LN2 (LIN) delivery system and conversion to N2 gas

[Icecoffee]

Hi all,

I would like to get some advise and help on this problem:

Our ultra-high vacuum vessel requires venting/purging (>15 m^3 volume) and I was charged the assignment to deliver dry gas for this process.

I did sized a compressed clean dry air system, dew point to be -100F (max I can go), with (After acfm and purge loss) approx. 430 scfm so the vaccum can be vented approx in 30-40 minutes, with water content about 1-2 ppm, the vaccum group wasn't happy at all and I was told water shall be <100 ppb at the worst...

Since I am also in process in designing a LN2 delivery system to the facility and I am told to find out a way to "boil-off" LN2 and "suck" that gasoues N2 out and deliver to the vacuum system. Sorry for being so vague. I really don't know where and how to start.... I am a bit lost and any pointers and suggestions to start would be grateful!!!

I also have questions on the "dryness" of the N2 gas boiled off from LN2, does anyone know how much water is in it? (ppm or ppb) I just don't think this N2 gas would be any dryer than say 1ppm... please help!! or please let me know if more information is required!

 

[Icecoffee]

Oh by the way, I will be talking to suppliers etc about LN2 system details however I do want to get inputs from all of you before I talk to those people (my experience is that they dragged me in circles..............)

 

[dcasto]

LIN is typically stored at 75 to 150 psig and -250 F (its corresponding temperature. As heat leaks into the vessel, vapors are vented off and can be used. If you need more flow, then vaporized are added and the streams (the vapors from atmospheric heating and from the vaporizers) and sent through a heater. Most of the heat to perform the vaporizing and heating comes from the atmosphere, and the exchangers are normally just a series of extended surface tubes stacked next to the LIN vessel. The LIN supplier will calculate how many sections of extended surface pipe you'll need based on your requirements. If you need to heat the N2 to warmer than about 25 Degrees F less than the atmospheric temperature, you'll be needing a heater. The heater will either be electric or fuel driven.