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Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part I: Analysis of the Anodic Gas Formation

  • Thematic Section: Green Rare Earth Elements--Innovations in Ore Processing, Hydrometallurgy, and Electrolysis
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Abstract

Neodymium metal is produced nowadays only via Chinese technology, by the electrolysis of neodymium oxide in a NdF3–LiF electrolyte at about 1050 °C. The process is not automated and is known to emit a large amount of perfluorocarbons (PFCs), with a tremendous greenhouse gas potential. The electrochemical system is analyzed by calculating the theoretical voltages of formation of the relevant anodic gas products. Linear voltammograms are conducted together with a simultaneous off-gas measurement to determine the dynamic behaviors of CO, CO2, CF4, and C2F6 in relation to the electrochemical behavior. The measurements show that the PFC emission starts with the occurrence of a partial anode effect, where the first CF4 is detected, and the anode is passivated partially. The direct enabling of CF4 formation activates the anode again, and at higher voltages, also C2F6 is formed. The critical current density and voltage of this partial anode effect are determined depending on the oxygen content of the electrolyte to be able to define a process window, with no PFC formation. An estimation of the off-gas emission continuously containing 7 % CF4 and 0.7 % C2F6 leads to an emission of about 20 million t CO2-eq. per year during the production of 30,000 t/a neodymium, which can explain a part of the gap between the amounts of atmospheric measured PFCs and the data from the aluminum and semiconductor industry. Minimizing the PFC emission must be the primary goal for the whole rare earth electrolysis.

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Notes

  1. Percentage in this work is by mass unless otherwise marked.

References

  1. Kingsnorth D (2015) The global rare earth industry today—plagued by illegal production in China. In: 11th International Rare Earth Conference, Metal Events Ltd’s, Singapore

  2. Gupta CK, Krishnamurthy N (2005) Extractive metallurgy of rare earths. CRC Press, Boca Raton, FL

    Google Scholar 

  3. Metal Events Ltd. (2014) Report of Metal Events Ltd’s 10th International Rare Earths Conference, 11–13 November 2014, Singapore

  4. Fu S (2007) Present condition of research and developing trend in the rare earth electrolysis cell. J Chin Rare Earth Soc 25:71–76 (Translated from Chinese)

    Google Scholar 

  5. Zhang Z (1995) The development of preparing RE metal by oxide electrolysis and the current situation in China. Non-ferr Metal Smelt 4:32–35 (Translated from Chinese)

    Google Scholar 

  6. Zhang Z et al (2001) Present situation and latest progress of process for producing metallic neodymium by electrolysis of neodymium oxide with fluoride salts. Non-ferr Smelt 30(2):23–25 (Translated from Chinese)

    Google Scholar 

  7. Wang J, Deng ZM, Zhang XL (2004) The test research on energy balance of 10 kA fluoride system in RE fused-salt electrolysis cell. Jiangxi Nonferr Metals 18(2):30–33 (Translated from Chinese)

    Google Scholar 

  8. Wen H et al (2004) Circular 10 kA molten salt electrolyzer for preparing rare earth metal. Ganzhou Keli Rare Earth New Materials Co., Ltd (CN 02240881.9) (Translated from Chinese)

  9. Vogel H, Friedrich B (2015) Development and research trends of the neodymium electrolysis—a literature review. In: GDMB (ed) Proceedings of the 8th European metallurgical conference (EMC) 2015

  10. Pang S et al (2011) Development on molten salt electrolytic methods and technology for preparing rare earth metals and alloys in China. Chin J Rare Metals 35(3):440–450 (Translated from Chinese)

    CAS  Google Scholar 

  11. Liu K-R et al (2001) Analysis of anodic gases in neodymium electrolysis. Chin J Nonferr Metals 11(6):1118–1121 (Translated from Chinese)

    CAS  Google Scholar 

  12. Keller R, Larimer KT (1997) Anode effect in neodymium oxide electrolysis. Rare Earths Sci Technol Appl III(IX):175–180

    Google Scholar 

  13. Li B, Liu S, Wang H, Zhao Z (2014) Electrochemistry for Nd electrowinning from fluoride-oxide molten salts. In: Neelameggham, NR et al (ed) Rare Metal Technology 2014 TMS, Warrendale, PA; Wiley, Hoboken, NJ, pp 95–98

  14. Zhang X, Deng Z, Wang J, You H (2003) Continuous electrolysis of RE metals with block-like multi-anodes. Jiangxi Nonferr Metals 17(3):28–30 (Translated from Chinese)

