Experimental study on the reaction kinetics of char combustion in a pressurized O2/H2O atmosphere

Pressurized O₂/H₂O combustion is a potential CCS technology. In this study, a pressurized horizontal furnace was used to prepare pyrolysis char under pressurized inert atmosphere, and then a pressurized drop tube furnace was used to carry out char combustion under pressurized O₂/H₂O atmosphere (5% O₂, 20% H₂O) at the same pressure and temperature as the pyrolysis process. The carbon conversion of char under different pressures (0.4/0.7/1.0 MPa), temperatures (900/950/1000 °C), and residence time (1.38/2.76/4.14 s) was studied by proximate analysis. The random pore model was used to calculate reaction kinetic parameters of char combustion at different pressures. The results show that when the pressure increased from 0.4 MPa to 0.7 MPa, the carbon conversion increased significantly, with the increment reaching up to 9.90 percentage points. The marginal diminishing effect became significant when the pressure was greater than 0.7 MPa. The reaction activation energy and pre-exponential factor at 0.4/0.7/1.0 MPa were 66.53/66.29/35.79 kJ/mol and 20.54/36.84/1.69 s⁻¹, respectively.