Coal Char Gasification in the Mixture of H2O, CO2, H2, and CO under Pressured Conditions

The kinetic study of coal char gasification at elevated pressure is very limited and much less than that at atmospheric pressure, especially in the mixture of H2O, CO2, H-2, and CO. The inhibition effect of H-2 and CO and a suitable reaction model are both needed to be studied under pressured conditions. A Langmuir-Hinshelwood (L-H) type model has been widely adopted to describe coal char gasification at atmospheric pressure. But its applicability to pressured conditions is questionable. In this paper, the experiments of coal char gasification in the mixture of H2O, CO, H-2 and CO were carried out using a modified pressured thermogravimetric analyzer (PTGA) system at 0.5 MPa and within 1148-1198 K. Experimental results indicate that the gasification reaction rates of H2O and CO2 under pressured conditions are much higher than those at atmospheric pressure, and the inhibition effects of H-2 and CO are also stronger. The kinetic parameters in L-H model were determined from pressured pure H2O and CO2 gasification (N-2 as diluent). And the applicability of L-H model to pressured conditions was verified. It is shown that the L-H models based on common or separate active sites assumptions could not give satisfactory predictions to experimental data. Finally, we proposed a modified L-H model. This model only needs several extra experiments to calculate the modification factor, and can describe char gasification in the mixture of H2O, CO2, H-2 and CO under pressured conditions very well.