ON THE FORMATION OF PERFLUOROCARBONS DURING NORMAL TECHNO-LOGICAL PROCESS OF OBTAINING ALUMINUM (THERMODYNAMIC ANALYSIS)

Autor: Mikhalev Yu.
Jazyk: ruština
Rok vydání: 2023
Předmět:
DOI: 10.5281/zenodo.7827806
Popis: The change in the Gibbs energy of the reaction occurring during the production of aluminum at the anode and taking into account the joint formation of carbon oxides CO2 and CO and perfluorocarbons CF4 and C2F6 during a normal technological process, and the electrode potential of the anode relative to aluminum are calculated. It is shown that the formation of perfluorocarbons during electrolysis together with carbon oxides is thermodynamically possible even near the equilibrium potential of the anode (≈ 1.2 V), and even more so when the back EMF reaches ≈1.8 V at industrial anode current densities. However, according to measurements on industrial cells in normal electrolysis, the concentration of perfluorocarbons in the off-gases is estimated at an average of 0.02%. The discrepancy between the results of thermodynamic analysis and measurements is explained by the reactions of CF4 and C2F6 with water vapor directly or with the participation of oxygen on the path of gases from the anode base to the sampling point. Аннотация Рассчитаны изменение энергии Гиббса реакции, протекающей при получении алюминия на аноде и учитывающей совместное образование оксидов углерода CO2 и CO и перфторуглеродов CF4 и C2F6 при нормальном технологическом процессе, и электродный потенциал анода относительно алюминия. Показано, что образование при электролизе перфторуглеродов совместно с оксидами углерода термодинамически возможно даже вблизи равновесного потенциала анода (≈ 1,2 В) и тем более, когда обратная ЭДС при промышленных плотностях анодного тока достигает ≈1,8 В. Однако согласно измерениям на промышленных электролизерах при нормальном электролизе концентрация перфторуглеродов в отходящих газах в среднем оценивается в 0,02%. Расхождение между результатами термодинамического анализа и измерений объясняется протеканием реакций CF4 и C2F6 с водяным паром непосредственно или с участием кислорода на пути газов от подошвы анода до места отбора проб.
Список литературы: 1. Ветюков М.М., Цыплаков А.М., Школьников С.Н. Электрометаллургия алюминия и магния. – М.: Металлургия, 1987. – 320 с. 2. Doreen M. M.R., Chin D. L., Lee J. K.C., Hyland M., Welch B.J. Sulfur and fluorine containing anode gases produced during «normal» electrolysis and approaching an anode effect // Light Metals.1998. P. 311 – 316. 3. Grjotheim K., Krohn C., Malinovsky M., Matiasovsky K., Thonstad J. Aluminium elec-trolysis. Fundamentals of hall-Heroult process.2nd edition. –Aluminium -Verlag, Dusseldorf. 1982. – 443 p. 4. Thonstad J., Felner P., Haaberg G.M., Hives J., Kvande H., Sterten A. Aluminium elec-trolysis. Fundamantal of Hall-Heroult process.3nd edition. –Aluminium -Verlag, Dusseldorf. 2001. – 359 p. 5. Dorreen M.M.R., Hyland M.M., Haverkamp R.G., Metson J.B., Jassim A., Welch B.J., Tabereaux A.T. Co-evolution of carbon oxides and fluorides during the electrowinning of alumini-um with molten NaF–AlF3–CaF2–Al2O3 electrolytes//Light Metals. 2017. P. 533 – 539. 6. Henry J. L., Hollida R. D. Mass spectrometric examination of anode gases from aluminum reduction cells // Journal of Metals. 1957. P. 1384 – 1385. 