基于循环经济概念下的废弃电路板的再利用

运用循环经济原理,讨论了废弃电路板回收利用的必要性和可行性,并对现有废弃电路板资源化技术进行了分析比较,得出机械-物理处理法是回收利用电路板的最佳选择.针对国外废弃电路板的机械回收利用现状,提出了在国内开展废弃电路板资源化、无害化处理研究的一些建议.     

废弃印刷线路热解回收研究进展

综述了近年来国内外废弃印刷线路板热解回收的研究现状，着重介绍了废线路板热解的产物利用、影响因素、动力学和机理等方面的研究进展，讨论了该技术亟待解决的问题和未来的研究方向。     

分级式冲击磨破碎废弃印刷电路板实验及功耗分析

针对废弃印刷电路板具有硬度高、韧性强的特点,采用具有冲击、剪切作用的分级式冲击磨对粗碎后的废弃印刷电路板物料进行细碎实验研究,根据实验数据,利用Rittinger面积学说对破碎功耗进行分析。结果表明:使用分级式冲击磨能够实现对废弃印刷电路板的充分破碎,并且当破碎粒径小于0.6 mm时,金属与非金属能够完全解离;分级式冲击磨破碎废弃印刷电路板过程中粒度分布规律符合Rosin-Rammler粒度特性方程式;随着破碎粒径的减小,破碎比表面功耗增大,当平均粒径小于0.312 mm时,比表面功耗急剧增加。     

一种真空热解废电缆回收装置

本装置采用真空加热裂解塑料外皮并配以对热解气体进行化学处理的方法来回收废电缆金属.本装置具有处理废电缆回收金属经济、干净,无废气、废水、废渣排放,对环境无二次污染.装置结构简单易操作,占地面积小,适合对大量废电缆回收金属使用.     

钻井废弃泥浆固化土力学特性试验分析

石油开采过程中产生大量钻井废弃泥浆,直接排放会造成环境污染,对钻井废弃泥浆进行处理势在必行。针对钻井废弃泥浆采用固化处理方法,并对固化土的力学特性进行系统试验分析。研究结果表明：固化土的应力应变曲线为应变软化型,发生脆性破坏;曲线峰值随着围压的增加和养护龄期的延长而升高;随冻融循环次数的增加而降低,6—8次后趋于稳定,冻融循环对固化土的强度影响明显。固化土发生刚度软化现象,E-ε曲线整体呈下降趋势,刚度随着围压的增加和养护龄期的延长而增加,随冻融循环次数的增加而降低,无量纲化割线模量与无量纲化主应力差的关系曲线由两部分组成,呈现倒C型。对固化土力学性能的研究有利于废弃泥浆的资源化再利用。     

印刷电路板振动特性及防振包装原理

将随机激励条件下的印刷电路板的防振包装模型简化为两自由度弹簧-质量系统,以内部易损元件的响应作为主要衡量指标,分析了印刷电路板的振动特性和防振包装原理.结果表明,采用两自由度模型能得到更为合理的结果,且简化模型中应采用等效质量代替印刷电路板的实际质量.     

不锈钢真空保温瓶的保温特性研究

提出了利用不锈钢保温瓶的保温特性和外胆表面温度分布曲线，推测了瓶口材料的传热、真空状态自由气体分子的传热和内外胆间的热辐射传热。最后讨论了保温特性的快速测量方法，保温瓶瓶口结构改进，以及利用瓶塞的热套作用改善保温特性的建议。本文观点同样适用于玻璃保温瓶。     

高速列车车厢用减振降噪材料的热解及燃烧特性研究

使用热重-差热分析仪研究氮气气氛中、不同升温速率下高速列车车厢用减振降噪的红磷阻燃丁基橡胶(RP/IIR)复合材料和氢氧化铝阻燃丁基橡胶(ATH/IIR)复合材料的热解特性,采用Kissinger法获得热解动力学参数;使用锥形量热仪研究不同热辐射强度下两种材料的燃烧特性,采用轰燃倾向指数、放热指数和发烟指数评价潜在火灾危险性。结果表明：两种材料的热解反应均为3个阶段,ATH/IIR复合材料的初始分解温度、终止分解温度、最大失重速率温度、残余量、平均表观活化能均高于RP/IIR复合材料的相应值,而质量损失率、热释放速率、产烟速率均小于RP/IIR复合材料的相应值,3个评价指数也一致较低。综合对比,ATH/IIR复合材料具有更好的热稳定性和更小的潜在火灾危险性。     

