Exhaust constituent emission factors of printed circuit board pyrolysis processes and its exhaust control

摘要

The printed circuit board (PCB) is an important part of electrical and electronic equipment, and its disposal and the recovery of useful materials from waste PCBs (WPCBs) are key issues for waste electrical and electronic equipmeN.T. Waste PCB compositions and their pyrolysis characteristics were analyzed in this study. In addition, the volatile organic compound (VOC) exhaust was controlled by an iron-impregnated alumina oxide catalyst. Results indicated that carbon and oxygen were the dominant components (hundreds mg/g) of the raw materials, and other elements such as nitrogen, bromine, and copper were several decades mg/g. Exhaust constituents of CO, H_2, CH_4, CO_2, and NOx, were 60-115, 0.4-4.0, 1.1-10, 30-95, and 0-0.7 mg/g, corresponding to temperatures ranging from 200 to 500 ℃. When the pyrolysis temperature was lower than 300 ℃, aromatics and paraffins were the major species, contributing 90% of ozone precursor VOCs, and an increase in the pyrolysis temperature corresponded to a decrease in the fraction of aromatic emission factors. Methanol, ethylacetate, acetone, dichloromethane, tetrachloromethane and acrylonitrile were the main species of oxygenated and chlorinated VOCs. The emission factors of some brominated compounds, i.e., bromoform, bromophenol, and dibromophenol, were higher at temperatures over 400 ℃. When VOC exhaust was flowed through the bed of Fe-impregnated Al_2O_3, the emission of ozone precursor VOCs could be reduced by 70-80%.