Continuous Nitrogen blanketing of manufacturing enclosure 1

[jlehane]

Hi,
In a manufacturing enclosure, it is required to maintain the oxygen level at between 1.9 and 2.38%.
Pure nitrogen is fed to the enclosure.
The enclosure is open to the atmosphere at several locations.
Do anyone have design guidelines for calculation of the theoretical flow rate of Nitrogen required to maintain the O2 level.
Many thanks.

 

[stookeyfpe]

See this thread:

http://www.eng-tips.com/viewthread.cfm?qid=196770&page=1

 

[twr]

What is the overall size of enclosure openings and what is the pressure difference from within the enclosure to the outside room? In addition to the references in the link, we use nitrogen blanket to preserve food grade oils and maintain final product quality.

 

[jlehane]

The overall size of the enclosure is approx 2.7m3.
The openings are 0.015m2 in total.
We don't have pressure readings from inside the enclosure so I don't know the differential pressure. I only know the pressure in the enclosure is positive in relation to the room.
Thank you.

 

[BenjaminM]

jlehane,

The method I use for purging our tanks is as follows:

Qv*t=V*ln((C1-C0)/C2-C0))

Qv = flow rate in CFM
t = time in minutes
V = Volume in foot cube.
C1 = Initial concentration in tank
C2 = Final Concentration in tank
C0 = Concentration of purge gas

Taking an 8000 gallon tank (1093 ft3) from 21% oxygen to 5% oxygen using nitrogen with 2% oxygen will take 100 minutes of purging.

I have monitored the outlet gas from our reactors being purged before and found the above equation to be relatively accurate.

So long as you maintain a constant flow of nitrogen into your enclosure, thus maintaining a slight, but constant DP, you should maintain your nitrogen blanket.

Of course limiting your leaks in the system will better increase your ability to maintain the conditions you desire.

I would have an air tester on hand to verify your blanket though.