Particle-scale investigation of oxy-fuel combustion in a pressurized fluidized bed

Abstract

A CFD-DEM model that includes chemical reactions such as fuel pyrolysis, combustion, gasification, volatile combustion, and the formation and reduction of gaseous pollutants was developed in the open-source MFIX. The extended model was validated at particle and reactor scales by comparison with experimental data. Subsequently, the model was applied to study the oxy-fuel combustion in a pressurized fluidized bed operating at varied pressures between 0.2 MPa and 0.8 MPa and O2 concentrations between 30 % and 50 %, yielding abundant particle-scale information. The results revealed that fuel combustion is positively impacted by volatile combustion. Raising the pressure or the O2 concentration, especially the pressure, enhances the combustion rate and temperature of fuel particles. The heat transfer of fuel particles during stable combustion is dominated by the reaction heat, followed by the convection heat, radiation heat, and particle–wall conduction heat, while heat conduction between particles can be safely ignored due to its small contribution. The heat and mass transfer of fuel particles is greatly improved under higher operating pressures but insignificantly affected by the O2 concentration of the combustion medium.