Eulerian-Eulerian and Eulerian-Lagrangian Simulations of a BFB

Modeling Approaches for Granular Flows

Jay Sanyal (jay.sanyal@ansys.com), 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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