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Flow regime prediction in a 3D spouted bed using MFiX-DEMย ยท Fluid flow through packed columns....

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Solutions for Today | Options for Tomorrow Flow regime prediction in a 3D spouted bed using MFiX-DEM Subhodeep Banerjee 1,2 , William Rogers 1 , Chris Guenther 1 1 National Energy Technology Laboratory, 2 Oak Ridge Institute for Science and Education April 25, 2018
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Page 1: Flow regime prediction in a 3D spouted bed using MFiX-DEMย ยท Fluid flow through packed columns. Chem. Eng. Prog., 48, 89-94. 12 โ€ข ๐‘ข๐‘ข. ๐‘š๐‘š๐‘š๐‘š. is the minimum superficial

Solutions for Today | Options for Tomorrow

Flow regime prediction in a 3D spouted bed using MFiX-DEMSubhodeep Banerjee1,2, William Rogers1, Chris Guenther1

1National Energy Technology Laboratory, 2Oak Ridge Institute for Science and Education

April 25, 2018

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โ€ข Spout-fluidized beds help suppress de-fluidization and agglomeration, enhance heat and mass transfer, facilitate the adjustment of operating parameters, extend the size range of particles

โ€ข The spout is a local high velocity region at the center of the bed where solid particles and voids (bubbles) move in a structured manner with little radial displacement

โ€ข Numerical simulations of spouted beds at the particle level are essential to understand flow behaviors that are crucial in the design and operation of systems

โ€ข Comparison and validation of numerical predications against experimental readings is necessary to evaluate the accuracy and applicability of computational models for spouted beds

Background and objectives

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โ€ข Different flow patterns depending on operating conditions can be broadly classified into five flow regimes1

Flow Regimes in Fluidized Beds

Fixed bed/ internal spout

Spout-fluidization

SluggingJet in fluidized bed

Spouting w/ aeration

1Zhang, J. & Tang, F. (2006) Prediction of flow regimes in spout-fluidized beds. China Particuology, 4(3-4), 189-193.

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โ€ข Spout channel does not penetrate through the bedโ€ข Only particles in the spout channel are movingโ€ข Stable particle configurationโ€ข Mildly fluctuating pressure drop with no periodicity

Internal spout

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โ€ข Spout channel penetrates the entire bedโ€ข Only particles in and close to the spout channel are fluidizedโ€ข Stable particle configurationโ€ข Slightly fluctuating pressure drop with minimal periodicity

Spouting with aeration

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โ€ข Particles in the upper part of the bed are fluidized and move gentlyโ€ข Spout channel is periodically blocked by particles from the annulusโ€ข Pressure fluctuations are small but regularโ€ข Clear dominant frequency associated with the time taken to remove the

blockage

Spout-fluidization

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โ€ข All particles moving and bubbles are continuously formed in the annulusโ€ข Spout channel present but periodically blocked or diverted through the

annulusโ€ข Bubbles are smaller than in the slugging bed regime so the associated

frequency is higherโ€ข Frequency spectra can be different for comparable operating conditions

based on relative frequencies of bubble formation and spout blockage

Jet in fluidized bed

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โ€ข All particles moving and slugs (bubbles with larger diameter than the bed) are continuously formed

โ€ข Large pressure drop fluctuations associated with formation of slugsโ€ข Distinct periodic behavior with a low(er) dominant frequency because the

slugs take time to form and propagate

Slugging bed

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Regime Frequency Shape Power

Internal spout No peak No peak Low

Spouting with aeration No peak No peak Low

Spout-fluidization High Narrow (< 0.5 Hz) High

Slugging bed Low Broad (> 1 Hz) High

Jet in fluidized bed Intermediate Intermediate High

Identifying flow regimes by pressure spectra

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Experimental setup & particle properties

โ€ Particles automatically in bed generated based on initial specified height

Property Experiment1 Simulation

๐‘‘๐‘‘๐‘๐‘ (mm) 4.04 ยฑ 0.02 4.04

๐œŒ๐œŒ๐‘๐‘ (kg/mยณ) 2,526 ยฑ 1 2,526

๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š (m/s) 1.77 ยฑ 0.03 1.97

๐‘’๐‘’๐‘›๐‘›,๐‘๐‘โ†”๐‘๐‘ 0.97 ยฑ 0.01 0.97

๐‘’๐‘’๐‘›๐‘›,๐‘๐‘โ†”๐‘ค๐‘ค 0.97 ยฑ 0.01 0.97

๐œ‡๐œ‡๐‘๐‘โ†”๐‘๐‘ 0.10 ยฑ 0.01 0.10

๐œ‡๐œ‡๐‘๐‘โ†”๐‘ค๐‘ค 0.10 ยฑ 0.01 0.10

# particles 44800 42840โ€ 

1Link, J. M., Cuypers, L. A., Deen, N. G., & Kuipers, J. A. (2005). Flow regimes in a spoutโ€“fluid bed: A combined experimental and simulation study. Chem. Eng. Sci., 60, 3425-3442.

