A reactive CFD model has been developed and implemented numerically in an in-house code for a coupled double loop circulation fluidized bed reactor. In the current work it is utilized for the chemical looping combustion (CLC) process but the model can easily be modified for exploring some other chemical looping processes. The air reactor and the fuel reactor are operated in fast fluidization regime and simulated separately in a simultaneous mode. The connections between the two reactors are realized through time-dependent inlet-outlet boundary conditions. The model predictions are validated by comparison with experimental data reported in the literatures. Good agreement is observed between the experiments and simulations. Using this model, fluid dynamics and chemical process performance of the double loop reactor is investigated. The results show that the methane is rapidly consumed at a very short entrance section of the reactor and the axial distribution of the oxygen is more smooth. Higher reactant residence time and fuel reactor temperature increase the conversion of methane and oxygen. The methane conversion could reach 95% during the current study. (C) 2017 Elsevier B.V. All rights reserved.