NATURAL GAS DEW POINT 3

[EMSOGI]

Need a formula or way to calculate natural gas hydrocarbon dew-point at given pressures (between 30 and 70 bar).
Any idea? I have HYSYS but I don't know which fluid package use (dew point seem to strongly depend on fluid package used).
Thanks in advance

Regards

lottol

 

[srfish]

Natural gas dewpoint calculations are difficult to be accurate if there are heavier components than C6. If you are interested, I will run a calculation for you. What is your composition and operating pressure ?

 

[MortenA]

lottol

Your statement " have HYSYS but I don't know which fluid package use (dew point seem to strongly depend on fluid package used" that you are working with stuff that you do not have the education for. Any chemical engineer should know at least WHY dew point is "stragely dependant" on chosen thermodynamic package.

I will strongly recommend that you either find somebody in-house who understands these matters or get outside assiatnce. There are lot of helopfull people on this site who will help you - but you must ask yourself these questions if you use this for any professional work:

-How will you document/QA this work?
-Can you reley on this source if work of this nature continues?

Best regards

Morten

 

[EMSOGI]

Morten, thank you very much your suggestion, it was really very helpful...
regards.

 

[MortenA]

I guess that you are being ironic - but im quite sincere and i'm not trying to patronise you!

Assuming that i was asked to do a stress calculation for a pipe then i would not try to figure out how tri-flex works - because even if i could make it work and found what i belived was the relevant parameters - how would i know if i could use the result for anything?

I would do what i recommend you: Find somebody how know piping design and let him solve the problem.

Your solution may be easier to solve on your own by finding a refernce work that will give you aproximately values for various P/T vaues.

Take my advice for what it is and realise that what you are asking for quite fundamental advice.

Best regards

Morten

 

[dcasto]

The whole natural gas industry is in a quandry to solve your problem. Suites have been filed and FERC has rendered opinions. Industry think tanks have written papers in the last 6 months. The entire LNG import system is at risk with this question.

The piece that the industry cannot agree upon is the physical description of what C6+ is when it comes out of the GC. Unless we want to wait for 24 hours to get that while our LNG ship is sitting on the dock and is gas is waiting to feed the city of New York....

 

[Ashereng]

Michell (Europe) and Ametek (North America) both make a hydrocarbon dew point analyzer.

Would this work for your application?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[MortenA]

dcasto I think that you may be overdoing it a little. I have been in the business for +10 years now as a chemical engineer mostly working with thermodynamics - and i have not heard that the situation has gove ballistic the last 6 months?

Anybody who knows chemistry knows that the different models yields different results - that this must be accounted for and the "black art" is then to chose the right model for the right circumstances - and to detect when the chosen model may not perform as you expect.

best regards

Morten

 

[dcasto]

The FERC docket was bogged down and finally issused oders that state, work it out pipelines.

UNITED STATES OF AMERICA 116 FERC *61,295
FEDERAL ENERGY REGULATORY COMMISSION
Before Commissioners: Joseph T. Kelliher, Chairman;
Suedeen G. Kelly, Marc
Spitzer,
Philip D. Moeller, and
Jon Wellinghoff.
Southern Natural Gas Company Docket No. RP04-42-000
ORDER DIRECTING UPDATE OF GAS QUALITY PROVISIONS
(Issued September 27, 2006)


Southwest Research is trying to develop on online physical meter because "....that the different models yields different results" so to be safe, pipelines have shut the gas in if any one model says there will be liquids dropping out. So until there is only one answer....

I'm not being harsh, its just that lawyers have taken over what we engineers know as a trivial thing has now become big money to them. Back to the original question by lottol, a simple equation for what end use, if its to answer the hotest dew point question, then the answer resides not with engineers but with the lawyers.

 

[MortenA]

well you guy have all the luck (and most of the lawyers) lol

It has not come to this in Europe yet anyway.

Best regards

Morten

 

[Monagas]

Mr.Lottol.

Maybe you could start your estimation using the peng -robinson model.

Then you could use the Gas Properties application of Hysys. This Application allows you to know the HHV, LHV, Hydrocarbon dew point and water dew point.

You could find information in the hysys handbook.

You need an answer to your question.

You dont need 10 years of experience and dont need to go to Europe.

God bless you

 

[dcasto]

I'll assume you don't need the exact dew point for legal reasons. The peng-robinson is one of the best with SRK a close second IMHO. Both of these are iterative in nature especilally solving for dew point.

WinSim has a subroutine that will allow you to use the program Kernal and set up an excel spread sheet so that the user only has to do an addin like routine and just fill in the spread sheet and it will calculate the dew point.

Between the PR and SRK you'll get the same answer with in a degree C for a given pressure. What really makes for the differnce is how you describe the C6+ from a typical gas analysis. The way you do that change the dew point 3 to 5 degrees C.