Optimization And Improvement Of Electrostatic Separation For Crushed Printed Circuit Boards

The waste electric and electronic equipment (WEEE) has been sharply increased in the past thirty years worldwide. As core of EEE, waste printed circuit boards (PCBs) also become an environmental problem. On one hand, waste PCBs consists of amount of toxic and harmful substance, which has negative effect on human health and environment. On the other hand, the waste PCBs have a high content of valuable metals, such as copper, silver and gold. Recycling of waste PCBs have been a great business in China and world. However, the recycling technology used in most area of China does great harm to environment. So developing an environmental-friendly recycling technology is very urgent right now. Electrostatic separation proved to be a good way to recycle waste PCBs after numerous experiments. It is a high efficient, low energy costing and green technology.Base on the previous research, the paper establishes a model between operation parameters and middling products. The model is set up by the central composite design. The model shows the best parameter setting (U=28.5 kV, N=60 rpm,α1 =25°,s1 =70 mm,α2=75°,s2 =90 mm) that can recycle waste PCBs.It proves external factors have negative effect on the electrostatic separation in this paper. The main external factors are nonconductive powder (NP) and relative humidity (RH). The paper suggests that NP content should be less than 10% (wt) in crushed PCBs, and RH should be controlled less than 60% when transporting and separating feeding materials. To overcome the negative effect of external factors, a robust design is built based on Taguchi methodology. According to the design, U=28.5 kV,N=60 rpm is recommend for strong robustness separation process.Amount of nonmetals in crushed PCBs result in contradiction between treating capacity and quality. It is recommended cyclone separation should be use as pretreatment. Besides, the cyclone separation can remove the NP substantially. The Barth model is present and used to design appropriate cyclone separator.