Precious Metal Distributions Between Copper Matte and Slag at High $$ P_{{{\text{SO}}_{ 2} }} $$ in WEEE Reprocessing

The distributions of precious metals (gold, silver, platinum, and palladium) between copper matte and silica-saturated FeOx-SiO2/FeOx-SiO2-Al2O3/FeOx-SiO2-Al2O3-CaO slags were investigated at 1300 °C and $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 = 0.5 atm. The experiments were carried out in silica crucibles under flowing CO-CO2-SO2-Ar gas atmosphere. The concentrations of precious metals in matte and slag were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High-Resolution Inductively Coupled Plasma-Mass Spectrometry, respectively. The precious metal concentrations in matte and slag, as well as the distribution coefficients of precious metals between matte and slag, were displayed as a function of matte grade. The present results obtained at $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 of 0.5 atm were compared with previous results at $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 of 0.1 atm for revealing the effects of $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 and selected slag modifiers (CaO and Al2O3) on precious metal distributions at copper matte smelting conditions. The present results also contribute experimental thermodynamic data of precious metal distributions in pyrometallurgical reprocessing of electronic waste via copper smelting processes.

Equilibrium of Copper Matte and Silica-Saturated Iron Silicate Slags at 1300 °C and $$ P_{{{\text{SO}}_{ 2} }} $$ of 0.5 atm

Experimental study on the phase equilibria between copper matte with silica-saturated iron silicate slags was conducted at 1300 °C and $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 = 0.5 atm. The high-temperature isothermal equilibration in silica crucibles under controlled flowing CO-CO2-SO2-Ar was followed by quenching in an ice–water mixture and direct phase composition analyses by an electron probe X-ray microanalyzer. The equilibrium compositions for matte and slag, as well as the distribution coefficients, were displayed as a function of matte grade. The data set obtained at $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 = 0.5 atm and the previous study at $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 = 0.1 atm by the authors enabled an investigation on the impacts of $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 as well as Al2O3 and CaO additions on phase equilibria in the multiphase copper matte smelting system. Thermodynamic calculations using MTDATA software were performed to compare the experimental results with modeling. The present results enrich the fundamental thermodynamic information for the matte/slag/tridymite/gas equilibria in the primary copper smelting process at high $$ P_{{{\text{SO}}_{ 2} }} $$ P SO 2 .

Experimental Determination of the Effect of CaO and Al2O3 in Slag Systems Related to the Conversion Process of High Copper Matte Grade

The slags generated in the conventional copper conversion process are mainly composed of Cu2O–Fe2O3–SiO2 with CaO, Al2O3, and MgO compounds—in concentrations up to 10 wt %. The present work contributes to the knowledge of the conversion process, generating experimental data for the phase diagrams of the Cu2O–Fe2O3–SiO2–Al2O3 and Cu2O–Fe2O3–SiO2–CaO systems. The experiments were carried out in a tubular furnace at temperatures of 1150 °C and 1200 °C, under a condition of saturation with tridymite and spinel. Once the equilibrium was reached, the samples were immediately quenched in water. The phases in the samples were observed through a scanning electron microscope (SEM) and the elemental composition of the phases were analyzed by means of energy-dispersive X-ray spectroscopy (EDS) detectors. The addition of Al2O3 and CaO into the Cu2O–Fe2O3–SiO2 system resulted in an appreciable displacement of the liquidus lines, corresponding to an expansion of the liquid in the tridymite primary phase field. The addition of CaO and Al2O3 combined was evaluated on industrial slags and from samples obtained in a Peirce–Smith furnace, with increasing amounts of CaO in the flux.

Prediction for Matte Grade in the Process of Copper Flash Smelting Based on QPSO-LSSVM

According to the complexity of the reaction mechanism and the requirement of the craft indicator during the process of copper flash smelting, the prediction model of matte grade was proposed by combining quantum particle swarm optimization algorithm (QPSO) with least squares support vector machine (LS-SVM) in this paper. Firstly, the nonlinear relation model between matte grade and craft indicators in copper flash smelting process was established by using the LS-SVM. Secondly, the parameters of LS-SVM were optimized by using the QPSO algorithm. Finally, the simulation results show that the maximum relative error of the matte grade is 0.47% and the relative root mean square error is 0.33%.Results indicate that the model can satisfy the requirement of production process and can be used to guide the practical production.

Activity of Lead in Copper Matte at Very Low Lead Concentration

The thermodynamic behavior of lead in Cu-Fe matte was investigated using a transportation technique where argon gas was bubbled into a bath of copper matte containing approximately 100 ppm lead at temperatures between 1300 and 1400 °C. The effect of flow rate, temperature and matte grade were investigated on the lead transport from a bath containing 100 grams of synthetic copper matte to the gas phase. The concentration of lead in the bath was followed with time. At argon flow rates between 3 l h1 and 18 l h−1, it was observed that the concentration change of lead in the matte was found to follow a first order relationship where the calculated concentration at time t, is of the form [Pb] = a.e−b.t, where a is equal to the initial lead content in ppm, [Pb]i, and b is an exponential term and t is time in minutes. The partial pressure of lead species in the gas phase was calculated from the concentration changes in the matte and from the bubbling gas rate. At gas flow rates between 3 and 9 l h−1, the lead removal appeared to be under equilibrium conditions. At higher gas flow rates, the apparent rate decreased, mainly due to splashing of matte into the cold zone of the furnace. In these experiments with Ar as the carrier gas, the sulphur and oxygen partial pressures of the melt were not controlled. Chemical analysis of the major components in the matte showed only random variation with bubbling time, and so a thermodynamic solution model for copper matte was used to calculate the equilibrium sulphur pressure expected. From this approach the proportion of Pb, PbS and Pb2 species in the gas could be calculated knowing the relevant reaction constants, e.g., PbS(g) = Pb(g) + ½S2(g). From the proportions of the lead species in the gas, the value of the lead activity coefficient with respect to the gas state could be determined. For a 50% copper matte, it was found that the activity coefficient increased with temperature, from a value of 0.8 at 1300 °C to 1.4 at 1400 °C. At the white metal composition, this value was 0.28 at 1300 °C. These results are compared with other relevant studies in the literature.