MULTIFLUID EULERIAN MODELLING OF DENSE GAS-SOLID FLUIDIZED BED HYDRODYNAMICS: INFLUENCE OF THE DISSIPATION PARAMETERS

• Published in: Chemical engineering science Vol. 63; no. 22
• Main Authors: Reuge, N, Cadoret, L., Pannala, Sreekanth, Syamlal, M, Coufort, C, Caussat, B
• Format: Journal Article
• Language: English
• Published: United States 01.01.2008
• Subjects: BOUNDARY CONDITIONS; COMPUTERIZED SIMULATION; ENGINEERING; FLOW MODELS; FLUID MECHANICS; FLUIDIZED BEDS; HYDRODYNAMICS; INTERNAL FRICTION; STRESSES
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2008.07.028

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 a videos of the fluidized bed. The Eulerian-Eulerian two fluid model MFIX was then used to simulate the experiments. Two different models for the particle stresses - Schaeffer (Syamlal et al., (1993), Schaeffer (1987)) and Princeton (Srivastava and Sundaresan (2003)) 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 from the Schaeffer model. Both free-slip and Johnson-Jackson boundary conditions give nearly identical results. An increase in 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 (φ) in the range 10 -40 does not affect the bed expansion, but its reduction significantly reduces the height of fluctuations.