Applications of Process Engineering Principles in Materials Processing, Energy and Environmental Technologies: An EPD Symposium in Honor of Professor Ramana G. Reddy: Electrometallurgy
Sponsored by: TMS Extraction and Processing Division, TMS Light Metals Division, TMS: Energy Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Shijie Wang, Rio Tinto Kennecott Utah Copper; Michael Free, University of Utah; Shafiq Alam, University of Saskatchewan; Mingming Zhang, Arcelor Mittal; Patrick Taylor, Colorado School of Mines
Monday 2:00 PM
February 27, 2017
Location: San Diego Convention Ctr
Session Chair: Shijie Wang, Rio Tinto Kennecott Utah Copper
Modeling of Aluminum Electrowinning in Ionic Liquid Electrolytes: Mingming Zhang1; Ramana Reddy2; 1ArcelorMittal Global R&D; 2The University of Alabama
A 3D mathematical model was developed for the batch reactor of aluminum electrowinning in ionic liquid electrolytes. This model describes the deposition process by incorporating the mass transport of participating ionic species, homogeneous chemical reactions within the diffusion layer, and the associated electrochemical kinetics. A number of process parameters affecting the current distribution were evaluated for optimal reactor performance, including current and potential distributions, concentration profiles, fluid flow distribution, and electrode configurations. The results indicated that the electrode configuration significantly affects the electrolyte fluid flow and current density distribution. The parallel electrode configuration (in line with electrolyte inlet) improved the convection and resulted in homogenous current density distribution as well as electrolyte fluid flow streamline and electroactive species distribution. Perpendicularly configured electrode resulted in a more complex hydraulic circuit within electrolyte domain, which has potential to cause non-homogenous deposits.
Electrochemical Processing of Rare Earth Alloys: Karen Osen1; Ana Maria Martinez1; Henrik Gudbrandsen1; Anne Store1; Ole Kjos1; 1SINTEF Materials and Chemistry
The light rare earth metals Nd, Pr, La, Ce as well as some alloys with Fe, are today produced in China by electrolysis in molten fluorides using oxide raw materials. A major challenge is to obtain a good cell operation without de-composing the electrolyte leading to emissions of perfluorinated carbon (PFC) green-house gases to the atmosphere. This work is focused on understanding the fundamental requirements to run the electrolysis cells for DyFe alloy production in an efficient and environmental friendly way. Electrolysis experiments was carried out in DyF3-LiF melts at 1050 °C. A Fe rod was used as consumable cathode and the (consumable) anode was made of graphite. To establish at which anode potential PFC occurred and thus enabling optimisation of the oxide batch feed rate, analysis of the anode gases was performed with Fourier Transform Infrared Spectrometer FTIR. The produced DyFe alloy was characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS).
Effect of Cobalt Concentration on the Potential for Oxygen Evolution from Pb-Ca-Sn Anodes in Synthetic Copper Electrowinning Electrolytes: Charles Abbey1; Michael Moats1; 1Missouri University of Science and Technology
It is well known that the addition of cobalt to copper sulfate - sulfuric acid electrolytes decrease the overpotential for oxygen evolution and decrease the rate of corrosion for Pb-Ca-Sn anodes. This effect, however, has not been adequately quantified in the presence of iron and manganese in these types of electrolytes. This work provides quantifiable data on the effect of cobalt concentration in range of 0 and 0.6 g/L in synthetic electrowinning electrolytes with and without the presence of iron. The effect of cobalt on anode potential was determined using 2 and 24 hour chronopotentiometry experiments followed by oxidized Pb-Ca-Sn surface characterization using electrochemical and physical methods. As expected, Pb-Ca-Sn potentials increased with decreased cobalt concentration over the range of 0-0.6 g/L Co. Two regression models were developed to allow plant operators the ability to predict anode potential as a function of [Co] with or without iron in the electrolyte.
Corrosion Resistance of Ni-P-Zn Alloy Deposit Coated Using a Sulfate Electroless Bath: Amir Kordijazi1; Mohsen Manjili1; 1University of Wisconsin–Milwaukee
Effect of Ni-P-Zn electroless bath parameters, such as concentration of reactants, pH level and deposition time, on corrosion characteristics of as-plated coatings were investigated. Energy Dispersive Analysis of X-ray (EDAX) was performed to calculate chemical composition of the deposited coatings. SEM imaging has been employed in order to study the surface morphology of the coated samples. Corrosion resistances of the obtained coatings were tested via potentiodynamic polarization experiment. According to the results, the optimal bath composes 10 g/l and 15 g/l of reducing agent and zinc agent, respectively. The pH value showed an amount of 10.5 and deposition time is 60 min. The solution results a coating layer which shows the best corrosion resistance with corrosion current density of 0.23 µA/cm².
