Optimizing kinetic evaluation through CFD-based analysis of heat and mass transfer in a high-pressure TGA

Abstract

Accurate measurement of heterogeneous reaction kinetics in thermogravimetric analysis (TGA) requires accurate estimation of concentration and temperature in the sample. However, this information is difficult to estimate during the measurement, especially at high temperatures and pressures. Computational Fluid Dynamics (CFD) is used to perform a comprehensive analysis of the temperature and species distribution throughout a high-temperature, high-pressure test rig, including temperature and species transport within the probe sample. The temperature and gas concentration within the sample are accurately calculated by CFD, providing a much deeper insight into the local temperature and species distribution. The numerical results show a significant decrease in gas concentration and temperature in the core region of the packed bed, indicating that bed diffusion dominates the overall conversion for the char reaction studied in this article. The re-evaluation based on the model considers the limitations of heat and mass transfer at each measurement point. This forms the basis for a novel, model-driven approach that derives heterogeneous kinetics from TGA measurements with significantly improved accuracy and reliability.