The population balance model (PBM) and the governing computational fluid dynamics (CFD) equations were solved numerically using the finite size domain complete set of trial functions method of moments (FCMOM) approach. The overall objective of this study was to demonstrate the effect of property variation of solid particles in the simulation, design, and scale up of fluidized bed processes. In this study, the process of coal char gasification in a fluidized bed at elevated temperature in the presence of hydrogen and steam as gasification media was simulated. The coupling of coal char size variations, hydrodynamics of the system, and heterogeneous gasification reaction rate was included in the simulation. The heterogeneous gasification reaction was modeled based on the available experimental data using the shrinking core model (assuming surface reaction is the limiting step). The simulation results showed that the effect of particle property variations (e.g., size) during a process such as gasification of coal char in a fluidized bed is significant in the modeling and design of such processes. (C) 2017 Elsevier B.V. All rights reserved.