Modeling kinetics and transport phenomena during multi-stage tire wastes pyrolysis using Comsol®

This paper is devoted to the modeling of the pyrolysis process in order to predict mass and heat loss profiles of a used tire sample and ultimately prevent eventual difficulties in pyrolysis reactors. Once assumptions are made, the thermal balances and kinetics of each reaction were written. The resolution of the differential equations allowed us to present the profile of heat variation within the sample as a function of temperature in a fixed bed reactor. The modeling is based on the energy behavior of each reaction, the rate conversion of which was also modeled and compared with that obtained experimentally. There is a satisfactory agreement between the theoretical and the experimental results in one hand and a good fit with experimental and regression results of other researchers in another hand. It was shown in particular, that some exothermic reactions intervene during the pyrolysis of the used tires. Indeed, the exothermic heat at the center of 2 cm particle exceeds 1500 kJ/kg which presents an economic and energetic payoff for the plant. It has also been noted that the small particle size can result in faster heat transfer and shorten the process completion time. At the same time, rapid heat transfer can trigger more endothermic reactions, increasing thus the overall energy consumption of the process.