polydispersity model development & validation: report on
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Polydispersity Model Development & Validation:
Report on Findings
NETL 2011 Workshop on Multiphase Flow Science
16 August 2011
Pittsburgh, PA
Ray Cocco
John Findlay
Roy Hays
SB Reddy Karri
Ted Knowlton
Jia-Wei Chew
Aaron Murray
Christine Hrenya
Sofiane Benyahia
Larry Shadle
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Project Goals & 2006 Technology Roadmap
Theme: Particle Size Distribution (PSD)
1. Continuum Theory for the Solid Phase
2. Improved Gas-Particle Drag Laws
3. Gas-Phase Instabilities: Turbulence Models
4. Data Collection and Model Validation
5. Project Management
Theory and Model
Development
Physical and
Computational
Experiments
Communication,
Collaboration, and
Education
Relevant Tracks in 2006
Technology Roadmap
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Project Scope: Work Breakdown Structure
Development, Verification, and Validation of Multiphase Models for Polydisperse Flows
Theory
Development
Data
Collection
Model
Validation
Program
ManagementDeliverables
1. Solid-Phase
Continuum
Theory
2. Gas-Solid
Drag
3. Gas-Phase
Turbulence
Simulations
Experiments
4.1 DEM (solids)
4.2 Eulerian-DEM
(gas-solid)
4.3 Low-velocity
fluidized bed
4.4 Cluster Probe
Development
1.1 Kinetic Theory
1.2 DQMOM
1.3 Incorporation of
KT and DQMOM
into MFIX
1.4 KT extension
to multiphase
2.1 LBM/DTIBM:
zero-mean vel.
2.2 LBM/DTIBM:
non-zero rel. vel.
2.3 LBM/DTIBM:
freely evolving
3.1 Polydisperse DNS
3.2 Multiphase Turb. Model
4.5 High-velocity
fluidized bed (PSRI)
4.6.1 Compare with
DEM data (4.1) and
low-velocity bed (4.3)
4.6.2 Liaison to NETL
riser data
4.6.3 Compare with high-
velocity data from
Eulerian-DEM (4.2),
PSRI (4.5), and
NETL (4.6.2)
5.1 Develop
Management PlanMonthly email updates
Quarterly reports
Annual reports
Final report
Approach
Scope
Cost Estimates
Schedule
Risk
Constraints
Assumptions
Communication
New theory into MFIX
Project Web Site:
http://www.psriextra.com/AR_
Polydispersity_Open/AR_Polydispersity_Open/Welcome.html
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Experimental Setups
Colorado Bubbling Bed / “Dilute” CFB
PSRI “Dense” CFB
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Particles
Colorado: sand
PSRI: glass beads and HDPE pellets
• Group B
• monodisperse, binary & continuous PSD’s
HDPE
dave= 650 μm
ρp = 900 kg/m3
Glass
dave = 170 μm
ρp = 2500 kg/m3
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Experimental Measurements
Bubbling Bed (Colorado)
• Axial segregation:
vacuum slice, sieve, and weigh
• Bubble frequency, velocity & size:
optical dual-fiber probe
CFB (Colorado & PSRI)
• Species flux: extraction probe
• Cluster freq., duration, & appear. prob.: optical fiber probe
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Comprehensive set of polydisperse data…
1. Chew, J. W., D. M. Parker, R. A. Cocco and C. M. Hrenya, “Cluster characteristics of continuous size
distributions and binary mixtures of Group B particles in dilute riser flow,” Chemical Engineering Journal,
submitted.
2. Chew, J. W., R. Hays, J. G. Findlay, T. M. Knowlton, S. B. R. Karri, R. A. Cocco and C. M. Hrenya,
“Cluster characteristics of Geldart Group B particles in a pilot-scale CFB riser. I. Monodisperse systems,”
Chemical Engineering Science, submitted.
3. Chew, J. W., R. Hays, J. G. Findlay, T. M. Knowlton, S. B. R. Karri, R. A. Cocco and C. M. Hrenya,
“Cluster characteristics of Geldart Group B particles in a pilot-scale CFB riser. II. Polydisperse systems,”
Chemical Engineering Science, submitted.
