s. austin, j. williams, s. smith and g. d. wesson

Prediction of the Separation Efficiency of Prediction of the Separation Efficiency of a 10 Mm Hydrocyclone Using Light a 10 Mm Hydrocyclone Using Light

Liquid Phase Particles Liquid Phase Particles

S. Austin, J. Williams, S. Smith and G. D. WessonDepartment of Chemical Engineering

FAMU-FSU College of EngineeringTallahassee, FL 32310

Presented at: 8th Annual International Petroleum and Environmental Conference

Houston, TXNovember 6-9, 2001

Presentation OutlinePresentation Outline• Motivation

• Hydrocyclone principles

• Particle separation theory

• Hydrocyclone performance measurements

• Separation experiments

• Results

• Conclusions and future work

• Acknowledgements

MotivationMotivationOil production

requires water treatment.

Required offshore constraint < 30 ppm of oil in water to environment

• Interest in down-hole separation

Hydrocyclone Operation PrinciplesHydrocyclone Operation Principles

• Tangential feed entry• Creation of core

vortex • High local

accelerations• Complex internal

flows• No moving parts

Liquid Particle -Fluid InteractionLiquid Particle -Fluid Interaction

• Liquid particles remain spherical• Particle diameter < 50 microns

• Rep <0.1 , i.e. creeping flow

• Incompressible fluids

Liquid Particle -Fluid InteractionLiquid Particle -Fluid Interaction

Stokes’ law l

D is p e r s e d P a r t i c le

d

C o n t in u o u s P h a s ec , c

e z

e

e r

F D F B

tCD VF 3

forceDrag

gF cdb

6

forceBouyant 3

Particle MotionParticle Motion

aVC

t

18

2

r

ua

a

2

onaccelarati lCentrifuga

, where

Terminal velocity Separation is a function of:

– Density difference– Particle size– Continuous phase viscosity– Cyclone diameter

Local accelerations in 10mm cyclone may approach 10,000 g

Measuring the PerformanceMeasuring the Performance

Many ways to measure hydrocyclone performance

– Due to different applications

“Traditional” separation measurement:

QQFFCCF F ffFF((ll))

QQUUCCU U ffUU((ll))

QQOOCCOO ffOO((ll))

f

f

f R

R

RE

1

E

1

WW

OO

F

O

F

O

F

O

O

O

feedinenteringoilofmass

placerightexitingoilofmassE

Separation EfficiencySeparation Efficiency

• Efficiency based on total fraction of concentration reduction or:

• Equivalent to “traditional” efficiency measurement

F

UFu C

CC

Separation TheorySeparation Theory

Grade underflow purity coefficient-separation efficiency for each particle size

Integrating over sizes yields overall separation efficiency

FF

uuFFu fC

fCfCG

F

uFFuu C

CCdfG

0

Grade Efficiency CurveGrade Efficiency Curve

Continuous function of particles sizes

Hydrocyclone performance is size dependent and GEC varies with particles size

Graphically represented as curve that is usually ‘S’ shaped

“Overall” separation efficiency is a result of the integration of the product of the GPC and the feed distribution

Grade Efficiency CurveGrade Efficiency Curve

Wesson & Petty 1994

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100

DROP DIAMETER, m icrons

UN

DE

RF

LO

W G

RA

DE

PU

RIT

Y C

OE

FF

ICIE

NT

5 0l

4

)2ln(exp1)(

50

50

l

l

llG

b

U

Separation ExperimentsSeparation Experiments

Flow DiagramFlow Diagram

Pump

P

F O

V1

V2

V3 V4

V5

FF

OF

UF

V6 V7

Stirrer

Drain

F neHydrocyclo

Tank

P

P

U

10mm Hydrocyclone10mm Hydrocyclone

2.5 mm2.5 mm

2.5 mm2.5 mm

1 mm1 mm

80 mm80 mm

10 mm10 mm

Experimental Flow LoopExperimental Flow Loop

tank

SampleCylinders

pump

hydrocyclone

Stirrer

Flow PredictionsFlow Predictions

Feed pressure varied from 60 - 160 psigFlow rates determined using stopwatchLinear regression

