Investigation of Kinetic, Thermodynamic and Performance Parameters during Devolatilization of Agricultural biomass Waste via TGA

Abstract

Agricultural biomass waste is a renewable energy source with numerous environmental benefits of particular importance in the bioenergy sector. This study examines the thermal decomposition behavior of khat stem (KS) as a renewable energy source using thermogravimetric analysis (TGA) during the pyrolysis process. The kinetic, thermodynamic, and performance parameters such as flammability, combustibility, ignition, and burnout were analyzed using TGA data collected at various heating rates (10, 20, 30, 40, 50, and 100 °C/min) in the temperature range of 30-800 °C in an inert atmosphere. The results show that KS has three distinct decomposition zones for water removal, hemicellulose, cellulose, and lignin degradation. The mass loss occurred mainly between 200 and 500 °C. The findings also revealed that increasing the heating rate caused the TGA/DTG curves to move to higher temperatures, possibly due to improved transport pathways, increased thermal energy, and thermal inertia. KS's activation energy and pre-exponential factor were 110.55 kJ/mol and 8.01E+11 min-1 using the Flynn-Wall-Ozawa (FWO) model and 106.06 kJ/mol and 1.29E+14 min-1 using the Kissinger-Akahira-Sunose (KAS) model. The difference between the average activation energy values and enthalpy change was approximately five kJ/mol using FWO and KAS models at different heating rates. The study found that KS has
low flammability, combustibility, ignition, and burnout temperatures at lower heating rates, making it a suitable renewable fuel resource that can replace fossil fuels.