Kinetic modelling of mixed plastic waste pyrolysis

Abstract

The study of plastic waste thermal decomposition and kinetics is a crucial step for optimal reactor design and the scale-up of pyrolysis technologies for chemical recycling. Kinetic parameters of individual and mixed plastic waste samples that resemble the main components of plastic waste streams (polyolefins and polyesters) were determined in this study using thermogravimetric analysis. Strong dependencies of activation energy on conversion were found for the mixtures, indicating that the process occurs in multiple steps and there are strong interactions between plastic components, lowering their activation energy during the decomposition. PP and LDPE decomposed via two separate steps whereas others decomposed via a single step process. For plastic mixtures, three dominant partially overlapping steps were identified. Kinetic deconvolution analysis improved model accuracy of mixtures and enabled the study of kinetic contributions and behaviour of individual steps. The models were then applied to predict experimental data at various heating conditions and plastic compositions.