Dem Modeling and Simulation of a Down-Flow Circulating Fluidized Bed

Abstract

A mathematical model based on the distinct element method (DEM) was developed to investigate the hydrodynamics in a gas-solid down-flow circulating fluidized bed reactor (downer). The models consist of the equations of particle motion and fluid motion. The contact force is calculated by using the analogy of a spring, dashpot, and friction slider. Simulation results show that the radial solids holdup and particle velocity profiles are uniform in the core region. Near the wall, the solids holdup is higher with lower particle velocity. An increase in the particle size decreases the solids holdup and increases the particle velocity. The solids holdup decreases with superficial gas velocity but increases with solids circulation rate. Particle velocity increases with gas velocity and solids circulation rate. The solids holdup and particle velocity are almost uniform along the height of the downer except near the distributor. The hydrodynamic behavior from this simulation showed trends similar to those of the experimental results. The results obtained from this model fit better with the experimental results than Kimm's and Bolkan's models do.

Scaling of catalytic cracking fluidized bed downer reactor based on CFD simulations—Part II: effect of reactor scale

“…The dynamic similarity was excluded in this scaling law. According to the gas and solid cocurrently ow in the gravitational direction, the uniform ow pattern in the downer reactor was obtained 49,50 resulting in less impact of dynamic similarity on the scaling up of this reactor type. Table 3 lists the conditions that were utilized to verify the scaling parameter.…”

Scaling of a catalytic cracking fluidized bed downer reactor based on computational fluid dynamics simulations

“…Less radial uniformities of ow behaviour were observed in large downer reactors. 25,54 Thus, the performance of the proposed scaling parameter, the dimensionless groups…”

Modeling of Chemical Vapor Deposition of Silane for Silicon Production in a Spouted Bed via Discrete Element Method Coupled with Eulerian Model

“…Hence this model provides more realistic results than the two-fluid flow model, particularly in the system with large particle and dense bed, i.e., spouted bed. This model is also known as an Euler–Lagrangian model and has been applied to monitor multiphase flow in fluidized beds. − The DEM model can be combined with heat transfer, , mass transfer, and chemical reaction. , This combined model can predict the hydrodynamics, concentration in gas, concentration in solid phases, and local temperature throughout the beds.…”