Pyrolysis kinetic behaviour and thermodynamic analysis of waste wind turbine blades (carbon fibres/unsaturated polyester resin)

This research aims to study the pyrolysis characteristics and thermodynamic analysis of waste wind turbine blades (WTBs: composed of carbon fiber/unsaturated polyester resin) using a thermogravimetric analyzer (TG). The distribution of pyrolysis vapor products and their chemical compositions were analyzed. Also, pyrolysis experiments were carried out at various heating conditions to examine its effect on the vapor composition, and their pyrolysis kinetics was simulated using several modeling routes. In addition, all degradation regions of WTBs were mathematically simulated. The results showed that WTBs are rich in carbon element (53–88 wt.%) and volatile matter (26–30 wt.%), whereas TG measurements revealed that WTBs can fully degrade up to 500°C with a mass loss of 31%. Carbonyl (C=O) was the major functional group in the released vapor with a constant intensity even when the heating rate changed, while styrene was the major Gas chromatography-mass spectrometry compound with a significant abundance of 87% (at 30°C/min) versus 84% (at 5°C/min). Finally, kinetic investigations manifested that WTBs with a specific configuration have lower average activation energies (Ea) estimated at 172 kJ/mol (KAS), 220 kJ/mol (FWO), 194 kJ/mol (Friedman), and 159 kJ/mol (Vyazovkin and Cai), and FWO provides the highest R² of 0.99. This decrease in Ea and the reaction complexity is caused by high conductivity of carbon fibers which helps in increasing the heat transfer and speeding up the reaction. The average enthalpy and Gibbs free energy were estimated in the ranges of 166–215 kJ/mol and 114–226 kJ/mol, respectively. Based on that, resin and carbon fibers can be recovered from WTBs using pyrolysis treatment.