Management of scrap computer recycling in Taiwan

It is estimated that approximately 300,000 scrap personal computers are generated each year in Taiwan [S.-L. Chang, A Study on the Scrap Computer Treatment Cost, Environment Protection Administration of Taiwan, December 1998 (in Chinese)]. The disposal of such a huge number of scrap computers presents a difficult task for the island due to the scarcity of landfills and incineration facilities available locally. Also, the hazardous materials contained (i.e., phosphor coatings of cathode ray tubes (CRTs), batteries, polychlorinated biphenyl capacitors, mercury-containing parts, liquid crystal display, high-lead content CRT funnel glass, and plastic containing flame-retardant bromine, etc.) in the scrap computers may seriously pollute the environment if they are not properly disposed of. Therefore, the EPA of Taiwan declared scrap personal computers the producer's recycling responsibility as of July 1997. Under this decree, the manufacturers, importers and sellers of personal computers have to properly recover and recycle the scrapped computers which they originally sell. On June 1, 1998, a producer responsibility recycling program for scrap computers was officially implemented in Taiwan. Under this program, consumers can bring their unwanted personal computers to the designated collection points and receive reward money. Currently, only six computer items are mandated to be recycled in this recycling program. They are notebooks, monitors, hard disks, power supplies, printed circuit boards and main frame shells. This article outlines the current scrap computer recycling system in Taiwan.     

Recovery of copper from printed circuit boards scraps by mechanical processing and electrometallurgy

The constant growth in generation of solid wastes stimulates studies of recycling processes. The electronic scrap is part of this universe of obsolete and/or defective materials that need to be disposed of more appropriately, or then recycled. In this work, printed circuit boards, that are part of electronic scrap and are found in almost all electro-electronic equipments, were studied. Printed circuit boards were collected in obsolete or defective personal computers that are the largest source of this kind of waste. Printed circuit boards are composed of different materials such as polymers, ceramics and metals, which makes the process more difficult. However, the presence of metals, such as copper and precious metals encourage recycling studies. Also the presence of heavy metals, as Pb and Cd turns this scrap into dangerous residues. This demonstrates the need to search for solutions of this kind of residue, in order to have it disposed in a proper way, without harming the environment. At the first stage of this work, mechanical processing was used, as comminution followed by size, magnetic and electrostatic separation. By this process it was possible to obtain a concentrated fraction in metals (mainly Cu, Pb and Sn) and another fraction containing polymers and ceramics. The copper content reached more than 50% in mass in most of the conductive fractions and significant content of Pb and Sn. At the second stage, the fraction concentrated in metals was dissolved with acids and treated in an electrochemical process in order to recover the metals separately, especially copper. The results demonstrate the technical viability of recovering copper using mechanical processing followed by an electrometallurgical technique. The copper content in solution decayed quickly in all the experiments and the copper obtained by electrowinning is above 98% in most of the tests.     

废旧印刷电路板中非金属材料资源化的新进展

目前对废印刷电路板(WPCBs)的资源化利用主要集中在金属部分,而对于占整体约60%但处理困难且经济效益相对较低的非金属材料部分的资源化和安全处置的研究则相对较少。然而WPCBs中非金属材料具有较高的回收利用价值,完全可以作为再生资源回收。如何处理好当前存在的二次污染及回收利用率低等问题以及寻找高效、简便和绿色的回收利用方法已是非金属材料资源化所面临的当务之急。在非金属材料的资源化方法中,物理回收法以处理工艺简单、成本低、资源利用率相对较高等优点而具有较大的发展优势,是最符合国内实情的一种资源化方法。     

Recycling of waste printed circuit boards: a review of current technologies and treatment status in China

From the use of renewable resources and environmental protection viewpoints, recycling of waste printed circuit boards (PCBs) receives wide concerns as the amounts of scrap PCBs increases dramatically. However, treatment for waste PCBs is a challenge due to the fact that PCBs are diverse and complex in terms of materials and components makeup as well as the original equipment's manufacturing processes. Recycle technology for waste PCBs in China is still immature. Previous studies focused on metals recovery, but resource utilization for nonmetals and further separation of the mixed metals are relatively fewer. Therefore, it is urgent to develop a proper recycle technology for waste PCBs. In this paper, current status of waste PCBs treatment in China was introduced, and several recycle technologies were analyzed. Some advices against the existing problems during recycling process were presented. Based on circular economy concept in China and complete recycling and resource utilization for all materials, a new environmental-friendly integrated recycling process with no pollution and high efficiency for waste PCBs was provided and discussed in detail.     

Waste Characterization by Scanning Electron Microscopy for Material Recovery

Worldwide legislation coming into force requires considering new waste streams in order to achieve higher targets for material recovery and recycling. It is necessary, therefore, to manage waste materials in which different components are linked together and contaminants of various origins are present. Waste materials thus need to be treated that have a complex and often unknown composition and present different structural, morphological, and chemical properties. The physical and chemical characterization of solid waste is an essential step for the development of suitable treatment strategies, aimed at the recovery of one or more waste components. Scanning electron microscopy appears to be in most cases very helpful for waste characterization, providing information on material size, shape, structure, texture, distribution, and composition. Examples of waste characterization through scanning electron microscopy, finalized to material recovery, are reported. The waste materials taken into consideration include solids of different nature, such as spent lead batteries, cathode ray tubes (CRT), and printed circuit boards (PCB).     

