Electrolytic recovery of metals in a spouted vessel reactor: An experimental and simulation approach

An experimental and modeling study is presented of metal recovery from acidified aqueous solutions in a particulate, spouted bed of conductive particles. In particular, copper recovery in a 12&inches; cylindrical spouted bed electrolytic reactor (SBER) was investigated experimentally. The effects of electric current, initial copper ion concentration, supporting electrolyte concentration, particle loading, liquid flow rate, and pH on copper recovery rate, current efficiency and energy efficiency of the electrolytic deposition process were investigated under galvanostatic conditions. In addition, a numerical kinetic model of electrochemical metal deposition and backstripping, coupled with mass transfer in the particulate cathode, was developed.; SBER hydrodynamics was studied in a rectangular spouted vessel, constructed for this purpose. Fluid velocities and pressures were measured by "scanning" the interior of the vessel at selected points using conical micro-pitot tube probes. The effects of particle size, inlet jet velocity, draft duct dimensions, and entrainment length on pressure drop, particle circulation rate, and velocity field are presented.; A three-dimensional, two-phase, Eulerian simulation was developed to describe the particle and liquid flows in the rectangular spouted vessel, using a finite volume technique. Model results, such as volume fraction, pressure and velocity fields, compared well with experimental data. The model was also extrapolated to investigate conditions for which experimental data were lacking. The model was able to predict the experimentally observed phenomenon of "choking" where the particle recirculation rate remains constant with increasing particle loading once a "critical" solids loading is achieved.; An axisymmetric version of the model was used to describe the cylindrical SBER and to determine the particle residence time distribution (RTD) and the effective mass transfer coefficient in the moving bed cathode. The role of the particle distributor in maintaining a sharp particle RTD in the moving bed cathode was confirmed, such that on average all particles experience approximately the same amount of time active in electrodeposition. It was also shown that particles spend >90% of the time in the moving bed cathode.