3 replies to this topic

[ssengr62]

Dear All,

I hope you are having good time.


I have an urgent request about finding Nitrogen gas volume.


Given Data: Tank Volume = 760 cu.m

This is Propane storage tank and we want to pressurize this tank upto 11.3 barg.

There are two cases:

Case 1: Pressurizing from 0(Zero)barg to 11.3 barg

Case 2: Pressurizing from 0(Zero)barg to 7 barg and then 7 barg to 11.3barg

I want to find the Nitrogen volume required which we have to buy. I think we need an additional volume for purging and inerting before pressurizing with nitrogen.


I am looking forward to your experiences and help.

Thank you so much in advance.

Best Regards

S. Sajid

PS: I calculated as follows:

Volume 760 cu.m
26839.4 cu.ft
Pressure 11.3 barg
12.3 bara
178.3992 psia
z 0.999
R 10.73 (ft^3*psia)/(lbmol*R) or 8.314 JK-1Mol-1
T 30 C
851.4 R

n= (P*V)/(z*R*T) 524.5858088 lbmol

Now at standard conditions the ideal gas law applies

R 10.73 (ft^3*psia)/(lbmol*R)
T 527.67 R
P 14.7 psia
n 524.5858088 lbmol
V= n*R*T/P 202051.1 cu.ft
5721.39 cu.m

[Neelakantan]

hi
i am sure you are not looking at decimal values or accuracy level to last m3 of gas; then the simple way to estimate is:
tank vol =760 m3
n2 in the tank (when pressurized to 11.3 barg, ie at 12.3 bara;) 760 x 12 = 9600 sm3 (ignoring temp effect, compressibility etc and rounding off to 800 m3 volume for tank)
n2 in the tank at 7 barg (ie 8 bara) = 6400 sm3; and n2 required from 7 barg to 11.3 barg = 3200 sm3;

now coming to drying and purging; it depends on your use of N2 intially; i would look at 5 cycles; pressurize 0 barg to 2 barg and depressurize to flare press ~0.2, 0.3 barg and repeat again; if you ensure all vents/drains are properly blown with n2 and no pockets are present, you should get at the end of the 5th cycle a good lab report for o2 and moisture. the gas required for this would be 12000 sm3; if you have good operation team you can do it even with 0~1.2 barg to 0.2 barg cycle; which would be ~7000 sm3 only.

if you are pressurising to 7 barg and 11.3 barg for leak test then you can use that N2 fto cut the cycle to 3 times initially; finally, if you are using your propane storage as N2 hold for drying other parts of the plant, then i would advise you ensure that your propane tank is dried first before building the stock

[S.Chittibabu]

http://www.cheresour...ion/#entry65867

check the volume required for purging and pressurising.

[ssengr62]

Thank you so much Mr. Neelakantan and Mr. S.Chittibabu