Optimization of electrostatic separation processes using response surface modeling

The efficiency of electrostatic separation processes depends on a multitude of factors, including the characteristics of the granular mixtures to be sorted, the feed rate, the configuration of the electrode system, the applied high-voltage, the environmental conditions. In a previous paper the authors demonstrated the possibility of optimizing the operation of industrial electrostatic separators using rather simple computed-assisted experimental design techniques. The aim of the present work is to analyze the peculiarities of application of a more sophisticated group of response surface experimental design techniques that make use of quadratic functions for modeling the electrostatic separation process. The 11 electrostatic separation tests, corresponding to a central composite design, were carried out on samples of chopped electric wire wastes. The CARPCO laboratory roll-type electrostatic separator employed for this study enabled a rigorous control of two factors: the applied high-voltage level and the speed of the rotating roll electrode. The objective was to maximize the benefits from the recycling of both constituents of the binary copper-PVC granular mixture. The optimum operating conditions computed with the quadratic model derived from the experimental results were in good agreement with the data of pilot-plant tests. The response surface methodology can be easily applied to most of the industrial applications of electrostatic separation technologies.