Characteristics And Optimization Design Of Integrated Air–Electrostatic Separation Process For Mixed Particles Of Crushed Printed Circuit Boards

Waste Electrical and Electronic Equipment (WEEE) is a kind of potential precious resource. As one of typical WEEE, the growth of quantity of waste printed circuit boards (WPCBs) is prominent because PCBs are widely subsistent in electric and electronic equipments. The recycling technology of WPCBs is important not only because WPCBs have complicated composition including some toxic parts, but they are also considered as"urban mineral resources". The corona electrostatic separation (CES) is an efficient method to recycle metals and non-metals separately from WPCBs. However, excessive nonmetallic materials contained in WPCBs lead to some problems for this technology, especially when particle size is below 0.3 mm. Therefore, a three-stage air separator was adopted as pretreatment for CES to work as'Integrated air-electrostatic separation process (AESP)'to overcome the weaknesses of CES.Base on the previous research, the influence mechanism of operation parameters of air separation (AS) was discussed from aspects of theoretical study and experiments. This paper established three models between operation parameters and experimental responses by the factorial design. They proved that the optimal parameter setting (α=45°,L=3cm,f=40Hz,S=15cm) can remove most of non-metals. This means when intake air volume from butterfly valve (Q0) was 0.0131 m3/s and intake air volume from bottom (Q1) was 0.0099m3/s, AS can achieve good preprocessing effects.Meanwhile, this paper explored the effects on AS of fine non-metallic particles (d≤0.15mm), large non-metallic particles (d>0.8mm) and different metal content. The experimental results indicated that AS can improve the metal content of feed materials of CES from 25wt% to more than 80wt%, and reduce sharply fine non-metals content to 25wt%.By contrast with traditional CES process, this integrated cyclone-electrostatic separation process had better performances: 1) the metal recovery rate of AESP (Ef) was kept more than 90%, and its improvement (G) increased by 5%-70%; 2) the middle products of AESP (MPf) was kept less than 4wt% (4g), and its reduction (MPd) reached 20%-58%. As the pretreatment of CES, air separation solved problems of traditional CES process by controlling the metal content and fine nonmetal content of feed materials of CES. Hence, integrated cyclone-electrostatic separation process was proves as a better new process for crushed waste printed circuit boards due to its high adaption and recovery rate.