Effect of Residence Time on Liquid Product Yield through a Designed Pyrolysis Reactor with Six Series-Connected Condensers

The objective of this study was to investigate the effect of residence time on the product yields of multilayer plastic (ML) waste through pyrolysis using a household reactor. The system employed six series-connected condensers operating without cooling water for heat transfer. The research focused on determining the optimal residence time within the range of 60–120 min, with a heating rate of 5–15°C/min. Liquefied petroleum gas (LPG) served as the primary fuel for the pyrolysis process, while non-condensable gases were recirculated into the burner as supplementary fuel. The study analyzed the characteristics and quantities of the resulting products: solid residue, liquid oil, and non-condensable gases. The results indicated that the proportion of non-condensable gases ranged from 27.1% to 47.1%, while the liquid yield condensed from four of the six condenser tubes varied between 46.5% and 59.1%. The pyrolysis of ML waste produced solid residue ranging from 6.8 % to 13.8 % of the total products. The residence time significantly influenced the liquid yield, with the maximum liquid product of 591 g per 1 kg of ML feedstock obtained at a residence time of 60 min. To characterize the liquid product as biofuel oil, its chemical composition was analyzed using distillation gas chromatography (DGC) and gas chromatography-mass spectrometry (GC/MS). The analysis revealed that the liquid product contained fuel oil components, including kerosene, diesel oil, benzene, and fuel oil. Additionally, the liquid product exhibited a high heating value of 10,691 cal/g. Furthermore, substituting pyrolysis gas for LPG significantly reduced LPG consumption. This study provides valuable insights into the development of community-based pyrolysis systems.