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Challenge Problem III . Larry Shadle , Mehrdad Shahnam Ray Cocco , Allan Issangya , Chris Guenther, Madhava Syamlal , James Spenik , J. Chris Ludlow, Frank Shaffer, Rupen Panday, Balaji Gopalan , and Rajiv Dastane, CFB X Workshop Sun River, Oregon May, 3, 2011.

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challenge problem iii

Challenge Problem III

Larry Shadle, MehrdadShahnam

Ray Cocco, Allan Issangya,

Chris Guenther, MadhavaSyamlal, James Spenik, J. Chris Ludlow, Frank Shaffer, Rupen Panday, BalajiGopalan, and Rajiv Dastane,

CFB X Workshop

Sun River, Oregon

May, 3, 2011

cfb validation test data and cfd expertise
CFB Validation Test Data and CFD Expertise
  • Extensive database of cold flow CFB Test Data at NETL.
  • Indexed chronologically by granular materials and operating conditions.
  • Nearly 10 years since last Challenge Problem Benchmark of Computer Models.
  • PSRI and NETL to provide the most comprehensive granular-flow Challenge Problem in the world.
  • Advanced measurements including High Speed Particle Imaging Velocimetry (HSPIV); LDV; axial, radial, and temporal profile data; gas and solids tracer measurements and much more.
challenge problem i ii
Challenge Problem I & II

Challenge Problem I



Industrial Scale

20-cm-Diameter & 40-cm-Diameter Riser

FCC & Sand

Responses from 10 Groups

Three groups were successful

“Models were not sophisticated enough to be used to predict all of the hydrodynamics in a CFB”.

Challenge Problem II



Industrial Scale

20-cm-Diameter riser with a blind tee and an elbow at the riser exit

FCC & Sand

Responses from 13 Groups

Range of total percent errors: 77 to 334%. The highest individual percent error was 838 %

“Models still needed substantial development to be able to predict CFB hydrodynamics”.

  • Ref:
  • Laguerie & Large, Fluidization VIII Workshop, 1995.
  • Kwauk and Yang, Fluidization X Workshop, 2001.
criticism previous experience
Criticism – Previous Experience

Test conditions:

  • Industrial scale too large
  • Asymmetric inlet and outlet too complex
  • Boundary Conditions need to be well defined

Data Quality:

  • Radial Fluxes need to integrate to solids flux.
  • Different measurements techniques need to produce consistent results


  • Want both experimentalist and modeler perspective
  • Opportunity to adapt model parameters
modeling benchmark
Modeling Benchmark

Validate Against Umf, Umb and Bed Density Data

Measuring Our Success, Targeting Our Challenges


Model Challenge Problems

Compare Against Results

Important Timeline

Refine Models

Jan 31, 2011:

Second Simulation

Results Due































May 9, 2010:

Problem Descriptions

Available at

Oct 30, 2010:



Results Due

Nov 1, 2010:

Experimental Data


May 2, 2011:

Workshop on

Results at CFB 10

Jul 30, 2011:

Publication of Results

challenge problem iii1
Challenge Problem III



16-m-Long &


CFB Riser


DP/DLvsUg in 6.5 cm ID FB

Group A & Group B



6-m-Long &


Bubbling FB


DP/DLvsUg in 15 cm ID FB


Geldart Group A

Geldart Group B


Gas Bypassing in Deep Beds

FCC Catalyst, Fines = 3% < 44 mm, Static Bed Ht. = 3.66 m, Ug= 0.46 m/s

6 in 15 2 cm dia minimum fluidization test unit
6-in (15.2-cm)-Dia Minimum Fluidization Test Unit

This test meant

for tuning

CFD models


Bubble Void Fraction

A voltage signal from one of the two sensors of the optical fiber bubble probe


Bubble Void Fraction = Fraction of Time the Probe is in Contact With a Bubble or Void


DP fluctuations were measured in each quadrant

Radial Orientation of DP Fluctuation Measurements and Bubble Probe Locations

bfb challenge problem
BFB Challenge Problem

Gas bypassing more likely for tall beds, low fines content and low gas velocity

modelers who were they
ModelersWho were they?
  • BFB
    • Software Developer (2)
    • University (1)
  • CFB
    • Software Developer (1)
    • University (2)
    • Government (2)
overall d p comparisons
Overall DP Comparisons

BFBDPbed± 95% CL, kPa

  • Simple minded comparison of DP fluctuations as process variability (not error).
  • Experimental variability compared to % difference:


  • Simulations were typically 20-30% different than the experimental mean.
  • The experimental %variability was from 6 to 13%.
riser test conditions
Riser Test Conditions


Statistical Experimental Design

Group A: CASE 1 Dilute

CASE 2 Core Annular

Group B: CASE 3 Dense Transport (near FFB)

CASE 4 Core Annular

CASE 5 Dense Suspension Upflow

Extend Factorial Matrix to Central Composite – Star points


















Ms, lb/hr

Coded Ms, lb/hr

18 20 22 24 26

Ug, ft/s

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Coded Ug, ft/s


riser flux measurements
Riser Flux Measurements
  • Three Techniques to Measure Flux
    • Direct solids sampling
    • Piezoelectric transducer
    • Calibrated Fiber Optic
  • Can Compare Integrated Results Against Spiral
  • Use Results to Validate CFD
  • Flux Predictions Part of the Challenge Problem

Mass flux- Piezoelectric probe

Developed at NETL

Piezoelectric transducer face

Piezoelectric transducer size

Dual piezoelectric transducer probe

Typical mass flux across riser diameter

Typical probe output


Light reception fiber

Light transmission fiber

Solids velocity and void fraction-fiber optic probe

Developed at NETL

Fiber probe showing light emission

Particle passing through 1st bundle

Fiber arrangement in bundle

ΔT - Velocity

Area – Void fraction

Typical particle velocity distribution across diameter of riser

Typical output from each bundle

Sampling rate – 12,500 samples/s

Jet Tracer Concentrations at 3 ElevationsGroup B solids injected 3.66 m above distributor with vs=3.75 m/s
  • Phosphorescent tracers enabled tracking solids injected into the riser.
  • Under conditions tested jet penetration was small; the peak did not reach the riser centerline when measured above the jet at ht/R = 1 and 2.



