Kinetic characterization of CO₂ gasification for coal-char: A case study

Gasification of coal under CO₂ environment is an attractive option for mitigating CO₂ emissions. Kinetic characterization of coal-char is beneficial for understanding its performance during gasification processes in practical systems. India has 4^th largest coal reserve in the world; however, very few studies have been conducted on Indian coal for assessing thermal as well as kinetic behavior during CO₂ gasification. Therefore, the present study aims to assess the reaction kinetics during CO₂ gasification of coal-char from Talcher, which has the largest coal reserve among Indian coalfields, using isothermal thermogravimetric analysis at 900–1050°C. The studied coals are of sub-bituminous to high volatile bituminous. It has moderately high ash yield (15–31%) and > 68% of reactive macerals. Specific surface area of char gradually increases from 2.83 m²/g to 42.71 m²/g with increase in temperature. Furthermore, the char surface area shows a strong correlation with the reactivity index. The kinetic parameters are determined by using first-order and nth-order kinetic models, namely, volumetric, shrinking core, and random pore models. The activation energy (E_a) shows a range of 118–194 kJ/mol and 162–213 kJ/mol for first order and nth-order models, respectively. The temperature significantly influences the reaction rate, suggesting a chemical reaction control zone for the studied temperature range. This study also highlights the morphological evolution of char pore structure with temperature.