Study of hydrodynamic characteristics of particles in liquid–solid fluidized bed with modified drag model based on EMMS

• Flow behavior of solid is simulated by Euler–Euler with modified drag model on EMMS.
• Modified drag model is characterized by treating dense and dilute phase as continua.
• The flow behavior of clusters can be predicted by modified EMMS drag model.
• This drag model predicts solid concentration is in good agreement with experiments.

Flow behavior of solid phases is simulated by means of Eulerian–Eulerian in a liquid–solid fluidized bed with modified drag model based on energy-minimization multi-scale (EMMS) method. The modified EMMS drag coefficient is characterized by the treatment of the particle-rich dense phase and the liquid-rich dilute phase as the two interpenetrating continua. It was shown that the modified EMMS drag coefficient can predict reasonably the solid concentration profiles in a liquid–solid fluidized bed. The distributions of solid velocity, granular temperature and granular pressure are predicted. The phenomenon of back-mixing near the wall is found in the liquid–solids fluidized beds.

Profile of particle concentration along the radial direction. This figure compares the experimentally time–average radial solid concentration profiles measured by Razzak et al. with simulation results. It can be seen that the concentration of particles is high near walls and low at the center. Simulations by modified EMMS drag model and Gidaspow drag model give a high concentration of particles in the center regime comparing to experimental data. Near the wall, the predictions by modified EMMS drag model are lower than experimental results. The difference of simulations using the modified EMMS drag model and Gidaspow drag model is obvious. At the radial dimensionless distance x/R less than 0.43, the predicted concentration of particles using the modified EMMS drag model is larger than that by Gidaspow drag model. However, it is reverse at the x/R larger than 0.43. The mean value of solids holdup is calculated from simulations. The values of mean solids holdup are 0.0803 and 0.0762 using modified EMMS drag model and Gidaspow drag model, respectively. The measured mean solids holdup is 0.0821. The simulated result from modified EMMS drag model is better in agreement with experimental data, particularly at high concentration of particles. It indicates that the flow heterogeneity becomes more obvious at high concentration of particles.Figure optionsDownload as PowerPoint slide