First N2 Assist Was a Success-ish

Performed my first N2 assist yesterday with cold gas (-78*C) and my dewaxing column at a similar temp. I run bi-directional, 2LB column, so I first let the systems vacuum suck the liquid solvent into the column from the bottom, shut the ball valve and let it soak for about 20 minutes. All was going well.

Liquid solvent was moving just fine, and I ran at about 50PSI until the dripping stopped. Pushed it a little higher and more solvent was released. Stopped dripping.

Yield seems really great, and it has an awesome color. However, I was left with a little over 1lb in the solvent tank. Yes, I ran the N2 into the vapor port. Is this normal to have remaining solvent in the tank when running cold with N2 assist? I was under the impression it would have pushed all solvent out and only N2 would remain, attractive because I could turn around, pull vac, and use the initial cylinder as a recovery cylinder as well. More pressure maybe?

Boy that 40CUF N2 tank went quicker than I thought… may have to upgrade to a 100.

How many lbs of solvent did you have in there? Most dip tubes don’t go all the way down and will leave a small amount of solvent left. My tank leaves about 15 ~ lbs in there

Little less than 10. Might just have to keep a extra pound or two in the tank.

First time with that tank, have you ran it empty before, or were just expecting it to? I was so disappointed when I saw all that was left in mine

Yeah, before running gas cold and using N2 I was pulling almost 100% solvent out of it. Definitely a disappointment to be sure, going to make the logistics of running multiple runs kind of a headache being left with two tanks partially full instead of one tank entirely full. Thankfully I have a third recovery tank, but it all just adds time.

Thinking about investing in larger tanks, I’m just running 30# at the moment, so usually a one and done.

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Were you possibly getting a vapor lock on the collection and couldn’t get everything to send over

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I run a similar setup, how much solvent do you safely fill your #30 tank to? i have a #30 tank as well, 6x24 collectiom

I think you can still pull a light vacuum from the vapor port on your recovery tank even with some solvent at the very bottom. Thats what I have been doing before I start recovery, and there is still a small amount of solvent at the very bottom of the tank. Idea being if your tank is on DI there shouldn’t be any vapor in there. Don’t want to misspeak but that is what I learned from @Dred_pirate … is that right @Dred_pirate?


That is correct. At the appropriate temps and only a small amount removes the nitrogen vapors and leaving the solvent at vacuum.

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