3D Computational-Fluid-Dynamics Modeling of Horizontal Three-Phase Separators: An Approach for Estimating the Optimal Dimensions

Ghaffarkhah, Ahmadreza; Shahrabi, Mohammadjavad Ameri; Moraveji, Mostafa Keshavarz

doi:10.2118/189990-pa

Cited by 13 publications

(10 citation statements)

References 10 publications

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“…As the fluid flows from the point of depressurization through the separator, varying rates of energy dissipation are experienced. 35 The understanding of the rate of gas evolution under a varying energy dissipation rate is essential as well. Thus, an understanding of the kinetic behavior of gas evolution under a varying supersaturation ratio and energy dissipation rate will aid in troubleshooting and debottling neck separation issues.…”

Section: Introductionmentioning

confidence: 99%

Impact of Supersaturation Ratio on the Kinetics of Gas Evolution at Elevated Pressures

2020

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The kinetics of gas evolution in supersaturated solutions is a critical uncertainty in the design and operation of gas/ liquid separators. Incorrectly predicting the amount of gas that evolves in a gas/liquid separator can lead to gas carry under with the liquid, resulting in equipment damage downstream of the separator. Central to addressing this problem is the measurement of the gas evolution rate at specific levels of supersaturation. The supersaturation ratio (S) is defined as S 1, where P g,o is the pressure before depressurization and P g,ss is the pressure after depressurization. Exxsol D-110, a model oil, was used as the liquid phase, and methane was used as the gaseous phase. The rate of gas evolution was investigated at six supersaturation ratios (0.15, 0.30, 0.70, 1.30, 2.00, and 2.83) and at three different rates of energy dissipation (mixing speeds: 100, 250, and 500 rpm). The rate of gas absorption into the oil was within 20% of the rate of gas evolution up to a supersaturation ratio of 1.30. At a supersaturation ratio of 2.83, the rate of gas evolution was higher than the rate of absorption. At a supersaturation ratio of 2.00, the rate of gas evolution was higher than the rate of absorption only at 500 rpm. Thus, the supersaturation ratio and the rate of energy dissipation (mixing speed/shear environment) are key parameters that affect the rate of gas evolution.

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Section: Introductionmentioning

confidence: 99%

Impact of Supersaturation Ratio on the Kinetics of Gas Evolution at Elevated Pressures

2020

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“…The model was able to predict the performance of the slug catcher for the corresponding operating conditions. Ghaffarkhah et al (2018) used CFD to model three-phase separation in a horizontal vessel to evaluate different vessel configurations and choosing the best. The volume of fluid (VOF) model was used for the continuous phase and a Lagrangian approach for tracking the movement of droplets and bubbles.…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation of a multi-branch gas–liquid pipe separator using computational fluid dynamics

Refsnes

Díaz

Stanko

2019

J Petrol Explor Prod Technol

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The present paper aims to evaluate the performance of a multi-branch gas-liquid pipe separator by means of 3D computational fluid dynamics. This type of separator is attractive for deepwater subsea hydrocarbon fields due to its compactness and reduced weight when compared against traditional gravity vessel separators. The focus of this paper is on studying the internal flow dynamics, the separation efficiency, and the performance with changing and transient operating conditions. Numerical simulations were performed on a numerical prototype of the separator using the inhomogeneous mixture model and assuming that both phases are continuous. Sensitivity analyses were performed on gas volume fraction, outlet pressures, and considering slug flow at the inlet with periods of 2 s and 8 s. The separation efficiency was quantified by calculating the liquid carry-over and gas blowby. For most of the operational conditions studied, separation occurred primarily in pipe branches closer to the inlet while those closer to the outlet exhibited a static liquid level. Reducing the gas outlet pressure caused the height of the liquid in the branches to be reduced. The inlet gas volume fraction did not affect significantly the separation performance, the flow distribution, nor the liquid level inside the separator. Separation efficiencies were not affected significantly with the presence of slugs; however, the liquid level in the branches oscillated significantly. The results and numerical models produced by this study could potentially be used to improve the understanding of this type of separators and improve its efficiency and system-level design. Keywords Gas-liquid separation • Subsea processing • Computational fluid dynamics List of symbols Variables Δy Thickness of cell closest to wall (m) u * Friction velocity (m/s) t Time (s) U Velocity vector U Velocity component (m/s) p Pressure (Pa, bara) g Gravitational acceleration (m/s 2) M p Momentum interphase (N/m 3) C D Drag coefficient d og Oil-gas interfacial length (m) t Turbulent viscosity (Pa s) k Kinetic energy (m 2 /s 2) p k Turbulent production (kg/m s 3) Greek symbols ρ Density (kg/m 3) μ Dynamic viscosity (Pa s) Volume fraction Turbulent dissipation rate (m 2 /s 3) Subscripts o Oil g Gas OG Outlet of gas OL Outlet of liquid p Generic phase "p" j Generic spatial coordinate i Generic spatial coordinate m Mixture Superscripts o Oil g Gas Abbreviations CFD Computational fluid dynamics GCU Gas carry under * M. Diaz

