Products and bromine migration characteristics of non-metallic components of waste printed circuit boards pyrolysis in a fluidized bed pyrolyzer

Abstract

This study investigated non-metallic components (NMCs) of waste printed circuit boards (WPCBs) pyrolysis in a fluidized bed pyrolyzer (FBP). The pyrolysis temperature was set at 350–750 °C. K2CO3, ZnO, CaO and Fe2O3 were added at the temperature of 650 °C to stabilize Br. The characterization of pyrolysis char, pyrolysis oil and pyrolysis gas were analyzed. Migration and transformation of Br in NMCs pyrolysis was investigate. Brominated epoxy resin cracking and Br fixation mechanism were proposed. Pyrolysis oil yield reached the highest at 650 °C. Phenols were the main components of pyrolysis oil, it increased with temperature and reached the highest at 650 °C. The proportion of esters and ketones were 2–4% and 2–3%, respectively. The secondary cracking during pyrolysis correlated the secondary release of CO2, CO, CH4 and H2. Br mainly distributed in pyrolysis oil in the form of HBr and reached the maximum at 550 °C. Organic bromides was mainly bromophenols in pyrolysis oil. Br distributed in pyrolysis char was mainly inorganic bromines in the form of brominated salts. Bromines in pyrolysis gas were mainly CH3Br, C2H5Br, C3H7Br, C3H5Br. K2CO3, CaO effectively promoted Br fixation through neutralization reaction, direct elimination and dissociation adsorption. ZnO, Fe2O3 promoted bromides cracking.