Abstract:The aim of this study was to improve the dissolution of copper sulfide ore composed mainly of chalcopyrite (1.21 wt %) and bornite (0.54 wt %) using a pretreatment before leaching. The effect of the pretreatment on copper sulfide dissolution was investigated using different types of leaching. Three sets of experimental tests were performed (flask, reactor and mini-column). Using experimental design, three operational variables in the ore pretreatment were evaluated: chloride concentration (20, 50 and 90 kg/t), repose time (7, 20 and 40 days) and repose temperature (20 and 50 • C). A maximum of 93% copper dissolution was obtained when the ore was treated with 90 kg Cl − /t ore, 40 d of repose time and 50 • C in flask leaching. Without any ore pretreatment, 53% copper dissolution was achieved. Using reactor leaching, an 85% copper dissolution was obtained using pretreatment stage. Without this pretreatment, only 55% copper dissolution was obtained. The final test, which involved leaching a pretreated ore in a mini-column at room temperature, yielded 49% copper dissolution. The data showed that repose time and temperature were the most important variables affecting copper extraction in the pretreatment stage. This study indicates that pretreatment has a positive effect on copper dissolution from primary copper sulfide ore in an acid-chloride medium. It also provides a feasible alternative for treating primary copper sulfide ores at the industrial level.

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The aim of this study is two-fold: first, to analyze the effect of stochastic uncertainty in the design of flotation circuits and second, to analyze different strategies for the solution of a two-stage stochastic problem applied to a copper flotation circuit. The paper begins by introducing a stochastic optimization problem whose aim is to find the best configuration of superstructure, equipment design and operational conditions, such as residence time and stream flows. Variability is considered in the copper price and ore grade. This variability is represented by scenarios with their respective probability of occurrence. The resulting optimization problem is a two-stage stochastic mixed integer nonlinear program (TS-MINLP), which can be extremely challenging to solve. For this reason, several solvers for this problem are compared and two stochastic programming methodologies are applied. The combination of these techniques allows the production of high quality solutions and an analysis of their sensitivity to epistemic uncertainty. The results show that the stochastic problem gives better designs because it allows operational parameters to adapt to the uncertainty of the parameters. The results also show that the flotation circuit structure can vary with the feed grade and copper price. The sensitivity analysis shows small to moderate variability with epistemically uncertain parameters.

The aim of this study is two-fold: first, to analyze the effect of stochastic uncertainty in the design of flotation circuits and second, to analyze different strategies for the solution of a two-stage stochastic problem applied to a copper flotation circuit. The paper begins by introducing a stochastic optimization problem whose aim is to find the best configuration of superstructure, equipment design and operational conditions, such as residence time and stream flows. Variability is considered in the copper price and ore grade. This variability is represented by scenarios with their respective probability of occurrence. The resulting optimization problem is a two-stage stochastic mixed integer nonlinear program (TS-MINLP), which can be extremely challenging to solve. For this reason, several solvers for this problem are compared and two stochastic programming methodologies are applied. The combination of these techniques allows the production of high quality solutions and an analysis of their sensitivity to epistemic uncertainty. The results show that the stochastic problem gives better designs because it allows operational parameters to adapt to the uncertainty of the parameters. The results also show that the flotation circuit structure can vary with the feed grade and copper price. The sensitivity analysis shows small to moderate variability with epistemically uncertain parameters.

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