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โ€ข Simulations performed in open source code MFiX-DEM1 โ€“ Multiphase Flow with Interphase eXchanges

โ€ข Soft-sphere model for particle collisions (๐‘˜๐‘˜๐‘›๐‘› = 10,000 N/m, ๐œ‚๐œ‚ = 0.97)โ€ข Interphase momentum transfer computed using Gidaspow drag law2 (based

on Wen & Yu model3 and Ergun equation4)

Simulation Approach

1Garg, R., Galvin, J., Li, T., & Pannala, S. (2012). Documentation of open-source MFIXโ€“DEM software for gas-solids flow. Retrieved July 31, 2017, from https://mfix.netl.doe.gov/documentation/dem_doc_2012-1.pdf.2Gidaspow, D. (1992). Multiphase Flow and Fluidization. San Diego, CA: Academic Press.3Wen, C. Y., & Yu, H. Y. (1966). Mechanics of fluidization. Chem. Eng. Prog. Symp. Ser., 62, 100-111.4Ergun, S. (1952). Fluid flow through packed columns. Chem. Eng. Prog., 48, 89-94.

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โ€ข ๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š is the minimum superficial fluid velocity needed to fluidize a bedโ€ข As gas flow into the packed bed is increased, the pressure drop ฮ”๐‘๐‘ across

the bed increases until the minimum fluidization conditionโ€ข At the minimum fluidization condition the net weight of the bed is exactly

balanced by ฮ”๐‘๐‘โ€ข Further increase in the superficial velocity results in no further increase in ฮ”๐‘๐‘

โ€ข Bubbles can cause ฮ”๐‘๐‘ to fluctuate but the average value should remain constant

Determining ๐’–๐’–๐’Ž๐’Ž๐’Ž๐’Ž in simulation

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Determining ๐’–๐’–๐’Ž๐’Ž๐’Ž๐’Ž in simulation

โ€ข Minimum fluidization occurs at intersection of linearly increasing pressure and constant pressure

โ€ข At minimum fluidization,ฮ”๐‘๐‘๐ฟ๐ฟ

= 1 โˆ’ ๐œ€๐œ€๐‘š๐‘š๐‘š๐‘š ๐œŒ๐œŒ๐‘ ๐‘  โˆ’ ๐œŒ๐œŒ๐‘š๐‘š g

๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š = 1.97 m/s๐œ€๐œ€๐‘š๐‘š๐‘š๐‘š = 0.365

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โ€ข Particles are visualized by their motion at ๐‘ข๐‘ข = {1.96, 1.97, 1.98 m/s}โ€ข Only few individual particles exhibit motion at 1.96 m/sโ€ข Significant number of particles fluidized at 1.97 m/s

Confirming ๐’–๐’–๐’Ž๐’Ž๐’Ž๐’Ž by visualization

๐‘ข๐‘ข=1.96 m/s ๐‘ข๐‘ข=1.97 m/s ๐‘ข๐‘ข=1.98 m/s

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Simulation test cases

Case ๐’–๐’–๐’ƒ๐’ƒ๐’ƒ๐’ƒ (m/s) โ„๐’–๐’–๐’ƒ๐’ƒ๐’ƒ๐’ƒ ๐’–๐’–๐’Ž๐’Ž๐’Ž๐’Ž ๐’–๐’–๐’”๐’”๐’”๐’” (m/s) โ„๐’–๐’–๐’”๐’”๐’”๐’” ๐’–๐’–๐’Ž๐’Ž๐’Ž๐’Ž

A 0.3 0.15 76 39

B 1.8 0.9 103 53

C 2.0 1.0 90 46

D 2.2 1.1 76 39

E 3.1 1.6 41 34

F 3.9 2.0 3.9 2.0

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Results and discussion โ€“ Case A

โ€ข Spout channel is evident but does not penetrate bed

โ€ข Kinetic energy of particles goes towards loosening the original closely packed configuration

โ€ข Frequency spectrum of pressure drop shows no periodicity

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โ€ข All three cases exhibit spouting behavior and have a similar overall shapeโ€ข Pressure spectra and particle velocities can differentiate the flow regimes

between these configurations

Results and discussion โ€“ Cases B,C,D

Case B Case DCase C

Page 18: Flow regime prediction in a 3D spouted bed using MFiX-DEMย ยท Fluid flow through packed columns. Chem. Eng. Prog., 48, 89-94. 12 โ€ข ๐‘ข๐‘ข. ๐‘š๐‘š๐‘š๐‘š. is the minimum superficial