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“…The Euler-Lagrangian formulation considers the fluid or continuous phase as a continuum and tracks the movement of individual particles of the discrete phase through space and time. 17 The dispersed phase is allowed to exchange momentum, mass, and energy with the fluid phase, whereas the Eulerian-Eulerian approach considers the two phases as interpenetrating continua and solves the conservation equations for each of the phases. 17 The Euler-Lagrangian approach is used in the present study as it is physically more suitable for fluid-particle interaction than the Eulerian-Eulerian model.…”

Section: Governing Equations For the Dispersed Phasementioning

confidence: 99%

“…17 The dispersed phase is allowed to exchange momentum, mass, and energy with the fluid phase, whereas the Eulerian-Eulerian approach considers the two phases as interpenetrating continua and solves the conservation equations for each of the phases. 17 The Euler-Lagrangian approach is used in the present study as it is physically more suitable for fluid-particle interaction than the Eulerian-Eulerian model. 18 As the particles occupy a low volume fraction, particle-particle interaction and impact of the discrete phase on the continuous phase are neglected.…”

Section: Governing Equations For the Dispersed Phasementioning

confidence: 99%

Effects of convergent–divergent vortex finders on the performance of cyclone separators using computational fluid dynamics simulations

Kumar

Jha

2019

SIMULATION

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This study investigates the effect of convergent–divergent vortex finders on the performance of cyclone separators, which is measured in terms of pressure drop and collection efficiency. Six cyclone models (two with uniform diameter and four with convergent–divergent vortex finders) were numerically simulated. The numerical simulations have been carried out using the commercial computational fluid dynamics code (CFD) Fluent v15. The simulation procedure has been validated using experimental data from the published literature where a good agreement between the numerical results and the experimental data is seen. A grid independence test has been carried out by using two levels of grids for correctness of our simulation. The Reynolds averaged Navier–Stokes (RANS) and continuity equations have been solved for the flow simulation. The Reynolds stress model is used for modeling the stress tensor and closing the RANS equations. The results show that a convergent–divergent vortex finder is capable of producing better performance (pressure drop and collection efficiency) than the uniform diameter cyclones. Only one performance parameter can be improved in uniform diameter cyclones. In comparison to the standard uniform vortex finder cyclones, the convergent–divergent vortex finder improves the pressure drop by 6% and also reduces the cut-size to 1.4 from 1.6 µm. It is further seen that decreasing the throat area or increasing only the lower diameter of the vortex finder causes the performance to degrade. This study proves that convergent–divergent instead of uniform diameter vortex finders can be used in gas cyclones for obtaining a better performance with the same geometry.

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3D Computational-Fluid-Dynamics Modeling of Horizontal Three-Phase Separators: An Approach for Estimating the Optimal Dimensions

Cited by 13 publications

References 10 publications

Impact of Supersaturation Ratio on the Kinetics of Gas Evolution at Elevated Pressures

Impact of Supersaturation Ratio on the Kinetics of Gas Evolution at Elevated Pressures

Performance evaluation of a multi-branch gas–liquid pipe separator using computational fluid dynamics

Effects of convergent–divergent vortex finders on the performance of cyclone separators using computational fluid dynamics simulations

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