7. Thonstad J., Utne I., Paulsen K.A., Svensen G. Sulphurous gases in aluminium electroly-sis // Proc. 6th Aust. Al smelting workshop. 1998. P. 369 – 380. 8. Li J., Li T., Zhang H., Wang J., Sun K., Xiao J. DFT Study on COS oxidation reaction mechanism // Light Metals. 2019. P.879 – 884. 9. Aarhaug T. A., Ratvik A. P.. Aluminium primary production off-gas composition and emissions: an overview // Journal of Metals. 2019. V.71, No. 9, P. 2966 – 2977. 10. Wong D. S., Marks J. Continuous PFC emissions measured on individual 400 kA cells// Light Metals. 2013. P. 865 – 870. 11. Wang G., Wang X., Zhu H. Perflourocarbon generation during electrolysis in molten fluoride//Energy Technology. 2011. P.131 – 135. 12. Milicevic K., Feldhaus D., Friedrich B. Conditions and mechanisms of gas emissions from didymium electrolysis and its process control //Light Metals. 2018. P.1435 – 1441. 13. Kjos O. S., Solheim A., Aarhaug T., Osen K. S., Martinez A. M., Sommerseth C., Gud-brandsen H., Støre A., Gaertner H. PFC evolution characteristics during aluminium and rare earth electrolysis // Light Metals. 2018. P.1449 – 1455. 14. Osen K. S., Martinez A. M., Gudbrandsen H., Støre A., Sommerseth C., Kjos O., Aar-haug T. A., Gaertner H., Chamelot P., Gibilaro M., Massot L. Perfluorocarbon formation during rare earth electrolysis // Light Metals 2018.P.1443 – 1448. 15. Fraser P., Steele P., Cooksey M. PFC and carbon dioxide emissions from an Australian aluminium smelter using time-integrated stack sampling and Gc-Ms, Gc-Fid analysis// Light Metals. 2013, P.871 – 876. 16. Marks J. Y. Trends in pot room emissions // Ninth Australasian aluminium smelting technology conference and workshops. 2007. 8 p. 17. Kjos O. S., Aarhaug T. A., Skybakmoen E., Solheim A. Studies of perfluorocarbon for-mation on anodes in cryolite melts // Light Metals. 2012. P. 623 – 626. 18. Fraser P., Trudinger C., Dunse B., Krummel P., Steele P., Etheridge D., Derek N., Por-ter L., Miller B. PFC emissions from global & Australian aluminium production // Ninth Australasian aluminium smelting technology conference and workshops. 2007. 6 p. 19. Минцис М.Я., Поляков П.В., Сиразутдинов Г.А. Электрометаллургия алюминия. – Новосибирск: Наука. 2001. –368 с. 20. Tabereaux A.T., Wong D. S. Awakening of the aluminum industry to PFC emissions and global warming // Light Metals. 2021. P. 554 – 564. 21. Batista E., Espinoza-Nava L., Tulga C., Marcotte R., Duchemin Y., Manolescu P. Low voltage PFC measurements and potential alternative to reduce them at Alcoa smelters // Light Met-als. 2018. P. 1463 – 1467. 22. Marks J., Nunez P. Updated factors for calculating PFC emissions from primary alumin-ium production// Light Metals. 2018. P. 1519 – 1525. 23. Li W., Xiping C., Jianhong Ya., Changping H., Yonggang L., Defeng L., Huifang G. Latest results from PFC investigation in China // Light Metals . 2012. P.619 – 622. 24. Åsheim H., Aarhaug Th. A., Ferber A., Kjos O. S., Haarberg G. M. Monitoring of con-tinuous PFC formation in small to moderate size aluminium electrolysis cells// Light Metals. 2014. P.535 – 539. 25. 25 Gylver. S. E., Follo Å. H., Aulie V., Granlund H. M., Sørhuus A., Sandnes E., Einarsrud K. E. On gaseous emissions during alumina feeding // Light Metals. 2021.P. 504 – 510. 26. Tabereaux A.T., Richards N.E., Satchel C.E., Composition of Reduction Cell Anode Gas During «normal» Conditions and Anode Effects//Light Metals. 