Thermal decomposition of wheat straw pellets in a nitrogen environment: Characterization using thermogravimetric analyzer

This experiment used a thermogravimetric (TG) analyzer within a nitrogen environment, investigating the thermal degradation patterns of wheat straw pellets (WSP) under temperatures ranging from 31 to 800°C and varying heating rates (5, 10, and 20 °C/min). Two pellet types were considered: T 1 (100% wheat straw) and T 2 (70% wheat straw, 10% sawdust, 10% bentonite clay, and 10% biochar). This study comprehensively analyzes WSP’s thermal degradation, emphasizing model selection, composition effects, heating rate, and temperature. Results highlighted higher volatile matter content and calorific value in WSP. Model-free methods were applied to analyze TG/DTG profiles, revealing three distinct zones in WSP thermal decomposition: drying, devolatilization, and carbonization. Devolatilization, especially its 1 st and 2 nd steps, was extensively examined, with a significant mass loss (approx. 65%) observed between 150 and 550°C. Higher heating rates induced a shift in thermogravimetric profiles to elevated temperatures. Maximum mass loss rates during devolatilization ranged from 4.41 to 16.28%/min for T 1 and 4.0 to 15.9% for T 2 pellets. Temperature significantly influenced mass loss and reaction rates, whereas heating rates had a negligible impact. Thermodynamic properties indicated equilibrium reactions during pyrolysis for both T 1 and T 2 pellets. Additionally, increasing heating rates correlated with an upward trend in the reactivity index. The findings contribute valuable knowledge for optimizing biomass utilization in combustion and pyrolysis processes.