Optimization of Microwave Roasting for Dechlorination of CuCl Residue under Oxygen-Enriched Condition

The clean utilization of the residue containing chloride, such as zinc oxide dust and CuCl residue, produced from zinc hydrometallurgy is very important for the recycle of valuable metals. In this paper, a new technology for dechlorination of the CuCl residue through thermal treatment with application of microwave and oxygen-enriched air roasting is brought out. And the response surface methodology (RSM) based on five-level, three-variable and central composite design (CCD) was used to optimize the operation parameters for increasing the dechlorination efficiency. The effects of temperature, roasting time and oxygen consumption on the dechlorination efficiency were studied and the optimal process conditions were identified. In addition, X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy were used to characterize the dechlorination process under the optimum condition. The results showed that the experimental data were fitted to a second-order polynomial equation. The optimized process conditions are identified to be a roasting temperature of 451℃, heating duration of 114 min and oxygen consumption of 2.4 times the theoretical oxygen demand. A dechlorination efficiency of 96.4% could be achieved at the optimal process conditions.