Kinetic modelling for thermal decomposition of agricultural residues at different heating rates

The purpose of this work was to establish the pyrolysis kinetics of agricultural biomass residues (mustard husk (MH), cotton stalk (CS), and groundnut shell (GNS)) using thermogravimetric analysis (TGA). TGA is carried out at different heating rates (5, 10, 30, and 50 K/min) under inert conditions in the temperature range of 303–1173 K. The iso-conversional methods of Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa were used to estimate the activation energy of the decomposition process. The Criado method, Coats-Redfern Method, and Direct Differential methods were used to model the kinetics, with the latter two methods providing a closer fit with the experimental data. The kinetics of thermal degradation were separately studied for three temperature zones represented as drying, active, and passive zones. The results of Coats-Redfern and Direct Differential methods showed that (i) the nth-order reaction model is applicable for all the samples with order of reaction in the active zone being around ~ 2.0–3.0, ~ 2.5–3.0, and ~ 3.0 for MH, CS, and GNS, respectively, and (ii) the D-3 model is applicable for all the samples in the passive zone.