Experimental investigation on the heat transfer characteristics in process of printed circuit boards pyrolysis under nitrogen flow.

ABSTRACT

Pyrolysis process has many advantages, if integrated in the process of precious metals recovery from scrap printed circuit boards (PCBs). The heat transfer characteristics of PCB during pyrolysis have a significant influence on the pyrolysis efficiency and energy consumption. In order to improve the heat transfer performance and efficiency of energy utilization and reduce the energy costs, a fixed bed pyrolysis experiment device was established and investigated experimentally under high temperature nitrogen flow. The temperature distribution of waste PCB particles layer was measured, and the heat transfer characteristics was investigated. The experimental results indicate that the size of the PCB particle has an obvious effect on the pyrolysis reaction time and the migration rate of pyrolysis. The larger the particle size is, the shorter the pyrolysis reaction time is and the faster the migration rate is. When the square particle sizes are 1.5 cm, 2.5 cm and 3.5 cm wide, the average migration rates of pyrolysis reaction zone along the vertical direction are 0.47 m/h, 0.50 m/h and 0.63 m/h, respectively. Pyrolysis region and pyrolysis state have obvious effects on the temperature rising rate and temperature gradient along vertical direction.