废弃印刷线路板共热解影响因素及热解产物表征

热解是资源化利用废弃印刷线路板的重要方法之一。分别以沸石和Fe₃O₄为共热解剂，探讨了共热解剂与废弃线路板的质量比以及热解温度对液相产物产率的影响，并对热解后固、液、气三相产物进行了表征。结果表明，共热解剂的添加不会影响热解油的产率，但可有效降低液相中溴化有机物的含量。热解液相产物组分分析结果表明，直接热解废弃线路板时会有大量溴化有机物释放到液相产物中。加入共热解剂后，苯酚及其同系物成为液相产物的主要成分，溴变成主要以无机溴化物的形式存在。同时，不同共热解剂对废弃线路板的热解影响也不同。Fe₃O₄共热解时，液相产物中小分子苯类物质更多，这可能是由于铁类物质对大分子有机物的分解作用更强。共热解剂在高温下比较稳定，热解后固体主要含有共热解剂、玻璃纤维以及重金属，而热解气的主要成分则为H₂、CH₄和CO₂。     

废弃印刷线路板热解能耗实验研究

开展了线路板热解能耗实验研究.研究表明:线路板热解能耗包括热解反应热、系统热容、系统散热损失.对于本研究固定床热解实验装置,FR4板的热解反应热总能耗占比24.68％,系统热容20.75％,散热损失54.66％;对于Teflon板,热解反应热总能耗占比14.58％,系统热容39.59％,散热损失45.82％.FR4、Teflon型线路板热解反应热分别为19.692 MJ/kg和11.374MJ/kg.每公斤FR4线路板产生的热解油热值约为4.50 MJ,热解气热值约为2.39 MJ.对于FR4板来说热解油和热解气作为燃料回收,热量仅为反应热的34.99％,不足以维持热解反应的持续进行.整个热解系统,系统热容和散热损失占比较大,热解工艺设计时,设计合理的加热方式保证线路板受热均匀和自动化监控停炉、起炉加热控制是节能的关键措施之一.同时添加催化剂以实现线路板较低的热解温度,减小平均升温速率也是提高热解技术处理废弃印刷线路板经济性的有效措施.     

废弃印刷线路板热重分析和动力学模型

利用差热热重分析仪对两种典型的废弃印刷线路板(FR4型、PTFE型)进行了热解实验研究.并利用SEM检测了热解残余物的元素组分.结果表明,PTFE型线路板的热解温度区间为500～600℃,而FR4型线路板仅为300-400℃.热解残余物中金属与玻璃纤维组分完全分离,金属与玻璃纤维保存完好于热解坩埚中.金属片主要含有铜、金、镍等组分;FR4型线路板热解残余物中的玻璃纤维片含有硅、氧、钙、碳和铝等组分,而PTFE型线路板热解后的玻璃纤维片含有硅、氧、铝、钙、钛等组分.利用Kissinger法求得两种试样的表观动力学参数,PTFE型线路板的活化能和指前因子分别为315.83 kJ/mol和1.57×1017min-1,FR4型线路板的活化能和指前因子分别为103.002 kJ/mol和4.127×108 min-1.     

废弃印刷电路板气化特性研究

在自行搭建的固定床上试验研究了不同粒径的印刷线路板在CO2气氛、不同温度下的气化特性实验。利用热重分析仪分析了不同升温速率时印刷线路板的气化特性。结果表明:随着升温速率增大,失重曲线向高温区移动;在300℃～380℃温度区间,气化反应剧烈进行。同时反应物颗粒尺寸以及气化终止温度都会对气化产物产生影响。     

气体停留时间对流化床褐煤热解产物的影响

在小型流化床热解反应器上,以小龙潭褐煤为热解原料,通过控制二次热解段尺寸和加热条件,研究不同热解温度(500~800℃)和热解气停留时间(5.5~18.7 s)对煤热解挥发产物产率及组分的影响。通过增加管径和增加长度控制气体停留时间,在各个温度下,均会出现焦油产率的下降,气体产率的上升,焦油气相二次反应更为明显。焦油中轻质组分的含量增加,其中苯、二甲苯及多环芳烃含量在较长停留时间下的增加明显,酚类及脂肪烃含量有所下降。焦油发生裂解、缩聚、加氢等二次反应,CO_2、CO等主要煤气组分均有所上升,并随温度的升高更为明显。     