Waste Characterization by Scanning Electron Microscopy for Material Recovery

Worldwide legislation coming into force requires considering new waste streams in order to achieve higher targets for material recovery and recycling. It is necessary, therefore, to manage waste materials in which different components are linked together and contaminants of various origins are present. Waste materials thus need to be treated that have a complex and often unknown composition and present different structural, morphological, and chemical properties. The physical and chemical characterization of solid waste is an essential step for the development of suitable treatment strategies, aimed at the recovery of one or more waste components. Scanning electron microscopy appears to be in most cases very helpful for waste characterization, providing information on material size, shape, structure, texture, distribution, and composition. Examples of waste characterization through scanning electron microscopy, finalized to material recovery, are reported. The waste materials taken into consideration include solids of different nature, such as spent lead batteries, cathode ray tubes (CRT), and printed circuit boards (PCB).     

Recovery of high purity precious metals from printed circuit boards

Waste printed circuit boards (WPCB) have an inherent value because of the precious metal content. For an effective recycling of WPCB, it is essential to recover the precious metals. This paper reports a promising method to recover the precious metals. Aqua regia was used as a leachant and the ratio between metals and leachant was fixed at 1/20 (g/ml). Silver is relatively stable so the amount of about 98 wt.% of the input was recovered without an additional treatment. Palladium formed a red precipitate during dissolution, which were consisted of Pd(NH(4))(2)Cl(6). The amount precipitated was 93 wt.% of the input palladium. A liquid-liquid extraction with toluene was used to extract gold selectively. Also, dodecanethiol and sodium borohydride solution were added to make gold nanoparticles. Gold of about 97 wt.% of the input was recovered as nanoparticles which was identified with a high-resolution transmission electron microscopy through selected area electron diffraction and nearest-neighbor lattice spacing.     

废旧电路板非金属材料粉的能量利用实验与分析

为了实现废旧电路板非金属材料粉的资源化再利用,通过对废旧印刷电路板非金属材料的焚烧过程和机理进行研究与分析,采用流化床焚烧装置处理已经被破碎的废旧印刷电路板非金属材料粉,在提取其中的玻璃纤维的同时,使非金属粉中的树脂尽量充分焚烧,并且测量排气温度,从而确定废旧印刷电路板中树脂焚烧之后能量利用的可行性。结果表明:在600℃的床温下,废旧电路板非金属粉已经充分燃烧并能提取出高纯度的玻璃纤维,同时焚烧烟气中存在大量可利用的热能,且二英排放符合环保要求。     

废旧印刷电路板中电子元器件回收处理技术进展

电子元器件广泛应用于电子电器设备中,但由于产品更新换代和电子电器产业市场的膨胀,大量的电子元器件被丢弃。对电子元器件的资源性和危害性进行分析,综合评述了电子元器件回收利用的最新研究进展和成果,主要包括电子元器件的拆卸技术(解锡方法和分离方法)和回收技术。在此基础上,提出了废旧印刷电路板中电子元器件的无害化和资源化回收研究新动向及发展建议。     

A novel hybrid network optimization model for printed circuit boards recycling: a circular economy perspective

Clean Technologies and Environmental Policy - The recycling of printed circuit boards, which accounts for a considerable monetary value in waste electrical and electronic equipment, has long been...     

A novel approach to recycling of glass fibers from nonmetal materials of waste printed circuit boards

The printed circuit boards (PCBs) contain nearly 70% nonmetal materials, which usually are abandoned as an industrial solid-waste byproduct during the recycling of waste PCBs. However those materials have abundant high-value glass fibers. In this study, a novel fluidized bed process technology for recycling glass fibers from nonmetal materials of waste PCBs is studied. The recycled glass fibers (RGF) are analyzed by determination of their purity, morphology and surface chemical composition. This process technology is shown to be effective and robust in treating with nonmetal materials of waste PCBs. The thermoset resins in the nonmetal materials are decomposed in the temperature range from 400 °C to 600 °C. And the glass fibers are collected at high purity and recovery rate by the cyclone separators without violating the environmental regulation. This novel fluidized bed technology for recycling high-value glass fibers from nonmetal materials of waste PCBs represents a promising way for recycling resources and resolving the environmental pollutions during recycling of waste PCBs.     

Assessment of removal of components containing hazardous substances from small WEEE in Austria

Minimum treatment requirements for waste electrical and electronic equipment (WEEE) established by Directive 2002/96/EC provide for the removal of specific components containing hazardous substances. To date, no comparative analysis of removal rates has been undertaken. The present paper examines the state of de-pollution of sWEEE in Austrian treatment plants. The mass of selected components removed and the corresponding mass of hazardous substances is compared to estimated values for sWEEE input material. The results obtained reveal that components are only partly removed, featuring a high variation between components and plants assessed. The overall rate of removal ranged from 72% of the estimated value for batteries to 21% of the estimated value for liquid crystal panels. This implies the forwarding of substantial quantities of hazardous substances to mechanical treatment processes, particularly relevant in terms of dispersion of pollutants. Furthermore, easily releasable pollutants, such as Hg from LCD-backlights, Cd from batteries or highly contaminated dust in general, pose substantial health risks for plant workers. Low removal rates of printed circuit boards, batteries and toner cartridges also lead to a reduction in quantities of valuable recyclable materials (precious metals, plastics).     

Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants

Conductive filament formation, a major cause of failures in printed circuit boards, is an electrochemical process that involves the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With an increasing potential to market “green” electronics, environmental and health legislations, and the advent of lead-free and halogen-free initiatives, newer types of printed circuit board materials are being exposed to ever higher temperatures during solder assembly. The higher temperatures can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effects of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards are not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.     

吸湿对印制电路板层压板热膨胀系数的影响

水分对印制电路板的可靠性有重要影响.电路板中的水分子可以改变电路基板的热性能及热力学性能,从而影响电路板及元器件的正常功能.研究了吸湿对两种无卤PCB及两种含卤PCB层压板热膨胀系数的影响,评价了IPC-TM-650 2.4.24测试方法中预处理方法对吸湿样品的适用性.结果表明,PCB层压板中的水分对PCB层压板的热膨胀曲线有明显影响,但传统的热膨胀系数计算方法并不能显示这种影响,对此作了详细分析并提出了改进建议.同时,IPC测试方法中的预处理可以降低湿度对样品热膨胀曲线的影响,但不能完全消除.     

废旧印刷电路板剪切式粉碎的试验研究

为实现废旧电路板的资源化利用,采用剪切式粉碎与球磨粉碎方式对电路板进行细碎的研究。结果表明:根据电路板层间剪切强度比较小的特点,采用剪切式粉碎方法可以有效对其进行粉碎并解离,并随着粉碎粒度的减小,各组分大小越均匀,解离越完全;与剪切粉碎效果相比,球磨粉碎易使电路板材料变薄,成片状薄板状,但不易被粉碎,粉碎的细度与均匀性不如剪切粉碎。     

废阴极射线管(CRT)玻璃资源化技术的研究进展

综述了国内外废阴极射线管玻璃资源化的研究现状,认为利用废阴极射线管玻璃制备建材、研制新型玻璃基材料具有工业化应用前景,湿法浸提-电沉积方法可成为有效的资源化技术。由于受技术和经济成本制约,目前多数研究仍停留在实验室阶段,环境友好、经济适宜和切实可行的资源化技术尚待开发。     

Environment-oriented project scheduling for the dismantling of buildings

This paper presents a case study for the environment-friendly dismantling and recycling of buildings. Based on material-flow management it is shown how the dismantling on the construction site can be improved using resource-constrained project scheduling. Computational results show that strict environmental requirements like high recycling quotas and the reduction of harmful substances in recycling materials can be satisfied. Moreover, a comparison with results in practice indicates that project scheduling helps to achieve economic advantages for environment-friendly dismantling and recycling strategies.     

Method for testing electronic-circuit tolerances by means of their functional element heat radiation

Conclusions The above method made it possible to simplify considerably the system used for detecting defective functional elements in the course of testing electronic circuits on printed boards, to raise testing trustworthiness, and to evaluate the reliability of the manufactured electronic circuits. The defect of this method consists of the required large amount of preparatory work. However, under mass-production conditions of electronic equipment and stringent requirements for its reliability this work fully pays for itself.This method can be used in automatic systems for detecting deficient electronic circuits on printed boards.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 59–61, August, 1980.     

基于废弃印刷线路板中非金属的复合板材制备

随着废弃电子电器产品的快速增长带来的环境问题日趋严重,废弃印刷线路板的资源化问题一直成为关注的焦点。着重研究了气流分选后得到的废弃印刷线路板非金属粉碎料的资源化再生制板材的可行性,探讨了不同填料粒径、投加量和改性剂下所得复合材料拉伸强度、弯曲和冲击强度的变化。研究表明以马来酸酐接枝聚丙烯（MAH-g-PP）作为改性剂,聚丙烯S700为基体树脂,在粒径范围为0.125～0.3mm的非金属粉碎料添加量为20%的条件下,板材力学性能较优,具有广泛的应用前景。     

A model for simulating the grinding and classification cyclic system of waste PCBs recycling production line

Crushing and separating technology is widely used in waste printed circuit boards (PCBs) recycling process. A set of automatic line without negative impact to environment for recycling waste PCBs was applied in industry scale. Crushed waste PCBs particles grinding and classification cyclic system is the most important part of the automatic production line, and it decides the efficiency of the whole production line. In this paper, a model for computing the process of the system was established, and matrix analysis method was adopted. The result showed that good agreement can be achieved between the simulation model and the actual production line, and the system is anti-jamming. This model possibly provides a basis for the automatic process control of waste PCBs production line. With this model, many engineering problems can be reduced, such as metals and nonmetals insufficient dissociation, particles over-pulverizing, incomplete comminuting, material plugging and equipment fever.