G. I. Nosov Magnitogorsk State Technical University (Magnitogorsk, Russia

Fadeeva N. V., Associate Professor, Candidate of Engineering Sciences, Associate Professor, natali_fadeeva@mail.ru
Orekhova N. N., Professor, Doctor of Engineering Sciences, Associate Professor, n_orehova@mail.ru
Kolodezhnaya E. V., Senior Researcher, Candidate of Engineering Sciences, kev@uralomega.ru
Musatkina E. N., Assistant, musatkina.yelena@mail.ru

In 2022, graphite was included in the list of strategic mineral resources of the Russian Federation. In addition to natural ores, the raw material base for flake graphite may also include iron-graphite dust (spill) generated in metallurgical production. This article discusses the basic principles behind air classification of the iron-graphite spill, which serves to separate the material into two streams with narrower size ranges for improved flotation selectivity of graphite particles. The particle size distributions have been studied for the original dust, its centrifugal impact milling products, and the relevant classification and flotation products. The work included an optical microscopic study of the resulting products and of the magnetic and carbon particle size distributions into size classes, as well as flotation experiments aimed to evaluate the classification efficiency. A comparison of the relevant Tromp curves has shown low separation selectivity, with the best results achieved with 0.1 mm grinding. The calculated Terra criterion has values of 0.5 to 0.9, which indicates predominant material composition-based separation in the classification process. It has been established that, when a centrifugal impact mill is used for grinding, iron-containing particles are separated from the surface of graphite flakes without disturbing the shapes of the particles being ground. The flotation process has high selectivity when a fine product with a narrow size range has been separated from the material ground to 0.1 mm. A graphite concentrate with a mass fraction of carbon of 94 % was obtained, with a recovery of 99.56 %.
The work was conducted with the financial support of the Russian Science Foundation within the framework of a grant for fundamental scientific and exploratory research in 2022–2023, agreement No. 22-27-20068, with the participation of the Central Research Laboratory of the Nanosteel Research Institute of the G. I. Nosov Magnitogorsk State Technical University.

1. Study on the EU’s list of critical raw materials. Final report. Brussels: European Commission, 2020. 157 p.
2. Zhang J., Liang C., Dunn J. B. Graphite flows in the US: Insights into a key ingredient of energy transition. Environmental Science & Technology. 2023. Vol. 57, Iss. 8. pp. 3402–3414.
3. On the state and use of mineral resources of the Russian Federation in 2021. State report. Moscow: VIMS, 2022. 626 p.
4. Kuo Sh.-L., Wu E. M.-Ya. Analysis on certain physical and resourceful properties of kish graphite containing materials. Journal of the Indian Chemical Society. 2020. Vol. 97, No. 11b. pp. 2490–2494.
5. Perepelitsyn V. A., Yagovtsev A. V., Merzlyakov V. N.,Koc hetkov V. V., Ponomarenko A. A., Ponomarenko Z. G., Kolobov A. Y. Perspective technogenic mineral resources for the production of refractories. Novye Ogneupory. 2019. No. 6. pp. 12–16.
6. Jara A. D., Betemariam A., Woldetinsae G., Kim J. Y. Purification, application and current market trend of natural graphite: A review. International Journal of Mining Science and Technology. 2019. Vol. 29, Iss. 5. pp. 671–689.
7. Orekhova N. N., Fadeeva N. V., Kolodezhnaya E. V., Efimova Yu. Yu. A study on the influence of the graphite flakes disintegration method on their dispersed composition, particle shape, and flotation performance. Obogashchenie Rud. 2022. No. 6. pp. 44–51.
8. Gorlova O. E., Sinyanskaya O. M., Tusupbekova T. Sh., Kolodezhnaya E. V. Flotation of copper smelter slags intensified by impact crushing. Tsvetnye Metally. 2023. No. 1. pp. 7–16.
9. Sinyanskaya O. M., Gorlova O. E. The use of impact crushers in the preparation of slag from the Balkhash copper smelter for flotation. Actual problems of modern science, technology and education. Abstracts of the 80th International scientific and technical conference. Magnitogorsk, April 18–22, 2022. Vol. 1. p. 36.
10. Fadeeva N. V., Orekhova N. N., Kolodezhnaya E. V., Nigmatova N. N. Study on the physical and chemical regularities of the kish graphite flotation process. Vestnik Magnitogorskogo Gosudarstvennogo Tekhnicheskogo Universiteta im. G. I. Nosova. 2022. Vol. 20, No. 4. pp. 37–46.
11. Laverty P. D., Nicks L. J., Walters L. A. Recovery of flake graphite from steelmaking kish. Report of investigations. U.S. Department of the Interior, 1994. 29 p.
12. Nicks L. J., Nehl F. H., Chambers M. F. Recovering flake graphite from steelmaking kish. JOM. 1995. Vol. 47. pp. 48–51.
13. Li J., Xu Z., Yang R., et al. Carbon cycle in a steelmaking mill: Recycling of kish graphite and its subsequent application for steelmaking carburant. Research Square. 19 September 2023. 18 p. DOI: 10.21203/rs.3.rs-3336245/v1
14. Karklit A. K., Aboskalov A. N. Graphite from metallurgical dust. Refractories and Industrial Ceramics. 1998. Vol. 39, pp. 334–336.
15. Li J., Liu R., Ma L., Wei L., Cao L., Shen W., Kang F., Huang Zh.-H. Combining multiple methods for recycling of kish graphite from steelmaking slags and oil sorption performance of kish-based expanded graphite. ACS Omega. 2021. Vol. 6. pp. 9868–9875.
16. Dmitriev A. V., Bocharnikov V. A., Velikodneva E. D., Basharin I. A. Chemical refining of flake cryptocrystalline graphite. Vestnik Yugorskogo Gosudarstvennogo Universiteta. 2014. Iss. 2. pp. 24–26.
17. Evseev N. S., Zhukov I. A., Belchikov I. A. A study of aerodynamics and fractional separation of fine particles in a separation chamber. Vestnik Tomskogo Gosudarstvennogo Universiteta. Matematika i Mekhanika. 2023. No. 83. pp. 74–85.
18. Zavyalov S. S., Mamonov R. S. Theoretical justification of pneumatic separation for copper sulfide ore enrichment. Gornyi Informatsionno-analiticheskiy Byulleten′. 2022. No. 11-1. pp. 199–209.
19. Krauze O., Buchczik D., Budzan S. Measurementbased modelling of material moisture and particle classification for control of copper ore dry grinding process. Sensors. 2021. Vol. 21, Iss. 2. DOI: 10.3390/s21020667