Eulerian-Eulerian and Eulerian-Lagrangian Simulations of a BFB
Modeling Approaches for Granular Flows
Jay Sanyal ([email protected]), Shailesh Ozarkar, Feng Liu, L. Srinivasa Mohan CFB-10, Sun River, Oregon May, 2011 ANSYS Inc Proprietary http://www.ansys.com
Eulerian-Lagrangian Modeling of NETL/PSRI BFB
Particulate Gas-Solid Flows
Modeling Gas –solid systems can include:
- Particle flow- Particle size distribution- Particle mechanics- Surface and morphology- Particle-particle interaction- Turbulence and dispersion- Reactions- Fluid forces and drag
Classification of Granular Flows
Introduction
Due to advances in computing, multiphase flows are an ever-expanding area of simulation in the process industryChallenging to model due to complex interaction between phasesFormulation of proper constitutive relations are key in predicting correct flow behaviorOccur across a wide spectrum of physical phenomenon and thus require a broad class of models for accurate prediction
Dilute disperse Dense disperse
One-Way Coupling Two-Way Coupling Four-Way Coupling
Inter-particle spacing
Volume fraction
110100
10-6 10-410-6
Eulerian-Lagrangian Models- Discrete Phase Model (point particles)- Macro-particle Model
Eulerian-Eulerian Model - Continuum description of phases- Collisions through KTGF (Gidaspow, 1990)
Hybrid Models (Popoff, 2007)- Eulerian primary phase- Lagrangian particulate phase
DEM (Dan Joseph, 2001)
CFD Validation of NETL/PSRI Bubbling Fluidized Bed Reactor
NETL/PSRI made detailed CAD geometry and data available for a BFB for validation Data provided for mean hydrostatic pressure measurements at various azimuthal and axial locations and its standard deviationSpecified PSD for a range of superficial gas velocitiesMaterial properties, composition and minimum fluidization conditions specified
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3 5CFD Modeling Parameters
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Case #3 modeled (3% fines), 2.44m static bed height, superficial velocity 0.6m/sTruncated geometry considered without the cyclonesDetailed sparger modelingActual PSD fitted to Rosin-Rammler distributionGibilaro (1985), Wen and Yu(1966) dragUnstructured hex/tet/prism mesh, 207K cellsOutlet solids recycled back through side inlet to maintain inventory
Solids loop
Sparger
Dense Phase DPM - 107k cells, 0.5e6
parcels- 91K cells, 5e6
parcels DEM
- 235K cells, 430K parcels
Eulerian-Eulerian Modeling of NETL/PSRI BFB
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Eulerian-Eulerian - Monodisperse solids(80 m)
- Bidisperse solids(80 and 30 m)
- InhomogeneousPBM and DQMOM
- KTGF aggregation and breakage(Fan, 2004)
Solids VOF 0s 10s 20s
Solids VOF 0.8s 56s 66s
Conclusions 9
Eulerian-Eulerian(E-E) and Eulerian-Lagrangian(E-L) models were successfully used to validate an industrial Bubbling Fluidized Bed ReactorThe E-E models clearly illustrate the benefits of including size distribution and phase separation through PBM The choice of drag law is critical in predicting the correct bed height over long timesE-L models are able to model polydispersity and are also computationally efficientFurther work is envisaged to investigate
- Different discretization schemes for the transport equations (E-E)- Include effects of size distribution on transport coefficients derived from KTGF (E-E and E-L)
Gas-liquidGas-Solid
Fluidized Bed with internals
Hopper
Graphics Courtesy: CSIROa, S. Sundaresanb, Petrobrasc
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