Liquid residence time for FKOD sizing? 2

[Renoyd]

Hello,
In my previous FKOD sizing experience, I didn't need to consider the liquid residence time, even the API recommended sizing method does not mention the liquid residence time requirements. In a recent heavy oil job, the FKOD is required to have 20 minutes residence time, is this normal? How to exactly define the liquid flow to the FKOD?

Thanks.

 

[cloa]

You should defince FKOD. People may not be familiar with that acronym.

 

[MortenA]

It dosnt sound like a KO drum - i assume its a horz. vessel?

20 min is a long time. The liquid flow will be a design basis. There are calculation methods for calculating the time gas bubbles takes to travel to the surface based on oil and gas properties.

Best regards

Morten

 

[chemjock]

This is not unusual. I have seen 30 minutes. The time allows pumpout of the drum at a reasonsible rate to a slop tank. If there is a two phase relief then the answer is obvious. Even if the drum has only vapor relief there is usually condensation from saturated vapors after a reliving indident.

 

[Renoyd]

Yes,Morten, it's a horrizontal vessel.

Chemjock,
FKOD's are normally sized to remove 300~600 micron droplets, and enough vapor space will do. Flare stacks can normally handle the small droplets without problem. What does the residence time has to do with the settling of liquids and vapor?