Optimal Conditions and Regularity of the Separation of Metal and Non-Metal of Wasted Print Circuit Board During Pyrolysis in a Rotary Furnace

Abstract

Recycling metal materials from waste printed circuit board (WPCB) in a pollution-free and efficient way holds significant importance for the comprehensive utilization of resources. This study used WPCB as raw material and conducted pyrolysis in rotary furnace. The variation of functional groups of WPCB and non-metallic part of WPCB (NM-WPCB) under different conditions was analyzed by thermogravimetric coupled Fourier transform infrared spectroscopy (TG-FTIR). The liquid-phase products were analyzed using gas chromatograph-mass spectroscopy (GC-MS), and the morphology of the solid-phase products and the contact surface of metal part and non-metal part of WPCB were determined by photography and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). The results indicate that the maximum weight loss rate of WPCB is 62.48% and the activation energy (E) is 29.84 KJ/mol. During the pyrolysis, the presence of Copper (Cu) can lower the beginning reaction temperature, facilitate the release of bromine and chlorine, accelerate the synthesis of lighter hydrocarbons, and increase the release of CO2. The optimal conditions are as follows: a retention time of 60 min at 150°C, and a filling capacity of 51.95 g/L, resulting in a 100% separation rate of metal and no crushing is needed. The liquid organic products obtained were merely phenol and o-cresol, and no halogen compound was found. The gases generated during pyrolysis process formed bubbles at the contact surface between metals and non-metals, reducing the bonding force between them. Moreover, under the influence of gravity and centrifugal force in rotary furnace, separation can occur at relatively low temperatures.

Keywords: Waste printed circuit boards, Pyrolysis, rotary furnace, separation rate of metals