Analysis of slag mode of blast furnace melting using model decision support systems

The article presents a balance model of the blast furnace process improved by the researchers from UrFU and PJSC “Magnitogorsk Iron and Steel Works” (MMK). It generally represents a system of deterministic dependencies characterizing the thermal, reduction, gas dynamic, blast and slag modes of blast furnace melting. The basic principle underlying the model is full-scale mathematical modeling. Indicators characterizing the properties of the final slag for implementation of normal slag mode of blast furnace melting (slag viscosity in the temperature range of 1350 – 1550 °C, as well as values of the slag viscosity gradients) were proposed. The slag viscosity gradient, along with the acceptable ranges of slag viscosity at different slag temperatures, are used in modeling the slag mode as limiting factors for the diagnosis of slag mode. Selection of the limit values of each of the ranges and the viscosity gradient is carried out by the method of expert evaluation. Structure of the model for calculating the parameters of the final slag is considered. Using a mathematical model of the blast furnace process, analysis of the slag mode of blast furnace melting was performed according to the actual indicators of their operation. It was established that desulfurizing ability of the slag is insufficiently used, as a result of which cast iron of reduced quality is smelted both in terms of content of sulfur and silicon. Change in characteristics of the slag mode, other things being equal, has a positive effect on gas permeability in the slag formation zone, reducing capacity of the gas and productivity of the blast furnace increase, as well as the consumption of coke decreases. The authors describe the results of design calculations of the MMK furnace performance indicators when changing the composition of loaded materials. Recommendations on the slag optimal basicity are given. Calculations showed that the optimal basicity of the final slag, which ensures its maximum liquid mobility, for operating conditions of blast furnaces of the combine is 1.04 – 1.05 for the CaO/SiO₂ ratio and 1.30 – 1.32 for the (CaO + MgO)/SiO₂ ratio.

1. Pavlov A.V., Polinov A.A., Spirin N.А., Onorin O.P., Lavrov V.V. Use of model systems for solving new technological problems in blast-furnace production. Metallurgist. 2017, vol. 61, no. 5-6, pp.  448–454. https://doi.org/10.1007/s11015-017-0516-7

2. Onorin O.P., Spirin N.A., Terent’ev V.L., Gileva L.Yu., Rybolovlev V.Yu., Kosachenko I.E., Lavrov V.V., Terent’ev A.V. Computer Methods of Blast-Furnace Process Modeling. Spirin N.A. ed. Yeka­terinburg: UGTU–UPI, 2005, 301 p. (In Russ.).

3. Spirin N.A., Lavrov V.V., Rybolovlev V.Yu., Krasnobaev A.V., Onorin O.P., Kosachenko I.E. Model Decision Support Systems in APCS of Blast Furnace Melting: Monograph. Yekaterinburg: UrFU, 2011, 462 p. (In Russ.).

4. Spirin N.A., Lavrov V.V., Rybolovlev V.Yu., Gileva L.Yu., Krasnobaev A.V., Shvydkii V.S., Onorin O.P., Shchipanov K.A., Burykin  A.A. Mathematical Modeling of Metallurgical Processes in APCS. Yekaterinburg: UrFU, 2014, 558 p. (In Russ.).

5. Bol’shakov V.I. Technology of Highly Efficient Energy-Saving Blast Furnace Melting. Kiev: Naukova dumka, 2007, 411 p. (In Russ.).

6. Tovarovskii I.G. Blast Furnace Melting. Dnepropetrovsk: Porogi, 2009, 765 p. (In Russ.).

7. Gimmel’farb A.A., Kotov K.I. Processes of Reduction and Slag Formation in Blast Furnaces. Moscow: Metallurgiya, 1982, 328 p. (In Russ.).

8. Gordon Y., Izumskiy N. Mathematical model and stabilization system for slag mode of blast furnace operation. In: Proceedings of AISTech-2017 Iron and Steel Technology Conf., Nashville, United States. 2017, vol. 1, pp. 797–805.

9. Jia R., Deng L., Yun F., Li H., Zhang X., Jia X. Effects of SiO2/CaO ratio on viscosity, structure, and mechanical properties of blast furnace slag glass ceramics. Materials Chemistry and Physics. 2019, vol. 233, pp. 155–162. https://doi.org/10.1016/j.matchemphys.2019.05.065

10. Shen X., Chen M., Wang N., Wang D. Viscosity property and melt structure of CaO–MgO–SiO2–Al2O3–FeO slag system. ISIJ International. 2019, vol. 59, no. 1, pp. 9–15. https://doi.org/10.2355/isijinternational.ISIJINT-2018-479

11. Zheng H., Ding Y., Zhou S., Wen Q., Jiang X., Gao Q., Shen F. Viscosity prediction model for blast furnace slag with high Al2O3 . Steel Research International. 2021, vol. 92, no. 1, article 1900635. https://doi.org/10.1002/srin.201900635

12. Jiao K., Zhang J., Liu Z., Chen C. Effect of MgO/Al2O3 ratio on viscosity of blast furnace primary slag. High Temperature Materials and Processes. 2019, vol. 38, pp. 354–361. https://doi.org/10.1515/htmp-2018-0019

13. Gan L., Lai C. A general viscosity model for molten blast furnace slag. Metallurgical and Materials Transactions B: Process Me­tallurgy and Materials Processing Science. 2014, vol. 45, no. 3, pp.  875–888. https://doi.org/10.1007/s11663-013-9983-9

14. Iida T., Sakai H., Kita Y., Shigeno K. An equation for accurate prediction of the viscosities of blast furnace type slags from chemical composition. ISIJ International. 2000, vol. 40, pp. 110–114. https://doi.org/10.2355/isijinternational.40.suppl_s110

15. Shu Q. A viscosity estimation model for molten slags in Al2O3–CaO–MgO–SiO2 system. Steel Research International. 2009, vol.  80, no.  2, pp. 107–113. https://doi.org/10.2374/SRI08SP085

16. Jiang D., Zhang J., Wang Z., Feng C., Jiao K., Xu R. A prediction model of blast furnace slag viscosity based on principal component analysis and k-nearest neighbor regression. JOM. 2020, vol. 72, no.  11, pp. 3908–3916. https://doi.org/10.1007/s11837-020-04360-9

17. Pavlov A.V., Onorin O.P., Spirin N.A., Polinov A.A. MMK blast furnace operation with a high proportion of pellets in a charge. Part  1. Metallurgist. 2016, vol. 60, no. 5-6, pp. 581–588. https://doi.org/10.1007/s11015-016-0335-2

18. Schlackenatlas. Verein Deutscher Eisenhüttenleute, Verlag Stahleisen, 1981, 282 p. (Russ. ed.: Atlas shlakov. Sprav. Moscow: Metallurgiya, 1985, 208 p.).

19. Voskoboinikov V.G., Dunaev N.E., Mikhalevich A.G. Properties of Liquid Blast Furnace Slags. Moscow: Metallurgiya, 1975, 182 p. (In Russ.).

20. Zhilo N.L. Formation and Properties of Blast Furnace Slags. Moscow: Metallurgiya, 1974, 120 p. (In Russ.).