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 4th 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 degrees 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 m(2)/g to 42.71 m(2)/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.