A Vapor-liquid separator is a vertical vessel into which a liquid and vapor mixture is fed and, in which, the liquid is separated by gravity, falls to the bottom of the vessel, and is withdrawn. The vapor travels upward at a design velocity which minimizes the entrainment of any liquid droplets in the vapor as it exits the top of the vessel.
The feed to a vapor-liquid separator may also be a liquid that is being partially or totally flashed into a vapor and liquid as it enters the separator.
A vapor-liquid separator may also be referred to as a flash drum, knock-out drum, knock-out pot, compressor suction drum or compressor inlet drum.
When used to remove suspended water droplets from streams of air, a vapor-liquid separator is often called a demister.
Where vapor-liquid separators are used
Vapor-liquid separators are very widely used in a great many indusries and applications, such as:
- Oil refineries
- Natural gas processing plants
- Petrochemical and chemical plants
- Refrigeration systems
- Air conditioning
- Compressor systems for air or other gases
- Gas pipelines
- Steam condensate flash drums
- Flash evaporation
- Vapor-compression refrigeration
- Souders-Brown equation (for sizing vapor-liquid separators)
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- David H.F. Liu (1997). Environmental Engineers' Handbook (2nd Edition ed.). CRC Press. ISBN 0-8493-9971-8.
- Stanley S. Grossel (2004). "Design and sizing of knock-out drums/catchtanks for emergency relief systems". Plant/Operations Progress (AIChE). 5 (3): 129–135. ISSN 0278-4513. Unknown parameter
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- High-Capacity Gas De-Entrainment (scroll to page 2 of the brochure)
- Experimental Characterization of High-Pressure Natural Gas Scrubbers by Trond Austrheim (PhD Thesis at the University of Bergen, Norway, 2006)
- Flash Steam Tutorial The benefits of recovering flash steam, how it is done and typical applications.
- Design Criteria for Vapor/Liquid Separators