【作者】 路洪洲；

【导师】 许振明；

【作者基本信息】 上海交通大学 ， 材料加工工程， 2007， 硕士

【摘要】 废弃电路板中蕴含的金属是天然矿藏品位的几十倍甚至几百倍,具有重要的回收价值。目前国内处理废弃电路板主要采用破碎后利用密度差的气流风选和水选进行金属与非金属的分选,存在效率低和二次污染等问题。电路板是玻璃纤维强化树脂等非金属材料和多种金属的混合物,其中金属和非金属紧密结合,分选难,在电子废弃物中最复杂、最难处理,处理时要求技术含量高。因此,本文采用剪切式旋转破碎机和冲击式旋转磨碎机进行两级破碎,达到金属-非金属充分解离的程度,然后应用辊式电晕-静电复合电场高压电选机,对已破碎的废弃电路板进行金属颗粒与非金属颗粒分选,同时对金属之间的分选进行理论分析和实验研究。系统地分析了高压静电分选过程的影响因素以及优化了工艺流程,并对电场强度分布、分选过程进行模拟,提出了理论模型和理论公式,为开发出废弃电路板无害化处理与资源化技术提供理论基础。利用Matlab和Ansys软件对分选空间的电场分布进行模拟,发现了电极位置、电极曲率以及电压强度等对接地电极表面以及空间电场分布有重要的影响,减小高压电极与接地电极间的距离,提高施加电压强度可以提高接地电极表面电场强度以及空间电场强度,增加静电极半径,适当减小静电极的角度,适当增大电晕电极角度,可以改变电场强度分布,改善分选效果,并通过试验对模拟结果进行了论证,得到了电场强度分布和分选效果较理想的分选工艺参数。在理论上分析了接地电极转速、物料形状对分选效率和金属、非金属富集品位的影响,建立了“荷电临界转速模型”、“脱辊临界转速模型”和颗粒的“形状感应荷电模型”,进而得到了最佳转速公式,提出了同时提高金属纯度和非金属回收率的方法:1)增加电晕极数量,增大电晕区宽度和电晕电场强度,从提高“荷电临界转速”角度来提高“脱辊临界转速”;2)在避免火花放电的前提下,提高应用电压并减少放电距离,以提高电晕电场强度及颗粒荷电量;3)增大GE(接地电极)的曲率以及调整电晕极位置,以到达在保证最大荷电的前提下减少颗粒在接地电极表面的电荷损失。本文量化了转速和物料形状对分选的影响。得到同一种导的物料的形状易分选难易程度:球状>丝状>片状。对利用高压静电分选技术用于不同金属间的分选在理论上进行了探讨,通过待分选物料的受力分析和轨迹模拟,证实该方法在理论上的可行性。经过系统的理论分析和大量的实验,作者确定了工艺流程,优化了工艺参数,为高压静电分选方法的研究奠定了理论基础,为该方法的工业应用创造了条件。更多还原

【Abstract】 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.更多还原