Defense Presentation

Department of Mechanical Engineering

Knowledge. Innovation. Leadership. www.me.iastate.edu



Hydrodynamic Characterization of 3D Fluidized Beds Using

Noninvasive TechniquesJoshua B. Drake

Department of Mechanical EngineeringIowa State University

Ames, IowaOctober 25, 2011






Outline

• Fluidization and Fluidized Bed Overview

• Experimental Setup

• Selected results• Repeatability and uniformity• Local gas holdup comparisons• Annular hydrodynamic

structure comparisons

• Conclusions and future work





• Thesis committee: • Dr. Heindel, Dr. Hu, Dr. Nelson, Dr. Olsen, Dr. Subramaniam

• Portions of this work were supported by Conoco-Phillips

• The X-ray facility used in this research was funded by the National Science Foundation under award number CTS-0216367 and Iowa State University

Acknowledgements





Fluidization and Fluidized Bed Overview






Fluidization Terms

• Fluidization: passing a gas vertically through a granular material until it achieves fluid-like properties

• Superficial gas velocity (Ug): volumetric gas flow rate divided by the column cross-sectional area

• Minimum fluidization velocity (Umf): the superficial gas velocity at which the particle drag is counterbalanced by gravity causing the bed to become homogeneously fluidized

• Gas holdup (e): the amount of volumetric gas in the system





Fluidized Bed Applications

• Gas Catalytic Reactions• Reaction takes place on the surface of the catalyst with the gas phase• Fluidized Catalytic Cracking and Fischer-Tropsch processes

• Gas-Phase Reactions• Solids used as a heat carrier for either heat exchange or a reaction• Thermal cracking and coking processes

• Gas-Solid Reactions• Both gas and solids are the reactants• Coal combustion and gasification, biomass pyrolysis and gasification, and

roasting and calcination

• Physical Processes• No chemical reaction takes place• Drying, heat exchange, and coating





Multiphase Flow Measurement

• Observational data:• Gas Holdup and Solids Concentrations• Bubble Size and Velocity• Liquid and Solid Velocities

• Techniques:• Global – system as a whole• Local – specific locations within the system• Invasive – destructive• Noninvasive – nondestructive





Experimental setup






Fluidized bed geometry

10.2 cm ID reactor 15.2 cm ID reactor





Fluidized bed geometry

61 cm

30 cm

15 cm

Freeboard chamber

Reactor chamber

Aeration plate

Plenum

Air inlet

Pressure tap

Side air injection port

61 cm

30 cm

15 cm

10.2 cm 15.24 cm





222 microns1 mm

222 microns

222 microns

1 mm

1 mm

500-600 mm particlesGlass beads:

Ground walnut shell:

Crushed corncob:





Geldart’s Classification (Geldart, 1973)

Fluidized bed material

• Bed Materials• Glass Beads• Density: 2600 kg/m3

• Diameter: 500-600 µm• Ground Walnut Shell• Density: 1200-1400 kg/m3

• Diameter: 500-600 µm• Crushed corncob• Density: 800-1200 kg/m3

• Diameter: 500-600 µm

• Geldart type B particles

• Materials sifted multiple times

0.1

1

10

10 100 1000(r

parti

cle

-rga

s) x

10-3

[kg/

m3 ]

dparticle [mm]

C

A

BD

GlassWalnut

Corncob





CsI phosphor screen & CCD camera

Lead shutters

Rotation ring

Test stand

15.2 cm fluidized bed reactor (in imaging region)

Image intensifier & CCD camera

X-ray sources

FB setup in XFloViz facility

(Heindel et al. 2008)





X-ray CT imaging

X-ray source (cone beam)

Single CT slice location

Object to image

Rotate source/detector pair or objectMultiple radiographs from different projections are reconstructed to show internal details of object cross-section

CT slice (2D; time averaged)

X-ray detector (imaging device coupled to a CCD camera)

Multiple CT slices “stacked” together to generate a 3-D image

(Heindel et al. 2008)





Beam hardening calibrations

• X-ray attenuation of low energy X-rays is typically much larger than for high energy X-rays causing portions of the CT to have false signals of lower density

