Thermodynamic and kinetic behaviors of coke gasification in N2-CO-CO2-H2-H2O

Changes in the gas balance components, carbon gasification rate and reaction enthalpy of carbon in reaction with CO2 and H2O were analyzed by thermodynamic calculations under different temperatures and pressures. The dynamic behavior of coke was simulated using a thermogravimetric method in N2CO-CO2-H-2-H2O, and the gasification reaction rate of coke and the controlling factors in the gasification process were analyzed. The results show that the effect of H2O on coke gasification is stronger than that of CO2. In the low temperature region, the reaction enthalpy of C and H2O is higher than that of C and CO2, and the reaction enthalpy of C and CO2 gradually becomes higher than that of C and H2O with increasing temperature. Increasing pressure can block the C gasification. Increases in temperature and in H2O volume fraction promote coke gasification; furthermore, the effective internal diffusion coefficient and the interfacial reaction rate constant of coke gasification gradually increase, and the improvement of the internal diffusion conditions is clearly greater than that of the interfacial reaction. In the process of coke gasification, with increasing temperature and H2O volume fraction, the gasification reaction region controlled by the interfacial reaction gradually increases. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.