Contact electrification and electrostatic interactions often occur in the fluidization process, which can significantly influence the dynamic behaviour of particles and the fluidization performance. In this study, a discrete element method coupled with computational fluid dynamics (DEM-CFD) is developed by implementing contact electrification and electrostatic interaction models and the combined effects of contact electrification and electrostatic interaction on fluidization are analysed. It is found that the charge of the particle system increases with the superficial gas velocity. Particles of different material properties (especially work function) can be bi-charged and form agglomerates. At low superficial gas velocities, the particle bed cannot be fully fluidized and the pressure drop tends to be stable rather than fluctuating as the gas flows through the micro-channels of the formed agglomerates. However, at high superficial gas velocities, the agglomerates can break, inducing strong fluctuation of the pressure drop. This implies that the electrostatic phenomena and fluidization behaviour can mutually influence each other during the process. (C) 2016 Elsevier B.V. All rights reserved.