Design & Functions of a Flare Knockout Drum

A flare knockout drum is a vessel primarily used to remove any liquids or liquid droplets from the flare gas. It is also known as a flash drum or a knockout pot.

The knockout drums are designed and sized according to a specific length-to-diameter ratio between 2 to 4 to maintain the vapour velocity low enough so that the liquids drop out or settle out. We dramatically reduce the speed of the gas so that the liquid droplets settle out. We manually drain or pump the liquids out regularly to ensure the flare KO is always empty of fluid.

Flare Knockout Drum Function

  • A knockout drum is used to remove any oil or water from the relieved gases.
  • Vapour travels upward at a designed velocity which minimizes the entrainment of any liquid droplets as it exits the top of the vessel.
  • Flares are important safety devices used in oil and gas processing. They safely burn excess hydrocarbon gases which cannot be recovered or recycled. During flaring, excess gases are burnt off in the flare system to produce water vapour and carbon dioxide.

Flare Knockout Drum Design & Sizing

  • Most knockout drums are horizontal. A horizontal knockout drum must have a diameter large enough to keep the vapour velocity low enough to allow entrained liquids to settle or drop out.
  • All flare systems are designed to include a liquid knockout drum.
  • As per the safety and industry standards, the particle size should be between 400 to 500 μm which is why most flares are crafted to allow liquids with a particle size less than 300 μm.
  • They are operated at an atmospheric pressure that allows the greatest liquid volume anticipated at the maximum rate of liquid pump out and build up.
  • For onshore operations, it is advised to allow a 10-minute liquid holdup and take 20% of the maximum liquid stream. For offshore activities, a separation-retention time of 1 – 3 minutes with regards to API gravity must be provided, and an emergency dump design without valves is recommended to handle the maximum liquid flow.
  • The maximum allowable working pressure (MAWP) of the knockout drum is typically kept at 50 pounds per square inch gauge (psig) to maintain an explosion.

Contact Us for Flare KO Drum Sizing, Design, Installation & Maintenance

At Aspire Energy Resources Inc., we offer high-quality vessel fabrication and design services. We can provide the best possible solutions when it comes to installing a flare KO drum. You can trust our reliable products to prevent liquids from getting into the flare stack, thus minimizing the risk of fire or an uncontrolled explosion.

To learn more about our products and services or to request a project discussion, get in touch with our consultants by calling 403-314-5422 or 1-800-993-9958.  You could also fill out our online form for a project quote.

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