High-voltage Electrostatic Separation For Fragmentized Printed Circuit Boards

Waste Printed Circuit Boards (PCBs) are worthy very much to recycle, because the metallic grade is more hundred times than the nature mineral resources. From now on, in china, air-float separation technology and water- float separation technology mainly are applied for the separation between metal and nonmetal basing on recycling Fragmentized waste PCBs, but there exists low efficiency and second pollution for the tow recycle methods. PCBs is composed by several metals and nonmetals including resin and Fiberglas etc, and metals and nonmetals are combined tightly, so it's difficult to be liberated and to be separated. In this paper, shearing machine and hammer grinder were combined to pulverize the waste boards, the metal and nonmetal on the PCBs and PWBs can be liberated availably, Then a roll-type corona-electrostatic high-voltage separator are applied to separate the metal and nonmetal, at the same time, A electrostatic separators/sizers (ESSs) is used to separate the mixed metals. A computational algorithm is employed to depict the cylinder-type electrode arrangements applied in some electrostatic processes generating non-uniform electric fields. Several factors influencing the separation process were analyzed system and the processes were optimized, and the electric field distribution and the separation process were simulated, some theoretical models and formulas were presented.The electric field distribution were simulated using Matlab software and Ansys software, the simulation showed that the position of the high-voltage electrodes, curvature of electrodes and applied voltage affect the electric field distribution and intensity, minishing the distance between the HVE (high-voltage electrodes) and GE (grounded electrode ),and enhancing theapplied voltage intensity could increase the electric field intensity of GE surface and space, increasing the radius of high-voltage state electrode, and decreasing the angle of state electrode and increasing the angle of corona electrode properly could change the electric field distribution, Laboratory studies and in-field observations showed that a appropriate electric field distribution and intensity and fine separation effect could be gained under the follow process parameters, voltage: 20-30kv, the angle of state electrode: 20°, the angle of corona electrode: 60°, etc.This paper analyzed the particle shape factor and rotates speed of GE that affected the efficiency of electrostatic separation, and addressed influence of the particle shape from both a computational and an experimental point of view. The conception of"detachment critical speed"and"saturation critical speed"were presented, the critical curve showed that the critical speed increases dramatically with decrease of particle size. Experiments carried out with the scrap Printed Circuit Boards confirmed the theoretical model, and the experimental results were in good agreement with the theoretical model. A furthest rotate speed formula was attained, and a method which could improve the both of recycles metal purity and reclaims efficiency of nonmetal simultaneity: 1) adding the amount of corona electrode and increasing the corona electric field intensity; 2) increasing the applied voltage intensity and minishing the distance between the HVE and GE; 3) increasing curvature of GE and adjust the position of corona electrode. The study showed that movement behavior of three shape particles was distinguishing: the sphere particles could be projected farther, subsequently cylinder particles, flake could be projected closer, and the experimental results were in good agreement with the theoretical predictions.The separation of the mixed metals is studied. A computer program was employed for analyzing the behavior of spherical particles in a two-dimensional electrode arrangement that models the actual electric field configuration of cylinder-type electrostatic separators/sizers. The actual granular mixtures with different specific mass and radius could be separatedtheoretically applying the cylinder-type electrostatic separation method.Through the systemic theoretical analyze and a mass of Laboratory experiments, the recycle process flow were confirmed and process parameters were optimized. The study is needed for the development of the electrostatic separation method and industry applications.