Qf = f(Po, Pu)

f)()()()()(Q 2/12/1f OUOUUO PePdPPcPbPa

Flow PredictionsFlow Predictions

Feed vs Prediction

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.0

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0

Feed Flow Rate, lpm

Pre

dict

ion

Flow Rate PredictionsFlow Rate Predictions

0 20 40 60 80 100 120 140 1600

40

80

120

160

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Qf, L/min

Dpo, psig

Dpu, psig

4.5-5.0

4.0-4.5

3.5-4.0

3.0-3.5

2.5-3.0

2.0-2.5

1.5-2.0

1.0-1.5

0.5-1.0

0.0-0.5

ExperimentExperiment• Determine optimum conditions which will give

the best separation efficiency

• Compare concentration separation efficiency with traditional way of determining efficiency.

Run Feed Press Drop, psig Flow rate,L/min

1 60 3.0

2 80 3.4

3 100 3.7

4 120 4.1

5 140 4.5

6 160 4.8

Solid-Liquid Separation Solid-Liquid Separation ExperimentsExperiments

Model DispersionModel Dispersion

Soda Lime Borosilicate Glass glass bubbles and water :

= 0.1 g/cm3

c = 1 cp (Cannon-Fenske viscometer)

lmean = 30 m

ResultsResults Conc vs. oil droplet sizes at 60 psi pressure drop

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 1 10 100 1000

Diameter, m

Vol

con

c., p

pm

feed

underflow

ResultsResults Conc vs. oil droplet sizes at 60 psi pressure drop

00.10.20.30.40.50.60.70.80.9

1

0.1 1 10 100 1000

Diameter, m

Gra

de

Pu

tiry

Coe

ffic

ien

t

4.85 lpm

2.8 lpm

ResultsResults Grade Purity Function vs. Diameter – 4.85 lpm

00.10.20.30.40.50.60.70.80.9

1

0.1 1 10 100 1000

Diameter, m

Gra

de

Pu

tiry

Coe

ffic

ien

t

4.85 lpm

)2ln(exp1)(

50

b

U l

llG

l50=10m

b=3

ResultsResults Overall efficiency vs. Feed flow rate

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

4.0 4.2 4.4 4.6 4.8 5.0

Feed Flow Rate (lpm)

Ove

rall

Eff

icie

ncy

ConclusionsConclusions

Glass bubbles-water separation– Best overall efficiency for feed

distribution occurs 4.8 lpm feed flow rate (P=200 psi)

– L50 = 10 m

Liquid-Liquid Separation Liquid-Liquid Separation ExperimentsExperiments

Model DispersionModel Dispersion

Vegetable oil dispersion in water:

= 0.1 g/cm3 (pycnometer)

d = 50 cp (Cannon-Fenske viscometer)

c = 1 cp (Cannon-Fenske viscometer)

30 dynes/cm (Pendant drop method)

ResultsResults Conc vs. oil droplet sizes at 60 psi P

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.1 1 10 100 1000

sizes, microns

Vol c

onc,

ppm

Feed

Underflow

ResultsResultsConc. vs oil droplet sizes at 160 P

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.1 1 10 100 1000

sizes, m icrons

Vo

l co

nc,

pp

m

Feed

Underflow

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0.1 1 10 100 1000

diameter, m

Gra

de

Pu

rity

Co

eff 3

3.4

3.7

4.1

4.5

4.8

Concentration G-curvesConcentration G-curves Grade Purity Coefficient vs. Oil droplet diameter at various flow rates

L/minL/min

lfC

lfClfClG

FF

UUFF

best GPC-curve

“Drop Breakup”

ResultsResults

The best “overall” efficiency?

Run Feed-pressure drop,psig

Flowrate, l/min Efficiency, u

1 60 3.0 63

2 80 3.4 53

3 100 3.7 56

4 120 4.1 56

5 140 4.5 55

6 160 4.8 32

ConclusionsConclusions

Oil-Water separation– Best overall efficiency for feed

distribution occurs 3.0 lpm feed flow rate (P=60 psi)

– Best GPC curve occurs at 3.7 lpm feed flow rate (P=100 psi)

Continued WorkContinued Work

• Investigate drop breakup

• Investigate source of ‘fish hook”

• Investigate use of back pressure to eliminate the air from the core vortex