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Results and discussion โ€“ Case B

โ€ข Very fast spout with no fluidization in the annulus

โ€ข Discernible โ€˜peakโ€™ with low power at a relatively high frequency

โ€ข Despite the slight periodicity, this configuration lies in the spouting with aeration regime

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Results and discussion โ€“ Case C

โ€ข Reduced spout velocity and more movement in annulus

โ€ข Peak is more distinct โ€“ narrower and with higher power

โ€ข Increased periodicity associated with intermittent blockage of spout by entrained particles from annulus but no clear dominant frequency

โ€ข Characterizes an intermediate regime between spouting with aeration and spout fluidization

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Results and discussion โ€“ Case D

โ€ข Further reduced spout velocity reflects in maximum bed height; annulus shows more particle movement

โ€ข Sharp peak shows clear dominant frequency at 6.5 Hz with very high power

โ€ข Second harmonic peak also visibleโ€ข Definitely in the spout-fluidization

regimeโ€ข Dominant frequency is in excellent

agreement with experimental data

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โ€ข Increased fluidization in annulus and lower velocity in spout are bothessential for spout-fluidization

โ€ข Peak becomes broader and shifts to the right

โ€ข Behavior closer to the intermediate regime

Results and discussion โ€“ Case D*๐‘ข๐‘ข๐‘ ๐‘ ๐‘๐‘ increased to 86 m/s with same ๐‘ข๐‘ข๐‘๐‘๐‘๐‘

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Results and discussion โ€“ Case E

โ€ข Annulus is completely fluidized and starts to bubble

โ€ข Spout channel period-ically diverted through annulus

โ€ข Flow configuration is an overlap of a spout-fluidized bed and a bubbling bed

โ€ข Somewhat wide peak at 3 Hz with power of 1600

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Results and discussion โ€“ Case F

โ€ข Particles across the bed shoot up rapidly forming bubbles larger than the bed width known as slugs

โ€ข Time scale of slug formation matches experiment

โ€ข Low frequency of 1.6 Hz agrees with experiment (but twin peaks instead of one wide peak)

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Parameter study: spring stiffness

โ€ข Many model parameters are indeterminate1

โ€ข ๐‘’๐‘’๐‘ก๐‘ก, ๐‘˜๐‘˜๐‘ก๐‘ก cannot be derivedโ€ข Physical values of ๐‘˜๐‘˜๐‘›๐‘› cannot be used

โ€ข Little to no effect on ๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š so differences in flow regimes cannot be attributed to differing โ„๐‘ข๐‘ข๐‘ ๐‘ ๐‘๐‘ ๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š and โ„๐‘ข๐‘ข๐‘๐‘๐‘๐‘ ๐‘ข๐‘ข๐‘š๐‘š๐‘š๐‘š ratios

โ€ข Investigate effects in spouting with aeration regime as it has largest particle velocities (collision forces largest)

โ€ข Spring stiffness is reduced to ๐‘˜๐‘˜๐‘›๐‘› = 100 N/mโ€ข Clear dominant frequency at 5.0 Hz with high

power of 5,300โ€ข Additional harmonic frequencies present

๐‘˜๐‘˜๐‘›๐‘›=10,000 N/m

๐‘˜๐‘˜๐‘›๐‘›=100 N/m

1Bakshi, A. et al. Multivariate sensitivity analysis of CFD-DEM: Critical model parameters and their impact on fluidization hydrodynamics, 2017 AIChE Annual Meeting, October 29-November 3, Minneapolis, MN.

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โ€ข Detailed numerical simulation of spouted bed experiment over a range of flow conditions corresponding to different flow regimes

โ€ข Spectral analysis of the pressure fluctuations are used to characterize the flow regimes accurately

โ€ข Flow regimes predicted by simulation are in excellent agreement with the experiment including good quantitative matches where applicable

โ€ข MFiX-DEM is a powerful tool for predicting key performance parameters for effective design, tuning and optimization of spout-fluidized systems

Conclusions

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This work was completed as part of NationalEnergy Technology Laboratory (NETL) research forthe U.S. Department of Energyโ€™s (DOE) CarbonStorage Program. This project was supported inpart by an appointment to the ResearchParticipation Program at NETL administered bythe Oak Ridge Institute for Science and Education(ORISE) through an inter-agency agreementbetween the DOE and EPA.

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Backup Slides โ€“ Fluidization Snapshots

๐‘ข๐‘ข=1.96 m/s ๐‘ข๐‘ข=1.97 m/s ๐‘ข๐‘ข=1.98 m/s

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Backup Slides โ€“ Bed Snapshots


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