Vapor Recovery Units, or VRUs, are commonly used in upstream oil and gas operations as well as many industrial applications to compress low-pressure gas. Examples include gas-lift, wellhead compression, tank battery vapor, and industrial tail gas recovery. The most common application is oil tank battery gas recovery, often immediately downstream of a Vapor Recovery Tower (VRT). The VRT allows for partial capture of the oil flash gas and helps avoid oxygen contamination which is a common problem with atmospheric tanks.
There are several different types of VRU compressors, and proper selection for the application is key to effective operation. This article focuses on four commonly used positive displacement compressors: reciprocating, flooded screw, rotary sliding vane, and liquid ring. A positive displacement pump provides a constant flow at a fixed speed, but actual flow will vary with inlet conditions. We will briefly review these and summarize the advantages and disadvantages of each.
Reciprocating compressors compress gas by repeatedly enclosing a fixed volume and moving it mechanically using pistons and cylinders. “Recips” are commonly used and can be installed in sequence to obtain multiple stages of compression.
Flooded screw compressors employ positive displacement using a single screw or male and female mating screws that rotate in the opposite direction to compress the fluid. Lubrication oil is injected into the compression chamber to cool and lubricate the compressor element and to reduce the return leakage to the intake.
Rotary vane compressors form a seal between vanes, the cylinder bore, and an eccentrically mounted rotor. As the rotor turns, the volume between the vanes decreases, compressing the gas prior to discharge.
Liquid ring compressors are similar to rotary vane units in that a spinning rotor is eccentrically located insider the compressor casing. However, the vanes are fixed into the rotor, which provides centrifugal force resulting in a cylindrical liquid ring against the interior wall of the casing. Multiple seals fill the space between the vanes of the impeller, forming compression chambers.
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Reciprocating |
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Flooded Screw |
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Rotary Vane |
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Liquid Ring |
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EcoVapor solutions work with any type of VRU. There are many excellent suppliers of Vapor Recovery Units and their service capabilities are critical in minimizing maintenance cost and achieving high uptime.
We recommend that the specifics of an application and an understanding of a supplier’s service capability be discussed prior to selecting the best method of compression for your operation.
About EcoVapor Recovery Systems
EcoVapor Recovery Systems provides solutions to pressing oil and natural gas production problems. EcoVapor’s technical team includes world-class engineers, not all from the oil and gas industry, sees challenges differently and encourages a culture of innovation. Our patented ZerO2 solution helps oil and gas producers Flare Less, Sell More. EcoVapor is headquartered in Denver, Colorado and has field locations in Greeley, Colorado and Midland, Texas.
Contact
Joe Hedges
Chief Commercial Officer
EcoVapor Recovery Systems
700 17th St., Suite 950
Denver, CO 80202
Phone: 844-NOFLARE (844-663-5273)
Email: Info@EcoVaporRS.com
Web: EcoVaporRS.com