Electrometallurgy 2020: Molten Salts
Sponsored by: TMS Extraction and Processing Division, TMS: Hydrometallurgy and Electrometallurgy Committee, TMS: Process Technology and Modeling Committee, TMS: Pyrometallurgy Committee
Program Organizers: Antoine Allanore, Massachusetts Institute of Technology; Michael Free, University of Utah; Georges Houlachi, Hydro-Quebec; Hojong Kim, Pennsylvania State University; Takanari Ouchi, University of Tokyo; Shijie Wang, Coeur Mining, Inc
Monday 2:30 PM
February 24, 2020
Room: 14A
Location: San Diego Convention Ctr
Session Chair: Antoine Allanore, MIT; Hojong Kim, Penn State; Takanari Ouchi, The University of Tokyo
2:30 PM Keynote
A Key Role for Electrometallurgy in Climate Change Mitigation: Adam Powell1; 1Worcester Polytechnic Institute
New technologies for climate change mitigation will require rapid and significant production scale-up for materials such as solar silicon, light metals for transportation, and rare earths for electric vehicle motors and wind turbine generators, as well as new processes for emissions-free ironmaking. In this context, electrometallurgy can potentially provide new process technologies which can scale quickly to meet global clean energy and efficiency needs. This talk will discuss several such candidate electrometallurgy technologies and their common features. For example, molten salt electrolysis with SOM anodes can directly reduce natural quartzite to solar silicon with no direct greenhouse emissions. Flow Electrolysis is a new method for direct oxide-to-metal powder reduction in aqueous solution with no direct greenhouse emissions. And there are other electrometallurgy technologies with potential for significant net-negative greenhouse emissions.
3:00 PM
Capital Cost Estimation for Electrochemical Processes: Caspar Stinn1; Antoine Allanore1; 1Massachusetts Institute of Technology
While the capital footprints for pyrometallurgy and hydrometallurgy are well-documented, limited literature exists for estimating the capital costs of electrowinning processes. Despite the use of electrolysis to produce key materials such as aluminum, copper, magnesium, sodium, zinc, and chlorine, a general model for the cost of an electrolytic facility based on operating parameters has previously not been proposed. In this study, reported capital investments for existing electrochemical facilities are examined to determine the economy of scale for electrolysis technology. Capital costs for electrowinning facilities are assessed in four parts: materials feed, electrolyzers, downstream product handling, and rectifier costs. The capital investments for electrolyzer cell technologies are explored as a function of operating parameters such current density, throughput, and temperature. Modern aqueous and molten salt electrolysis technologies are shown to be cost competitive, while emerging molten oxide and sulfide technologies may exhibit lower capital costs due to higher supported current densities.
3:20 PM
Electrolytic Extraction of Liquid Copper and Iron from Chalcopyrite Ore: Lucas Rush1; Caspar Stinn1; Andrew Caldwell1; Mary Elizabeth Wagner1; Ryohei Yagi1; Katrin Daehn1; Antoine Allanore1; 1Massachusetts Institute of Technology
Chalcopyrite ore (CuFeS2) is the principal mineral resource for copper metal. In the conventional pyrometallurgical route, oxygen is used to separate copper from sulfur and iron, releasing gaseous sulfur dioxide (SO2) and slag containing iron oxide (FeO) as low-value byproducts. Alternatively, electrolysis of the chalcopyrite ore would allow the direct separation of elemental copper, iron and sulfur, with few process steps, high energy-efficiency, and no by-products. The development of an electrolytic method producing liquid copper was previously hindered by the high electronic conductivity of the sulfide melt, but recent investigations (Sokhanvaran et al., 2016) show copper can be extracted with a suitably ionically-conducting supporting electrolyte. Here, we show for the first time that both metallic copper and iron can be extracted from natural chalcopyrite ore while generating elemental sulfur using only electricity.
3:40 PM
Development of a Magnesium Metal Production Process Using North Korean Magnesite: Jungshin Kang1; Tae-Hyuk Lee1; Young Min Kim2; Jin-Young Lee1; 1Korea Institute of Geoscience and Mineral Resources; 2Korea Institute of Materials Science
Conventional and novel magnesium production processes were investigated in order to produce high-purity magnesium metal from North Korean magnesite. In the conventional process, 99.8 % magnesium metal was obtained through the electrolysis of MgCl2 obtained at 973–1040 K using 300 A electrolysis cell with 7.0 V applied, and current efficiency was 83.9 %. This process is proven technology; however, in order to resolve environmental issues such as the generation of chlorine gas, an investigation of the electrolysis of MgO using liquidus metal cathode such as tin for the production of Mg alloys in MgF2-LiF salt at 1083 K at 3.0 V was also conducted. The current efficiency was 75.8–85.6 %. In addition, 99.999 % magnesium metal was obtained from Mg alloys through vacuum distillation at 1200–1300 K. Therefore, this study demonstrates that the use of North Korean magnesite for magnesium production via electrolytic method is feasible.