    CAS  Google Scholar 

  15. Cheng YD, Liang Y, Tao D (2011) Clean production technology in electrolysis process in a rare earth plant. Chin Rare Earths 32(5):92–96 (Translated from Chinese)

    Google Scholar 

  16. Ou YH, Zhou CS (2006) Study on the recovery and utilization of smoke dust in rare earth electrolysis. Jiangxi Nonferr Metals 20(1):33–36 (Translated from Chinese)

    Google Scholar 

  17. Chase R et al (2005) PFC emissions performance for the global primary aluminum industry. In: Kvande, H (ed) Light Metals 2005, pp 279–282

  18. Marks J (1998) PFC emission measurements from ALCOA aluminum smelters. In: Welch BJ (ed) Light Metals 1998, TMS, Warrendale, PA, pp 287–291

    Google Scholar 

  19. Thonstad J, Sverre R, Keller R (2013) On the mechanism behind low voltage PFC emissions. In: Sadler B (ed) Light Metals 2013. TMS, Warrendale, PA; Wiley, New York, pp. 883–885

    Google Scholar 

  20. Vogel H, Friedrich B (2016) Reducing greenhouse gas emission from the neodymium oxide electrolysis: Part II. Basics of a process control avoiding PFC emissions. J Sustain Metall (unpublished article)

  21. Stefanidaki E, Hasiotis C, Kontoyannis C (2001) Electrodeposition of neodymium from LiF–NdF3–Nd2O3 melts. Electrochim Acta 46(17):2665–2670. doi:10.1016/S0013-4686(01)00489-3

    Article  CAS  Google Scholar 

  22. Stefanidaki E, Photiadis GM, Kontoyannis CG et al (2002) Oxide solubility and Raman spectra of NdF3–LiF–KF–MgF2–Nd2O3 melts. J Chem Soc Dalton Trans 11:2302–2307. doi:10.1039/b111563b

    Article  CAS  Google Scholar 

  23. Liu KR et al (2001) Theoretical decomposition voltage for some related substance on neodymium electrolysis. Chin Rare Earths 22(2):30–33 (Translated from Chinese)

    CAS  Google Scholar 

  24. Thonstad J, Utigard TA, Vogt H (2000) On the anode effect in aluminum electrolysis. In: Peterson RD (ed) Light Metals 2000, TMS, Warrendale, PA, pp 131–138

  25. Neumüller O (1979) Römpps Chemie-Lexikon. Franckh’sche Verlagshandlung, Stuttgart

    Google Scholar 

  26. Groult H et al (2007) Characteristics of the fluorocarbon surface film generated on carbon anode during F2 evolution in molten KF–2HF. J Electrochem Soc 154(6):331–338

    Article  Google Scholar 

  27. Bai L, Conway BE (1990) Electrochemistry of anodic fluorine gas evolution at carbon electrodes: Part II. Studies on the ‘CF’ film by the current-interruption, AC impedance, ESCA and auger techniques. J Appl Electrochem 20(6):916–924. doi:10.1007/BF01019566

    Article  CAS  Google Scholar 

  28. Vogt H (2013) On the various types of uncontrolled potential increase in electrochemical reactors—the anode effect. Electrochim Acta 87:611–618. doi:10.1016/j.electacta.2012.09.051

    Article  CAS  Google Scholar 

  29. Hall C (2009) Key greenhouse gases and global warming potentials. http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm. Accessed 24 Feb 2016

  30. Iffert M, Opgen-Rhein J, Ganther R (2002) Reduction of CF4 emissions from the aluminum smelter in Essen. In Schneider W (ed) Light Metals 2002, pp. 297–304

  31. Wong DS, Fraser P, Lavoie P et al (2015) PFC emissions from detected versus nondetected anode effects in the aluminum industry. JOM 67:342–353. doi:10.1007/s11837-014-1265-8

    Article  CAS  Google Scholar 

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Authors and Affiliations

  1. IME Institute of Process Metallurgy and Metal Recycling, RWTH Aachen University, Intzestraße 3, Aachen, Germany

    Hanno Vogel, Benedikt Flerus, Felix Stoffner & Bernd Friedrich

Authors
  1. Hanno Vogel
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  2. Benedikt Flerus
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  3. Felix Stoffner
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  4. Bernd Friedrich
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Correspondence to Hanno Vogel.

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The contributing editor for this article was Bart Blanpain.

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Vogel, H., Flerus, B., Stoffner, F. et al. Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part I: Analysis of the Anodic Gas Formation. J. Sustain. Metall. 3, 99–107 (2017). https://doi.org/10.1007/s40831-016-0086-0

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  • DOI: https://doi.org/10.1007/s40831-016-0086-0

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