Combustion of electronic wastes using a drop tube furnace

High temperature combustion is a key during the pyrometallurgical recycling for electronic wastes. Former researches relating to thermal treatment concentrated on thermal decomposition during electronic wastes pyrolysis and oxidation, using e.g. thermogravimetric analysis (TGA) or lab-scale batch-feeding furnace. In the present research, a bench-scale incineration system was developed to study the combustion of electronic wastes and the emission characteristics. The system features a continuously-fed drop tube furnace. By using it, the combustion proceeds under comparable conditions and the emitted flue gas is steady & uniform, the thermodynamic equilibrium approach for conversions of inorganic halogen could be investigated. It also equips with a cooling & sampling unit for investigating the emission of post-combustion area. The effects of operating conditions on the completeness of combustion and the emission of inorganic Br for waste printed circuit boards were investigated systematically by using this furnace. Under the proposed conditions, the combustion is quiet complete and more than 99.89% organobrominated compounds contained in raw materials are destroyed and convert to HBr & Br₂ in flue gas. The two forms of inorganic bromine seem reach thermodynamic equilibrium within 0.25 s. Further experiments could provide the datum for analyzing the combustion performance, the emission characteristics of organic pollutants and the mechanism of chlorinated dioxins (PCDD/Fs) & brominated dioxins (PBDD/Fs) formation by fly ash catalyzed de novo synthesis.