A three dimensional (3D) model based on a Eulerian-Lagrangian framework was developed for a full-loop simulation of the oxy-fuel combustion that occurs in a circulating fluidized bed (CFB). The solid phase was described using the Multi-Phase Particle-In-Cell approach and the turbulence of the gas phase was predicted by a large eddy simulation, with a conversion model for coal particles implemented to consider the devolatilization in this model. Furthermore, heterogeneous and homogeneous combustion reactions were also considered. This model was tested against the experimental data from a pilot-scale 0.1MW(th) CFB combustor in terms of the hydrodynamics, temperature and gas component characteristics. The gas-solid flow and combustion characteristics under different conditions were numerically studied. The simulation results indicated that the furnace contained a typical structure with a dilute phase at the top and dense phase at the bottom. Increasing the O-2 concentration at the inlet increased the temperature in the furnace. The emission of CO2 gradually decreased as the O-2 concentration at the inlet increased. Meanwhile, an increase in the O-2 concentration could effectively decrease the CO emission in the flue gas. Moreover, the appropriate selection of coal particle size could improve the combustion efficiency. (C) 2019 Published by Elsevier B.V.