“RUSAL Engineering-Technological Center” LLC, Saint Petersburg, Russia:

D. V. Finin, Principal Researcher of the Pyrometallurgical Group, Process Engineering Department, Alumina Production Office

“RUSAL Achinsk” JSC, Achinsk, Russia:
A. V. Kuranov, Senior Foreman Sintering Process

Siberian Federal University, Krasnoyarsk, Russia:
O. N. Kovtun, Associate Professor at the Department of General Metallurgy, e-mail: okovtun28@yandex.ru
L. P. Kolmakova, Associate Professor at the Department of Non-Ferrous Metallurgy, e-mail: kolmakoval2010@mail.ru

Sintering of nepheline ores at alumina refineries is an energy consuming process involving considerable operating costs. RUSAL Achinsk – or, Achinsk Alumina Refinery – has a number of competitive advantages such as being located close to the source of raw materials and consumers of metallurgical alumina, having their own thermal power plant running on cheap coal and making by-products, which make it one of the most cost-effective companies of the group. Optimisation of rotary kiln process involving optimised chemical composition and size distribution of burden, enhanced heat transfer, reduced heat losses and increased kiln unit power has almost reached its limit. Solutions that can revolutionize sintering process due to adoption of different instruments are still under development and will require capital investment. Considering that fuel accounts for a great share of the cost, one of the ways to reduce sintering costs would be identifying and adopting less expensive fuel. For RUSAL Achinsk, such less expensive fuel would be black coal from the Kuznetsk deposit and low-ash brown coal from the Kansk-Achinsk basin. Compared with black coal, brown coal has lower calorific capacity, high humidity, high volatile-matter content and low ash content. The paper features thermograms of black and brown coals produced by simultaneous thermal analyser. The thermograms indicate that the combustion of brown coal is more intense and initiates sooner, which, under otherwise equal conditions, will provide a short inflexible flame and will require corrections to the combustion mode for achieving desired cake quality. The difference between the sintering process relying on brown coal versus the one relying on black coal is shown in distribution bar charts for burden and dust consumption and temperature. The obtained data suggest that the adoption of pulverized brown coal would ensure uncompromised kiln efficiency and cake quality.

1. Finin D. V., Barbakadze L. G., Nurgaliev R. F., Teliatnikov G. V., Panov A. P. Operational Efficiency Evaluation of Rotary Sintering Kilns and Calciners at JSC RUSAL Refineries. 17^th International symposium of ICSOBA. Montreal, Canada, 2006. pp. 302–311.
2. Cherkasova M. V., Brichkin V. N. Current trends in processing of low-quality aluminium materials and how they influence the alumina raw materials base. Gornyy informatsionno-analiticheskiy byulleten. 2015. No. 19. pp. 167–172.
3. Finin D. V., Barbakadze L. G., Staroverov A. A., Telyatnikov G. V. Developing the process of alumina sintering at RUSAL sites. Tekhniko-Ekonomicheskiy Vestnik RUSALa. Glinozemnoe proizvodstvo. 2007. No. 18. pp. 39–43.
4. Wang Xing Li. Alumina production theory & technology. Changsha : Central South University. 2010. 411 p.
5. Aleksandrov A. V., Nemchinova N. V., Fedotova E. A. Improving the quality of aluminium-containing cake in a rotary kiln. Processing of natural and man-made materials : Research papers. Irkutsk : PRINTU, 2016. pp. 57–60.
6. Kozlov A. A., Kolmakova L. P., Kovtun O. N. Analysing burden preparation for nepheline ore sintering at Rusal-Achinsk JSC. Eurasian Union of Scientists (ESU). 2018. No. 11. Part 8. pp. 20–22.
7. Aleksandrov A. V. Optimisation of alumina production through achieving optimum phase composition of nepheline cake : PhD dissertation. Irkutsk, 2017. p. 157.
8. Finin D. V., Gorbachev S. N., Kravchenya M. A. Use of brown coal for alumina sintering at alumina refinery. Proceedings of the 31^st International Conference IKSOBA of the 19^th International Conference “Aluminium of Siberia” – 2013 : Research papers. Krasnoyarsk : Verso, 2013. pp. 420–425.

9. Detkov S. P., Borzov A. I., Goncharov N. V., Mavrin V. A. The relevance of onsite processing of coal from the Kansk-Achinsk basin. Ugol. 2003. No. 7. pp. 47–49.
10. Roy D. M. Studies in the System CaO – Al₂O₃ – SiO₂ – H₂O: III, New Data on the Polymorphism of Ca₂SiO₄ and Its Stability in the System CaO – SiO₂ – H₂O. Journal of the American Ceramic Society. 1958. Vol. 41, No. 8. pp. 293–304.
11. Smith D. K., Majumdаr A., Ordway F. The crystal structure of γ-dicalcium silicate. Acta Crystallographica. 1965. Vol. 17. pp. 787–795.
12. Anikeev V. I., Dolgireva K. I., Skoptsov A. M. Adoption of coal as fuel for sintering kilns. Aluminium of Siberia – 2001 : Research papers. Krasnoyarsk, 2001. pp. 279–283.