3:40 PM Break
Cobalt Electrodeposition from Cobalt Chloride Using Urea and Choline Chloride Ionic Liquid: Effect of Temperature, Applied Voltage, and Cobalt Chloride Concentration on Current Efficiency and Energy Consumption: Andrea Kim1; Ramana Reddy1; 1University of Alabama
Electrodeposition of cobalt from cobalt chloride using the urea and the choline chloride ionic liquid (2:1 molar ratio) was studied to search the optimized parameters for the higher current efficiency. The cyclic voltammetry was tested with 0.2M CoCl2 using various scan rates to determine the reduction potential in Urea/ChCl at 323K. Based on the data from cyclic voltammetry test, the transfer coefficient and the diffusion coefficient were calculated as 0.22 and 3.38×〖10〗^(-6)cm2/s, respectively. The parameters for electrodeposition of cobalt were various temperatures (323K to 383K), applied potentials (2.4V to 3.3V), and concentration of CoCl2 (0.2mol/L to 0.5mol/L). Current efficiency and energy consumption were calculated to investigate the optimal condition for the electrodeposition of cobalt. The highest current efficiency (95%) was obtained under the temperature 323K, the applied voltage 2.7V, and concentration 0.5mol/L of CoCl2. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used for the characterization of cobalt deposits.
Mathematical Modeling of Molten Salt Electrolytic Cells for Sodium and Lithium Production: Donghui Li1; Lei Gao1; Boyd Davis2; Rüdiger Schwarze3; Amjad Asad3; Christoph Kratzsch3; Kinnor Chattopadhyay1; 1University of Toronto; 2Kingston Process Metallurgy inc; 3TU Bergakademie Freiberg
Sodium (Na) and Lithium (Li) are produced using molten salt electrolysis. The electrochemistry of the electrolyte is well-researched; however, there are benefits to understanding the melt flow and implications on it for cell design modifica-tions. The basic configuration of alkali metal cells is the Downs cell. This consists of a central anode surrounded by a cathode, and this geometry was the basis for this mathematical modeling study. The behavior of gas bubbles in molten elec-trolyte was studied in both Na and Li cells through the use of computational fluid dynamics (CFD) techniques. The distance between the anode and the cathode was varied in the CFD model to ascertain whether strong circulatory flows would change significantly in the cell. The standard k-ε turbulence model was used to mimic turbulent flow, and a two-way coupled Discrete Phase Model (DPM) was adopted to simulate flotation behavior of chlorine bubbles, and liquid metal drop-lets. The liquid metal distribution on the free surface was predicted using the Volume of Fluid (VOF) multi-phase model.
An Investigation on the Kinetics and Mechanism of Alkali Reduction of Mine Waste Containing Titaniferous Minerals for the Recovery of Metals: Stephen Parirenyatwa1; Animesh Jha1; Lidia Escudero Castejon1; Sergio Sanchez-Segado1; Yotamu Hara1; 1University of Leeds
In a world where declining ore grades are increasingly common, it has become necessary to process low-grade feedstock. Carbothermic reduction in the presence of alkali (Na2CO3) has been adapted to beneficiate waste that contains titaniferous minerals (TiO2 ca.12 wt. %), in order to recover valuable constituents such as TiO2, Fe and V2O5. The waste from vanadium metal processing has environmental legacy as it leaves nearly 1 wt.% V2O5 process waste, which is environmentally problematic due to V5+ ions in contact with water and soil. This investigation focuses on the kinetics and mechanism for alkali reduction of mineral waste bearing 10-12 wt.% TiO¬2, which we studied in the 1073K-1323K range. The thermogravimetric analysis (TGA) technique was used to record weight loss data. Two distinct regimes demonstrated mixed-control kinetics: 1) at low temperatures the activation energy was found to be 199kJ.mol-1, which corresponds to the outward diffusion of O2- ions; and 2) at high temperatures the calculated value was 130kJ.mol-1, which is consistent with the activation energy for the outward diffusion of Fe2+ ions. The metallic iron, sodium titanate and sodium aluminosilicate phases that formed were characterised using X-ray powder diffraction (XPRD) and scanning electron microscopy (SEM) techniques, and their significance for metal recovery is explained.