Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part II: Basics of a Process Control Avoiding PFC Emission - International Journal of Nonferrous Metallurgy

IJNM > Vol.6 No.3, July 2017

International Journal of Nonferrous Metallurgy

Volume 6, Issue 3 (July 2017)

ISSN Print: 2168-2054 ISSN Online: 2168-2062

Google-based Impact Factor: 0.63 Citations

Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part II: Basics of a Process Control Avoiding PFC Emission ()

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DOI: 10.4236/ijnm.2017.63003 1,554 Downloads 3,129 Views Citations

Author(s)

Hanno Vogel, Bernd Friedrich

Affiliation(s)

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

ABSTRACT

The neodymium electrolysis produces unnecessary high emission of CF₄ and C₂F₆. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy to the aluminum electrolysis can reduce the PFC emission to a great extend and keep the process in a green process window. Therefore, a theoretical analysis is done of the cell voltage of the industrial neodymium electrolysis in dependence on the neodymium oxide concentration in the electrolyte. The analysis shows the different contributions to the cell voltage focusing on the impact of the anodic overvoltage on the cell voltage, by which the electrolysis process can be controlled. The model of the cell voltage is evaluated by laboratory neodymium electrolysis with a similar setup as the industrial cell. The relation of the oxide concentration, the anodic current density and the cell voltage with the cell resistance are measured. The continuous off-gas measurements show the gas concentration and PFC emissions. The effect of Nd₂O₃ feeding on the galvanostatic electrolysis is analyzed as well. Based on the results a process control strategy is proposed similar to the aluminum electrolysis strategy. The green process window is in a narrow oxide concentration range, making a continuous and precise oxide feeding essential.

KEYWORDS

Rare Earth, Neodymium, Electrolysis, Greenhouse Gas Emission, Process Control

Share and Cite:

Vogel, H. and Friedrich, B. (2017) Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part II: Basics of a Process Control Avoiding PFC Emission. International Journal of Nonferrous Metallurgy, 6, 27-46. doi: 10.4236/ijnm.2017.63003.

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