How to predict slugs with Hysys 1

[silviaeliana]

I have tried to use the "Do Slug Tool Calculations" option in Hysys (pipe segment) to evaluate the pipeline slugging. The Slug Tool Results table displays the following results: Position, Status, Frequency , Slug Length, Bubble Length, Film Holdup, Velocity, Pressure Gradient and Length Ratio Slug/Bubble. I would like to know how to interpret the results ("Slug Results") and find out the Slug Volume from the above data. I would appreciate if anybody share their past experience on estimating the Slug Volume using Slug Tool Results in Hysys 8

 

[mdepeche]

while I prefer Olga / Leda models for these simulations, I would suggest the specialized textbooks for a detailed analysis of the different aspects which can influence the results,
for a short introduction and discussion see for example,

https://www.spe.org/dl/docs/2014/Trick.pdf

but it's a complex matter requiring specific knowledge of different aspects as phase equilibria, dynamics etc.

 

[silviaeliana]

to mdepeche

I apreciate the time that you spend answering me but I must use Hysys because is the software that I have acces.
Thank you very much

 

[georgeverghese]

Is this an offshore submarine pipeline going up a riser into a fixed platform or may be an FPSO or similar?

 

[silviaeliana]

Is a horizontal pipeline (with up and down zones)constructed by ERFV material buried 0,8 mts. Is on-shore

 

[georgeverghese]

Slug volume for inclusion into the liquid phase volume of a slugcatcher / inlet vessel is derived from the controlling case of either of the following:
a)simulation studies for pigging combined with a set of operating procedures that are assumed to be carried out in preparation for pipeline pigging.
b) Also another scenario is ramp up simulation where flow is ramped up at a max permissible controlled rate from zero to full flow with initial condensate holdup as being that which has stabilised with pipeline at minimum permissible flow.

In both cases, you must derive a plan on how to deal with high volume slug flows on a temporary basis, which is what is in excess of design case normal condensate arrival rates, after the slug handling volume is fully utilised. Study cases I've come across include those where the slug handling volume is meant to handle case (b), and volumes arriving beyond this (in case (a)) spills over into temporary peak flow handling facilities.

This slug handling volume estimation has little to do with the much smaller slugs that are generated in the course of normal steady state operation (hydrodynamic slugging). Talk to a dynamic simulation specialist company to help out with this study.

 

[MortenA]

What he want to do is to use a SS simulator to predict the volume required in his inlt separator/slug catcher.

This is generally not possible. Sorry. You might as well "pick a number". I often used 1/2 a riser volume - and compared to e.g. OLGA this is surpricingly accurate for a area with a flat surface. This is only operational slugging for steady state and will not be true for ramp up/ramp down, pigging etc.

This may not be what you will like to hear but you just cant do what you are asking for!

 

[silviaeliana]

To MortenA

I don't want to disagree with you but please read the document attached. On the third point Aspentech assures that you can obtain the slug size from Slug page of the Flow assurance tab

https://www.aspentech.com/email/email_archive/optimize-qa.pdf

 

[georgeverghese]

It is not clear from your first post if you are interested in derivation of a suitable slug handling volume good for :

a)normal operations, due to steady state hydrodynamic slugging
or
b)if you want to do unsteady state simulations as I had indicated earlier (pigging or ramp up) with a given slug handling volume.

If it is the former, I dont have any first hand experience on this. But I would hazard a guess and suggest using a slug volume that covers say 90-95% of the frequency range of all predicted slug lengths for the entire permitted turndown range for this pipeline.

From the Year 2011 Aspentech webinar Q&A, it appears that OLGA - steady state model is now included in the Hysis-Aspentech suite.

 

[silviaeliana]

To Georgeverghese:
I'm trying to analize case a).
Thank you very much for your advice.
I'll try your suggestion

 

[MortenA]

well 8 is a rather old version. I cant remember if this feature came before or after. You could upgrade or maby the result you are searching for is there somewhere. Still i maintain: There are many kinds of slugs and you cant cover these with a ss MODEL.

Best regrads, Morten

 

[silviaeliana]

I have proposed to my client to do a test for validate the model. I let to know how it goes.
I appreciatte if someone have other comments or suggestions.