9 replies to this topic

[VIrendra20911]

In a pipe line of 1.5 kms and 6 inch diameter , 95% of ethylene and 5% nitrogen by volume are there.
Now according to process Requirement these 5 vol% nitrogen has to be removed from a pipeline by pressurization and depressurization technique.
We are pressurize this pipeline by ethylene upto 8 barg and depressurize upto 0.5 barg. So how much time it will need to reduce N2 concentration upto 0.5 vol%.
I need theoretical formula and guidance for this.

[Bobby Strain]

Pipelines are usually purged to remove undesired material. Pipeline scrapers make the purging more efficient.

 

Bobby

[latexman]

I think guidance from NFPA 69 on "Explosion Prevention Systems" would be relevant.

[shvet1]

 So how much time it will need to reduce N2 concentration upto 0.5 vol%.
I need theoretical formula and guidance for this.

https://law.resource...urging.2001.pdf

https://santa.com.tr...-Explosions.pdf

https://www.boconlin...410-166975.pdf 

Formulas above relate to vessels and short pipes where introduced and displaced gases can be mixed together more or less. Note for long or/and stagnant branched pipes methods other than pressure swing (e.g. vacuum swing, gas slug or pig) might become more cost or/and time effective.

Edited by shvet1, 03 November 2022 - 12:33 AM.

[breizh]

Hi,

Consider reading the document attached, you should find what you are looking for.

Good luck

Breizh 

[VIrendra20911]

Thank you all for showing interest and I respected your answers.
Mostly I go through the all pdf which has given but still I can't get proper equations for my question.

In one pdf I found it for oxygen displacement but it has written that this is only applicable for oxygen displacement.

So guide me more on this.

[breizh]

Hi,

The only way to get a right answer is to perform analysis at the outlet of the pipe, continuous monitoring or regular sampling. 

Check with your lab what kind of support you can get or ask a third party (contractor).

Consider the new documents attached to get an estimate. 

 

notes:

*If the contaminant is N2 instead of O2 it should not be difficult.

**K = 0.25 for pipe, this means a safety factor of 4 to take into account the non-homogeneity. 

 

Good luck, 

 

Breizh 

[shvet1]

 So guide me more on this.

CEN/TR 15281 annex B can be applied to any gases pair if you apply appropriate constants as formulas stipulated are for general gas services. Just use k for ethylene instead of an inert gas. In your case safety factor is the only issue as you apply formulas for a vessels to a long pipe where good mixing conditions can not be reached and controlled.

Edited by shvet1, 07 November 2022 - 10:45 PM.

[breizh]

Hi,

The doc referenced above,

Breizh

[Nikolay_]

Hi,

 

Temperature and mass flow of ethylene? What time did you calculate?