snow R. B. Orthosilicate-Iron Oxide Portion of the System CaO–‘FeO’–SiO2. Journal of the American Ceramic Society. 2006. Vol. 38, Iss. 8. pp. 264–272.
13. Dohlen M., Dierks Ch. Sustainable resource saving through the converter slag usage. Chernye Metally. 2019. No. 8. pp. 37–41.
14. Schüler S., Markus H.-P. Quality of electric arc furnace slag from high-grade steelmaking as a function of metallurgy. Chernye Metally. 2015. No. 9. pp. 31–41.
15. Khojiev Sh. T., Sultonov Kh. Sh., Kadirov N. A., Gaibnazarov S. B. Improving the technology of producing iron ore agglomerate using polyethylene waste. Chernye Metally. 2024. No. 10. pp. 4–8.
16. Zhang H., Li B., Wei Y. et al. Effect of CaO on copper loss and phase transformation in copper slag. Metall. Mater. Trans. B. 2022. Vol. 53. pp. 1538–1551.
17. Tretyakov Yu. D. Solid-phase reactions. Moscow : Khimiya, 1978. 360 p.