Validation and Comparison of Discrete Element Model and Two-Fluid Model for Dense Gas-Solid Flow Simulation in a Fluidized Bed

Abstract

Two-fl uid model (TFM) and discrete element model (DEM) are the two most widely used methods for numerical simulation of dense gas-solid fl ow in a fl uidized bed. It is of great interest to investigate the diff erences in the physics of these two models and their applicability regime in modeling the dense gas-solid fl ow accurately. In this study, a quasi-2D spouted fl uidized bed was simulated by DEM and TFM separately. In DEM, the hydrodynamic fl ow fi eld is computed by solving the incompressible continuity and Navier-Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. The results show that the TFM cannot predict the evolution of the bubbles in the fl uidized bed accurately, but it could predict the height of the bed bett er in the initial period of fl uidization. Compared to the TFM, it is found that the DEM is closer to the experiment in determining the changes in the bubble shape, bed pressure fl uctuations, and particle velocity; however, the bed height predicted by DEM is slightly lower than the experimental value. The TFM simulations based on the Eulerian approach although computationally more effi cient are not very accurate in capturing the fl ow features of the fl uidized bed. It is concluded that for accurate simulation of transient dense gas-solid fl ow simulation of a fl uidized bed, DEM should be used and not the TFM based on the kinetic theory of granular fl ow.

Numerical Simulation of Combustion and Characteristics of Fly Ash and Slag in a “V-type” Waste Incinerator

“…The secondary air inlet velocity was 9.161 m/s, the temperature was 464.55 K, the mole fraction of O 2 was 0.21 and the mole fraction of N 2 was 0.79. The pressure outlet boundary condition was adopted for the flue gas outlet [21] with the outlet pressure at −60 Pa, and the total reflux temperature was 900 K. The P-1 model with a small calculation amount suitable for combustion equipment with complex geometric structures was adopted for the radiation modeling, and cooperated with the gray-gas mass weighted summation method to solve the absorption coefficient. 'PRESTO!'…”