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: T1 (100 % wheat straw) and T2 (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 1st and 2nd 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 T1 and 4.0–15.9 % for T2 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 T1 and T2 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.