TG–MS study of the thermo-oxidative behavior of plastic automobile shredder residues

Abstract

Automobile shredder residues (ASR) are materials that are rejected in the metal recovery process for end-of-life vehicles (ELV). These residues are composed of such materials as plastics, foams, glasses, rubbers, textiles, remaining metals and soils. ASR disposal is a difficult task, due to increasingly restrictive re-use policies. The pyrolytic reuse of ASR is one important option for energy recovery. The gas release behavior of pyrolyzed ASR was measured using a TG–MS apparatus, and this thermo-oxidative process was observed under different N2/O2 volume ratios. The final weight/initial residue weight ratio for pyrolyzed ASR decreased from 43.4% to 10.1% with increasing oxygen concentrations. The production rates of hydrogen, methane and carbon dioxide also varied with different N2/O2 volume ratios. The maximum emission of hydrogen and methane occurred when the thermo-oxidative atmosphere was entirely N2. Temperature had a positive impact on hydrogen production, and the methane emission ratio reached a peak at the second shoulder of the devolatilization stage during which stage organic polymers were emitted. A peculiar characteristic of ASR is its content of nitrogen. The effects of ASR nitrogen content on N2O and NOX emissions were investigated in detail. NH3 was the dominant nitrogen species that was released during ASR pyrolysis. N2O is highly temperature-sensitive and decomposes to N2 at temperatures greater than 900°C.