Nitrogen Filling Preservation Calculation

[lgracio]

Hi Everybody,

Someone could help me solving the following problem which consists on filling a pressure vessel with nitrogen for preservation and I need to know how many nitrogen cylinders I have to purchase?

The apparatus is maintained at vacuum pressure of 1,5 millibar where the nitrogen will filled in until the internal pressure of 0,5 bar is reached.

The apparatus has the internal volume of 48720 liters. How many standard nitrogen cylinders should I purchase for this filling conditions?

Thanks for all.

Luís Grácio
Mechanical Engineer (Engineering Solutions)
Portugal-Setúbal

 

[gr2vessels]

Luis,
Remember: PV/T=constant. For simplicity you could consider T=constant, hence P1V1=P2V2.
P1= Nitrogen bottle pressure [bar]
V1=Volume of compressed Nitrogen [m3]
P2=0.5 bar
V2=48.72 m3
Cheers,
gr2vessels

 

[lgracio]

Thanks gr2vessels

How many bottles of N2 should I order if the bottle have 9,4m3 N2 content at 200 bar pressure.

Bottles are from Air Liquide: Reference B50.

Luís Grácio
Mechanical Engineer (Engineering Solutions)
Portugal-Setúbal

 

[gr2vessels]

You need V1 = P2 x V2 / P1 = 0.5 x 48.72 / 200 = 0.1218 m3
As far as your bottle concerns, the 9.4 m3 is a gross exageration. A typical G bottle has about 40-50 litres of N2 at 200 bar. That means for 0.5 bar you require, consider the bottle empty when finished pressurizing the vessel. Hence the 0.1218 m3 of gas you need 0.1218/0.05=2.436 bottles, ie 3 bottles to purchase and use 2.5 bottles.
Cheers,
gr2vessels

 

[jamesl]

I think the pressure used in the calc should be absolute pressure, not gauge pressure. This will make a big difference in your result.

 

[r6155]

I think you need another quantity of nitrogen to sweep the air, before filling with nitrogen.

Regards
r6155