Separator internal anti-foam spraying 1

[Trond]

Hi all,

we are doing a detailed design of a oil & gas production platform for a client. The oil separation takes place in 3 stages, a pretty conventional set-up. We have provided anti-foam injection points (quills) upstream of the inlet to the first two separators, but the client has requested that we in addition provide an internal spray system for both separators.

None of us have not come accross this arrangement before(including the client!). If we provide an internal spray system with atomizing nozzles, the fine droplets will most likely be swept out of the vessel with the gas, and if we provide a perforated pipe, the holes will need to be big enough not to get blocked, but yet small enough to keep anti-foam chemical consuption at a reasonable level.

I would be very interested in hearing from anyone who has experience from similar systems, or any ideas/suggestions.

Cheers,

Trond

 

[spekuljak]

Right! Antifoam sprays is not a good solution. A suggestion is to premix the relative small antifoam stream with a small part of the treated oil (a recycle), to give a higher rate to the injection stream, allowing a good distribution on the perforated pipe distributor. Spekuljak.

 

[Montemayor]

Trond:

Bear in mind that this is a fine example of a rare situation where a client paints himself into an expensive corner with his special request. Now, I (like yourself) don't particularly like it when a client paints himself into a corner; but when this is clearly pointed out to him as well as all the expensive repercussions, I'm more than certain he will understand and work with you to alleviate your process design dilemma.

In order to allow the Client to specify Ad Hoc a special way that he wants a job done, the contract you must be working under must classify this request as a "Change Order" - the ugliest and nastiest word that a client can hear! If you, as the contractor, don't have contractual freedom to determine where the injection points should be, then the client takes the liability of performance off your shoulders with his insistance and specifications. This is great news for a contractor, but will the damn thing work? The problem then converts itself to a situation where the separators are going to either be physically larger (Oh great! This is just the right effect one needs on an offshore platform!) or more separation equipment will be required downstream (worse!). This is a certainty if you are going to cause more liquid-vapor mixed phase with your injection of the anti-foam. I can't see any logical person argueing against this effect. This is the point where a client has to be taught or shown what their request will cost in terms of money and platform space. I'm certain they will stop and listen to reason when this is calmly explained to them. Money and space can attract un-divided attention when one is designing an offshore platform.

I have been in similar situations and I have felt a lot of empathy for the client's engineer who knows that at that point his client company has legally assumed a large, un-accustomed and unwanted process responsibility and a rather large bill for extra work that was unforeseen at the time of the contract. Letting an engineering contractor do what he does best is always the "right" answer. If reasoned with, the client will surely see that insistance on his method(s) will only liberate you, the contractor, from your contractual liabilities and guarantees. That's not too smart because he's not making the best use of his money.

In the past, when I have confronted client companies with the above reality, they have always resorted to reason and cooperation with me, their contractor. Hell, that's why they hired me: because they trust me to do the best job for them and they rely on my expertise. An honest client-contractor relationship is one where you tell them all the truth and you cooperate with them to resolve common problems as safely and cost-effective as you can.

I hope this experience helps.

Art Montemayor
Spring, TX