Tracer Injection

Riser gas solids flow

overall d p comparisons1
Overall DP Comparisons

CFBDPRiser± 95% CL, kPa

  • Simple minded comparison of DP fluctuations as process variability (not error).
  • Experimental variability compared to % difference:


  • Simulations were 5-80% different than the experimental mean.
  • The experimental %variability was from 2 to 13%.
axial pressure profiles for group b
Axial pressure profiles for Group B

5 Model Simulations Submitted (+1 Revisions):

Simulations better in dilute cases, getting relatively low dP/dL at higher loadings.

Inlet and outlet effects simulated about 50% of the time.

group b particle velocities across riser group b at 8 88 m above distributor
Group B particle velocities across riser Group B at 8.88 m above distributor
  • Velocities measured with dual multi fiber optic bundles and HS PIV at various elevations going only to center.
  • Group B cases demonstrate:
    • the agreement in both techniques,
    • parabolic flow profiles increasing with Ug, and
    • preferred method to characterize process variability/experimental uncertainty

Figure 4. Particle velocity for all test cases across riser at several axial locations as measured by fiber optic probe.

jet penetration
Jet Penetration

Jet penetration across radius of CFB riser from point of injection

  • Penetration simulated accurately in DSU case 5 (CFB1)
  • Penetration was over predicted (CFB1) both:
    • at lowest gas velocity Case 3 and
    • In core annular Case 4
  • No Penetration was predicted (CFB2)
transients power spectrum for group b pressure fluctuations polyethylene beads cases 3 4 and 5
Transients - Power Spectrum for Group Bpressure fluctuationspolyethylene beads Cases 3, 4, and 5.
  • 4 Simulation results Submitted:
  • Frequency dependence similar for data and simulations.
  • Mean dominant period of 8 sec observed for cases simulated (except CFB4).
  • Amplitude trends similar, models generally higher…
  • Amplitude variations for different axial locations were not simulated for different cases.
  • Drop offs in amplitude for cases 3&5, minimum in case 4 in fully developed region (@5m)
revised simulations
Revised Simulations
  • Revisions
    • BFB1: Longer Duration, revised data summary calculations
    • CFB5: Coarser grid (3.39M to 0.5M cells) from 63 to 4 hr to simulate 1s.
  • Results
    • BFB1 revisions similar but tended slightly away from test results dP/dL(z)
    • CFB5 similar with greater spatial variations.
axial profiles cfb5 revised with coarser grid
Axial Profiles - CFB5 Revised with Coarser Grid
  • Experimental data is represented by symbols with dashed lines 95%CL on regression.
  • Simulations are solid lines.
  • Revised simulations (coarser grid) are the jagged lines.

Ms ↑

DP/DL ↑es↑

axial profiles cfb5 revised with coarser grid1
Axial Profiles - CFB5 Revised with Coarser Grid
  • Simulations and experimental data taken in two lines across the riser- inline with the inlet and outlet and perpendicular to them.
  • HS-PIV data statistically indistinguishable from FO data
  • Neither coarse or fine resolution simulations displayed asymmetry

Ms ↑

DP/DL ↑es↑



  • Your comments and suggestions are sought to improve the process and advance the state of the art.
  • Challenge problem III test data benchmarks the resources required to simulate multi-phase flow streams on industrial scale. https:\\
  • Data sets have been vetted and will remain available to continue to serve as model validation test cases.
  • Challenge Problem must be conducted more than once a decade by 7 or8 organizations.
  • CFD codes are in their infancy… and given the resources and time, can simulate industrial scale multiphase processes.

Proposed Future Direction at NETL

  • Strategy and Approach:
    • Challenge Problem III; CFB X Workshop Lessons Learned
      • Benchmark industrial scale non-reacting fluid dynamics periodically (5-7 years)
      • Full loop simulation
      • Obtain greater response (Academia, Vendors, Nat’l labs)
      • Devise small scale tests to benchmark critical complex physics (low particle count, < 2 week simulation on PC):
        • 1). Small scale fluidized bed; HS-PIV on rectangular bed
        • 2). Particle Wall impacts; “Wall effects”
        • 3). Granular T or Particle-Particle collisions; vertical shaker tests
      • Note: want simultaneous gas and solids flow fields, bubble and cluster formation
    • Validate reacting flow process of interest
      • Reacting gas absorption and evolution in small scale; Carbon Capture Unit (C2U)
      • Gasification of size and density fractions; PSU Drop tube furnace
  • Challenges:
    • Characterize/validate process performance of transient models.
    • Interference from diagnostic probes in smaller process units.
  • Describe what you will do for rest of FY
  • Describe what you will do next FY
  • Address decision points (if any)
  • Provide a schedule, with milestones and a Gant chart, if required