4. Chew, J.W., D. M. Parker, and C. M. Hrenya, “Elutriation and species segregation characteristics of
polydisperse mixtures of Group B particles in a dilute CFB riser,” AIChE Journal, submitted.
5. Chew, J. W., R. Hays, J. G. Findlay, T. M. Knowlton, S. B. R. Karri, R. A. Cocco and C. M. Hrenya,
“Reverse Core-Annular Flow of Geldart Group B Particles in Risers,” Powder Technology, submitted.
6. Chew, J. W., R. Hays, J. G. Findlay, T. M. Knowlton, S. B. R. Karri, R. A. Cocco and C. M. Hrenya,
“Impact of material property and operating conditions on mass flux profiles of monodisperse and
polydisperse Group B particles in a CFB riser,” Powder Technology, in press.
7. Chew, J. W., R. Hays, J. G. Findlay, T. M. Knowlton, S. B. R. Karri, R. A. Cocco and C. M. Hrenya,
“Species segregation of binary mixtures and a continuous size distribution of Group B particles in riser
flow,” Chemical Engineering Science, in press.
8. Chew, J. W. and C. M. Hrenya, “Link between bubbling and segregation patterns in gas-fluidized beds with
continuous size distributions,” AIChE Journal, in press.
9. Chew, J. W., J. Wolz, and C. M. Hrenya, “Axial segregation in bubbling gas-fluidized beds with Gaussian
and lognormal Distributions of Geldart group B particles,” AIChE Journal, 56, 3049-3061 (2010).
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Bubbling Bed: Segregation and Bubbling
scont= 1 perfect segregationscont= 0 perfect mixing
• As distribution width , segregation then (binary: monotonic )
• As distribution width , all bubble characteristics
• Explanation: segregation level tied to thickness of bubble-less layer
lognormal PSD lognormal PSD
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CFB: Axial Segregation
h /
HBinary Mixture Continuous PSD
Binary: As height , % of massive at some locations
Continuous: As height , % of massive at all locations
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CFB: Cluster Frequency
• Axial position has large influence on profile
• Binary composition and continuous PSD width have impact at high h/H
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CFB: ElutriationB
ina
ry M
ixtu
reC
on
tin
uou
sP
SD
Trends of binary and continuous appear similar, but x-axes are different…
elutriation
fines comp.
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CFB: Elutriation w/ same x-axes
mass % of fine mass % of fine mass % of fine
Bin
ary
Mix
ture
Con
tin
uo
us
PS
D
• Elutriation trends of binary and continuous PSD’s are in stark contrast
• Explanation: as continuous width (mass % of fines ), dfine and elutriation easier
dsm increases
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Aside: How well do kinetic theories predict continuous PSD‟s?
Basic Idea: How to accurately represent a continuous PSD using the
transport coefficients for „s‟ discrete species.
d1 d2
d1 d2 d3
d1 dn…
Fre
quency
s=2
σ1=? σ2=?
φ 1=? φ 2=?Q1: What method do we choose to find σ‟s
and φi‟s for given φ?
A1: moment-based methods=3
σ1=? σ2=? σ3=?
φ 1=? φ 2=? φ 3=?Q2: What value of „s‟ is required for
„accurate‟ representation of
continuous PSD?
A2: “collapsing” of transport coefficients
from new kinetic theory
(Garzo, Hrenya & Dufty, PRE, 2007)
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Preliminary Answer…
Distributions investigated
• Lognormal ( /dave = 90%)
• NETL coal
• NASA lunar simulant (OB-1)
Comparison with MD data of
Dahl et al (Powder Tech, 2003)
• Simple shear flow
• Discrete approximation with 3
particles (s=3) provides similar
accuracy as monodisperse theory
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Summary
• Binary and continuous PSD’s display different
qualitative trends
bubbling bed: axial segregation
CFB: axial segregation, elutriation
• Preliminary work indicates discrete kinetic theory can
approximate well a continuous PSD with a fairly small
number of size species