Oxy-fuel combustion is one of the most promising technologies for enabling CO2 capture. In order to understand the oxy-fuel combustion behavior in fluidized beds, 3D Eulerian-Lagrangian simulations based on the multiphase particle-in-cell (MP-PIC) scheme were carried out. The gas field was modelled by means of large eddy simulation (LES), and the particle field was described by a discrete particle method. Comprehensive reaction models including devolatilization, char combustion, combustion of volatiles, and production of pollutants were incorporated into the scheme. A micro-fluidized bed reactor with an online mass spectrometer was used to verify the simulation. The present CFD simulation was able to reproduce different gas-solid flow structures and describe the dynamic process of gaseous product formation. Based on the simulations, some useful information that is difficult to obtain from physical experiments was obtained, including the distributions of particle concentration, gas and particle velocities, temperature, and pollutant emissions. Finally, combustion characteristics are discussed in relation to the four well-established gas-solid flow structures, i.e. bubbling, fluidization, turbulent fluidization, and pneumatic conveying. It was found that the turbulent fluidization and fluidization flow structures are more suitable for oxy-fuel combustion in fluidized beds. (C) 2019 Elsevier B.V. All rights reserved.