Separator types

Conventional separators can be oriented vertically or horizontally, with each orientation having advantages and disadvantages.  Horizontal vessels are generally preferred for high liquid rates, liquid slug mitigation, and three-phase separation.  Vertical vessels are generally preferred for high gas volume fraction flows such as scrubber applications.  General guidance on the selection of the most common designs can be found in the following references:

-API Recommended Practice 12J Ninth Edition, September 2024, Process Design of Oil and Gas Separators and Scrubbers.

-GPSA Handbook Section 7, 14^th Edition.

-Norsok Standards P-002 Process System Design, 2014.

These designs include:

-Vertical two-phase separator with inlet diverter and mist eliminator with/without an agglomerator

-Horizontal three-phase separator with flooded or spill-over weir

-Horizontal three-phase separator with oil bucket and water weir, requiring no active interface control

-Horizontal three-phase separator with boot for low water rates

Vertical three-phase separators are typically not used due to the difficulty of achieving good liquid flow distribution and short separation lengths.

For an overview of separators, refer to Oil and Gas Separators

For design of horizontal and vertical vessels, refer to Separator design

Alternative Designs

In addition to the conventional designs, there are many alternative designs that may provide an advantage in specific circumstances

Double tube/Double barrel horizontal separator

Horizontal double-barrel two-phase separator for low liquid rates.

Figure 1 illustrates a horizontal double barrel two-phase separator, which is used for low liquid rates. An improved quality of the liquid stream can generally be anticipated, although constructing this vessel is typically more challenging and costly to build compared to a conventional vessel.

Split flow - central or dual inlets

In some cases, for high gas rates, it is advantageous to split the flow through a central inlet/dual outlets (Figure 2) or dual inlets/central outlet (Figure 3) separator. The division of flow through either two inlets or two outlets allows the vessel to reduce velocity in the separation region.

These split flow designs are similar to  standard separators acting in parallel, increasing the throughput while reducing manufacturing, installation, and operational costs of the vessel. For floating facilities, the liquid level in the center of the vessel is more stable so that  the platform tilt has less effect on the operation (e.g. level controls) of devices located there.

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  Fig. 2—Two-phase separator with center inlet cyclones and dual outlets for a floating structure.

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  Fig. 9b—Two-phase separator with dual inlet cyclones and center demisting cyclones for a floating structure.

Other types of separators

Cyclone/centrifugal separators

Several designs of gas-liquid separators are available employing centrifugal force to improve separation, particularly in compact and inline separation applications. By centrifugal force, the swirling action of the gas stream enables separation of the denser phase droplets from the gas stream.  Examples of centrifugal separators include:

-Gasunie cyclone - Figure 4

-Gas Liquid Cylindrical Cyclone (GLCC) - Figure 5

-Axial Flow Cyclone Separators – Figure 6

Although such designs can result in much smaller sizes, they are not typically utilized in production operations because their design is sensitive to flow rate and they require more pressure drop than other configurations.

Reverse flow or axial flow cyclones as discussed in “Mist Eliminators” have also been bundled for removing mist as shown in Figure 6.

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  Fig. 4—Gasunie cyclonic scrubber (courtesy of CDS Separation Technologies Inc.).

Figure 5 - Schematic of GLCC separator.

Figure 6 - A horizontal mist eliminator with a bundle of axial flow cyclones. (Courtesy of Jonell Systems)

Filter separators

If gas needs to be polished to remove all solids and liquid down to a level of around 1 micron, a filter-separator (Figure 7) is a common piece of equipment. For gas scrubbing, filter-separators are generally comprised of an inlet section to distribute flow, a filter cartridge section to remove particulate and coalesce liquids, a separator section (e.g. mesh, vane packs) to remove the coalesced liquids, and separate sump sections for the inlet and separator sections.

Figure 7 - A schematic of a horizontal Filter-Separator vessel (courtesy of Jonell Systems)

Gas Coalescers

For the highest levels of cleanliness, a gas coalescer (Figure 8) is generally used, and most designs will remove solid and liquid contaminant to 99.98% of 0.3 micron and greater contaminant.  Typical designs consist of an inlet knockout and distribution section, a coalescer cartridge section, an outlet disengagement section, and separate liquid retention and control for the inlet and outlet sections. Coalescers are also available for liquid-liquid systems.

Figure 8 - Schematic of a vertical and horizontal Gas-Coalescer vessel (courtesy of Jonell Systems).

Noteworthy papers in OnePetro

Hixson, J.C., Sheridan, E. and Ayling, I. 2013. Downhole Oil and Water Separation: A New Start. IPTC-16914-Abstract presented at the International Petroleum Technology Conference, Beijing, China, 26-28 March. http://dx.doi.org/10.2523/16914-ABSTRACT.

Kelamis, P.G., Huo, S.D., Luo, Y. and Zhu, W.H. 2013. Iterative Dip-Steering Median Filter: A New Approach to Separation of Simultaneous Sources. IPTC-17000-Abstract presented at the International Petroleum Technology Conference, Beijing, China, 26-28 March. http://dx.doi.org/10.2523/17000-ABSTRACT.

Davidson, E., Mota, L., Mosley, N., Chimara, G., Morrison, A.K. and Archibald, I. 2012. New and Effective Filter Cake Removal Optimizes Water Injectivity. SPE-151683-MS presented at the SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, USA, 15-17 February. http://dx.doi.org/10.2118/151683-MS.

External links

Types of Separators

See also

Oil and gas separators

PEH:Oil_and_Gas_Separators