Microwave drying of CuCl residue from hydrometallurgical zinc recovery process

CuCl residue is a hazardous waste from the hydrometallurgical zinc recovery plant. It is very difficult to recycle due to complicated composition, highly corrosive nature, and refractory characteristics. Recently, a new process of microwave drying and roasting was successfully developed to produce both CuO solid and HCl gas products from the CuCl residue. In this paper, the dielectric property of the CuCl residue was measured under different moisture contents. The microwave absorption characteristics of the CuCl residue improved considerably as its moisture content increased. Laboratory-scale drying tests were conducted to evaluate the kinetics of microwave drying and to optimize the operation parameters. The efficiency of microwave drying was further demonstrated in industrial-scale level by microwave dryer developed in in-house. Finally, the drying mechanism of microwave heating of the sticky material was discussed and several measurements were optimized/implemented to intensify the drying process.