Two-stage thermochemical conversion of polyethylene terephthalate using steam to produce a clean and H₂- and CO-rich syngas

This study deals with thermochemical conversion of polyethylene terephthalate using steam and a two-stage process having fluidized bed packed bed reactors. In the study, the temperatures of the fluidized bed reactor and packed reactor were varied in the range of 600–800 and 700−800 °C, respectively. In the experiments, active carbon used as a tar removal additive sharply increased the yields of syngas, char, H₂, and CO and decreased the condensed tar yield. Although toluene, styrene, naphthalene, biphenyl, and anthracene were found in the syngas obtained without active carbon, none were found in the experiment with active carbon. The tar content in the gas with active carbon was 13 mg/Nm³. A high tar-cracking reactor temperature and a high steam/fuel ratio favored the production of syngas and H₂. In the present study, the highest H₂ yield was 93 g/kg-feed, the highest H₂ content in syngas was 53 vol%, and the CO yield was 418 g/kg-feed. Also, a long-term thermochemical conversion of PET was explored for 4 h, and there were no operational problems during the experiment. In the long-term operation, tar appeared only after 2 h reaction time, and anthracene appeared only in the gas sample drawn after 4 h reaction time.