Solvent recovery issues, SOP critique?

1lb CLS

  1. solvent tank in a residential deep freezer until the process starts.
  2. material column sleeve packed with material and sleeve packed with dry ice, 30 min cooldown.
  3. 6” x 12” Recovery tank is submerged in a 5 gal bucket about 8-10” in alcohol dry ice slurry
  4. pull solvent tank from the freezer and place on the scale, connect, vac whole system including the line to the solvent tank.
  5. ball valve closed to recovery pot.
  6. 10-15min psi hold test/additional chilling
  7. solvent introduced to the material column, once I see the scale is no longer moving I start the countdown of 15-60 min soak time (depending on quantity). I leave the valve to the solvent tank open during this time assuming its rise in temp will provide pressure that aids in fully saturating the material in the column. I do not have but need a gauge on the material column.
  8. open ball valve to the recovery tank.
  9. when roughly the same amount of solvent as the initial fill required has been pulled from the butane tank I close off the ball valve again to the recovery pot.
  10. let butane soak 5 min.
  11. open ball valve and attempt to collect the remaining solvent from the material column.
  12. close ball valve to the recovery tank.
  13. Move recovery pot from dry ice and submerge in 10+” of 120-140 degree (tap hot) water.
  14. Move solvent tank to dry ice/alcohol slurry recovery tank was just in.
  15. Recover until either negative pressure or until the viscosity appears correct for minimal loss/ need to scrape after the pour off.

At step 12 I’ve left the machine to sit for 5 min to 1 hour after I stopped seeing drips of butane via the sight window. When I close off the ball valve between the material column and collection pot and open the valve on the top of the material column I have pressure (no gauge). I’ve exhausted off the pressure and removed the material column multiple times to find liquid butane just pooled in the ball valve/hemispherical adapter/filter plate and sometimes it’s even still dripping from the material. It doesn’t happen every time but it seems to happen more when I use less butane (3.5.4lbs of solvent) vs more (6lbs solvent). My solvent is 70Iso/30N. What am I doing wrong that’s preventing me from collecting all the butane when I’m sure I have a 30 degree F temp difference? Are there any other process flaws you see? Thanks!

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  1. Don’t put solvent tanks in any freezer! Bad idea, if you got leak add compressor, boom…

  2. Is ur collection pot on dry ice slurry as well, iso and propane a bitch…move cold to colder! If not cold enough collection it’s wanting to hang out in the coldest place, hydrocarbons has funny effect w gravity
    Next till u master take ball valve out and blast fast…

  3. Have you pressure tested ur system for leaks? This could slow recovery

If recovery tank empty make sure to vacuum down the entire system before starting RECOVER… everything but the extractor of course,lines and all!

  1. fair
  2. collection pot is under dry ice and slurry about 75%. maybe 50% is usually slurry and the top 25% is dry ice that isn’t under alcohol.
  3. under negative pressure it will hold a vac for over an hour every run with no issues.
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Burry that collection! If it’s bubbling hard when adding dry ice u need to be colder to pull it passively…

Are you VACing the whole system down to full - vac before running?

What’s your filters?

yes i am vacuuming the system and the hose to the solvent tank completely prior.

i’m recovering right now actually and just buried it completely and made sure it’s slurry all the way to the lid. I’ve been being cheap on dry ice I guess that’s been costing me.

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This is one of the most important aspects of running passive. You can’t cheap out on dry ice. If you do, it’s just gonna cost you time. Sometimes, it can be $10-15 worth of dry ice and save an hour, if not more depending on how short you are.

I don’t know how many times I’ve cheaped out on dry ice and it cost me time.

Making sure you tank is actually chilled to will save you time. I recover on the liquid side of my tanks so as the vapor comes Into my tanks it passes threw the liquid gas first instantly condensing it. I actually have to throttle my recovery because I’m afraid on how violently my collection tank is reacting.


the first time i tried it that way it took FOREVER. I was being SUPER cheap back then hell i think i was trying to use ice and salt lol. I’ll give that a try and i’ll stop being cheap on dry ice.


How much dry ice do you Thank I’m going to need for distilling my cls, it’s a 3x38 sleeved spool, and a 8x14 collection pot? Kinda excited but definitely cautious

Also if I get a chest freezer without and disable the de iceing mechanism, would it be safe enough to freeze my master cool solvent tank?

I may be mistaken, but I think all chest freezers do not have a de-icing (defrost) function.

From the site: ‘chest freezer (which, in case you were wondering, are always manual defrost)’

This is due to how defrost works, it cycles the freezer off to get things warm. Chest freezers are for long term frozen storage.

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