Can Flare Kod Be At Atmospheric Pressure 1

[zamakaze]

In a low pr. flare system can a the flare ko operating pr. be kept at atmospheric?


Since pr. at flare tip is atmospheric then how flare ko can be atmospheric? would it not be always higher than atmospheric due to backpressure?

attachd sketch

 

[The Obturator]

You might want to cancel and repost your query in a more appropriate section of the forums, such as the Pipelines, piping and fluid mechanics engineering or Boiler and pressure vessel engineering.

*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[don1980]

The pressure in the flare KO drum is equal to the pressure drop in the system between the drum and the exit of the flare tip. If this pressure drop is approx zero then the pressure in the KO drum will be approx zero. But that's not a desirable condition. You want to have some small amount of pressure drop in this system. No pressure drop means the system (piping, flare stack , and flare tip) are oversized, which will result in performance/safety problems (air ingress, short flare tip life due to flame inside the tip) in addition to wasting money.

 

[MortenA]

addding to don1980: it also means that you should not overburden your LP flare system if you are looking at adding new soruces to this...

 

[shvet]

Speaking of elevated flare (as shown on sketch of topicstarter) the pressure in KOD is not "kept" (controlled). The pressure in such KOD is self controlled by ratio of molecular weight (MW) of purging gas, height of flarestack and pressure drop in flarestack. If purging gas has low MW, flarestack is high and flowrate of purge gas is low (due to construction of gas seal) or equals nul then pressure in the lowest point of flare system is negative, usually minus 0.5-1kPa.

This situation is usual for complex refineries having hydroprocesses like reforming, hydrotreating because of relatively high content of H2 in fuel gas as fuel gas is used for continious purging of flare mains. Air sucking caused by vacuum is the reason of internal explosions in flares. Explosion is the reason (in it is turn) of design pressure of flare system is recommended 3.5 barg. For example of internal explosion caused by vacuum see video attached.

Speaking of enclosed/ground flare the answer depends on configuration of flare system.

https://files.engineering.com/getfi...c4e-63a3a40ba146&file=Flare_header_blowup.mp4