Process integration of E-waste carbonization and High-gravity rotating packed bed for optimal gold recovery and the fine particles reduction

摘要

Urban mining that uses an electronic waste recycling process is an emerging industry that is used to recover several high-value precious metals to reduce natural degradation and depletion. To obtain these precious metals more effectively, integrated circuit (IC) chips are pretreated using a carbonization process. In this study, the gold stripping efficiency for various types of IC chips was evaluated. To reduce the carried fine particle emitted from the exhaust gas of the carbonization process, a high-gravity rotating packed bed (HiGee RPB) generating micromixing the gas and liquid phases under a centrifugal force was applied. The performance in terms of particle removal efficiency under different high-gravity factor and gas-to-liquid ratio was determined. The result indicated that a pyrolysis temperature of 800 degrees C gives the maximum gold stripping efficiency of 99.8% and a minimum particle concentration of 23 mg m(-3). The particle removal efficiency increased as the high-gravity factor and liquid flow rate increased. An empirical model is used to describe the particle collection mechanism based on the experiment data and control variables. The mechanism includes Brownian diffusion, inertial impaction and interception, which affect the removal efficiency for different particle sizes. Finally, the process was optimized in terms of the removal efficiency and the energy consumption using a response surface model. A minimum level of energy consumption with a particle emission concentration of 16.9 mg m(-3) is necessary for the IC chip carbonization process.