Numerical simulation based on computational particle fluid dynamics (CPFD) model was carried out in a two-dimensional fluidized bed of Geldart A particles which was previously used by Zhang et al. (2009) to study the effects of louver baffles on bed hydrodynamics and gas mixing. With the help of bubble-based energy-minimization multi-scale (EMMS) drag model, the simulation successfully predicted most of the hydrodynamic results which were highly agreeable with experimental results. However, gas tracing simulation was found to depart far from experimental results due to lack of modeling of porous structure of FCC particles. A direct method to characterize solids back-mixing strength based on the simulated internal circulation fluxes was established. The results not only proved the strong suppression of solids back-mixing by louver baffles, but also validated the feasibility of the two indirect measures used in the previous experiment to characterize solids back-mixing strength. Louver baffles' ability to break up bubbles was also proved. Under low superficial gas velocities, their vanes can split bubbles directly. However, it acts as a distributor under high superficial gas velocities. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.