Research on the microwave pyrolysis behavior of automotive shredder residue

The recycling of end-of-life automobiles has become one of the most important issues facing various countries. At present, the main approach to processing these automobiles involves recycling, which, after dismantling and crushing, creates residual materials known as automotive shredder residue (ASR). ASR is mainly recycled through incineration or landfill disposal, which can cause environmental pollution and waste of resources. Pyrolysis, an emerging ASR treatment method, is widely considered an ideal alternative. While traditional electric pyrolysis has the advantages of high energy consumption and low heating rate, microwave pyrolysis offers higher heating coefficient, lower energy consumption, and greater environmental protection. Therefore, based on the microwave pyrolysis technology, this work investigates the thermal analysis kinetics and pyrolysis of whole components of ASR. The results revealed that the average activation energy of ASR reached 93.476 kJ/mol, as calculated using the Flynn–Wall–Ozawa (FWO) method, and the reaction model was close to the diffusion-control model. Furthermore, the residence time and heating temperature have a great influence on the product composition and yield and affect the occurrence of secondary reactions, and the microwave power influences the rate of ASR cracking and the rate of energy transfer of the products, in which the microwave power has the greatest influence on the gaseous products. The H₂ content increased from 1.097 to 2.565 wt.%, while the methane content increased from 0.781 to 2.687 wt.%. Moreover, the yield of aromatic hydrocarbons in the liquid product increased with the increase of residence time, and the aromatic hydrocarbon product content increased from 31.67 to 44.39 wt.%. Finally, the increase in heating temperature decreased the yield of aromatic hydrocarbons in liquid products, while the increase of microwave power initially decreased and then increased the yield of aromatic hydrocarbons in liquid products. The findings of this work provide theoretical and experimental references for ASR microwave pyrolysis.