CFD Workshop, Pittsburgh, PA 5/5/2010

An Experimental Determination of Jet Penetration Into A CFB Riser

J. Christopher Ludlow - NETLJames L. Spenik – REM EngineeringLawrence J. Shadle - NETL

NETL 2010 Workshop

OnMultiphase

Flow Science

2

Outline

• Motivation – “Why Bother?”• The Experiment – “How Are We Going To Do This?”• The Jet – “What We’d Like to Control”• The Raw Data – “What Do We Get?”• The Reduced Data – “What Does This Mean?”• Summary – “So What?”

3

Motivation

• Many transport reactor and CFB designs require solids feed at locations other than bottom

• Solids mixing and residence time distribution depends on how far the solids penetrate into the flow

• Supply experimental data for model validation

4

“Three” Measurement Techniques Used

• Particle tracking of phosphorescent jet within the riser uses sensitive photodetectors

– Two axial positions (15 cm and 30 cm above jet entrance)

– 11 radial positions

• Detection of radial component of jetparticle velocity uses a small piezoelectric pressure transducer.

• Solids mass flow in the jet measured using a 12 cm wide “Spiral” in feed line

5

Solids Transport Air

Packed Bed Solids Feed

Spiral Solids Feed Measurement

Ultraviolet Light Source

Sensitive Photodetectors

Sensitive Photodetectors

Phosphorescent Solids Jet

Upward Solids Flow

Piezoelectric Impact Probe

Experimental Setup

Solids move air

6

Experimental Conditions

1.425.4916.640.97SN7

2.837.6216.640.97SN6

11.347.6236.830.99SN5

11.347.6216.640.99SN4

11.347.6216.640.95SN3

11.347.6237.180.97SN2

11.347.628.530.97SN1

11.347.6216.640.97SN0

Circ ratekg/s

Riser Airm/s

Ujetm/s

Void fraction

Std No.

Riser conditionsJet conditions

Riser Air Aeration

ID=0.305 m

Move Air

0.25 m elev.

Spiral 3.6 m elev.

To Bag House

Jet 15.4 m

Particle Diameter (um) 750Particle Density (gr/cc) 0.867

4 m

7

The Jet• Want to independently set…

– Average solids mass flow in jet• Solids mass flow set by…

– adjusting solids transport air– solids move air– pressure drop across solids feed system

• Measured using Spiral– Average solids fraction in jet

• Depends on solids velocity in transport line– function of transport air flow– move aeration air flow– solids feed pressure drop

•)(*)(*)(

)(

particleAreaFlowVelocitySolidsFlowMassFractionSolids

ρ=

8

Solids Transport Air

Packed Bed Solids Feed

Spiral Solids Feed Measurement

Ultraviolet Light Source

Sensitive Photodetectors

Sensitive Photodetectors

Phosphorescent Solids Jet

Upward Solids Flow

Piezoelectric Impact Probe

Jet Solids Velocity

Solids move air

• Two photo receivers, one at beginning and one at the end of the transport line

• Actual solids velocity determined by cross correlating two signals• Solids Fraction calculated from actual solids velocity and measured mass flow (feed spiral)

0

0.5

1

1.5

2

2.5

3

800 900 1000 1100 1200

Volta

ge

Samples

Solids Velocity Determination

0

0.5

1

1.5

2

2.5

3

800 900 1000 1100 1200

Volta

ge

Samples

Solids Velocity Determination

9

Video clips of Jet in RiserGs=0 kg/m2-s, Ug=7.6 m/s

Front View

Side View

10

Raw DataParticle Tracking

Phosphorescent Particle Tracking

•Net response calculated by subtracting average dark response from average lit response•Net photo response measured 15 cm and 30 cm above jet entrance and at 11 different radial positions•Photo response for each radial profile normalized by dividing each net response by maximum net response for that experiment

.00

.01

.02

.03

.04

.05

.06

.07

.08

20 40 60 80 100

Mea

sure

d Ph

oto

Resp

onse

(v)

Time (s)

Typical Photo Response for Phosphorescent Jet Particle Tracking (13 cm from wall)

15 cm

30 cm

.00

.02

.04

.06

.08

.10

.12

.14

20 40 60 80 100

Mea

sure

d Ph

oto

Resp

onse

(v)

Time (s)

Typical Photo Response for Phosphorescent Jet Particle Tracking (18 cm from wall)

15 cm

30 cm

11

Reduced DataParticle Tracking

-.20

.00

.20

.40

.60

.80

1.00

1.20

0 2 4 6 8 10 12

Nor

mal

ized

Sig

nal

Distance From Wall (in)

6" SN#6

Calc

JP359

JP361

JP366

JP370

JP374

JP387

•Normalized response graphed as a function of radial position

•Resultant data fit with 4th order polynomial

•Location of peak calculated

•Width of curve determined at one half maximum peak value

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12N

orm

aliz

ed S

igna

l

Distance From Wall (in)

