Pipeline used as LPG Storage 1

[barilko]

I need to run an LPG pipeline 6 km from a gas plant to a pumping station. The elevation drops continuously by 100m with slopes of 1 to 2.5%.

I also need 2500 m3 of LPG storage.

The intent would be that rather than installing an 8" pipeline solely for transportation, I would install 2x 20" pipelines that would also act as storage. As the pipeline fills with liquid, vapour is displaced upslope.

Pipelines would be setup with pig barrels to allow internal inspection and cleaning.

Does anyone have experience combining the two?
Any ideas on how to measure liquid level?

 

[BigInch]

If you make it as an LPG pipeline, it will not be convenient to operate it with vapor in there. You should keep the pressure high enough to avoid vapor formation. If you want to use the pipeline for storage, go ahead, but always keep the pressure in the pipeine high enough to avoid vapor formation. High pressure shock waves could develop each time pressure rises and a vapor pocket collapses. Flow control is impossible when you have liquid full of vapor pockets. Equipment damage is highly likely when slugs of liquids hit. You should also have a pressure relief valve to ensure that high ambient temperatures do not exceed the design pressure of the pipeline. Draw off the LPG through a pressure control valve keeping high backpressure in the line. The draw off pipeline could be run as a vapor only line if pressures there are limited to the vapor phase. Use a pressure relief valve to ensure that pipe remains in the vapor phase.



Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[stanier]

I would be interestred to see the life cycle costs for this solution rather than the conventional transport pipeline and storage bullets.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[dcasto]

strainer, I'm with you, I estimate that the 2 lines cost twice as much as tanks and 1 smaller line. The operations headache and I see the design having pumps on each end in order to make it work.

 

[Compositepro]

Doing what you propose also means that liquid flow in the pipeline would be due to gravity only. Liquid pumped into the pipeline would drain downhill while displacing vapor uphill.

 

[stanier]

Hi dcasto,

The nom de plume is Stanier after the great British locomotive engineer of last century not strainer?

http://www.lner.info/eng/stanier.shtml

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[BigInch]

Lifecycle costs and safety risk factors of a zero footprint storage facility would certainly favor using the line pack of a long presumedly buried pipeline. Why not one 30" rather than the 2x20", I couldn't tell you, but presumedly somebody knows a reason for that. I'd just keep the pipeline pressure high thereby keeping the gas full of liquid, provided the temperature cooperated, just taking off what I needed either as, again a liquid, or no reason that the takeoff couldn't be a vapor downstream of a pressure regulator, from my perspective. Why not let him do it if he wants to? Its his money.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[racookpe1978]

In a flowing situation, a pipeline will be continuously losing heat energy to the surrounding dirt through the insulation - at least until "all" the dirt gets as cold as the LNG. Which won't happen realistically. But at least all the very cold LNG is replaced by new LNG, and the heat loss can be tolerated.

Here, in a static stored long "tank" with much, much more surface area per length (or per cubic volume, depending on how you look at it) than a conventional tank, and many thousand times more area than a sphere, you'll be continuously "heating up" the LNG since the dirt will not reach equilibrium.

If not a textbook problem, where will you find a convenient but accessible and available-for-sale continuously sloped hillside 6 km long to bury the pipes?

 

[BigInch]

NOT. It is LPG.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[racookpe1978]

Thank you.

 

[barilko]

The reason I'm exploring the possibilities is that the plants have limited footprint to support aboveground storage. Remote plant location limits pre-fab'd bullet size such that at least 10-15 will be required. This also creates the potential for major accident hazard compared with mounded storage or pipelines.

Cost of bullets ($6m) + small 8" pipeline ($2M) is roughly same as a single large pipeline ($8M). x2 smaller lines was considered due to ability to phase capital since full 2500 m3 was not needed at plant startup.

I'll attach a schematic and an elevation drawing of what I am trying to describe.

The product is a propane / butane mixture. Similar to a storage bullet, the pipeline will operate at the vapour pressure corresponding to the temperature of the product.

Notionally, I've selecteed a low spot between two plants for the pump station. Gentle slopes will have the pump station in the liquid phase and the vapour phase at the plants.

Multiphase flow would behave similar to a finger slug catcher where liquid would run along the bottom of the pipe, vapour along the top..... assumption is that there are no major pockets.

 

[barilko]

Schematic sketch

 

[BigInch]

Gentle slopes will have the pump station in the liquid phase and the vapour phase at the plants.Multiphase flow would behave similar to a finger slug catcher where liquid would run along the bottom of the pipe, vapour along the top..... assumption is that there are no major pockets.

Hummm... it seems that you wern't listening.

What reason do you have to believe that flow will be liquid at the bottom and vapor at the top? Or when you are flowing downhill, vapor will rise to the inlet? At what liquid to gas ratio flowrate will mist flow begin, wave flow? At what flowrate will slug flow begin? Don't think about 2 phase flow operations until you have those and the other flow regimes bracketed and you know that you can operate within the proper range.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus