Gas-solid flow in CFB riser was simulated by a combined approach of computational fluid dynamics (CFD) and discrete element method (DEM). A new cluster analysis method based on image calibration and processing technique was developed to obtain overall

axial and radial distributions of clusters in fluidized beds as well as cluster characteristics in terms of inclination angle

degree of sphericity

and aspect ratio of long over short axis. The clusters showed a wide distribution with mainly small clusters and large clusters formed in the regions near the wall. Along the height direction of the riser

the amount of clusters first increased and then gradually decreased. In addition

clusters were most likely to exist in the form of non-spherical aggregates with large inclination angle and aspect ratio between 2 and 4.