Chemical Recycling of WEEE Plastics—Production of High Purity Monocyclic Aromatic Chemicals

Tobias Rieger,Matthias Franke,Jessen C Oey,Volodymyr Palchyk,Andreas Hornung,Alexander Hofmann

doi:10.3390/pr9030530

Abstract

More than 200 kg real waste electrical and electronic equipment (WEEE) shredder residues from a German dismantling plant were treated at 650 °C in a demonstration scale thermochemical conversion plant. The focus within this work was the generation, purification, and analysis of pyrolysis oil. Subsequent filtration and fractional distillation were combined to yield basic chemicals in high purity. By means of fractional distillation, pure monocyclic aromatic fractions containing benzene, toluene, ethylbenzene, and xylene (BTEX aromatics) as well as styrene and α-methyl styrene were isolated for chemical recycling. Mass balances were determined, and gas chromatography–mass spectrometry (GC-MS) as well as energy dispersive X-ray fluorescence (EDXRF) measurements provided data on the purity and halogen content of each fraction. This work shows that thermochemical conversion and the subsequent refining by fractional distillation is capable of recycling WEEE shredder residues, producing pure BTEX and other monocyclic aromatic fractions. A significant decrease of halogen content (up to 99%) was achieved with the applied methods.

Highlights

Waste electrical and electronic equipment (WEEE) represents a significant source of almost all precious and critical metals, but their recovery potential is far from being fully exploited as things stand today
Real WEEE shredder residues were thermally converted by means of pyrolysis at 650 ◦ C with a residence time of 30 min
Liquid, and gaseous products were yielded from this process; these products will be termed solid residue, condensate, and gas hereinafter, respectively

Summary

Introduction

Waste electrical and electronic equipment (WEEE) represents a significant source of almost all precious and critical metals, but their recovery potential is far from being fully exploited as things stand today. At the end of state-of-the-art WEEE treatment processes, one or more output fractions are left behind, which are usually sent to landfills or to energetic utilization in waste incinerators WEEE and its output fractions contain high-quality plastics like HIPS, ABS, epoxy resins, PS, PE, PP, and PVC [5,6,7]. These plastics show high concentrations of flame retardants (FR) as TBBPA, DDO, HBCD, and DDE [3], resulting in bromine and chlorine concentrations of 0.6–4.0 wt.% [8].

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Discussion

Conclusion