废弃印刷线路板高温燃烧时溴的迁移转化特性研究

利用管式炉在空气气氛下进行了废弃印刷线路板的燃烧试验,研究了温度、钙基添加剂、硫,以及不同的Ca/Br摩尔比和S/Br摩尔比对溴的迁移转化的影响。试验结果表明,随着温度的升高,烟气中HBr的转化率降低,而溴分子的转化率升高,且溴分子的转化率始终高于HBr的转化率;钙基添加剂对烟气中HBr的转化率影响不大,但基本上能促进残渣中的溴向烟气中的溴分子转化,效果随着Ca/Br摩尔比的增加有所变化;硫的添加能够有效促进烟气中的溴分子向HBr转化,也能降低烟气中无机溴的转化率。     

废旧线路板真空热化学处理设备的设计

针对目前国内尚未有人对线路板废渣进行专门研究,提出利用真空热化学处理手段,并配合两至三级冷凝处理产生的有害气体,从而回收利用液体产物及热能。着重介绍前期整套设备的设计,通过传热学和反应釜设计原理计算设计出反应罐的尺寸,根据两级冷凝所产生液体产物的要求,算出一级冷凝出口气体温度和第二级冷凝设备的换热面积。     

基于GRNN的生物质真空热解液化过程优化研究

以油菜秸秆为原料,采用真空热解系统进行了制取生物油的正交试验研究,基于广义回归神经网络(GRNN)原理,建立了以热解终温、体系压力、升温速率和保温时间为输入变量,生物油产率和能量转化率为输出变量的预测模型,并以生物油产率和能量转化率为目标开展了系统参数的优化,对优化结果进行了试验验证。研究结果表明,经训练后的GRNN预测模型输出的生物油产率和能量转化率的预测值与试验值吻合较好;当热解终温为486.8℃、体系压力为5.0 kPa、升温速率为18.1℃/min、保温时间为55.0 min时,最高生物油产率和能量转化率分别为43.6%和35.5%。经试验验证,优化结果较为精确。     

城市固体废弃物典型组分的快速热解产气特性研究

选取城市固体废弃物中的常见六种组分(纸屑、厨余、织物、木屑、塑料、橡胶)作为实验物料进行快速热解实验。在所得实验数据的基础上对热解气体产物的组成以及变化情况进行了分析，并研究了热解混合气的热值随时间变化的情况。通过研究有助于对热解产物进行预测，且能够深入地了解热解机理。     

稻壳连续热解特性研究

在自行研制的生物质连续热解反应装置上进行稻壳连续热解和二次裂解实验研究。随着稻壳热解温度的提高,炭产率降低,气体产率增加,液体产率先增加后减少;随着滞留时间的减少,炭产率、液体产率增加,气体产率减少。稻壳热解气以CO2和CO为主,且二者为竞争关系,热解温度提高,CO2产量降低,CH4、H2、C2H4、C2H6产量增加,CO的产率变化不大;滞留时间对热解气组分影响不大。二次裂解温度提高,裂解气中的H2、CH4、C2H4含量明显增加,二次裂解温度为800℃时,H2产率达到12%。稻壳500℃热解挥发物600℃二次裂解木醋液中醋酸含量高达49.44%,焦油中检测到的物质主要为丙酮和异丙醇。     

Air-breathing miniature planar stack using the flexible printed circuit board as a current collector

To maximize power density, the volume of a fuel cell stack should be reduced by miniaturizing the stack components. In this study, thin flexible printed circuit board was utilized as a current collector in order to reduce an air-breathing monopolar stack's volume. Also, the effects of varying the geometry and opening ratios of the ports to the cathode on stack performance were evaluated in order to determine the optimal cathode structure. Use of the thin current collector and cathode port optimization resulted in an output of 3.5 W from an 18 cm³ stack (power density of 350 mW/cm²). The effects of orientation under passive air-breathing operation were determined to be nearly negligible. All data was measured at ambient pressure and temperature, baseline conditions for mobile fuel cell intended for use in consumer electronics.     

Rapid cold start of proton exchange membrane fuel cells by the printed circuit board technology

Cold start from subzero temperature is one of the key barriers, which prevents proton exchange membrane fuel cell (PEMFC) from further commercialization. In this paper, we have applied the printed circuit board (PCB) technology to study the current density distributions of PEMFC and optimized the technology under rapid cold start. The results show that increasing the initial load, and the setup temperature can help to lower the cold start time and achieve rapid warm-up of PEMFC. The cell can be rapidly cold started for 10 s at −5 °C and 55 s at −10 °C under 0.2 V operation condition, but it failed at −15 °C and −20 °C. The inlet region and middle region produce half of the total current before the overall peak current density is reached, which is important for the successful cold start. Based on these characteristics, we optimized the rapid cold start strategy by co-operation of hot reactant gas and waste heat generation of PEMFC. It becomes possible to start up the PEMFC at temperatures down to −20 °C with about 20 min.     

