A New Particle Cluster Diameter Model for Fluidized Bed

Particle cluster is the characteristic structure in gas-solid fluidization. It is of great importance in hydrodynamic modeling and simulation of fluidized bed. Generally, there are two main factors to describe a particle cluster: the cluster density denoting the solid volume fraction inside a cluster and the cluster diameter denoting the scale of a cluster. Recent reports show that the cluster density can be correlated with average solid volume fraction and operating condition of fluidized bed. However, it is still very hard to determine the cluster diameter via experimental method, due to its irregular shape and transient characteristics. The present work makes use of the recently developed cluster density model and the energy minimization multi-scale (EMMS) model to analyze the fluidization system. And the particle cluster diameter is finally obtained through this analysis and energy minimization restrictions. This new cluster diameter model has been used in the EMMS/DP model to deduce a corresponding drag force model, and is finally applied in some riser simulations. The simulation results agree well with experimental results under different operating conditions, proving the high accuracy in riser simulation of the new cluster diameter model.