12" SN#6

Calc

JP359

JP361

JP366

JP370

JP374

JP387

SN6 - 15 cm Above Jet

SN6 - 30 cm Above Jet

0 5 10 15 20 25

Distance From Wall (cm)

0 5 10 15 20 25

Distance From Wall (cm)

12

Summarized Experimental Results

Riser Air (m/s)

Circ. Rate (kg/s)

Riser Pressure

Drop (kPa)

Void Fraction

Ujet

(m/s)

Radial Peak Location (m)

Half-Height Width (m)

Radial Peak Location (m)

Half-Height Width (m)

SN0 7.62 11.34 16.53 0.97 16.64 0.08 0.13 0.08 0.15SN1 7.62 11.34 16.94 0.97 8.53 0.05 0.1 0.05 0.11SN2 7.62 11.34 16.39 0.97 37.18 0.13 0.18 0.14 0.17SN3 7.62 11.34 16.65 0.95 16.64 0.1 0.12 0.1 0.15SN4 7.62 11.34 16.56 0.99 16.64 0.06 0.11 0.07 0.14SN5 7.62 11.34 17.25 0.99 36.83 0.11 0.15 0.12 0.17SN6 7.62 2.83 6.36 0.97 16.64 0.05 0.19 0.08 0.16SN7 5.49 1.42 8.97 0.97 16.64 0.09 0.15 0.13 0.2

0.15m Above JetRiser Conditions Jet Conditions 0.30 m Above Jet

13

Summarized Experimental Results

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20

Hal

f-H

eigh

t Wid

th (m

)

Riser Pressure Drop (kPa)

Jet Half-Height Width

15 cm VF 0.95

30 cm VF 0.95

15 cm VF 0.97

30 cm VF 0.97

15 cm VF 0.99

30 cm VF 0.99

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 5 10 15 20

Peak

Loc

atio

n (m

)

Riser Pressure Drop (kPa)

Peak Location from Jet Wall

15 cm VF 0.95

30 cm VF 0.95

15 cm VF 0.97

30 cm VF 0.97

15 cm VF 0.99

30 cm VF 0.990

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 10 20 30 40

Peak

Loc

atio

n (m

)

Jet Gas Velocity (m/s)

Peak Location from Jet Wall

15 cm VF 0.95

30 cm VF 0.95

15 cm VF 0.97

30 cm VF 0.97

15 cm VF 0.99

30 cm VF 0.99

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40

Hal

f-H

eigh

t Wid

th (m

)

Jet Gas Velocity (m/s)

Jet Half-Height Width

15 cm VF 0.95

30 cm VF 0.95

15 cm VF 0.97

30 cm VF 0.97

15 cm VF 0.99

30 cm VF 0.99

14

Solids Transport Air

Packed Bed Solids Feed

Spiral Solids Feed Measurement

Ultraviolet Light Source

Sensitive Photodetectors

Sensitive Photodetectors

Phosphorescent Solids Jet

Upward Solids Flow

Piezoelectric Impact Probe

Jet Penetration – Particle Impact

Solids move air

0

0.1

0.2

0.3

0.4

0.5

-0.01 0.01 0.03 0.05

Volts

Time (s)

Radial Solids Flux Determination

•Horizontally oriented probe allows for the detection of radial solids flow•Number of strikes per time interval allows for the determination of mass flux in the radial direction•Probe located directly opposite jet•Number of impacts measured as a function of radial position

15

Reduced Data - Particle Impact

-4

-2

0

2

4

6

0

50

100

150

200

250

300

0 0.1 0.2 0.3 0.4

ln m

ass

flux

Mas

s flu

x (k

g/m

-s2 )

Distance from jet (m)

Mass flux

ln mass flux

• Radial mass flux calculated from number of particle impacts

• Natural log of flux plotted versus distance from jet

• Slope of linear portion used to characterize jet penetration

)(

)(*

AreaDetector

WeightParticleSingleSecond

StrikesofNumber

FluxSolids

=

16

Particle Impact Decay Rate Measured In-line With Jet

25

35

45

55

65

0 10 20 30 40

Jet velocity (m/s)

Pene

tratio

n co

eff

ln (k

g/s/m

3 )

vf = 0.99vf = 0.97vf = 0.95

1

03

2

5

4

• Jet penetrates farther as jet gas velocity increases (penetration coefficient smaller)

• Can’t tell if penetration of jet is a function of jet void fraction

0.000

10.000

20.000

30.000

40.000

50.000

60.000

70.000

0.94 0.95 0.96 0.97 0.98 0.99 1.00

Pene

trat

ion

Coef

ficie

nt

(ln k

g/s-

m2 )

Jet Void Fraction

17

Summary

• Phosphorescent bed material was used to track jet material inside the riser

• Jet spreads as material is carried up riser

• Higher jet gas velocity carries material into riser further (seen in tracer and impact data)

• Higher gas velocity results in slightly broader jet distribution

• Jet void fraction has little effect on penetration