Thermogravimetric Study of the Kinetics of the Reaction C + CO₂ under Pore-Diffusion Control

• Main Authors: Igor Donskoy, Aleksandr Kozlov
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Energies
• Subjects: gasification; thermogravimetry; thermokinetic analysis; diffusion processes
• Online Access: https://www.mdpi.com/1996-1073/14/7/1886

This study presents experimental studies of charcoal gasification with CO₂ at different heating rates (1, 5, 10, 20, and 50 K min⁻¹). The kinetics of the reaction C + CO₂ under pore-diffusion control is studied. We propose a new method for the proper determination of activation energy during the processing of thermogravimetric curves of porous carbon gasification under conditions of pore-diffusion resistance. The results of the inverse kinetic problem solution are compared with different hypotheses about the regime of the investigated heterogeneous reaction process (kinetic, diffusion, pore-diffusion). The change of reaction regimes from kinetic to diffusion is detected during charcoal gasification at different heating rates. At heating rates of 5–20 K min⁻¹, the values of activation energy of carbon gasification reaction in the carbon dioxide atmosphere, obtained by the proposed method, closely match the data found in the previous studies. The use of diffusion models in the processing of thermogravimetric curves determines the conditions under which conventional kinetic models fail to provide adequate information about the temperature dependence of the heterogeneous reaction rate.