Experimental Study On The Heat Transfer Characteristics Of Waste Printed Circuit Boards Pyrolysis

With the advent of the electronic era, printed circuit boards(PCBs) as important component of electronics devices production are increasing. Thus, great attention has been paid on how to make the procession of PCBs harmless, recycling and large-scale. Although pyrolysis technology in processing waste PCBs is maturing, it is essential for large-scale procession of PCBs to resolve problems that a pyrolysis furnace has a low heat utilizing efficiency resulting from quite large percentages of heat loss. Therefore, it has been a hot studying topic how to improve the heat transfer intensity between PCBs' particles in the pyrolysis furnace, enhance the heat utilizing efficiency and the pyrolysis rate to optimize the design of pyrolysis furnaces.Present paper concentrated on experimental study on the heat transfer characteristics of waste PCB under Pyrolysis. By the combining experiment and theories in thermal engineering, environmental engineering and chemical engineering, the temperature distributions in the specially-designed pyrolysis furnace with stirring apparatus have been measured including ones in the two comparative experiments of heating FR4 boards and ceramic particles(inert material) and the two comparative experiments of FR4 boards pyrolysis with and without stirring, and the energy-consuming analysis experiment of the pyrolysis furnace without stirring is also conducted. Also, further discussions on the mechanism of FR4 boards pyrolysis were explored, dynamic parameters under pyrolysis calculated and preliminary proposals on building the heat transferring simulating model were also given. Further, the establishment of a single FR4 board particle pyrolysis model has been preliminary studied.Experimental studies found that the temperature of each point is substantially the same at a certain vertical height; temperature gradient is gradually decreasing with the elevation in heights at the same radial space from the bottom of the pyrolysis furnace, and gas produced from FR4 boards pyrolysis can contribute to heat transfer and make the pure conduction transform to the mixed heat transfer of conduction and convection. Stirring can improve heat transfer, make the increase in temperature under pyrolysis much higher than that without stirring and force the temperature to distribute uniformly. Also, stirring can enhance the pyrolysis rate of FR4 boards to make the layered phenomena obvious in the pyrolysis furnace and enlarge the completely pyrolyzed region. Further, the pyrolysis furnace has a low heat utilizing efficiency with the absorbing heat less than30.26% of the total energy.Measures can be taken to improve the heat utilizing efficiency. It is important to optimize the design in the height of a pyrolysis furnace and in the stirring apparatus. Moreover, it is significant to recycle the heat from pyrolysis gases in the procession of FR4 boards to achieve the purpose of energy saving.