Liquid CO2 Pipeline

[robert5891]

Hey Everyone,

I'm new to the forums and had a question regarding the design of liquid CO2 pipelines. The pipeline is around 180 miles long, and 8" O.D. The end pressure needs to be around 1200 psi. Now, PipeCalc is the software that I am using for my other long distance pipeline calcs. However, I'm not sure which equation would best govern the behavior of liquid CO2. Does anyone have any suggestions as to what equation would effectively model the behavior of liquid CO2 and take into account effects from change in elevation.

Thanks,
Robert

 

[zdas04]

First you have to determine if the line is running full. There is an equation that says Q=10.2*ID^2.5 with Q in gpm and ID in inches. If your flow rate is greater than Q, then the line can be assumed to be running full and the only elevations that matter are the ends.

If your flow rate is less than Q then you have some serious problems ahead of you. First, some of the CO2 will flash as it goes over hills--flashing CO2 can get really cold and 180 miles of cryo pipe is pretty expensive. Second, you have to provide pumping hp to overcome the hydrostatic head of the highest hill.

You need to provide more info if you want a decent response.

David

 

[MortenA]

zdas04

I dont follow you. What do you mean by "running full"? Surely you can operate a line full of liquid at 0.00000001 m/sec liquid velocity? It sound to me that you are thinking about a selfdraining pipe?

Robert be aware that co2 is not a typical compound and that many simulator will have problems - especially if you a close to the L/V interface. Get a Moillier diagram and check. You should rememeber to do a "slag flow" check (is that what you are aiming at zdas04 although i cant see how this would be a problem running at low velocities). By this i mean check that the pressure when going uphill dosnt cross the flash point at the given temperature when the pressure in the pipeline decreases due to loss of static head going uphill.

For your reference i have a link to an excellent little co2 thermodynamics primer incl. a good Moullier diagram here:

http://www.union.dk/media/CO2-GB.pdf

Best regards

Morten

 

[katmar]

Robert, with all respect to David and Morten, you should not be asking for "tips" on how to design a 180 mile liquid CO2 pipeline. You should be speaking to consultants who have a verifiable track record in this field. This is not something to do from first principles - serious relevant experience is required.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[zdas04]

Morten,
I do a lot of work with produced water lines in the Rockies and a lot of what I do is troubleshooting why pump discharge pressures are significantly higher than design. What I generally find is that if the flow rate is less than the "Sealing Flow Rate" equation above, that the downhill portions will outrun the uphill portions and result in a discontinuous fluid system (i.e., gas or steam breaks out and collects on the top of hills and you don't get the rebound effect on the downhill part). This negates any "monometer effects" and results in phase change and high discharge pressures.

David

 

[BigInch]

Cascade flow over multiple high points. Pump discharge pressure rises to the sum of all uphill column weights.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MortenA]

OK - that's what I referred to as slag flow. So we more or less agree. But as katmar pointed out - a 180 miles pipeline is not something you design based on advice from this site

 

[BigInch]

"slack" flow

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[robert5891]

I'm not designing this on my own, we have experienced people working on the project. I'm looking for resources or literature that I can go to, to point out design considerations and equations/ empirical formulas I can use to get a general idea of what will happen.

 

[BigInch]

Usually flow equations themselves do not take care of elevation changes. You have to carry those along separately.

I think BWR would be OK, as long as you stay above 1150 psig and temperatures remain close to normal ambients.

Whether your software will handle 2 phase flow, or slack flow, is another question, most don't. And if they do, you can't count on getting a close approximation to what you may eventually see out there, so its best to work with conservative ranges and STAY well inside the full flow liquid range.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[katmar]

Robert, I am pleased to hear that you are simply looking for extra info. That being the case, you have received some good advice already from David, Morten and BigInch. If you search here on "slack flow" you will probably find several threads discussing similar problems.

At 1200 psi there is not much difference between the densities of liquid and vapor CO2, so the VLE modeling may not be too critical.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[MortenA]

Biginch - I think i made that spelling error before? - but you are rigth - slack

Best regards

Morten

 

[MortenA]

If you are a member of SPE try to search their data base. You will discover that there are a huge number of wells with co2 injection (EOR)and thousands of miles of pipeline with HP co2 in the states.

Best regards

Morten