Investigation on pyrolysis kinetics and thermodynamic parameters of soybean straw: a comparative study using model-free methods

Thermochemical conversion of surplus agro-residue for energy generation has gained renewed attention due to its abundant availability throughout the world. Although, it still needs the thermodynamic and pyrolysis kinetic background that plays an important role in the effectual design of thermochemical conversion reactors such as pyrolyzers and gasifiers. In the present study, the thermal profile (mass loss vs. temp) for soybean straw was examined at 20, 30, and 40 degrees C/min heating rates under a non-isothermal condition in an oxygen-limiting environment through a thermogravimetric analyzer (TGA). The pyrolysis kinetic parameters (activation energy and pre-exponential factor) were evaluated by applying isoconversional model-free methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink, and Vyazkovin. The average values of activation energy for KAS, FWO, Starink, and Vyazkovin models were recorded to be around 150, 155, 147, and 153 kJ/mol, respectively. Thermodynamic variables (change of enthalpy, entropy, and Gibbs free energy) for soybean straw were also computed. The average values of enthalpy for FWO, KAS, and Starink were recorded to be 151, 147, and 142 kJ/mol, respectively. The obtained simulation findings of pyrolysis kinetic and thermodynamic variables are in good agreement.

Automated summary

In this study, the thermochemical and pyrolysis characteristics of soybean straw were investigated using thermal analysis methods. The kinetic parameters and thermodynamic variables were calculated through modeling and simulation, and the results were in good agreement with experimental data.