• Aluminum and copper filters placed in front of the X-ray source reduce low energy X-rays

• Analysis of the X-ray attenuation behavior in the observed material at various thicknesses is completed yielding a fifth-order polynomial curve fit applied to all CTs of the observed material

Uncorrected image Corrected image





Calculating Gas Holdup

• Time-average gas holdup can be calculated from local voxel intensities for the dynamic system (I), a gas-only system (Ig), and the solid particle (Ip):

• Use static bulk bed intensity (Ib) to replace particle intensity:

• Assume homogeneous granular material for bulk density:

• Rearranging yields time-average gas holdup from measured quantities:

pg

g p

I II I

e

b pgb

g p

I II I

e

bgb

p

1 re

r

( )b g gbg

g b

I I I II I

ee





X-ray CT slices

• CTs show local time-average gas holdup anywhere within the imaging region• Cylinder 10.2 cm or 15.2 cm in diameter by ~23 cm high with a ~0.4 mm resolution

• 2-D “slices” extracted from CT data

• CT slice locations:

3D Image x-slice y-slice

z-slice

Inje

ction

por

t

xyz





Selected results


• Repeatability and uniformity• Local gas holdup comparisons• Annular hydrodynamic structure comparisons





Minimum fluidization velocity without side-air injection

• Umf decreases with:• Material density

• As material density decreases, energy needed to move particulate decreases

Glass Beads Walnut Shell Corncob Glass Beads Walnut Shell CornUmf,0 Average (cm/s) 21.7 18.4 17.1 20.2 16.3 16.8Qmf,0 Average (L/min) 105.3 89.3 83.2 220.6 178.4 183.7

10.2 cm FB 15.2 cm FB





Gas holdup repeatability test conditions

• Reactor ID:• 15.24 cm

• Flow conditions:• Ug = 1.50 and 3.00Umf each without side-air

injection

• Bed materials:• Glass beads• Crushed walnut shell

• Five tests completed at each Ug with each bed material

• Quantitative e data shown across the bed at various heights bisecting the bed through the side-air port

(Drake and Heindel, 2011a)





Gas holdup repeatability results for walnut shell and glass beads

00.10.20.30.40.50.60.70.80.9

11.11.21.31.41.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

h/D

[-]

Gas Holdup [-]

Test 1Test 2Test 3Test 4Test 5

Glass BeadsD = 15.24 cmUg = 1.50UmfQs = 0.00Qmf

00.10.20.30.40.50.60.70.80.9

11.11.21.31.41.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

h/D

[-]

Gas Holdup [-]


Glass BeadsD = 15.24 cmUg = 3.00UmfQs = 0.00Qmf

00.10.20.30.40.50.60.70.80.9

11.11.21.31.41.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

h/D

[-]

Gas Holdup [-]


Walnut ShellD = 15.24 cmUg = 1.50UmfQs = 0.00Qmf

00.10.20.30.40.50.60.70.80.9

11.11.21.31.41.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

h/D

[-]

Gas Holdup [-]


Walnut ShellD = 15.24 cmUg = 3.00UmfQs = 0.00Qmf

Ug = 1.5Umf Ug = 3Umf

Gla

ss B

eads

Wal

nut S

hell






Gas holdup repeatability results for glass beads

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]

x-z Test 1 y-z Test 1x-z Test 2 y-z Test 2x-z Test 3 y-z Test 3x-z Test 4 y-z Test 4x-z Test 5 y-z Test 5

Glass BeadsD = 15.24 cmUg = 1.50UmfQs = 0.00Qmfh = 0.50D 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]


Glass BeadsD = 15.24 cmUg = 3.00UmfQs = 0.00Qmfh = 0.50D

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]



0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]




h =

0.5D

h =

1D(Drake and Heindel, 2011a)





Gas holdup uniformity test conditions

• Reactor ID:• 15.24 cm

• Flow conditions:• Ug = 1.50 and 3.00Umf

without side-air injection

• Bed materials:• Glass beads• Ground walnut shell

• One test completed at each Ug with each bed material

• Quantitative e data shown across the bed at various heights bisecting the bed along each angle indicated