1995. P. 325 – 333. 27. Batista E., Dando N. R., Menegazzo N., Espinoza-Nava L. Sustainable reduction of an-ode effect and low voltage PFC emission // Light Metals. 2016. P. 537 – 540. 28. Li W., Zhao Q., Qiu S., Zhang S., Chen X. PFC survey in some smelters of China // Light Metals. 2011. P. 357 – 360. 29. Marks J., Bayliss C. GHG measurement and inventory for aluminum production // Light Metals. 2012. P. 805 – 808. 30. Wang D.S., Marks J. Continuous PFC emissions measured on individual 400 kА cells // Light Metals. 2013. P. 865 – 870. 31. Jassim A., Akhmetov S., Welch B. J., Skyllas-Kazacos M., Bao J., Yao Yu. Studies on Background PFC (mission in Hall-Héroult reduction cells using online anode current signals // Light Metals. 2015. P. 545 – 550. 32. Jassim A., Jabri N. A., Akhmetov S., Whitfield D., Welch B. Toward minimizing the of co-evolution of PFC emission in EGA smelter // Light Metals. 2020. P. 817 – 826. 33. Zarouni A. A., Zarouni A. A. DUBAL's experience of low voltage PFC emissions // Proceedings of the 10th Australasian aluminium smelting technology conference. 2011. 7 р. 34. Solheim A. Reflections on the low-voltage anode effect in aluminium electrolysis cells// Light Metals. 2022. P. 971 – 978. 35. Москвитин В. И., Николаев И.В., Фомин Б.А. Металлургия легких металлов. –М.: Интермет Инжиниринг. 2005. – 416 с. 36. Gudbrandsen H., Richards N., Rolseth S., Thonstad J. Field study of the anodic over-voltage in prebaked anode cells //Light Metals.2003. P. 323 – 328. 37. Cheung C., Menictas C., Bao J., Skyllas-Kazacos M., Welch B. J. Frequency response analysis of anode current signals as a diagnostic aid for detecting approaching anode effects in alu-minum smelting cells // Light Metals.2013. P. 887 – 892. 38. Dubois C., Espinoza-Nava L. Low and high voltage PFC slope coefficient monitoring during pot start-up // Light Metals. 2021. P. 432 – 440. 39. Espinoza-Nava L., Dubois Ch., Batista E. Method development to estimate total low voltage and high voltage PFC emissions // Light Metals. 2020. P.758 – 765. 40. Haupin W.. Interpreting the components of cell voltage // Light Metals. 1998. P.531 – 537. 41. Коган В.Б. Теоретические основы типовых процессов химической технологии. –Л.: Наука. 1977. – 592 с. 42. Герасимов Я.И., Древинг В.П., Еремин Е.Н. и др. Курс физической химии. Т.1. – М.: Химия, 1970. – 592 с. 43. Haupin W., Kvande H. Mathematical model of fluoride evolution from Hall-Heroult cells // Proceeding of the international Jomar Thonstad symposium. Norway, Trondheim. 2002. P.53 – 65. 44. Grjotheim K., Kvande H. Introduction to aluminium electrolysis. –Aluminium-Verlag, Dusseldorf. 1993. – 260 p. 45. Haupin W., Kvande H. Thermodynamics of electrochemical reduction of alumina // Light Metals. 2000. P. 379 – 384. 46. Haupin W., Seger E.J. Aiming for zero anode effects// Light metals. 2001. P. 329 – 335. 47. Tabereaux A. Maximum anode effect voltage // Light metals. 2005. P. 405 – 410. 48. Nissen S. S., Sadoway D. R. Perfluorocarbon (PFC) generation in laboratory-scale alu-minum reduction cells // Light Metals.1997. P. 159 – 164. 49. Thonstad J., Utigard T.A., Vogt H. On the anode effect in aluminum electrolysis // Light Metals. 2000. P. 249 – 256.
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