Prediction of the Separation Efficiency of a 10 Mm Hydrocyclone Using Light Liquid Phase Particles

1
Prediction of the Separation Efficiency of a 10
Mm Hydrocyclone Using Light Liquid Phase
Particles

• S. Austin, J. Williams, S. Smith and G. D. Wesson

Department of Chemical Engineering FAMU-FSU
College of Engineering Tallahassee, FL 32310
Presented at 8th Annual International Petroleum
and Environmental Conference Houston, TX November
6-9, 2001
2
Presentation Outline

• Motivation
• Hydrocyclone principles
• Particle separation theory
• Hydrocyclone performance measurements
• Separation experiments
• Results
• Conclusions and future work
• Acknowledgements

3
Motivation

• Oil production requires water treatment.
• Required offshore constraint
• lt 30 ppm of oil in water to environment
• Interest in down-hole separation

4
Hydrocyclone Operation Principles

• Tangential feed entry
• Creation of core vortex
• High local accelerations
• Complex internal flows
• No moving parts

5
Liquid Particle -Fluid Interaction

• Liquid particles remain spherical
• Particle diameter lt 50 microns
• Rep lt0.1 , i.e. creeping flow
• Incompressible fluids

6
Liquid Particle -Fluid Interaction

• Stokes law

7
Particle Motion

• Separation is a function of
• Density difference
• Particle size
• Continuous phase viscosity
• Cyclone diameter
• Local accelerations in 10mm cyclone may approach
  10,000 g

• Terminal velocity

8
Measuring the Performance

• Many ways to measure hydrocyclone performance
• Due to different applications
• Traditional separation measurement

QOCO fO(l)
QFCF fF(l)
QUCU fU(l)
9
Separation Efficiency

• Efficiency based on total fraction of
  concentration reduction or
• Equivalent to traditional efficiency
  measurement

10
Separation Theory

• Grade underflow purity coefficient-separation
  efficiency for each particle size
• Integrating over sizes yields overall separation
  efficiency

11
Grade 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

12
Grade Efficiency Curve

• Wesson Petty 1994

13
Separation Experiments
14
Flow Diagram
15
10mm Hydrocyclone
2.5 mm
2.5 mm
80 mm
10 mm
1 mm
16
Experimental Flow Loop
hydrocyclone
Stirrer
Sample Cylinders
tank
pump
17
Flow Predictions

• Feed pressure varied from 60 - 160 psig
• Flow rates determined using stopwatch
• Linear regression
• Qf f(?Po, ?Pu)

18
Flow Predictions
19
Flow Rate Predictions
20
Experiment

• 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
21
Solid-Liquid Separation Experiments
22
Model Dispersion

• Soda Lime Borosilicate Glass glass bubbles
  and water
• ?r 0.1 g/cm3
• ?c 1 cp (Cannon-Fenske viscometer)
• lmean 30 mm

23
Results

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

24
Results

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

25
Results

• Grade Purity Function vs. Diameter 4.85 lpm

26
Results

• Overall efficiency vs. Feed flow rate

27
Conclusions

• Glass bubbles-water separation
• Best overall efficiency for feed distribution
  occurs 4.8 lpm feed flow rate (DP200 psi)
• L50 10 mm

28
Liquid-Liquid Separation Experiments
29
Model Dispersion

• Vegetable oil dispersion in water
• ?r 0.1 g/cm3 (pycnometer)
• ?d 50 cp (Cannon-Fenske viscometer)
• ?c 1 cp (Cannon-Fenske viscometer)
• ? ? 30 dynes/cm (Pendant drop method)

30
Results

• Conc vs. oil droplet sizes at 60 psi DP

31
Results

• Conc. vs oil droplet sizes at 160 DP

32
Concentration G-curves

• Grade Purity Coefficient vs. Oil droplet
  diameter at various flow rates

L/min
best GPC-curve
Drop Breakup
33
Results

• 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 ?
34
Conclusions

• Oil-Water separation
• Best overall efficiency for feed distribution
  occurs 3.0 lpm feed flow rate (DP60 psi)
• Best GPC curve occurs at 3.7 lpm feed flow rate
  (DP100 psi)

35
Continued Work

• Investigate drop breakup
• Investigate source of fish hook
• Investigate use of back pressure to eliminate the
  air from the core vortex