High Temperature Electrochemistry IV: Session III
Sponsored by: TMS Extraction and Processing Division, TMS: Nuclear Materials Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Prabhat Tripathy, Batelle Energy Alliance (Idaho National Laboratory); Guy Fredrickson, Idaho National Laboratory

Tuesday 2:00 PM
March 16, 2021
Room: RM 40
Location: TMS2021 Virtual

Session Chair: Michael Simpson, University of Utah


2:00 PM  
Validated Modeling of Quartzite Reduction to Solar Silicon by Molten Salt Electrolysis: Aditya Moudgal1; Mohammad Asadikiya1; Jacob Hazerjian1; Vicky Luu1; Ariana Ly1; Adam Powell1; Uday Pal2; Yu Zhong1; 1Worcester Polytechnic Institute; 2Boston University
    This talk presents a validated Finite Element Analysis (FEA) model of coupled current density distribution, fluid flow with magneto-hydrodynamics (MHD) and heat and mass transfer in molten salt electrolysis reduction of quartzite (SiO₂) to solar silicon. The electrolyte is MgF₂-CaF₂ eutectic with additions of CaO to enhance SiO₂ solubility, and YF₃ to reduce corrosion rate of yttria-stabilized zirconia (YSZ) solid oxide membrane (SOM) anodes. The FEA model and experiments show effects of stirring on current density distribution, of current and the boundary layer on electrolyte composition adjacent to the cathode and YSZ SOM, and of current density on temperatures and conductivities. The FEA model also estimates performance characteristics of an industrial silicon electrolysis cell, including MHD stirring using the magnetic field generated by the current bus (SOM anodes do not provide gas lift stirring). Finally, a techno-economic model estimates process cost, energy consumption, and direct and indirect greenhouse gas emissions.

2:30 PM  
A Comparative Study of Working Electrode Materials for Voltammetry Measurements in LiCl–Li2O Salts: Guoping Cao1; Ammon Williams1; Michael Shaltry1; 1Idaho National Laboratory
    For safeguards purposes in reprocessing spent nuclear fuels, it is desired to monitor the uranium oxide reduction (OR) process in LiCl‒Li2O salt system, and cyclic voltammetry (CV) has been proposed for monitoring the OR process. For long term CV monitoring of the OR process, a corrosion-resistant, durable working electrode (WE) is needed. In this study, different materials including 316SS, tantalum, molybdenum, tungsten, platinum, and iridium were evaluated as potential WE materials based on chemical inertness and sensitivity in detecting Li2O and other chloride salts in the OR electrolyte. The experimental results show that (1) when operated in the cathodic potential, 316SS exhibits reasonable corrosion resistance and sensitivity; (2) iridium can be operated in both cathodic and anodic potentials and is the most corrosion resistant; and (3) platinum is limited to the anodic potential range, exhibits reasonably good corrosion resistance, and is the most sensitive to Li2O concentrations in the salt.

3:00 PM  
Liquid Bipolar Electrode for Extraction of Aluminium and PGM Concentrate from Spent Catalysts: Andrei Iasinskii1; Peter Polyakov1; Dmitriy Varyukhin1; Sai Krishna Padamata1; 1Siberian Federal University
    Liquid bipolar electrodes (LBE) were proposed for the extraction of noble metals from spent catalysts by the electrometallurgical method with the production of aluminium and oxygen. The two-sectioned electrolysis cell divided by the LBE for the one-step extraction was designed. The first section acts as the aluminium reduction cell; the second one plays the role of the aluminium refinery cell. The noble metals are collected in the LBE while the carrier (Al2O3) is decomposed to oxygen and aluminium which is transferred through the second section to be collected in the cathode. The effect of the spent catalysts content in the melt on the electrode processes and carrier dissolution kinetics was studied for molten fluoride systems at 800 °C. The dissolution rate lays in the range from 0.0123 to 0.0291 g kg-1 s-1. The extraction of Pt to the LBE reached more than 99%. This method can be applied for the treatment of catalyst based on γ-Al2O3 carrier with a minor content of other oxides (SiO2, Fe2O3, MgO, TiO2, CeO2).