Mathematical Modelling of Microwave Pyrolysis

Abstract

Abstract This study deals with a detailed numerical investigation of the microwave heating process in plastic pyrolysis. The pyrolysis of high-density polyethylene (HDPE) was studied using a single-mode microwave cavity, TE10 mode, at 2.45 GHz with two different absorbents, as carbon and silicon carbide, and the results were compared. The temperature distribution inside the sample was determined by solving the conservation equations coupled with the microwave and chemical kinetic equations. Lambert’s law was applied to describe the electromagnetic field in the microwave cavity. The effective heat capacity method was used to account for the latent heat in the melting range of plastic. The heat of the reaction was taken into account using first-order kinetic equations assuming a single-step reaction. One-dimensional model equations were solved using the finite difference method utilising MATLAB codes. The model developed in this study provides a better understanding of the fundamental mechanisms of the microwave pyrolysis of HDPE based on a combination of electromagnetic field and thermal models. The primary focus was to incorporate and investigate the effect of the phase changes and reaction during microwave pyrolysis. The results show that the temperature profile strongly depends on the physical properties of the material. Silicon carbide provides more uniform heating distribution compared with carbon.