Critical comparison of hydrodynamic models for gas-solid fluidized beds-Part II: freely bubbling gas-solid fluidized beds

In very dense regions in the fluidized bed the KTGF based on instantaneous binary collisions needs to be extended for additional frictional stresses in addition to the kinetic and collisional transport mechanisms. The extra frictional stresses were implemented via a relatively simple semi-empirical closure model and proved to have a significant influence on the predicted bubble size, rise velocity and visible bubble flow rate, where the model predictions strongly depend on the empirical constants. To further enhance the performance of the KTGF to describe the hydrodynamics of freely bubbling beds a more fundamental description of the frictional stresses on the particle level should be incorporated.