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Magna, UT, United States

Zeng W.,University of Utah | Wang S.,Rio Tinto Kennecott Utah Copper | Free M.L.,University of Utah
Journal of the Electrochemical Society | Year: 2016

Copper electrorefining tests were conducted in a pilot scale cell made of transparent cell walls, allowing direct observation and microscopic video recording of the electrolyte flow. Fluid flow velocities in the gaps between adjacent anodes and cathodes were measured by analyzing the recorded video using a video analysis and modeling software. Modeling and simulation of copper electrorefining in this cell were performed using COMSOL Multiphysics, a finite element method simulation software. The flow velocity field results from modeling agree reasonably well with the measured electrolyte velocities. The transport of slime particle in electrolyte flow was also simulated and the appearance frequencies of slime particles in the domain within 200 microns from cathode surface at different positions of cathodes were compared with impurity levels in the copper cathodes harvested from experimental tests. The results show good correlation especially with the total concentration of major impurities. Thus the cathodic contamination can be predicted by the slime particle appearance frequency in front of the cathode. © The Author(s) 2016.

Zeng W.,University of Utah | Free M.L.,University of Utah | Wang S.,Rio Tinto Kennecott Utah Copper
Journal of the Electrochemical Society | Year: 2016

Four series of copper electrorefining tests were performed using four different types of anodes, which have different inclusion types. Test results show that the high impurity anodes and the scrap cycle anodes have more inclusions associated with the Pb-Bi-S compounds that show evidence of sintering at 50°C, whereas the low impurity anodes and the strip cycle anodes have more inclusions related with the Pb-Bi-S-As compounds that demonstrate evidence of sintering above 65°C. Inclusion (slime) particles sinter and adhere to the anode surface, which happens at lower temperatures for the high impurity anodes and the scrap cycle anodes. Correspondingly, there are different slime distributions for each type of anode. The anode slimes layers in front of anode surfaces for different types of anodes were observed and analyzed by SEM/EDS. Results show significant effects of particle sintering near anode surfaces, which was also demonstrated by slime size distributions at different cell temperatures. Experimental results demonstrate that slime particle sintering and coalescence can improve anode slime adhesion and reduce the amount of suspended slimes, which are a major source of copper cathode contamination. Arsenic content in copper anode and cell temperature are major factors affecting slime sintering and coalescence. © The Author(s) 2015. Published by ECS.

Wang S.,Rio Tinto Kennecott Utah Copper
JOM | Year: 2013

When we appreciate the digital revolution carried over from the twentieth century with mobile communication and the Internet, and when we enjoy our high-tech lifestyle filled with iDevices, hybrid cars, wind turbines, and solar cells in this new century, we should also appreciate that all of these advanced products depend on rare earth metals to function. Although there are only 136,000 tons of annual worldwide demand, (Cho, Rare Earth Metals, Will We Have Enough?)1 rare earth metals are becoming such hot commodities on international markets, due to not only to their increasing uses, including in most critical military hardware, but also to Chinese growth, which accounts for 95% of global rare earth metal production. Hence, the 2013 technical calendar topic, planned by the TMS/Hydrometallurgy and Electrometallurgy Committee, is particularly relevant, with four articles (including this commentary) contributed to the JOM October Issue discussing rare earth metals' resourcefulness and recovery. © 2013 TMS.

Wang S.,Rio Tinto Kennecott Utah Copper
JOM | Year: 2011

Although it looks similar to tin, tellurium is a metalloid chemical element which is used in a variety of industries, primarily in the form of an additive to an assortment of compounds and alloys. As solar cell technology has improved the cadmium telluride (CdTe) PV modules have become among the lowest-cost producers of solar electricity. Consequently, interest has recently been focused on tellurium recovery. In this paper, tellurium's availability and its distribution in general metallurgical processing is summarized and analyzed. Because tellurium is the scarcest of all the byproducts and mainly recovered from copper sulfides, hydrometallurgical recovery of tellurium from electrolytic copper anode slimes is described. © 2011 TMS.

Zeng W.,University of Utah | Wang S.,Rio Tinto Kennecott Utah Copper | Free M.L.,University of Utah
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2016

Copper electrorefining tests were conducted in a pilot-scale cell under commercial tankhouse environment to study the effects of anode compositions, current density, cathode blank width, and flow rate on anode slime behavior and cathode copper purity. Three different types of anodes (high, mid, and low impurity levels) were used in the tests and were analyzed under SEM/EDS. The harvested copper cathodes were weighed and analyzed for impurities concentrations using DC Arc. The adhered slimes and released slimes were collected, weighed, and analyzed for compositions using ICP. It was shown that the lead-to-arsenic ratio in the anodes affects the sintering and coalescence of slime particles. High current density condition can improve anode slime adhesion and cathode purity by intensifying slime particles’ coalescence and dissolving part of the particles. Wide cathode blanks can raise the anodic current densities significantly and result in massive release of large slime particle aggregates, which are not likely to contaminate the cathode copper. Low flow rate can cause anode passivation and increase local temperatures in front of the anode, which leads to very intense sintering and coalescence of slime particles. The results and analyses of the tests present potential solutions for industrial copper electrorefining process. © 2016 The Minerals, Metals & Materials Society and ASM International

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