印刷线路板热解过程中的传热传质及其对热解反应的影响

Taking aim at the current problems of the complexity of pyrolysis reaction mechanism and the lack of heat and mass transfer investigation in the pyrolysis process of printed circuit boards, this project will study the heat and mass transfer characteristics and its effect on the pyrolysis reaction about a single circuit board particle and the printed circuit boards particle layers in a moving bed. . The characteristics of heat and mass transfer in the pyrolysis process of printed circuit boards and its effect on the pyrolysis reaction is going to be investigated in the following aspects: 1) By experimental researching and numerical modeling,the variation of temperature and volatiles of the single particle and particle layers is studied quantitatively,the migration law of heat and mass transfer will be confirmed. 2)By experimental researching and numerical modeling, the difference of the internal temperature distribution of the single particle and the discrepancy of the gas and solid temperature distributions along the height direction of moving bed between considering the pyrolysis reaction heat and ignoring the pyrolysis reaction heat are compared and analyzed, the relationship between the pyrolysis reaction heat and the physical heat transfer in the pyrolysis process of printed circuit boards will be determined.3)By theoretical analysis and numerical modeling, the contact heat transfer way and heat-transfer mechanism will be confirmed, and some valuable heat transfer correlations could be obtained.4)Taking aim at different conditions, the pyrolysis reaction time, the pyrolysis product yield and the pyrolysis product component are contrasted by experimental researching, the effect of heat and mass transfer on the pyrolysis reaction process of printed circuit boards will be determined . . By finishing these researches, the pyrolysis reaction mechanism of printed circuit boards could be deeply comprehended, and this will provide theoretical basis and scientific guidance for the optimization design of pyrolysis reactor.

针对线路板热解反应机理复杂、传热传质研究基础薄弱的现状，本项目将对线路板单颗粒及移动床中颗粒料层热解过程的传热传质特性及其对热解反应的影响等进行研究。研究内容如下：1）通过数值模拟和实验，对单颗粒和移动床内颗粒料层热解过程中的温度、未析出挥发分等随时间的变化特征深入研究，明确传热与传质的迁移规律；2）通过实验和数值模拟，比较考虑热解反应热和忽略热解反应热两种情况下线路板颗粒内部温度分布及沿移动床床高方向气固温度分布和热渗流作用区域的差异，揭示热解化学反应热与物理传热之间的相互作用关系；3）通过理论分析和数值模拟，明确线路板颗粒之间的接触传热途径和传热机理，获得有价值的传热准则关联式；4）针对不同工况，实验考察热解反应时间、产物产率和产物成分的变化，确定传热与传质对热解反应过程的影响。该研究可以丰富和发展线路板热解反应机理理论，为优化热解反应器设计提供理论基础和科学指导。

随着人们对电子产品的需求不断增加，电子产品更新速度的加快，印刷线路板（PCB）作为电子产品最基本和必不可少的部件，废弃数量也十分巨大。因此，废弃印刷线路板减量化、资源化、无害化的要求越来越迫切。本项目研究了线路板单颗粒及移动床中颗粒料层热解过程的传热传质特性及其对热解反应的影响。本项目研究内容如下：1）针对单颗粒线路板热解过程，建立了颗粒内部传热的数学模型，利用有限元法计算了热解过程中线路板颗粒内部温度分布随时间的变化规律，并讨论了各参数对模型的影响。2）利用自行设计的移动床热解实验装置，对印刷线路板基板进行了实验研究，研究了给料速率、热气体入口速度和温度等对上述变量的影响以及变量间的内在联系，揭示传热与传质间的耦合机理。3)采用高温热氮气对FR-4型废弃线路板颗粒和滑石瓷陶瓷片进行热解试验分析确定线路板热解过程中热解化学反应热与物理传热之间的相互作用关系，为热解过程中传热传质提供理论分析与实验支持。4）通过COMSOL Multiphysics 5.4模拟移动床中PCB颗粒之间的接触传热。通过系数形式偏微分方程模块、固体和流体的传热模块、表面对表面辐射模块及层流模块，并进行固体和流体传热与表面对表面辐射传热的多物理场耦合，以及固体与流体传热模块与层流模块的耦合，分析了移动床内异形线路板颗粒之间的接触传热特性。该研究对于PCB热解过程的高效传热和传质、提高热利用效率和热解速率、优化热解设备的设计和运行，对废弃印刷线路板实现批量化处理具有重要的研究价值和实际意义。