Evaluation of a filtered model for the simulation of large scale bubbling and turbulent fluidized beds

Abstract

Full 3D flow simulations of lab and industrial scale dense fluidized beds were carried out using a filtered Eulerian-Eulerian approach. Filtered closures for interphase momentum exchange, solids stresses and additional wall corrections were implemented in the standard equations of motion.These closures had a very large effect on overall model performance when solved on the large cell sizes required for computationally affordable 3D fluidized bed simulations. Numerical experiments conducted under different fluidization conditions showed that the current model formulation performs well over a wide range of operating conditions. It was found that additional modelling accounting for flow non-uniformity is essential under certain fluidization conditions. The current method for dealing with flow non-uniformity by means of wall corrections yielded good results under vigorous fluidization, but caused a slight inaccuracy at low fluidization velocities. In general, comparisons to a wide range of experimental data showed good quantitative agreement, suggesting that the formulation of the filtered model is highly generic.The filtered approach was also successfully verified in a large scale bubbling fluidized bed reactor by comparisons with a highly computationally expensive, well resolved, non-filtered flow simulation.

Fine-grid two-fluid modeling of fluidization of Geldart A particles

“…And it compensates the lack of highly resolved simulation with grid size smaller than 10 times the particle diameter, as discussed in Section 2.2.3 for the case of riser of Li and Kwauk [8]. In literature, the filtered TFM approach has been verified by simulation of a large-scale bubbling fluidized bed reactor and thereby comparisons to experimental data and highly resolved simulation results [23,74]. Therefore, here we will focus on the evaluation of TFM for simulating CFB riser.…”

Grid independence behaviour of fluidized bed reactor simulations using the Two Fluid Model: Effect of particle size

“…However, the additional modelling included in this filtered approach introduces a substantial degree of uncertainty simply due to the complex nature of the subgrid clustering phenomena. After more than a decade of development, current closures for the drag and solids stresses appear to function reasonably well with uncertainties still present in areas with large flow gradients such as nearwall regions [12]. A first closure for first order heterogeneous reactions has recently been proposed [13] and heat transfer correlations are yet to be developed.…”

Gas Switching as a Practical Alternative for Scaleup of Chemical Looping Combustion

“…In the case of the GSC concept, a filtered approach is applied to facilitate the simulation of an industrial‐scale fluidized bed. A more detailed outline of the equation systems in question can be viewed in previous papers on PBCLC and GSC …”

“…Am ore detailed outline of the equations ystems in question can be viewed in previous papers on PBCLC [22] and GSC. [23] Kinetics Closuresf or reaction kinetics form av ery importantp art of this work and are therefore discussed in more detail. Because significant uncertainty exists about the kinetics of powdered and pelletized ilmenite under pressurized conditions,s everal different kinetic assumptions are evaluated and compared.…”