Multi walled carbon nanotubes based micro direct ethanol fuel cell using printed circuit board technology

Multi walled carbon nanotubes (MWNTs) have been synthesized by chemical vapour deposition technique using AB₃ alloy hydride catalyst. Platinum supported MWNTs (Pt/MWNTs) and platinum-tin supported MWNTs (Pt–Sn/MWNTs) electrocatalysts have been prepared by chemical reduction method. MWNTs and electrocatalysts have been characterized by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM) and Energy dispersive X-ray analysis (EDAX). The anode and cathode electrodes for DEFC have been fabricated using Pt–Sn/MWNTs and 1:1 Pt/MWNTs + Pt/C electrocatalyst respectively. Performances of Direct Ethanol Fuel Cell (DEFC) with these electrodes have been studied at different temperatures of the membrane electrode assembly at ambient fuel conditions and the results have been discussed. A maximum power density of 38.6 mW/cm² at a current density of 130 mA/cm² is obtained. A six cell planar Micro Direct Ethanol Fuel Cell (μ-DEFC) stack was also constructed using these electrocatalysts and etched printed circuit boards as anode and cathode current collectors. A maximum power density of 2 mW/cm² was achieved when the μ-DEFC was operated in air breathing mode at room temperature. This enhancement of the performance may be attributed to dispersion and accessibility of MWNTs support and Pt–Sn in the electrocatalyst mixture for ethanol oxidation reaction.     

烟杆热解固体产物性质及其影响因素研究

利用热重分析仪和马弗炉研究了温度和时间对烟杆热解固体产物性质(工业分析组成、发热量等)的影响.在温度为300～600℃,热解时间为30 min和60 min两种工况条件下,分别研究了烟杆热解固体产物性质随温度的变化.结果表明,随着热解温度的升高,热解固体产物中固定碳比例和发热量先升高后降低,在550℃时达到最高值.热解...     

桉树类生物质热解及产物释放特性研究

采用热重红外联用方法研究不同升温速率下桉树枝和桉树皮的热解特性和热解气体产物的释放特性,对比分析两者的差异性及差异机理。结果表明:桉树枝热解过程主要分为干燥、热解和碳化3个阶段,热解速率较快,气体产物释放主要集中在热解阶段进行,主要气体产物有烷烃、醇、酚、醛、羧酸、酮等多种有机气体产物和少量CO,CO2;桉树皮热解过程分为干燥、进一步干燥、热解反应、碳化及高温持续碳化5个阶段,相比桉树枝热解速率明显较低。桉树皮热解反应阶段在450⁵50℃和650550℃和650⁸00℃两个高温区间存在较为剧烈的碳化反应过程,主要气体产物为CO2和CO。     

Development of open-cathode polymer electrolyte fuel cells using printed circuit board flow-field plates: Flow geometry characterisation

Open-cathode air-breathing fuel cells have the advantage of reduced system complexity and simplified operation, as oxygen is taken directly from ambient air without the need for blowers/compressors. In this study, printed circuit boards (PCBs) are used as flow-field plates. The use of PCBs offers the potential for significant cost reduction due to their well-established manufacturing processing and low materials cost. This study investigates the effect of varying the cathode geometry (parallel and circular) and opening ratios (43%, 53% and 63%) on fuel cell performance using polarisation curves, electrochemical impedance spectroscopy (EIS) and thermal imaging. The results obtained indicate that circular openings afford lower Ohmic resistance than parallel flow-field designs, which helps improve contact between the gas diffusion layer and flow-field plate. However, flow-field plates with circular openings suffer from greater mass transport limitation effects. Likewise, greater opening ratios offer better mass transport but increased Ohmic resistance as a result of the reduced area of lands/ribs. The thermal imaging results reveal lower temperature in the middle of the fuel cell due to “bowing” of the printed circuit board flow field plates which reduces the local current density. A trade-off between these factors results in a design with a maximum area specific power density of 250 mW cm⁻².     

Design, fabrication and performance evaluation of a miniature air breathing direct formic acid fuel cell based on printed circuit board technology

A miniature air breathing compact direct formic acid fuel cell (DFAFC), with gold covered printed circuit board (PCB) as current collectors and back boards, is designed, fabricated and evaluated. Effects of formic acid concentration and catalyst loading (anodic palladium loading and cathodic platinum loading) on the cell performance are investigated and optimized fuel concentration and catalyst loading are obtained based on experimental results. A maximum power density of 19.6 mW cm⁻² is achieved at room temperature with passive operational mode when 5.0 M formic acid is fed and 1 mg cm⁻² catalyst at both electrodes is used. The home-made DFAFC also displays good long-term stability at constant current density.