玻璃纤维/环氧树脂复合材料热解特性研究

采用热重-差热分析仪研究玻璃纤维/环氧树脂复合材料在空气及氮气氛围下不同升温速率的热解特性规律。结果表明,在空气气氛下,热解分为两个阶段;氮气气氛下,热解只存在一个热分解阶段,与空气气氛相比热解初始分解温度较高,热解温度范围变窄,失重速率明显变大。在两种气氛下,玻璃纤维均不参与热解。随着升温速率的增加,热解反应各阶段的起始温度、终止温度、最大失重速率温度均向高温方向移动,热解温度范围大小都基本保持不变。氮气气氛下使用Kissinger法、FWO法和Starink法计算出玻璃纤维环氧树脂的平均表观活化能分别为106.42、123.09和119.48kJ/mol。复合材料活化能随转化率的增加而升高,表观活化能保持在一定数值范围内且数值相近,热解反应比较稳定,具有较低A值,表明其具有较强的热稳定性。     

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。     

Recovery of metals from waste printed circuit boards by a mechanical method using a water medium

Research on the recycling of waste printed circuit boards (PCB) is at the forefront of environmental pollution prevention and resource recycling. To effectively crush waste PCB and to solve the problem of secondary pollution from fugitive odors and dust created during the crushing process, a wet impacting crusher was employed to achieve comminution liberation of the PCB in a water medium. The function of water in the crushing process was analyzed. When using slippery hammerheads, a rotation speed of 1470 rpm, a water flow of 6 m³/h and a sieve plate aperture of 2.2 mm, 95.87% of the crushed product was sized less than 1 mm. 94.30% of the metal was in this grade of product. Using smashed material graded −1 mm for further research, a Falcon concentrator was used to recover the metal from the waste PCB. Engineering considerations were the liberation degree, the distribution ratio of the metal and a way to simplify the technology. The separation mechanism for fine particles of different densities in a Falcon concentrator was analyzed in detail and the separation process in the segregation and separation zones was deduced. Also, the magnitude of centrifugal acceleration, the back flow water pressure and the feed slurry concentration, any of which might affect separation results, were studied. A recovery model was established using Design-Expert software. Separating waste PCB, crushed to −1 mm, with the Falcon separator gave a concentrated product graded 92.36% metal with a recovery of 97.05%. To do this the reverse water pressure was 0.05 MPa, the speed transducer frequency was set at 30 Hz and the feed density was 20 g/l. A flow diagram illustrating the new technique of wet impact crushing followed by separation with a Falcon concentrator is provided. The technique will prevent environmental pollution from waste PCB and allow the effective recovery of resources. Water was used as the medium throughout the whole process.     

Recovery of metal fractions from waste printed circuit boards via the vibrated gas-solid fluidized bed

The vibrated gas-solid fluidized bed based on fluidized separation technology was used to recycle the metallic fraction of waste printed circuit boards (WPCBs). The size fraction composition and element distribution of the crushed products were analyzed by sieving and X-ray fluorescence, respectively. The contents of Cu, Zn, Fe and Ti in various size fractions had significant differences, resulting in preliminary enrichment. The performance of vibration on the fluidization characteristics of WPCBs powder was described. With fluidization number, vibration frequency and vibration amplitude as variables, the separation performance of WPCBs powder under various operational conditions was studied. With the optimum operated conditions, the optimal recovery rates of metallic fraction of the three size fractions of 1–0.5 mm, 0.5–0.25 mm and 0.25–0.125 mm were 88.53%, 95.61% and 82.28%, respectively. The vibrated gas-solid fluidized bed can effectively enrich and recover the metallic fraction of WPCBs, providing convenience for subsequent separation.     

Bioleaching of metal concentrates of waste printed circuit boards by mixed culture of acidophilic bacteria

Metal concentrates of printed circuit boards (PCBs) are the residue valuable metals from which non-metallic components are removed. The non-metallic components show bacterial toxicity in bioleaching process and can be recycled as well. In this study, the effects of initial pH, initial Fe(II) concentration, metal concentrate dosage, particle size, and inoculation quantity on the bioleaching were investigated so as to determine the optimum conditions and evaluate the feasibility of bioleaching of metal concentrates of PCBs by mixed culture of acidophilic bacteria (MCAB). The results showed that the initial pH and Fe(II) concentration played an important role in copper extraction and precipitate formation. Under the optimized conditions of initial pH 2.00, 12 g/L initial Fe(II), 12 g/L metal concentrate dosage, 10% inoculation quantity, and 60-80 mesh particle size, 96.8% the copper leaching efficiency was achieved in 45 h, and aluminum and zinc 88.2% and 91.6% in 98 h, respectively. All findings demonstrated that metals could be efficiently leached from metal concentrates of waste PCBs by using the MCAB, and the leaching period was shorten from about 8 days to 45 h.     

