Determination and reasonableness analysis of kinetic parameters for coal combustion

Accurately determining the kinetic triplet (activation energy (E), pre-exponential factor (A), and mechanism function) for coal combustion is crucial for elucidating reaction mechanisms and optimizing combustion processes, yet existing methods have limitations in simultaneously obtaining and validating these parameters. In this study, lignite (HM) was analyzed using thermogravimetric analysis (TGA) at heating rates of 10, 15, and 20 °C/min. Four isoconversional methods (FWO, KAS, Starink, and Friedman) were compared for calculating E. The Coats-Redfern method was subsequently employed to determine A and mechanism function. Finally, the isokinetic temperature (Tiso), derived from the kinetic compensation effect, was compared with the experimentally observed maximum reaction rate temperature (T4) to validate the kinetic triplet. Results indicate that the FWO method provides the best linear fit and is the most effective approach for calculating E. The E during HM combustion stage decreases from 119.20 to 57.60 kJ/mol with increasing conversion (average 83.06 kJ/mol), and the A decreases correspondingly. The mechanistic functions for HM combustion stage at heating rates of 10, 15, and 20 °C/min are 21−α−12−1, 1−2/3α−1−α23, and α+1−αln1−α, respectively. The agreement between Tiso and T4 exceeds 96%, confirming the reliability of the kinetic parameters. Prior to T4, the reaction rate is primarily controlled by E; after T4, it is governed by A. The proposed kinetic model yields reliable parameters, enhancing the predictive accuracy of numerical combustion simulations and providing a theoretical foundation for optimizing boiler operating conditions. This contributes to improved combustion efficiency and reduced pollutant emissions.