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 Presented at: 8 th Annual International Petroleum and Environmental Conference Houston, TX November 6-9, 2001

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

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

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

Liquid Particle -Fluid Interaction Liquid particles remain spherical Particle diameter < 50 microns Re p <0.1, i.e. creeping flow Incompressible fluids

Liquid Particle -Fluid Interaction Stokes’ law

Particle Motion 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 Performance Many ways to measure hydrocyclone performance – Due to different applications “Traditional” separation measurement: Q F C F f F (l) Q U C U f U (l) QOCO fO(l)QOCO fO(l)QOCO fO(l)QOCO fO(l)

Separation Efficiency Efficiency based on total fraction of concentration reduction or: Equivalent to “traditional” efficiency measurement

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

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

Grade Efficiency Curve Wesson & Petty 1994

Separation Experiments

Flow Diagram

10mm Hydrocyclone 2.5 mm 1 mm 80 mm 10 mm

Experimental Flow Loop tank Sample Cylinders pump hydrocyclone Stirrer

Flow Predictions Feed pressure varied from psig Flow rates determined using stopwatch Linear regression Q f = f(  P o,  P u )

Flow Predictions

Flow Rate Predictions

Experiment Determine optimum conditions which will give the best separation efficiency Compare concentration separation efficiency with traditional way of determining efficiency. RunFeed Press Drop, psigFlow rate,L/min

Solid-Liquid Separation Experiments

Model Dispersion Soda Lime Borosilicate Glass glass bubbles and water :  = 0.1 g/cm 3  c = 1 cp (Cannon-Fenske viscometer) l mean = 30  m

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

Results

Results Grade Purity Function vs. Diameter – 4.85 lpm

Results Overall efficiency vs. Feed flow rate

Conclusions Glass bubbles-water separation –Best overall efficiency for feed distribution occurs 4.8 lpm feed flow rate (  P=200 psi) –L 50 = 10  m

Liquid-Liquid Separation Experiments

Model Dispersion Vegetable oil dispersion in water:  = 0.1 g/cm 3 (pycnometer)  d = 50 cp (Cannon-Fenske viscometer)  c = 1 cp (Cannon-Fenske viscometer)  30 dynes/cm ( Pendant drop method )

Results Conc vs. oil droplet sizes at 60 psi  P

Results Conc. vs oil droplet sizes at 160  P

Concentration G-curves Grade Purity Coefficient vs. Oil droplet diameter at various flow rates L/min best GPC-curve “Drop Breakup”

Results The best “overall” efficiency? RunFeed-pressure drop,psig Flowrate, l/min Efficiency,  u      

Conclusions 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 Work Investigate drop breakup Investigate source of ‘fish hook” Investigate use of back pressure to eliminate the air from the core vortex