Kinetics of coal char gasification with CO2: Impact of internal/external diffusion at high temperature and elevated pressure

A pressurized wire-heating reactor (PWHR) that can provide experimental conditions up to pressures and temperatures of 50 atm and 1750 K, respectively, was developed to evaluate the intrinsic reaction kinetics of CO2 gasification for Berau sub-bituminous coal char (Indonesian coal) at elevated pressure using a synchronized experimental method. This synchronization system consists of a thermocouple wire for both heating and direct measurement of the particle temperature and a photodetector sensor for measuring the intensity of the luminous emission from the reaction particle to determine the ignition/burnout points. The intrinsic reaction kinetics obtained from PWHR, which was analyzed from nth order reaction rate equations, was verified by comparison with TGA results. The internal/external effectiveness factor was analyzed to determine the effects of high pressure (up to 30 atm) and temperature (up to 1723 K) on char-CO2 gasification. Accordingly, the intrinsic activation energies based on nth order reaction rate equation were determined to be 152 kJ/mol (via TGA, 75 μm char particle), 150 kJ/mol (via TGA, 800 μm char particle), and 149.2 kJ/mol (via PWHR, 800 μm char particle).