Enhanced Mechanistic Model and Field-Application Design of Gas/Liquid Cylindrical Cyclone Separators
- L.E. Gomez (U. of Tulsa) | R.S. Mohan (U. of Tulsa) | Ovadia Shoham (U. of Tulsa) | G.E. Kouba (Chevron Petroleum Technology Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- June 2000
- Document Type
- Journal Paper
- 190 - 198
- 2000. Society of Petroleum Engineers
- 4.3.4 Scale, 4.6 Natural Gas, 5.6.4 Drillstem/Well Testing, 4.4.3 Mutiphase Measurement, 4.1.2 Separation and Treating, 5.2.1 Phase Behavior and PVT Measurements, 1.6.9 Coring, Fishing, 4.1.5 Processing Equipment, 5.3.2 Multiphase Flow, 5.3.4 Integration of geomechanics in models
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An existing mechanistic model for prediction of the hydrodynamic flow behavior in a gas-liquid cylindrical cyclone (GLCC) separator has been enhanced. The main enhancement incorporated is a flow pattern dependent nozzle analysis of the cylindrical cyclone inlet for prediction of the gas and liquid tangential velocities at the GLCC entrance. Four typical field GLCC systems were designed for actual industrial applications using the proposed model. These include multiphase metering loop with both single-phase and multiphase flow meters, and pre-separation and full separation configurations. The field applications demonstrate the cylindrical cyclone capabilities and its potential impact on the petroleum industry.
Multiphase separation technology has advanced slowly and incrementally for several years. A new look and the infusion of novel ideas and concepts are now needed to develop breakthrough technologies in this area for the 21st century. In the past, the petroleum industry has relied mainly on the conventional vessel-type separator, which is bulky, heavy and expensive, to process wellhead production of oil-water-gas flow. Economic and operational pressures continue to force the petroleum industry to seek less expensive and more efficient separation alternatives in the form of compact separators, such as the gas-liquid cylindrical cyclone (GLCC). The compact dimensions, smaller footprint, and lower weight and cost of the cylindrical cyclone have a potential for cost savings to the industry, especially in offshore applications. Also, the cylindrical cyclone reduces the inventory of hydrocarbons significantly, which is critical for environmental and safety considerations.
A schematic of the cylindrical cyclone separator is shown in Fig. 1. The cylindrical cyclone is a vertically installed pipe mounted with a downward inclined tangential inlet, with outlets provided at the top and bottom of the pipe. It has neither moving parts nor internal devices. Due to the tangential inlet, the flow forms a swirling motion producing centrifugal forces. The two phases of the incoming mixture are separated by centrifugal and gravity forces. The liquid is forced radially towards the wall of the cylinder and is collected from the bottom, while the gas moves to the center of the cyclone and is taken out from the top. Currently, the cylindrical cyclone finds potential application as a gas knockout system upstream of production equipment. Through control of the gas-liquid ratio (GLR), it enhances the performance of multiphase flow meters, multiphase pumps, and de-sanders. Other applications are in portable well testing equipment, flare gas scrubbers, and slug catchers. The cylindrical cyclone is also being considered for downhole separation, primary surface separation (onshore and offshore), and subsea separation.
A lack of understanding of the complex multiphase hydrodynamic flow behavior inside the cylindrical cyclone inhibits complete confidence in its design and necessitates additional research and development. Knowledge of the hydrodynamic flow behavior would enable cylindrical cyclone users to correctly predict the performance of the cylindrical cyclone and to carry out appropriate designs for all configurations and applications. It is the objective of this investigation to develop an enhanced mechanistic model based on the preliminary model developed by Arpandi et al.1 Suitable submodels are developed for prediction of the inlet flow pattern and the tangential velocities of the gas and liquid phases at the cylindrical cyclone entrance. The developed model will be used for designing cylindrical cyclone systems for field applications.
Review of the Literature
Being a new technology, very little information is available about the understanding of the performance and the optimum design of cylindrical cyclone separators. Also, only few related experimental investigations have been carried out. Mathematical models for cyclone separators have been developed only for single-phase or homogeneous dispersed flow. Lack of holistic models to represent the hydrodynamic flow behavior in cylindrical cyclone separators has hindered the development of suitable simulators and their use in field application design. Following is a brief overview of pertinent literature on some important aspects of the compact separation technology research.
Experimental Studies and Applications.
Most of the previous work on compact separators has been based on field or laboratory equipment experimental testing. Davies,2 Davies and Watson,3 and Oranje4,5 studied compact separators for offshore production and concluded that cyclone type separators are suitable for applications on offshore platforms. Bandopadhyay et al.6 of the Naval Weapons Research Laboratory considered the use of cyclone type gas-liquid separators to separate hydrogen bubbles from liquid sodium hydroxide electrolyte in aqueous aluminum silver oxide battery systems. The design parameters for the cyclone separator developed by Nebrensky et al. 7 included a tangential rectangular inlet equipped with a special vane-and-shroud arrangement to change the inlet area. Zhikarev et al. 8 developed a hollow cyclone separator for gas-liquid separation with a rectangular and tangential inlet near the bottom of the cyclone. Cowie9 acquired data on vertical caisson slug catchers and studied their performance for radial and tangential inlet configurations. Kolpak10 and Weingarten et al.11 developed a cylindrical cyclone with spiral vane internals (the Auger separator) that exhibited gas carryunder between 2 and 18% in field tests. A new separation method, the Maxigee, based on very high "g" force and unusual thermal characteristics in vortex tubes, was introduced by Fekete.12 Recently, Movafaghian 13 presented a detailed report on the effects of fluid properties, inlet geometry, and pressure on the flow behavior in the cylindrical cyclone.
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