Effect of Temperature and Vapor Residence Time on the Micropyrolysis Products of Waste High Density Polyethylene

Thermal degradation of plastics is a promising technology for addressing the waste management issues of landfill disposal, while obtaining useful products. Primary thermal degradation of polymers usually yields a large quantity of high molecular weight compounds with a limited applicability, making necessary a secondary degradation to improve the product quality. In this study, pyrolysis vapors from waste high density polyethylene (HDPE) were subjected to secondary degradation by varying the temperature and vapor residence time (VRT) in the reaction zone of a new two-stage micropyrolysis reactor (TSMR) attached to a commercial micropyrolysis unit. Temperature and VRT variations showed a strong effect on the product distribution, with low temperature (625 °C) and short VRT (1.4 s) producing a wide range of gases and liquid products and with high temperature (675 °C) and long VRT (5.6 s) producing mostly hydrocarbon gases and mono- and polyaromatics. The results showed a good agreement with previously reported product distributions for larger-scale pyrolysis reactors and were well explained by known degradation mechanisms.