Large-scale internally circulating flows of gas and particles might form under unevenly distributed fluidized air in a fluidized bed. Compared with bed materials, the present study investigated dissimilar particles with different sizes and density moving and mixing through the developed image technique in an internally circulating fluidized bed (ICFB). The concentrations of the tracer particles were obtained by the image analysis method. The inhomogeneity degree and lateral dispersion coefficients of the tracer particles were also calculated, with the results indicating that the degree of inhomogeneity decreases with the increasing dispersed time. The lateral dispersion coefficients of tracer particles with a lower density (for a similar diameter) are larger than those with a higher density. It is clear that the different air distribution methods play an important role in the lateral dispersion of the tracer particles. (C) 2017 Elsevier B.V. All rights reserved.