Software used for supercritical CO2 pipeline transportation

[tag10]

Please advice me, in order to know what are the typical softwares used for supercritical CO2 pipeline transportation, for the following pipeline parameters:
- Inlet Operating Pressure is 120 bar;
- Operating Inlet Temperature is 32 deg.


From my point of view, the software must be used for steady state and dynamic analysis, in order to simulate the procedures for start-up, shut down and blow down of the pipeline (which might lead to very low temperatures and formation of solid CO2)

I am also interested to know if the software is made for:
- pure CO2
or
- CO2 with impurities.

Thank you very much for your help.

 

[BigInch]

That's quite a wish list, based on the limited experience with CO2 pipelines in the world. Most typical is to consider just a pure steady state fluid with allowances made for impurities based on extrapolations into relatively unknown territory.

Some work has been done using Stoner Pipeline Simulator and Pipeline Studio, probably only steady state modes, but the programs do have transient capabilities that might be utilized, although I can't say for sure if it can be applied to dense phase and I doubt 2-phase, if you mean gas/liquid. Best thing is to give them a call. You might also try calling the Olga2000 group.

Please let us know what they say.

What would you be doing, if you knew that you could not fail?

 

[ibby003]

I would like to know what software to use too! For blowdown, I was wondering about using the Hysys Depressure Utility. You don't need the dynamic license to run this, just the regular Hysys license. However, Hysys probably won't predict solid CO2 very well so it might not be that realistic. And above that, I think the depressure utility was intended for PSV type blowdowns (ie relatively quick say within 15 minutes) and not long pipeline section blowdowns (which might take several days).

From my looking so far, it appears that a key problem is heat transfer between the pipeline and the soil it's buried in. This is a key factor in converting from what the phase envolope pressure / temperature shows for adiabatic blowdown and what will REALLY happen when the pipeline cools and transfers heat with surroundings.

Good luck and like BigInch said, let us know what you find!

 

[BigInch]

You should not have such long sections to blowdown. The pipeline mainline block valves would be closed and each segment blown down separately. There should be no reason that you would want to blow down more than one, or maybe two segments on a pipeline anyway. Pipeline valves must be spaced an appropriate distance from each other such that any released CO2 would not be enough to smother a nearby village. That would usually require a closer spacing than what your "days of blowdown time" would imply. Perhaps only 4 to 6 hour blowdown times per segment. Segments probably being 10 to 25 km apart, on a normal diameter pipeline.

Hysis probably works well as long as you maintain ONE phase in any given scenario, but I don't use it, so I can't be sure about that. If you get a CO2 freezing temp, the scenario finishes at that point with a CO2-ice plug. Higher temperature areas downstream to the BD would however presumably continue to blow down until they froze too. Continuing the scenario after that point would probably be pointless, it won't get below freeze temperature. Just assume any remaining gas will continue to exit at the blowdown at a much reduced rate and perhaps not freeze again. That would continue until pressure is depleted or the ice plug melts again. You could start a new reduced picture scenario with that condition, if there was anything of interest left of the outcome.

What would you be doing, if you knew that you could not fail?

 

[davefitz]

Don't be surprised if the simulation is not very accurate when the bulk fluid is slightly above the "psuedo critical temperature" and the fluid at the wall boundary layer is below this temperature- the change in physical properties at that point is dramamtic, and simply using a mean fluid temperature to compute wall friction will not cut it.

 

[MortenA]

Warning here: Dont use HYSYS (otr to the best of my knowledge any other standard process simulation tool) for CO2 work that could take co2 into the solid phase. HYSYS simply dosnt handle this phase transition and will never report it (although a warning about co2 freeze-out may appear). Also, HYSYS is (still) not suited for dynamic simulation of pipeline in the stadard package.

Best regards

Morten

 

[tag10]

Until now I found that OLGA has been developed for simulation of pressurized systems and is used for systems of several hundred bar and down to ambient. Most of the testing and data is related to 10-100 bar systems.
I am interested to take into account pressure between 150 bar down to ambient, so there is an issue with the maximum pressure value.


MortenA you told us to not use HYSYS. Can you recommend us another software?

Thanks.

 

[MortenA]

I would say, that for pure CO2 use a p,H diagram. I have in other treads given a reference i think is excellent:

http://www.union.dk/ref.aspx?id=105.

OLGA, as far as i know uses external engines e.g. PVTsim to calculate "black oil properties" in a "P/T" grid and the intrapolates the actual properties. And if the external engine cant handle a solid co2 phase you are the same place. On the other hand, you could use HYSYS f you afterwards revieved the results with respect to the formation of a solid phase and disregarded the results when such a phase should exist. Best regards

Morten

 

[BigInch]

Stoner will model dense phase CO₂

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[MortenA]

So will HYSYS, but it just wont handle a transgression into the dense phase. It wont even predicts that the dense phase occurs (except with a CO2 freezeout warning

 

[BigInch]

Right. Only one phase is permitted, but you really only need to know when it freezes, then stop the sim. Surely nobody would want to simulate a push of a frozen CO₂ slug, never mind actually do it.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[MortenA]

Thats of course a methode and i agree with it. Just wanted to note it since a less experienced engineer may overlook this and trust the software too much ;-)