Pyrolysis and gasification-melting of automobile shredder residue

Abstract

Automobile shredder residue (ASR) from end-of-life vehicles (ELVs) in Korea has commonly been disposed of in landfills. Due to the growing number of scrapped cars and the decreasing availability of landfill space, effective technology for reducing ASR is needed. However, ASR is a complex mixture, and finding an appropriate treatment is not easy on account of the harmful compounds in ASR. Therefore, research continues to seek an effective treatment technology. However, most studies have thus far been performed in the laboratory, whereas few commercial and pilot studies have been performed. This paper studies the pyrolysis and gasification-melting of ASR. The pyrolyis characteristics have been analyzed in a thermogravimetric analyzer (TGA), a Lindberg furnace, and a fixed-bed pyrolyzer to study the fundamental characteristics of ASR thermal conversion. As a pilot study, shaft-type gasification-melting was performed. High-temperature gasification-melting was performed in a 5000 kg/day pilot system. The gas yield and syngas (H2 and CO) concentration increase when the reaction temperature increases. Gas with a high calorific value of more than 16,800 kJ/m3 was produced in the pyrolyzer. From the gasification-melting process, syngas of CO (30∼40%) and H2(10∼15%) was produced, with 5% CH4 produced as well. Slag generation was 17% of the initial ASR, with 5.8% metal content and 4% fly ash. The concentration of CO decreases, whereas the H2, CO2, and CH4 concentrations increase with an increase in the equivalence ratio (ER). The emission levels of dioxin and air pollution compounds except nitrogen oxides (NOx) were shown to satisfy Korean regulations. Implications: In Korea, automobile shredder residue management has been a big issue. However, ASR has been regarded as a waste, not a useful compound to produce energy. In this study, the authors analyze syngas production of ASR by pyrolysis and high-temperature gasification-melting. The authors can obtain high-quality syngas from the pyrolyzer and gasification-melting system. Notably, gasification-melting has been performed in a 5000 kg/day pilot system, to produce syngas and obtain the primary operation data for scale-up and commercialization. Syngas production is achieved with slag and metal as the residues and slight emission of air pollutants including dioxin.