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TUSTP 2003 By Ciro A. Pérez May, 2003 DOE Project: HORIZONTAL PIPE SEPARATOR (HPS © )
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Objectives Physical phenomena in HPS Modeling approach Experimental program Conclusions - Future work Topics
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Study the behavior of oil-water mixtures in horizontal pipes Develop a mechanistic model that predicts separation efficiency for given fluids, geometry and flow rates Compare/refine model with data obtained in this study and from literature Study effects of using manifolds to install multiple separators in parallel Objectives
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Objectives Physical phenomena in HPS Modeling approach Experimental program Conclusions - Future Work Topics
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Zone 1Zone 2 Zone 3 Zone 4 Oil Oil with Water droplets Packed water droplets in oil Packed oil droplets in water Water with Oil droplets Water Physical phenomena in HPS Inlet Direction of flow Outlets
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Oil-Water mixture enters HPS, with droplet distribution function of processes upstream. Some mixing can occur at inlet (Zone 1) Inside HPS the velocity decreases, turbulence decreases (laminar flow might be reached), settling and coalescence are promoted (Zone 2), layers begin to develop Up to 6 layers can develop (Zone 3): -Pure Oil -Oil with water droplets -Packed water droplets in oil -Packed oil droplets in water -Water with oil droplets -Pure water Eventually steady state is reached (Zone 4) Physical phenomena in HPS
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Regimes of operation in HPS Laminar flow is desirable as it promotes segregation Oil is more likely to flow to be in laminar flow conditions due to higher viscosity So, desirable flow regimes are: -Laminar Oil Flow - Laminar Water Flow -Laminar Oil Flow - Turbulent Water Flow Study flow in HPS requires: -Steady state conditions: max segregation -Transient conditions: how long it will take Physical phenomena in HPS
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Objectives Physical phenomena in HPS Modeling approach Experimental program Conclusions - Future work Topics
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Previous studies Proposed model Modeling approach
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Previous studies a.1D Mechanistic approach: Barnea-Brauner (1991) b.2D Analytical approach (for laminar flows): Brauner (1998) c.Numerical approach -Shoham-Taitel (1984, gas-liquid) -Elseth et al. (2000, VOF method) -Gao et al. (2003, VOF method) 1D mechanistic approach leads to simple solutions, so it will be used as an initial approach Modeling approach
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Proposed model: 1- 1D stratified flow pattern model is applied for given fluids and flow rates. If flow is stable, flow characteristics are given by the model 2- If flow is unstable, following procedure applies: -An amount of more viscous phase is assumed to flow to the less viscous phase -For this new flow rate, properties are calculated for mixture, segregated flow is assumed, and stability is checked. Migration stops when stability is reached -No convergence means non segregated flow Modeling approach
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Preliminary results Model tested against experimental data (Shi et. Al (2000)) Test conditions: -Oil properties: 3 cp, 800 kg/m 3 -Water properties: 1 cp, 1100 kg/m 3 -Pipe: 0.1 m ID, 18m long -Mixture velocity: 0.4 to 3 m/s -Water Cut: 0.2, 0.4, 0.6, 0.8 Trallero (1995) model used, Sheltering Factor assumed 0 Increased interfacial friction factor as mixing and waves form at the interface Modeling approach
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Results: Pure oil and water layer thickness Modeling approach
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Objectives Physical phenomena in HPS Modeling approach Experimental program Conclusions - Future work Topics
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Test Section Experimental program
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Calibration: Level: Pipe centerline was leveled in +-3/32” range from the horizontal Level sensors: For operating conditions, level meters are able to detect continuous interface with error of 3/32” Experimental program
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Typical level meter signal at interface Experimental program Sensor stem gap: 7/32”
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Pitot / Isokinetic sampling probe Previous works: -Khor, Mendes-Tatsis and Hewitt (1996) -Vedapuri, Bessette and Jepson (1997) -Shi, Cai and Jepson (1999) -Cai, Gopal and Jepson (2000) Experimental program
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Pitot / Isokinetic sampling probe Characteristics -ID= 3/16” -OD= 11/32” -Operating dP: 0 to 1” H 2 O, accuracy dP 0.15% -Range of operation:. Min. velocity: 0.06 m/s (error 10% ). Max. velocity : 0.7 m/s (error 0.073% ) Experimental program
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Photo of assembled probe: Base Pitot Pressure outlets Sampling outlet Experimental program
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Pitot / Isokinetic sampling probe in place Experimental program
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Pitot / Isokinetic sampling probe - Calibration results for single phase Experimental program
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Pitot / Isokinetic sampling probe -Problems when measuring oil-water flow. After flushing with oil, water floods pitot, capillarity causes oscillations in dP while flooding -Improved with wider pressure taps. dP values to be taken at initial plateau, before flooding occurs. Experimental program Plateau Flooding
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Calibration results: Effects of oil-water flow Pitot filled with oil, mixture flowing Vsl=0.6 m/s, WC 60% Experimental program
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Objectives Physical Phenomena in HPS Modeling approach Experimental program Conclusions/ Future Work Topics
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Initial model for all flow conditions is proposed. Actual model underpredicts thickness of pure fluid zones Model requires higher interfacial shear stress when mixing layers are present Pitot measurements for low velocities are affected by capillarity in pitot pressure taps Measurement criterion was adapted for this condition Conclusions/Future Work
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Measurement of velocity profiles for experimental matrix Measurement of hold up for experimental matrix Hold up/Interfacial friction factor adjustment with experimental data and literature data Future work
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Questions? HORIZONTAL PIPE SEPARATOR (HPS©)
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