4:00 PM
Development of a Novel Magnesium Metal Production Process by Electrolysis of Magnesium Oxide Using a Tin Metal Cathode: Tae-Hyuk Lee1; Young Min Kim2; Jin-Young Lee1; Jungshin Kang1; 1Korea Institute of Geoscience and Mineral Resources; 2Korea Institute of Materials Science
In this study, a novel magnesium production process by utilizing electrolytic method was investigated in order to produce high-purity magnesium metal from magnesium oxide. Electrolysis of magnesium oxide was conducted using a liquidus tin cathode and a carbon or platinum anode in eutectic MgF2-LiF molten salt at 1083 K under an applied voltage of 3.0 V. As a result, the Mg-Sn alloy such as Mg2Sn was obtained with a current efficiency of 68.2 % under certain conditions. To produce high-purity magnesium metal from the Mg-Sn alloy, vacuum distillation was conducted at 1200 K for a duration of 5-10 h. After the distillation, magnesium metal with a purity of 99.999 mass% was obtained, and the concentration of magnesium in the residue was 0.16 mass%. Therefore, the electrolytic process developed here is feasible for the production of high-purity magnesium metal from magnesium oxide via an environmentally-sound method.
4:20 PM Break
4:35 PM
A 3-D Numerical Model to Predict Low Temperature Aluminum Electrochemical Process Using Ionic Liquids as Electrolytes at Different Boundary Conditions: Aqi Dong1; Laurentiu Nastac1; Ramana Reddy1; 1University of Alabama
Electrochemical separation of aluminum from mixed scrap under low temperature using ionic liquids electrolytes is an energy efficient and environmental benign metal extraction technology. A 3-D numerical model was developed to predict this electrochemical process. The influence of batch reactor geometries, number of electrodes and distance between electrodes, reactor domain and inlet temperature, and inlet flow velocity to the current density was studied. Three kinds of ionic liquids [EMIM]CL, [BMIM]CL and [HIMIM]CL were compared. An uncertainty analysis of electrolytes parameters such as electrical conductivity, thermal conductivity, density, specific heat and viscosity was also conducted. The results give some reference values for different boundary conditions and indicate that to achieve a larger current density, the inlet temperature should be as high as the domain temperature. It also shows that the electrical conductivity plays a decisive role for determining the current density. Those simulation results were also verified by experimental data.
4:55 PM
Enhanced Aluminum Electrorefining Process from Aluminum Alloy Scraps via Surface Engineering: Yifan Wang1; Ruigang Wang1; 1University of Alabama
To meet the growing demand for recycling aluminum (Al) more economically, it is critical to explore novel or optimize conventional methods to produce high-purity aluminum from aluminum alloy scraps. Electrorefining with ionic liquid (IL) electrolyte has gained considerable attention in aluminum recycling as a low-cost process, due to its low temperature requirement and zero pollutant emissions. However, the formation of dendrite structure has been reported as an adverse feature, which leads to low density of Al deposition, dendrite-induced short circuits between anode and cathode, and additional cost for further processing. In this work, the effects of several electrorefining process parameters (surface roughness of substrate, applied potential, electrolyte temperature, and stirring rate) on the formation of Al dendrite microstructure will be discussed in order to achieve dendrite-free electrodeposition of high purity Al on different substrate materials.
5:15 PM Cancelled
Electrorefining of Molten Iron: William Judge1; Gisele Azimi1; 1University of Toronto
As global production of iron and steel continues to rise exponentially, so does the demand for better quality steels with lower levels of residuals. Thus, there is an urgent need to develop new efficient and low cost processes to clean these impurities from molten steel. In the present work, we demonstrate a novel electrorefining process for refining impurities from molten iron. While existing technologies seek to manipulate partial pressure, slag chemistry, or steel chemistry to achieve refining, the present process performs refining by imposing an electromotive force between molten iron and an electrolyte. We demonstrate electrochemical decarburization of molten iron over the entire composition range from the eutectic (4.3wt% C) to 50 ppm C. The results show molten electrorefining may be used to produce ultra-low carbon steel containing <1 ppm C while remaining competitive with conventional processes on an energy basis.
5:35 PM Cancelled
Aluminum Extraction by Al-Si-Fe Alloy Electrolysis: Huan Shuxing1; 1Northeastern University
With the rapid development of the aluminum industry, the contradiction between the supply shortage of bauxite and alumina has become more prominent. If aluminum can be extracted from the aluminum-containing waste produced by the factory, especially Al-Si-Fe alloy, the problem of insufficient aluminum resources in China can be alleviated. In this paper, metal aluminum was extracted by electrolysis with Al-Si-Fe alloy as a soluble anode in NaCl-KCl-Na3AlF6 low temperature melts. The liquidus temperature and conductivity of the electrolyte were measured, and the influencing factors of current efficiency during electrolysis were discussed. The results show that when the molar ratio of NaCl-KCl-Na3AlF6 is 0.48: 0.48: 0.04, the liquidus temperature of the electrolyte was relatively low and the conductivity was high. When the electrolysis experiment was conducted in the above electrolyte with a current density of 0.2 A·cm-2 at 690 ºC for 1.5 h, a high current efficiency of 77.6% can be reached.