Gas holdup uniformity results @ h = 0.75D

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]

15 deg 105 deg30 deg 120 deg45 deg 135 deg60 deg 150 deg75 deg 165 deg90 deg 180 deg


0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]



0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]


Walnut ShellD = 15.24 cmUg = 1.50UmfQs = 0.00Qmfh = 0.75D 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]


Walnut ShellD = 15.24 cmUg = 3.00UmfQs = 0.00Qmfh = 0.75D


Gla

ss B

eads

Wal

nut S

hell






Gas holdup uniformity results @ h = 0.25D

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]



0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]



0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]


Walnut ShellD = 15.24 cmUg = 1.50UmfQs = 0.00Qmfh = 0.25D 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

Gas H

oldu

p [-]

r/R [-]


Walnut ShellD = 15.24 cmUg = 3.00UmfQs = 0.00Qmfh = 0.25D


Gla

ss B

eads

Wal

nut S

hell






Local gas holdup test conditions

• Reactor ID:• 10.16 cm and 15.24 cm

• Flow conditions:• Ug = 1.25, 1.50, 1.75, and 2.00Umf

Qs = 0.00, 0.05, 0.10, 0.15, and 0.20Qmf

• Bed materials:• Glass beads• Ground walnut shell• Crushed corncob

• One test completed at each Ug and Qs in each reactor with each bed material

• Quantitative and qualitative e data shown across the bed at various heights bisecting the bed through the side-air port

(Drake and Heindel, 2011b)





CT ImagesG

lass

bea

ds @

Ug =

2U

mf a

nd Q

s = 0

.2Q

mf






Gas holdup results for glass beads

focus on flow condition variation







focus on flow condition variationUg = 1.5Umf

h = 0.5D h = D







focus on flow condition variation







focus on flow condition variationQs = 0Qmf

h = 0.5D h = D






Gas holdup results for bed material variation






Gas holdup results for bed material variation

h = 0.75D

Ug =

2U

mf

Ug =

1.5

Um

f

Qs = 0Qmf Qs = 0.1Qmf






Annular gas holdup test conditions

• Reactor ID:• 10.16 cm• 15.24 cm

• Flow conditions:• Ug = 1.25, 1.50, 1.75, and 2.00Umf

Qs = 0.00, 0.05, 0.10, 0.15, and 0.20Qmf

• Bed materials:• Glass beads• Ground walnut shell• Crushed corncob

• One test completed at each Ug and Qs in each reactor with each bed material

• Annularly averaged e data shown as qualitative 2D maps and quantitative plots of half the bed

(Drake and Heindel, 2011c)





Data smoothing

• Local time-average gas holdup is averaged along concentric annular rings from the bed center to the reactor wall at all heights

• Noise in the averages increases as r → 0

• Noise is smoothed using a curve fitting function






Annular gas holdup results for glass beads focus on bed

diameter variation(Drake and Heindel, 2011c)





Annular gas holdup results for glass beads focus on bed

diameter variation(Drake and Heindel, 2011c)





Annular gas holdup results for glass beads focus on flow

condition variation(Drake and Heindel, 2011c)





Annular gas holdup results for glass beads focus on flow

condition variationGlass beads

Ug = 2Umf varying h h = 0.75D varying Ug






Annular gas holdup results for bed material variation

D =

10.

2 cm

Ug =

2U

mf

Ug =

1.5

Um

f(Drake and Heindel, 2011c)





Annular gas holdup results for bed material variation






Conclusions and future work






• Calculating local time-average gas holdup using X-ray CTs is highly repeatable

• Fluidization uniformity increases with bed height• Causes:

• Increased mixing

• Local time-average gas holdup is affected by changes in Ug, Qs, bed material density, and jetting• Causes:

• Increased mixing• A decrease in the amount of energy needed to move bed particles

• The only significant changes in εg due to changes in reactor size are from differences in circulation patterns and average bed heights• Causes:

• Major losses from wall effects

Conclusions





• Four different annular hydrodynamic structures can be identified• Aeration jetting• Bubble coalescence regions• Bubble rise paths• Particle shear zones

• Annular hydrodynamic structures change shape, size, and location due to changes in Ug, bed diameter, and bed material density.

