Efficiency of the separator 4

[oilgas80]

Hi All,

What's the meaning of efficiency of the separator?

Thank you.

regards,
oilgas80

 

[Eltron]

Without knowing what type of separator or what kind of process you're talking about the answers that are going to follow will be of limited use. Generally the efficiency of a separator is measured as a percentage of whatever you're trying to remove from your main stream. For example: if you have a separator with a 90% efficiency that removes water from air, and your air stream contains 50g water, then 45g of water will be removed (leaving you with 5g in your air stream).

Hope that helps.

 

[Montemayor]

Eltron is absolutely correct. The question is too general and unspecific with no basic data to explain or describe what the writer is talking about. It would seem that oilgas80 thinks there is only one, universal "separator" (his separator, of course) set of rules and nomenclature that a separator god enforces. There is no such animal.

Efficiency on separation of liquid-gas phases (assuming that's what is being referred to) can also be based on the liquid "particle size" removed (or "separated") from the gaseous mixture.

But that all depends on what the original phrase was meant to mean or how it is defined for that specific write-up.

Based on the amount of data and information given, the answer is: nobody really knows or can tell. A lot of people will guess and contribute some wild ideas; but the net result is that more information is needed.

 

[oilgas80]

Hi Eltron & Montemayor,

I appologies for my mistake.

This is basically a Horizontal 3 phase separator. It's 48" X 10' S/S.

The question i received from my collegue is how to calculate the efficiency of the separator at 50bar/1.5 million cubic meter gas capacity?

Hope now i posted the question correctly.

Thank you.

regards,
oilgas80

 

[Montemayor]

Oilgas80:

There’s nothing to apologize to me for. I believe I understood the nature of your question and I tried to answer it appropriately. As a ChemE, I’ve been fortunate in working around the petroleum production arena in several manners. I’ve worked for companies who designed and fabricated 3-phase oil-gas separators. The name, 3-phase, is a misnomer I believe, because only 2-phases are involved: an oil+water liquid phase mixture and a hydrocarbon gaseous phase. Nevertheless, that’s what they’re known as. I’ve also done process design around the production coming out of such vessels. I’ve never designed them and I don’t believe an average engineer gets much of a chance to do so unless he/she are working for the very specialized companies who do this specific type of design and fabrication. There are maybe 5 to 10 such credible or recognized companies in the North America. I say “recognized” because a lot of faith and confidence is put on their back to produce the specified and desired product. Sometimes, depending on circumstances, some design liability is involved – depending on contractual arrangements and terms. Therefore, the subject of “efficiency” is not discussed until one gets into a contract with such a company. Of course, if a purchaser is going to hold the designer’s feet to the fire, the price and contractual terms go up proportionately. After all, fair is fair.

Sooner or later particulate size comes into the picture when the term efficiency is employed in this type of separator. And that’s where the “problems” start. If you are linked or deeply immersed in the oil business, you must have had some contact with or own a copy of John Campbell’s two volumes: “Gas Conditioning and Processing”. If you haven’t read Volume I, I strongly recommend you do so, especially Chapter 8, “Process Vessel Specification”. Campbell deals with this subject in a manner that is more specific and practical than even the GPSA does – which is admirable. On separator sizing, John is very frank and direct: “Do not be naïve. Most published capacity curves are for ideal conditions. Use them cautiously.” He further adds: “It is almost impossible to measure particle sizes in plant service.” I certainly agree. He goes on to deal with the subject of efficiency in a general and unspecific manner. How can you talk of efficiency of particle removal when you can’t measure the particles? And even if you could, the particles of liquids continually change in diameter as they progress in a process line. It is a difficult subject for any practical engineer – except for an academician.

Two persons who claim to have measured and tabulated oil-gas separation are Dr. W.D. Monnery and Dr. W.Y. Svrcek (University of Calgary) in Canada. However, I believe they get the particle size “identified” by back-calculation, I think – not by actual measurement. I have a report on a series of tests done by them and I believe you can download it from the Internet. I don’t have any website identified, but you can try Google.

That’s as close to talking separator efficiency as I’ve been able to identify. I’m sorry if I can’t give you any more information. It’s not a very easy subject to talk about or much less to try to measure in the field.

 

[krossview]

Dear All,

Here is the link of the referenced article

http://www.ptac.org/env/dl/envf0112p.pdf

Art, thanks for the article references as I have been looking for some time to get some more clarity on this grey topic.

Krossview

 

[krossview]

The link above is only the summary version.
Here is the link to the full document by Monnery and Svrcek.

http://www.ptac.org/env/dl/envp0102.doc

The authors do calculate the droplet size and compare it against known publications instead of measuring actual droplet size and efficiency.

Peerless Manufacturing has developed the Laser IsoKinetic Sample (LISP, which is capable of measuring the actual droplet size and separation efficieny in a separator.

http://www.peerlessmfg.com/pdf/care_06LISP.pdf

Pall is another vendor who utilizes a Liquid Aerosol Separation Efficiency (LASE) to measure coalescer performance.

http://www.pall.com/articles_chemical_5205.asp

The real removal efficiency remains a guessing game for a lot of separators currently in operation. Unless you deal with a reputable vendor like Art point out.

I trust these links are useful to spread the knowledge, that the technology is available to measure separation efficiency. Off course common sence and good engineering judgement still need to prevail to interpret the results.

Krossview

 

[Montemayor]

Krossview:

Thanks are due you not only from me, but from a host of people out there who have been struggling to identify separator performance for many years. Progress has been made in identifying a factor that has kept us in the dark for a long time and your research comes at a time when it can be of great help to a lot of us.

Thanks again.