Thermal degradation and pyrolysis kinetics of two Indian rice husk varieties using thermogravimetric analysis

Agricultural crop residues are making significant inroads in the broad spectrum of lignocellulosic biomass for energy recovery and in realizing prospective potential of bio-based economy. In the present work, comprehensive physicochemical characterization of two rice husk varieties (RH-B and RH-P) of Indian origin, their thermal degradation behavior, and pyrolysis kinetics were studied via thermogravimetric analysis. Thermogravimetric experiments were conducted at five heating rates, viz. 2, 5, 10, 15 and 20°C/min. The activation energy for the thermal decomposition was calculated using Coats–Redfern and Distributed Activation Energy Model (DAEM) method. The ash content was found to be significantly less in RH-P (10.17 wt%) vis-a-vis RH-B (20.07 wt%) which infers that there will be fewer residues left after pyrolysis as compared to RH-B. The cellulose and hemicellulose contents put together was high in RH-P (60.1 wt%) as compared to RH-P (56.92 wt%), which was reflected in terms of average weight loss of 55.15% and 41.863% for RH-P and RH-B, respectively, just above 230ºC due to rapid decomposition. The maxima of the f(E) curve was found to appear at 192.77 kJ/mol and 229.12 kJ/mol for the RH-B and RH-P, respectively. The experimental data for the pyrolysis of RH-B and RH-P were found to fit well with the Ginstling–Brounshtein diffusion model from amongst various solid-state kinetic models.