3 replies to this topic

[jprocess]

Dear All,
I have read about Flare KO Drum that it should be horizontal and we should not use demister pad for it!
Could you please explain about the reason(s)?!
Thanks in advance.
Best Regards.

[Sandeep01]

Vertical flare drums are common in the industry.

This being the last vessel in the flare system, a demister should not be used for fear of its choking/clogging (e.g. under a possible fire scenario), thus not permitting flow and resulting in overpressure of the Flare KOD. If unavoidalble, a demister could be used provided suitable pressure protection is provided for. This is NOT common in the industry, and not a preferred option.

Regards
Sandeep

[vkiocl]

If there is any entrainment in the gas from KOD to flare water seal,it should get overflowed via the overflow line in the water seal inside the flare structure.Hence demister is not required,i think.
vijay

[Art Montemayor]

Let's stop and think first about what the operation is and what it requires/doesn't require to bring about the desired results:

1. A horizontal drum inherently can handle a large liquid capacity; therefore, it is usually the orientation of choice when considering a flare K.O. Drum design. It not only offers a large liquid retention capability, it also offers the lowest superficial vapor velocity as opposed to a vertical orientation. Therefore, the vapor disengagement is superior in a horizontal orientation. The large liquid reservoir capability allows it to be used for emergency discharged liquid fluids that must be separated prior to flaring the associated gas(es).

2. The objective of the K.O. Drum is to prepare the separated vapors/gases for subsequent burning in the downstream flare. Flares burn vapors; they don't burn liquids. Why would any self-respecting Chemical Engineer design and employ internals such as a de-mister pad in order to increase the quality of the size/quantity of liquid particles going to flare? The flare doesn't care what it incinerates and within a certain range of particle sizes, it will burn all vapors and liquid droplets. The droplet size produced by a simple vane separation device is more that sufficient for effective flaring. In fact, I've seldom even used vanes (never de-mister pads) because if I design a conservative superficial velocity in the horizontal K.O. Pot, that will be more than sufficient for flaring. Of course, a lot depends on what type/kind of liquids you are dealing with; but in the normal, usual situations a horizontal K.O. pot without any fancy internal is all that is needed.

3. A practical reason for not using internals is that sooner or later you will have to inspect and/or replace and service them. You don't want to send someone into any vessel if you can avoid it - much less a vessel that doesn't have a turn-around period available. Sending someone into a confined vessel space is just asking for trouble. You should avoid it whenever you can. Unless you have strong safety, operational, or economic reasons I would definitely never use any internals in a flare K.O. Drum.