A Comprehensive Pathway on the Determination of the Kinetic Triplet and the Reaction Mechanism of Brewer's Spent Grain and Beech Wood Chips Pyrolysis

This study paves a strategy to better understand the thermal conversion of biomass residues. In particular, a comprehensive study to determine the multi‑step reaction model to describe the pyrolysis process of brewer’s spent grain (BSG) from Pilsner and Weizen malts and beech wood chips has been presented.Here an approach has been developed by using the independent parallel reactions model and the corresponding kinetic parameters have been optimised iteratively by the non-linear least squares analysis. To obtain kinetic parameters, reliable initial guess and boundary values for numerical optimisation process are needed. To this aim, integral isoconversional methods (by using Kissinger-Akahira-Sunose and Starink methods), Kissinger method and master plots have been solved using four different heating rates.For brewer’s spent grain and beech wood chips, similar mechanisms of the decomposition reaction have been observed. The mechanism of lignin is quite complex but, thanks to the comprehensive approach proposed in this study, a modelling of the thermal decomposition of lignin with a single kinetic triplet has been obtained. The results of the optimisation process show that the nucleation and growth, and nth order reaction mechanisms dominate the pyrolysis of the studied biomasses