Microwave pyrolysis of polyethylene terephthalate (PET) plastic bottle sheets for energy recovery

Recovering energy from plastics not only mitigates the energy crisis, but also reduces the environmental pollution. In this study, microwave pyrolysis of polyethylene terephthalate (PET) plastic bottle sheets as affected by sheet size (2.5 × 2.5, 5.0 × 5.0, 7.5 × 7.5 and 10 × 10 mm 2 ), silicon carbide load (20, 25, 30, 35 and 40 g), and pyrolysis temperature (450, 500, 550, and 600 °C) was investigated. The results showed that increases in the sheet size increased the average heating rate (19.99–33.22 °C/min), solid yield (10.33–24.33 wt%), gas yield (15.00–35.67 wt%), recovered energy efficiency (10.16–25.34%) and overall energy efficiency (4.62–14.12%). Increases in the silicon carbide load first decreased and then increased the average heating rate (22.04–104.64 °C/min), whereas increased the solid yield (4.33–25.33 wt%), gas yield (8.00–40.33 wt%), recovered energy efficiency (4.21–25.34%) and overall energy efficiency (2.51–14.12%). Increases in the pyrolysis temperature first increased and then decreased the solid yield (22.33–35.67 wt%), gas yield (24.00–40.00 wt%), and the recovered energy efficiency (22.16–34.35%). The optimum condition was at 10 × 10 mm 2 sheet size, 35 g silicon carbide load and 550 °C pyrolysis temperature with 35.67 wt% solid yield, 40.00 wt% gas yield, 34.38% recovered energy efficiency and 18.35% overall energy efficiency. The results presented in this study supply method and data for energy recovery from PET plastic bottle sheets. • Microwave pyrolysis of polyethylene terephthalate plastic bottle sheets was detailed. • Effects of sheet size, silicon carbide load and pyrolysis temperature were studied. • The average heating rates were between 19.99 and 104.64 °C/min. • The recovered solid products were in the range of 4.33–35.67 wt%. • The recovered energy efficiencies were 4.21–34.35%.