Insights into the decomposition kinetics of groundnut shell: An advanced isoconversional approach

In this work, the thermal decomposition kinetics of groundnut shell is investigated using a novel isoconversional approach. It combines the mathematical deconvolution approach with the isoconversional kinetic analysis methods. The thermogravimetric data of groundnut shells at six different heating rates ranging from 5 to 40 K min−1 has been used to make kinetic and thermodynamic predictions for the pyrolysis process. Extensive results on effective activation energy, pre-exponential factor, reaction mechanism, free energy change, entropy change and enthalpy of the process are discussed in detail. Groundnut pyrolysis is envisioned to occur via the independent decomposition of three pseudocomponents, i.e., cellulose, hemicellulose, and lignin. The estimated values of activation energy for each pseudocomponent show a weak dependence on conversion. The model predicts average activation energy of 126.17, 125.41, and 80.04 kJ mol−1 for the first, second, and third pseudocomponent. The decomposition of cellulose and hemicellulose is observed to follow first and second-order kinetics respectively. The lignin decomposition is governed by a three-dimensional diffusion-based model. The work demonstrates an efficient, novel strategy for identifying the prominent independent reactions occurring in the overall decomposition process of biomass. The kinetic and thermodynamic results presented here are crucial for designing pyrolysis reactors with groundnut shells as the potential feedstock.