Siberian Federal University, School of Non-Ferrous Metals and Material Science, Krasnoyarsk, Russia

S. А. Khramenko, Associate Professor of the Department of Metallurgy of Non-Ferrous Metals, Candidate of Technical Sciences, e-mail: Sergey.khramenko@mail.ru

Siberian Federal University», School of Mining Geology and Geotechnology, Krasnoyarsk, Russia

А. N. Anushenkov, Head of the Department of Underground Mining, Doctor of Technical Sciences, e-mail: Aanushenkov@sfukras.ru

LLC The Engineering and Technology Centre (RUSAL ETC), Krasnoyarsk, Russia

S. А. Zykov, Manager

In the Soderberg technology with an upper current line, the anode is formed as a result of self-sealing of the anode mass in the zone of the plastic coke-pitch composition, while as a result of the sublimation of volatile components of pitch and coke, a stream of coking gases is created, and porosity is formed. The purpose of the work is to determine and numerically evaluate the role of porosity in the gasification of anodes. For this purpose, cores were taken from disconnected electrolyzers, from which samples from different temperature zones were obtained. To evaluate the gasification of the Soderberg anode, samples of the material of self-igniting anodes of aluminum electrolyzers that were shut down during major repairs were examined. Cores with a diameter of 50 mm were taken by vertical drilling of the anode. The total length of the sample was 130 cm. After excluding the unroasted upper part of the core, which was unsuitable for conducting preliminary physico-mechanical tests, the samples were divided into five parts with a length of 20 cm. Standard physico-chemical properties and pore size distribution were studied on these samples (using mercury porosimetry). The determination of mercury porosity of carbon and other porous materials has a number of features that relate to the nature of the interaction of most materials with mercury. Under normal conditions, mercury does not wet and impregnate porous materials well. Therefore, mercury porosimeters are used to study porosity, which can create high pressure up to 60 tons in small volumes. The device consistently pumps mercury into the porous structure, filling first the large pores, then the small ones. Therefore, the pore size distribution curve has the opposite direction from large to small pores. The results of vertical probing of the anode showed that the porosity of the ano de of the 930 ^oC isotherm represents a system of large pores with a size from 30 to 6 microns, with an increase in temperature to 940–950 ^oC, the porosity transforms into a pore system with the appearance of an additional maximum in the range of 2.6...0.14 microns. It is shown that pores with a size of 2.6...0.14 microns are the most active in CO2 gasification of the Soderberg anode and increase its excess consumption by 18.2%. Reducing unproductive consumption can be achieved by reducing porosity at the stage of anode formation and adjusting the depth of immersion of the anode in the electrolyte.

1. Yanko E. А. Anodes of aluminum electrolyzers. Мoscow: Ruda i Metally, 2001. 670 p.
2. Engvoll M. A., Oye H. A., Sorlie M. Gas reactivity inside industrial anodes. Light Metals. 2002. pp. 561–568.
3. Ziegler D. P. Sub-surface carbon dioxide reaction in anodes. Light Metals. 2011. pp. 901–906.
4. Feng B., Bhatia S. K. Variation of the pore structure of coal chars during gasification. Carbon. 2003. Vol. 41, Iss. 3. pp. 507–523.
5. Furquim B. D., Pomarico W., Ferra o F., Fernandes R. S., Maestrelli S. C. Dry aggregate particle size distribution optimization for Soderberg anode paste production applied to aluminum industry. Mater. Sci. Forum. 2014. Vol. 802. pp. 291–296.
6. Putri E., Brooks G., Snook G. A., Lossius L. P. et al. Diffusion measurements of CO2 within carbon anodes for aluminium smelting. Light Metals. 2020. pp. 1183–1888.
7. Sadler B. A., Algie S. H. A porosimetric study of sub-surface carboxy oxidation in anodes. Light Metals. 1991. pp. 594–605.
8. Putri E., Brooks G., Snook G. A., R rvik S. et al. Understanding the anode porosity as a means for improved aluminium smelting. Light Metals. 2018. pp. 1235–1242.
9. Khramenko S. A., Cherskih I. V. et al. Investigation of a self-igniting anode by vertical probing. Vestnik RUSALa. 2012. No. 1. pp. 14–20.
10. Solheim A. Practical implications of some interfacial processes in alumina reduction cells. 11 th Austral Asian Aluminium melting Technology Conference. Dubai, United Arab.
11. Buzunov V. Yu., Zykov S. A., Khramenko S. A.Developing a technique to estimate the anode paste impregnation degree. Tsvetnye Metally. 2018. No. 11. P. 51–55.
12. Buzunov V. Yu., Zykov S. A., Khramenko S. A. Pre-baked anode structure and properties as a function of the Blaine number. Tsvetnye Metally. 2022. No. 5. P. 41–47.