yep.
you’ll have to decide for yourself where you want to place the cutoff for “stop venting”, because there will always be some butane even if your tank is well below the boiling point.
…and I don’t recommend the “try setting it on fire” approach, despite having threatened such on numerous occasions.
Thanks for the help!
they sell gas leak detectorss
ain’t it weird though… bc we set propane torches at work on fire everyday, turn on the gas strike a match and poof the rose bud torch is lit…
but God I wouldn’t check for leaks this way w me rig lol crazy crazy cyclopath crazy
the petroleum industry finds flaring appropriate…the trick is setting it on fire early rather than late.
Say you had butane at -50C in a tank pressurized
With N2 at 100 psi, let the system come to equilibrium. What makes you think the mole fraction of N2 in solution would be insignificant?
I.e., in regards to added vapor pressure if the system were allowed to re-equilibrate to room temp? N2 is non polar why wouldn’t it readily dissolve?
Someone should do this experiment in a Parr reactor with a 5000 psi gauge… I think you might be surprised.
Certainly the solubility at room temp is negligible…but that is the source of excess pressure hazard? I have seen a white butane tank split open in such a manner.
the easiest N2 implementation involves never actually emptying your solvent tank. that way the N2 never leaves that tank (only provides head pressure).
assuming you keep your solvent tank well below zero, you can vent to 0PSI (actually pull vac if you’ve cold enough and have the right tooling) before recovery.
with a thermocouple in the solvent tank, a scale, and sight glasses, I’ve looked at the above solution fairly extensively. the guidance I gave my crew was
a) use phase diagram. make sure you’re below boiling point of solvent mix.
b) use scale when venting. how much weight did you loose? aim for “none”.
c) watch the solvent. once it starts to bubble you’re venting solvent.
d) use the detector. calibrate it using the above.
44northorganicfarms:
I think now you understand why I suggested
Some professional help on staff.
Thanks that was very helpful !
Only question I have is about this
Wouldn’t this cause there to be remaining solvent in my material column if I don’t push N2 threw it? Thanks again 
Look up Raoult’s Law - the vapor pressure is way higher for N2, therefore it will occupy the headspace mostly
I don’t have a real lab . I’m just some one using a little 1 pound cls on my front porch . But I’m trying to get my license for a lab next year so I’m in the process of trying to learn and perfect a system that I can then scale up for my future licensed lab . But I don’t see myself having the capital to pay anyone for professional help even once I get my license . But eventually if I get the money I can definitely see having a professional on staff being a huge help . That’s the goal , but seems like it’s years away at best . I definitely understand where ur coming from tho
depends on how you play the rest of the game.
you can certainly get most of the solvent out. either actively or passively. I’d prefer to save pumps for active column recovery only. haven’t had the opportunity to run that way yet.
you can get more out if you heat the columns.
or cool the collection.
if you want to push N2 all the way through to collection, you’re going to have to cool the collection to vent, or recover and then vent. that last option gets dangerous if you add pumps.
Thank you that was a tremendous help
Just because you’ve vented all available n2 pressure from the tank, doesn’t mean you vented all of the n2
N2 is heavy and will sit in your vessels unless a vacuum is pulled
Absolutely true, AND, doesn’t make a huge difference when you’re playing with small volumes of butane in a non-production environment (I’ve played this with high propane blends, and it definitely slows recovery, just not enough that I’d be willing to use a rotary vane on it & the air-Venturi pump never showed 
)
Thanks I wasn’t aware of that. How do you pull a vacuum on a tank with butane in it?
Free MIT courses ! This is amazing!
Venturi vacuum
Remember when you showed up and some motherfucker suggested you read?
There is a huge wealth of information here, and it used to be a lot easier to find…