CFD Simulation of Single-Phase and Two-Phase Flow in Gas-Liquid Cylindrical Cyclone Separators
- Ferhat M. Erdal (U. of Tulsa) | Siamack A. Shirazi (U. of Tulsa) | Ovadia Shoham (U. of Tulsa) | Gene E. Kouba (Chevron Petroleum Technology Company)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- December 1997
- Document Type
- Journal Paper
- 436 - 446
- 1997. Society of Petroleum Engineers
- 5.2.2 Fluid Modeling, Equations of State, 5.1.8 Seismic Modelling, 4.1.2 Separation and Treating, 1.6.9 Coring, Fishing, 5.9.2 Geothermal Resources, 5.3.2 Multiphase Flow, 4.6 Natural Gas, 5.6.4 Drillstem/Well Testing, 4.2.3 Materials and Corrosion, 4.2 Pipelines, Flowlines and Risers, 5.3.4 Integration of geomechanics in models, 4.1.5 Processing Equipment, 4.4.3 Mutiphase Measurement, 4.3.4 Scale
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The petroleum industry has shown interest in utilizing the Gas-Liquid Cylindrical Cyclone (GLCC) separator as an alternative to the vessel-type separator. Thus, it is important to develop predictive tools for design and to improve the technology of the GLCC. Previous studies have resulted in mechanistic models capable of predicting the operational envelope for liquid carry-over. However, these models do not address details of the complex flow field in the GLCC and related phenomena such as gas carry-under. This paper presents computational fluid dynamics (CFD) simulations of single-phase and two-phase flow in several GLCC configurations. The CFD simulations are compared with experimental data including tangential velocity profiles and tangential velocity decay. Good agreement is observed between the data and the simulations. An axisymmetric model for the GLCC is also developed. The axisymmetric simulations, which are computationally efficient, give good results as compared to the three-dimensional simulations. Preliminary two-phase flow simulations are also performed to predict the gas void fraction distribution in the GLCC.
The Gas-Liquid Cylindrical Cyclone (GLCC) separator is simple, compact and low weight, and has low capital and operational costs. The GLCC has a wide variety of potential applications, varying from only partial separation to a complete phase separation. Currently, the design of GLCC units is based on limited experience, without a high degree of confidence. Despite reliable predictive tools, several cases of successful application of GLCC separators have been reported for multiphase separation, metering and pumping. GLCC's are also utilized for portable well testing meters and for a limited range of gas/liquid separation such as for wet gas.
A representation of the available literature on cyclone separators and related physical phenomena is given in the list of references.1-21 A review of the literature reveals that very little information is available about the optimum design and performance of GLCC's. Furthermore, existing mathematical models of cyclone separators have been limited to single-phase flow with low concentration of a dispersed phase. No reliable models are available for cyclones (conical or cylindrical) that are capable of simulating full range of multiphase flows entering and separating in a cyclone.
The GLCC is shown schematically in Fig. 1. The gas and liquid mixture flows through an inclined inlet section, to enhance stratification, prior to reaching a tangential inlet slot. As a result, a swirl is formed causing the gas and liquid to separate due to the centrifugal force. The liquid moves toward the wall and downward, while the gas flows to the center and exits from the top. For certain operating conditions, some liquid droplets flow with the gas and move up toward the gas leg. This phenomena is referred to as the liquid carry-over. On the other hand, gas bubbles may be entrained with the liquid and exit from the bottom of the GLCC (gas carry-under).
Based on experimental and theoretical studies performed at The University of Tulsa,22,27 a mechanistic model has been developed to predict the operational envelope for liquid carry-over and bubble trajectories. However, the model does not address details of the complex flow behavior in the GLCC and related phenomena such as gas carry-under and separation efficiency. The understanding of the flow behavior in the GLCC is essential for development of a comprehensive model to predict gas carry-under. In the present work, computational fluid dynamic (CFD) simulation is carried out to shed more light on details of the flow behavior in the GLCC. In this study, commercially available CFD code, namely, CFX is utilized to simulate both single-phase and two-phase (gas-liquid) flow in several GLCC configurations.
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