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.     

废印刷电路板非金属粉与埃洛石纳米管对不饱和聚酯热稳定性和阻燃性能的影响

为减轻废印刷电路板非金属粉(WPCBP)在回收过程中对环境的污染和资源的浪费,实现WPCBP在聚合物基体中的高值化利用,将粉碎干燥后的WPCBP与埃洛石纳米管(HNTs)添加到不饱和聚酯树脂(UPE)基体中,制备了一种新型环保的WPCBP-HNTs/UPE复合材料。利用SEM和TEM对两种填料的结构形貌及其在复合材料中的分散状况和界面结合进行了表征,采用热失重分析仪、锥形量热仪、极限氧指数仪等对WPCBP-HNTs/UPE复合材料的热稳定性和阻燃性能进行了系统的研究。结果表明,WPCBP和HNTs能够显著提高复合材料的热分解稳定性和阻燃性能。通过SEM和EDS对复合材料燃烧后的碳渣进行了分析,并探讨了阻燃机制,分析了WPCBP和HNTs对WPCBP-HNTs/UPE复合材料的力学性能和热变形性能的影响。     

Innovative method for removing bromine in waste printed circuit boards: Ultrafine milling and porous media loaded debromination agent

Resin is the main harmful substance in waste printed circuit boards (WPCBs) due to the presence of harmful bromine. In this study, the methods of ultrafine milling of resin and loading debromination agent on porous gasification slag were proposed to improve the debromination effect. The morphology, composition and phase of the gasification slag and resin were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results show that the residual carbon in the gasification slag has porous structure, which contributes to the loading of debromination agent. The specific surface area and porosity of gasification slag before and after acid treatment were analyzed by BET. Using the porous properties of gasification slag, different debromination agents were attached to prepare efficient debromination agents, which were adopted for thermal debromination of resin in WPCBs. Subsequently, ICP-MS was used to determine the content of bromine in pyrolysis residue. The results show that when FeCl₂/FeCl₃ was used as the debromination agent, the debromination efficiency was only 67.19% and 58.29%, while using gasification slag-FeCl₂/FeCl₃ composite, the debromination efficiency can be increased to 81.63% and 76.25%. Therefore, the cooperative treatment can realize the resource utilization of the two wastes.     

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.     

Conversion of bromine during thermal decomposition of printed circuit boards at high temperature

The conversion of bromine during the thermal decomposition of printed circuit boards (PCBs) was investigated at isothermal temperatures ranging from 800°C to 1100°C by using a quartz tube furnace. The influence of temperature, oxygen concentrations (0%, 10% and 21% in the nitrogen-oxygen atmosphere) and content of steam on conversion of bromine was studied. With the increment of temperature, the conversion from organic bromine in the PCBs to inorganic bromine in the gaseous fraction increased from 69.0% to 96.4%. The bromine was mainly evolved as HBr and Br(2) in oxidizing condition and the Br(2)/HBr mass ratio increased at stronger oxidizing atmosphere. The experimental results also indicated that the existence of steam can reduce the formation of Br(2). Furthermore, co-combustion of PCBs with S and CaO, both as addition agents, was investigated, respectively. In the presence of SO(2), Br(2)/HBr mass ratio obviously decreased. Moreover, the utilization of calcium oxide can efficiently promote the conversion of organic bromine to inorganic bromine. According to the experimental results, incinerating PCBs at high temperature can efficiently destroy the organobrominated compounds that are considered to be possible precursors of polybrominated dibenzeo-p-dioxins and dibenzofurans (PBDD/Fs), but the Br(2) and HBr in flue gas should be efficiently controlled.     

A new two-roll electrostatic separator for recycling of metals and nonmetals from waste printed circuit board

The electrostatic separation is an effective method for recycling waste electrical and electronic equipment (WEEE). The efficiency of electrostatic separation processes depends on the ability of the separator. As a classical one, the roll-type corona-electrostatic separator has some advantages in recycling metals and plastics from waste printed circuit board (PCB). However, its industry application still faces some problems, such as: the further disposal of the middling products of the separation process; the balance of the production capacity and the good separation efficiency; the separation of the fine granular mixture and the stability of the separation process. A new "two-roll-type corona-electrostatic separator" was built to overcome the limitation of the classical one. The experimental data were discussed and the results showed that the outcome of the separation process was improved by using the new separator. Compared with the classical machine, the mass of conductive products increases 8.9% (groups 2 and 3) and10.2% (group 4) while the mass of the middling products decreases 45% (groups 2 and 3) and 31.7% (group 4), respectively. The production capacity of the new machine increases, and the stability of the separation process is enhanced.