Thermal degradation properties, kinetic, thermodynamic and reaction mechanism of pyrolysis of biomass shells: pistachio, almond, walnut and hazelnut as bioenergy potential

The study investigates thermal degradation behaviors of pistachio (PS), almond (AS), walnut (WS), and hazelnut (HS) shells that are vegetal biomass sources using thermogravimetric analysis (TGA/DTG) methods and under high temperatures. The study was conducted in nitrogen at 298-1173 K heat intervals, at 5, 10, 20, and 25 K.min-1 heating rates. Using data achieved as a result of thermal characterization procedures, model-free Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and model-based Coats-Redfern (CR) methods are used to investigate kinetic and thermodynamic parameters including Ea, Delta H, Delta S, Delta G, and pyrolysis reaction mechanism. Two regions in (0.1 <= alpha <= 0.5) and (0.55 <= alpha <= 0.9) intervals are created based on the change of Ea values of pistachio, almond, and hazelnut shells based on alpha. The best model in Region I was determined to be one of the diffusion (D) models while in Region II, it was determined to be one of the nth-degree chemical reaction (F) models.