Simulation and Validation Studies of Impurity Particle Behavior in Copper Electrorefining

Abstract

A model based in COMSOL Multiphysics consisting of an electrorefining cell was utilized to simulate copper electrorefining. Concentration and electrolyte density profiles were generated as electrochemical simulation results. Fluid velocity field, particle trajectories, and particle distribution maps were generated to study impurity particle behavior in electrolyte. A three factor designed set of boundary conditions was used to determine the effects of inlet flow rate, temperature, and current density on impurity particle behavior in electrolyte and the associated distribution on the cross section (slice) 100 microns away from the front surface of the cathode during copper electrorefining. The number of impurity particles on the cross section was counted for each set of boundary conditions. The model data for impurity particle distribution was compared with measured impurity particle contamination at the cathode surface, and the results show a very good correlation, which suggests the model is reasonable. The model results show the three factors have significant effects on the number of impurity particles on the cross section. The impurity particle counts at the corner positions of the slice are much higher than those at the center position of the slice. Possible explanations for the simulation results are proposed.

A Comparative Study of Electrolyte Flow and Slime Particle Transport in a Newly Designed Copper Electrolytic Cell and a Laboratory-Scale Conventional Electrolytic Cell

“…On the other hand, slime particles, especially small and light ones, can be carried by electrolyte flow in electrorefining cells and transported to the domain near the cathode, where they can get entrapped in the cathodic deposit. 9,10 Thus, electrolyte flows in electrolytic cells, especially in the inter-electrode domains, are significant and need to be well controlled. Since upward flow can keep slime particles in suspension and exert potential harm to the cathode, downward flow would be favored along both the anode and the cathode as it facilitates the settlement of slime particles.…”

“…Since upward flow can keep slime particles in suspension and exert potential harm to the cathode, downward flow would be favored along both the anode and the cathode as it facilitates the settlement of slime particles. [9][10][11] Conventional electrorefining cells generally have inlets at positions near the cell bottom and outlets at the cell top. This design exerts upward flows in the cell and, as a matter of fact, the inlet flow under the design has less effect on the flow fields at the inter-electrode domains than the natural convection.…”

“…Due to electrolyte density gradients (the electrolyte becomes heavier and heavier when it flows near the anode and becomes lighter and lighter when it flows near the cathode), a looping flow pattern (downward flow along the anode and upward flow along the cathode) is developed within each inter-electrode domain. 9,10,[12][13][14][15][16][17] Furthermore, conventional electrolytic cells usually have problems such as low limiting current density and copper depletion zone near the cathode. 6,18,19 With poor convection, the diffusion boundary layer at the cathode is thick and copper ions are not transported efficiently in the bulk solution.…”

“…This cell has its inlet at the top and its outlet at a lower position, which is opposite to a laboratoryscale conventional cell that has been previously modeled. 9 Also, the inlets and outlets are closer to the inter-electrode domain, and there is more space under the electrodes in the newly designed cell. Note that the laboratory-scale conventional cell is not a perfect representative of real industrial conventional electrolytic cells due to laboratory restrictions.…”

Studies of Anode Slime Sintering/Coalescence and Its Effects on Anode Slime Adhesion and Cathode Purity in Copper Electrorefining

“…However, if the slimes layer is dense and thick with smaller pore sizes, Cu 2 O can be present in the layer. Secondly, NiO, Ni-Fe oxides and Kupferglimmer are insoluble when exposed to the electrolyte.…”