Knockout Drum Liguid Phase Discharge Piping

[nikolastrojman]

Hi,

I have a simple question. Can anybody tell me is it possible to connect liquid phase discharge line of the Knockout Drum directly
to the flare header the same way the gas discharge line of the drum is conected to the header (see attachment).

Thanks in advance.

 

[vt2012]

If you do that then what is the point of having the liquid knockout in the first place? The liquid knockout is to ensure you have a dry gas going to the flare (I have seen issues plugging up flame arrestrs, etc. with liquid in the vent). You will likely need to find somewhere to put the recovered liquid phase.

 

[EmmanuelTop]

Gas phase is discharged from a PSV, whereas the liquid phase flows to the flare on level control? Something is wrong in this concept.

What is the purpose/service of the vessel, and why would you want to direct liquid phase to the flare?

Dejan IVANOVIC
Process Engineer, MSChE

 

[zdas04]

Unless your liquid is flammable, this would be a real problem. You have dynamic problems like mentioned above with flame arresters and pilot lights etc, but any liquid that doesn't spew out the end of the flare header will stand in the flare piping just begging to create corrosion cells and flow restrictions.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[MortenA]

I would say that you should run your discharge to closed haz. drain instead.

 

[georgeverghese]

A few things wrong here :

a) Process liquids should not be routed to a gas phase flare header - liquids in this header can generate severe slug forces during a blowdown event / high flow relief event and damage flare piping. Process liquids, if they must be routed to the flare KOD, should be routed through a collection header dedicated for liquids only. The flare gas collection headers in this plant must also, for the same reason, slope continously all the way down to the flare KOD.

b) The RV on this process KOD should have its exit sloping DOWN into the flare header, not sloping up. So this RV should be relocated.

 

[SNORGY]

There is likely more than meets the eye in the sketch. I'd bet a beer that the vessel is not a knockout drum at all, it is probably a filter or flash separator or some such device with a pressurized drain to flare, via which liquids can be blown out for element maintenance. The "knockout" (FKOD) is probably somewhere downstream of this equipment. A P&ID would help.

 

[MortenA]

@Sorgy, i think your are rigt. Also it looks as if the pipe for discharging liquids does not have an automated level control. In this case i would be OK with a connection directly to the flafre header (as the 3D print shows)

Best regards, Morten