Modelling of axial and radial solid segregation in a CFB boiler

Since solid exhibits a wide particle size distribution (PSD) in a circulating fluidized bed (CFB) boiler, it is difficult to predict the hydrodynamic behavior. Therefore, a model based on the semi-empirical approach is developed to approximate the local particle size distribution in CFB. The core/annulus flow structure is applied to this model and the particles in the bed are discretized into several size groups. The model accounts for the disintegration and shrinking of coal particles during the combustion process of each group of particles. It shows that coarser particles are gathered near the walls and the average particle diameter decreases along the boiler height, and this trend is more significant in the splash region. Moreover, coal combustion behavior affects both axial and radial segregations in a CFB boiler. All these phenomena are discussed against experimental data reported in literature.