Concentration of dioxin congeners in different phase products from a thermal process of end of life automobile shredder dusts

Automobile shredder residue (ASR) dusts are generated from a shredding facility that recovers steel by sorting shredded end-of-life vehicles (ELVs). One of the recycling technologies with maximum recovery rate and less volume to be disposed could be thermal processes. The proposed thermal method is a combined process with pyrolysis or gasification at substoichiometric air conditions and melting of remained product to generate slag as reusable of recycled materials. Therefore, the intermediate or final products generated during the series of processes, which are gas, oil, char, and slag, would be used as fuels or usable materials for further recycling. Before utilizing such products, they must be proven to be nonhazardous by analyzing for contamination of toxic substances such as dioxins. In this study, dioxin concentrations and distributions of congeners in products such as gas, oil, char, and slag from pyrolysis and melting process of ASR dust, and dioxin concentrations in ASR dust, were analyzed to compare the products of pyrolysis. In addition, the emission characteristics of dioxin at different air/fuel ratios and the distribution of dioxin concentrations in melting slag were investigated. ASR dust was found to contain about 6 pg toxic equivalent quantity (TEQ) per gram of dioxins with predominantly more chlorinated congeners. Product gas at in substoichiometric oxygen supply (gasification) showed 75 times higher concentration of dioxins than that with no oxygen (pyrolysis). Oil produced by pyrolysis contained more chlorinated dioxins and char product showed higher dioxin concentration than with oxygen. All products-gas, oil, and char-tended to include more furans than dioxins because of lack of oxygen during pyrolysis. Results will be used as basic data for developing pyrolysis, gasification, and melting technologies of ASR dust in future.