Pyrolysis Kinetics and Thermodynamics of Typical Plastic Waste

Global plastics production increased over the past few decades, and some alternatives that have been developed to manage plastic wastes are recycling and the energy-recovery method. It is important to better understand the reaction mechanism and kinetic model of plastic waste pyrolysis. The pyrolysis kinetics and thermodynamic parameters of polyvinyl chloride (PVC) cable sheath were studied in detail. The Flynn-Wall-Ozawa (FWO) method was used to calculate the activation energy values, and the Coats-Redfern (CR) model-fitting method was used to determine the reaction mechanism. Three pyrolysis stages can be found in three temperature ranges. The first two stages correspond to the conversion rate of 0.10-0.60 and 0.60-0.85, respectively. The estimated activation energy values range from 132.78 to 149.5 kJ mol(-1) with a mean value of 141.54 kJ mol(-1) at the first stage, while they fall in between 193.85 and 266.44 kJ mol(-1) with a mean value of 235.37 kJ mol(-1) at the second stage. The contracting-area model and the fifth-order model are recommended to describe the pyrolysis reaction mechanisms of PVC cable sheath at the first two stages, respectively. The thermodynamic parameters were also calculated to prove the feasibility of plastic pyrolysis into energy and provide strong support for establishing the pyrolysis model and optimizing the actual reaction device.