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Application of Circuit Analysis to the Simulation of Rare Earth
Element Solvent Extraction Circuits
Kris Strickland, Aaron Noble
Virginia Tech
Tom Larochelle
L3 Process Development
Paul Ziemkiewicz
West Virginia University
ABSTRACT: The chemical similarity of the rare earth elements (REEs) necessitates large and complex solvent
extraction (SX) separation circuits. While in theory, simulation can be used to facilitate the design process, in
practice the effort required to build and calibrate a simulation model coupled with the scale and complexity of
these SX circuits dramatically increase the computational resources needed to accurately model the process. This
complexity in turn makes them difficult to optimize in a rigorous manner. The current work builds upon prior
chemical equilibrium-based models (e.g., Larochelle and Kasaini (2016) Turgeon et al. (2023)) by applying a
novel circuit analysis framework for multi-unit SX circuits. This approach significantly improves computation
efficiency and provides tractable methodology for circuit optimization.
INTRODUCTION
Rare Earth Elements (REEs) are considered critical materi-
als by many international organizations given their preva-
lence in technology and defense applications as well as their
high potential for supply chain disruptions. While several
ore deposits and unconventional resources show economic
potential, numerous challenges in the downstream benefici-
ation, separation, and refining restrict the number of viable
REE sources. Of particular note, the chemical and physi-
cal similarity of the REEs makes the separation of adjacent
REEs particularly challenging. This challenge is then inten-
sified given the high purity requirements for individually
separated rare earth end products and tight tolerances on
impurities.
Currently, solvent extraction (SX) using phosphorus-
based acidic extractants is the most widely used process
for the separation of REEs. Nascent technologies, such
as ion exchange (Chen et al., 2022), ion chromatography
(Fernández and García Alonso 2008 Inoue et al., 1996),
molecular recognition (Seisenbaeva 2020), ionic liquid-
based separation (Chi-Linh Do-Thanh, Huimin Luo, and
Sheng Dai 2023 Kaim, Rintala, and He 2023), and oth-
ers (Chen et al., 2022) have been proposed and are under
development. However, there are no reports of commer-
cial implementation at scale. Solvent extraction remains
the preferred method, given its robustness, operability,
and proven capability in producing high purity products.
Conversely, solvent extraction circuits operate on subtle dis-
tinctions in chemical affinity due to their similar electronic
Application of Circuit Analysis to the Simulation of Rare Earth
Element Solvent Extraction Circuits
Kris Strickland, Aaron Noble
Virginia Tech
Tom Larochelle
L3 Process Development
Paul Ziemkiewicz
West Virginia University
ABSTRACT: The chemical similarity of the rare earth elements (REEs) necessitates large and complex solvent
extraction (SX) separation circuits. While in theory, simulation can be used to facilitate the design process, in
practice the effort required to build and calibrate a simulation model coupled with the scale and complexity of
these SX circuits dramatically increase the computational resources needed to accurately model the process. This
complexity in turn makes them difficult to optimize in a rigorous manner. The current work builds upon prior
chemical equilibrium-based models (e.g., Larochelle and Kasaini (2016) Turgeon et al. (2023)) by applying a
novel circuit analysis framework for multi-unit SX circuits. This approach significantly improves computation
efficiency and provides tractable methodology for circuit optimization.
INTRODUCTION
Rare Earth Elements (REEs) are considered critical materi-
als by many international organizations given their preva-
lence in technology and defense applications as well as their
high potential for supply chain disruptions. While several
ore deposits and unconventional resources show economic
potential, numerous challenges in the downstream benefici-
ation, separation, and refining restrict the number of viable
REE sources. Of particular note, the chemical and physi-
cal similarity of the REEs makes the separation of adjacent
REEs particularly challenging. This challenge is then inten-
sified given the high purity requirements for individually
separated rare earth end products and tight tolerances on
impurities.
Currently, solvent extraction (SX) using phosphorus-
based acidic extractants is the most widely used process
for the separation of REEs. Nascent technologies, such
as ion exchange (Chen et al., 2022), ion chromatography
(Fernández and García Alonso 2008 Inoue et al., 1996),
molecular recognition (Seisenbaeva 2020), ionic liquid-
based separation (Chi-Linh Do-Thanh, Huimin Luo, and
Sheng Dai 2023 Kaim, Rintala, and He 2023), and oth-
ers (Chen et al., 2022) have been proposed and are under
development. However, there are no reports of commer-
cial implementation at scale. Solvent extraction remains
the preferred method, given its robustness, operability,
and proven capability in producing high purity products.
Conversely, solvent extraction circuits operate on subtle dis-
tinctions in chemical affinity due to their similar electronic