• 2D local time-average annular gas holdup maps can be used as benchmarks for computational fluid dynamic simulation validation and comparison

Conclusions





• X-ray Particle Tracking Velocimetry• Could help with reactor design and scale up for different processes• Could help validate circulation patterns in the bed

• Possible problems:• Increased Ug will make image capture of the particle difficult, in turn, increasing

particle detection error• Low Ug increases the particles chances of becoming trapped between jets from the

aeration plate

Future work





• X-ray Bubble Tracking Velocimetry• Could help with reactor design and scale up for different processes• Could help validate gas flow patterns through the bed

• Possible problems:• Increased Ug will make image capture of bubbles difficult, in turn, increasing bubble

detection error• Bubble overlap• Poor virtual bubble reconstruction assumptions

Future work





Journal PapersDrake, J. B. and Heindel, T. J., (2011). “Comparisons of annular hydrodynamic structures in 3D fluidized beds using X-ray CT.” Journal of Fluids Engineering, In Review.

Drake, J.B. and Heindel, T. J. (2011). “Comparisons of gas holdup in cold flow fluidized beds.” Chemical Engineering Science, To Appear.

Drake, J.B. and Heindel, T. J. (2011). “The repeatability and uniformity of 3D fluidized beds.” Powder Technology 213, 148-154.

Min, J., Drake, J. B., Heindel, T. J., and Fox, R. O. (2010). "Experimental validation of CFD simulations of a lab-scale fluidized-bed reactor with and without side-gas injection." AIChE Journal 56: 1434-1446.

Ford, J. J., Heindel, T. J., Jensen, T. C., and Drake, J. B. (2008). "X-ray computed tomography of a gas-sparged stirred-tank reactor." Chemical Engineering Science 63(8): 2075-2085.





Conference PapersDrake, J. B., Kenney, A. L., Morgan, T. B., Heindel, T. J. (2011). “Developing tracer particles for X-ray particle tracking velocimetry.” ASME-JSME-KSME Joint Fluids Engineering Conference 2011, Hamamatsu, Shizuoka, Japan.

Heindel, T. J., Jensen, T. C., Drake, J. B., McCormick, N., and Riveland, M. L. (2010). “3D X ray CT imaging of ‐cavitation from a butterfly valve.” 7th International Conference on Multiphase Flow, Tampa, FL, United states.

Drake, J. B., Tang, L., and Heindel, T. J. (2009). “X-ray particle tracking velocimetry in fluidized beds.” 2009 ASME Fluids Engineering Division Summer Conference, Vail, CO, United States.

Drake, J. B., and Heindel, T. J. (2009). “Repeatability of gas holdup in a fluidized bed using x-ray computed tomography.” 2009 ASME Fluids Engineering Division Summer Conference, Vail, CO, United States.

Drake, J. B., Franka, N. P., and Heindel, T. J. (2008). “Developing X-ray particle tracking velocimetry for applications in fluidized beds.” 2008 ASME International Mechanical Engineering Congress and Exposition, Boston, MA, United States.

Meyer, T. R., Schmidt, J. B., Nelson, S. M., Drake, J. B., Janvrin, D. M., and Heindel, T. J. (2008). “Three-dimensional spray visualization using X-ray computed tomography.” ILASS Americas, 21st Annual Conference on Liquid Atomization and Spray Systems. Orlando, FL, United States.

Franka, N. P., Drake, J. B., and Heindel, T. J. (2008). “Minimum fluidization velocity and gas holdup in fluidized beds with side port air injection.” ASME Fluids Engineering Division Summer Meeting, Jacksonville, FL, United States.





Hydrodynamic Characterization of 3D Fluidized Beds Using

Noninvasive TechniquesJoshua B. Drake

Department of Mechanical EngineeringIowa State University

Ames, Iowa


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