Highly efficient PM2.5 filtration has been obtained experimentally using a fluidized bed. In this work, a CFD-DEM simulation was conducted to investigate the effects of operating conditions such as the superficial velocity, fluidization state, and PM size. These effects were assessed in terms of the capture ratio and the forces acting on the PM. A high collection efficiency is reproduced at PM diameters of less than 20 mu m and superficial velocities of 0.3-0.6 m/s. Most of the PM is captured by adhesion in the bottom two to six layers of bed particles, where the void fraction is low. The adhesion force is the dominant force, and the drag force is negligible even at a superficial velocity of 0.6 m/s. After the PM is captured, it moves with the bed particles in this system. The adhesion force is still dominant for a 30 mu m PM at 0.4 m/s. The capture ratio is 87.5%. However, the PM-bed particle collision velocity increases with increasing superficial velocity, and the repulsive force becomes large. The capture ratio decreases dramatically with increasing superficial velocity. The repulsive force becomes dominant for PM diameters above 40 mu m, and most of the PM cannot be filtered. (C) 2020 Elsevier B.V. All rights reserved.