The particle size distribution (PSD) is known as an important parameter affecting the hydrodynamic behavior of fluidized beds. In this study, extensive experimental data for fluidization of particles with different PSDs in tapered fluidized beds was presented. In the experimentations, three Geldart B powders with four average diameters and various PSDs were used. The experimental results showed that the minimum fluidization velocity (U-mf) for particles with flat and binary size distributions were roughly the same; moreover, they were up to 25% larger than the U-mf values for narrow cut particle size distribution. The U-mf values for Gaussian size distribution were lower than those of narrow cut PSD by about 15%. Using the experimental data and dimensional analysis, several empirical models for evaluating the minimum fluidization velocity for different PSD types in tapered fluidized beds were developed. The influence of operating conditions and geometric parameters of tapered fluidized beds recast into five dimensionless groups were included in the new empirical models. Comparing the predictions of the proposed models with the experimental data shows that the maximum absolute error for different PSDs was <18%. The average deviations of the proposed models from the experimental data are, respectively, 5.3%, 5.4%, 6.4% and 5.9% for narrow cut, Gaussian, flat and binary size distribution. The experimental data for different PSDs was also compared with the predictions of the available models for minimum fluidization velocity and the importance of particle size distribution was discussed. The effects of average particle size, initial bed height and tapered angle on U-mf were also investigated and an increase of lira with increasing these parameters was observed. (C) 2018 Elsevier B.V. All rights reserved.