Combustion characteristics of waste printed circuit boards in thermogravimetric analyzers

Abstract

High temperature combustion is crucial for the most promising pyrometallurgical processing among the present processing methods of waste printed circuit boards (PCBs). This article reports the experimental studies of pyrolysis and combustion characteristics of waste PCBs using thermogravimetric analysis (TGA) techniques, and inorganic bromine (HBr+Br2) evolution during the temperature ranges based on the TGA data using the batch reactor system. Emphasis is laid on the weight loss in predevolatilization stage and the volatiles evolution. In the predevolatilization stage, there are 0.7% and 1.0% weight losses under pyrolysis and combustion condition respectively. The evolution of inorganic bromine contributes 85% and 90% to the two weight losses respectively. Remarkably, in the stage of volatiles rapid evolution, compared with that under pyrolysis condition, the volatiles evolution decreases by 22.8 wt % under combustion condition. Besides, 62 wt % of the original bromine evolves in the form of HBr during this stage, and 67% HBr in effluent converts to Br2. Based on these findings, the primary mechanism of weight loss in the predevolatilization stage and the volatiles evolution were discussed and analyzed. The findings are valuable for the combustion organization practice of waste PCBs. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1105–1110, 2014