A population balance approach to predict the performance of continuous leaching reactors: Model validation in a pilot plant using a roasted zinc concentrate

A Population Balance model for the continuous leaching of a roasted zinc concentrate was developed. The Maximum Mixedness and the Segregated Flow approaches were chosen to model the flow patterns and mixing conditions in the reactors. In order to compare these approaches and validate the proposed model, leaching experiments were carried out in a pilot plant. For that, it was also determined the residence time distributions in this plant reactors. As a result, it was observed that the Segregated Flow did not represent the actual pilot plant operation, since the conditions in which the Segregated Flow is recommended (i.e. segregation in the micromixing of the slurry phase, low diffusivity, and high slurry viscosity) were not present. On the other hand, using the Maximum Mixedness resulted in an excellent agreement between the experimental and modeled data (mean absolute error of 0.5% for the zincite conversion). This indicates that the complex particulate phenomena that occur during the leaching, as well as the flow patterns in the continuous reactors were adequately accounted in the model. Therefore, a robust tool for the design and control of leaching plants is delivered, since it is able to predict the effect of operational parameters (e.g. particle size distribution, solid/liquid ratio, feed flow rate) on the reactors performance. This can lead to better decision-making and costs reduction, contributing also to the prediction of problems faced in the operation of these plants. In a direct application of the developed model, it was predicted that the pilot plant could operate with the doubled capacity.