Multifluid Eulerian modeling of dense gas–solids fluidized bed hydrodynamics: Influence of the dissipation parameters

Abstract

Computational fluid dynamic (CFD) models must be thoroughly validated before they can be used with confidence for designing fluidized bed reactors. In this study, validation data were collected from a fluidized bed of (Geldart's group B) alumina particles operated at different gas velocities involving two fluidization hydrodynamic regimes (bubbling and slugging). The bed expansion, height of bed fluctuations and frequency of fluctuations were measured from videos of the fluidized bed. The Eulerian-Eulerian two fluid model MFIX was used to simulate the experiments. Two different models for the particle stresses-Schaeffer [Syamlal, M., Rogers, W., O'Brien, T.J., 1993. MFIX documentation: theory guide. Technical Report DOE/METC-94/1004 (DE9400087), Morgantown Energy Technology Centre, Morgantown, West Virginia (can be downloaded from Multiphase Flow with Interphase eXchanges (MFIX) website http://www.mfix.org ); Schaeffer, D.G., 1987. Instability in the evolution equations describing incompressible granular flow. Journal of Differential Equations 66, 61-74.] and Princeton [Srivastava, A., Sundaresan, S., 2003. Analysis of a frictional-kinetic model for gas-particle flow. Powder Technology 129(1-3), 72-85.] models-and different values of the restitution coefficient and internal angle of friction were evaluated. 3-D simulations are required for getting quantitative and qualitative agreement with experimental data.The results from the Princeton model are in better agreement with data than that from the Schaeffer model. Both free slip and Johnson-Jackson boundary conditions give nearly identical results. An increase in coefficient of restitution (e) from 0.8 to 1 leads to larger bed expansions and lower heights of fluctuations in the bubbling regime, whereas it leads to unchanged bed expansion and to a massive reduction in the height of fluctuations in the slugging regime. The angle of internal friction () in the range 10-40 • does not affect the bed expansion, but its reduction significantly reduces the height of fluctuations.

Two-fluid modeling of cratering in a particle bed by a subsonic turbulent jet

“…Since performing three-dimensional simulations is computationally prohibitive for the current case, the effect of the wall was investigated using two-dimensional, Cartesian (2D Cartesian) simulations. Reuge et al [62] found that 2D Cartesian simulations of fluidized beds had predictions similar to those of three-dimensional simulations. Figure 9a and 9b provide the domain and computational mesh, respectively, for the 2D Cartesian simulations without a wall.…”

Multifluid Eulerian modelling of a silicon Fluidized Bed Chemical Vapor Deposition process: Analysis of various kinetic models

“…When using 800 g of powders (for all runs except run A12), and a gas velocity around 30 cm/s, the mean bed height has been roughly estimated as equal to 30 cm (from measurements performed in a glass column at ambient temperature, see [18]). The cooling of the region below the distributor was responsible for significant thermal gradients all along the bed height during silicon deposition [17].…”

“…To calculate the solid phase stress tensor in the plastic regime, both Schaeffer [21,22] and Princeton [23] models were tested. The summary of the governing equations is given in [17], the expressions of the granular stress models employed are given in [18] and the details can be obtained from MFIX documentation [19,21].…”

The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study

“…Both Eulerian-Eulerian two-fluid model (TFM) and Eulerian-Lagrangian discrete particle model (DPM) are used to study the effect of particle-particle and gas-particle interactions on the hydrodynamics of BFBs, however, most of them are devoted to Geldart B and D particles (for example, Goldschmidt et al, 2002;Goldschmidt et al, 2001;Hoomans et al, 1996;Kuipers, 2003, 2007;Lu et al, 2005;Reuge et al, 2008;Wang et al, 2008;Xu et al, 2007). Those studies concluded that particleparticle interaction significantly affected the bed hydrodynamics.…”