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Butane recovery

I have instructions for extracting pure essential oil from plant material using butane. The problem I have with it is that at the end, the butane is vented. I just don't feel right about venting unburned hydrocarbons into the atmosphere. I've been looking at glass lab equipment (distillation tubes, connectors, etc). I have no background in chemistry, but it seems to me it shouldn't be too difficult to put something together using standard glass lab equipment to capture, distill and reuse the butane.

Butane boils at 31 degrees Fahrenheit and is heavier than air. At the end of the process, the oil is scraped from the bottom of a drying dish.

Does anyone have any suggestions on how to put something like this together?

Thanks

lemonie4 years ago
You could just "flare" the butane?

L
GlobalVillageIdiot (author)  lemonie4 years ago
If, by flare, you mean burning it as it is being vented, I'm considering it. I think that's a better way to go than venting it unburned.

But it'll be a few months before I start building a prototype, so I have time to continue searching for ideas.

I've been learning about the different kinds of condenser's, used in laboratory distillation and this looks promising. The set-ups I've looked at were intended for vapor, lighter than air instead of heavier. I still think this is doable.
That is what I meant. But I think you'd be better with supercritical carbon dioxide. That is the way to go, but all-metal kit. There's a lot of scCO2 stuff if you look for it. (inc. de-caffienated tea/coffee).

L

GlobalVillageIdiot (author)  lemonie4 years ago
I like supercritical CO2 but it seems a lot more complex and expensive (the latter being more important right now). Do you know of any plans for a DIY version?
I don't know of any plans, but this gives a bit of something and some pictures:
www.chem.leeds.ac.uk
You'll be right, but butane is hazardous, flammable, a bit toxic and probably inclined to "stick" to your extracts (minor problem).

L

Mongpoovian4 years ago
If you've got access to lab glassware, one of the easiest and most effective ways to trap a gas like that would be with a cryo (or dewar-type) condenser. If you're willing to drop some more serious coin, you can buy a one-piece dewar-style distillation apparatus. Drop your cooling bath of choice (dry ice/ethylene glycol is a good, non-flammable pick) in the condenser, and just let the butane evaporate freely.

On the budget side of things, a coil of copper tubing running through a sealed cup full of the same cooling bath would do well.

As long as you have air (or nitrogen, or whatever gas you feel like using) purging through your flask full of goodies, the butane should collect in a (cooled) recieving flask quite nicely.
GlobalVillageIdiot (author)  Mongpoovian4 years ago
Access to lab glassware is easy enough. There are plenty of Scientific Supply companies who will sell you what you need. I'm just not sure what I need.

I've been looking at different kinds of condensers. The Liebig style are the cheapest. The type I've been looking at the most is the Reflux condensers. They are cheaper than the Dewar condensers and do have a coil through the middle.

The problem is, I don't KNOW which one is right for the job. So what if I go with one that doesn't quite do it? Or buy one that is a lot more expensive than what I need. I'm hoping someone who knows chemistry will see this thread and knows the answer.

The collection flask is another problem. The instructions I've seen for this kind of extraction has you scraping the oil off the bottom of the collection plate with a razor. Difficult to do with a flask.

A new problem I've realized, is getting the recovered butane into a storage container. A small refrigerator pump might do it (from one of those small, dorm type refrigerator might work.
The problem you'll run into with any reflux condenser (Liebig or otherwise) is that you still have to run cold liquid through it somehow. If you have a pump that can handle very cold/thick liquids, it would work quite nicely.

I suggested the dewar condenser because that's what I use in the lab to condense gases and very low-boiling point solvents (like ammonia). It's the simplest to use operationally (no tubes or pumps needed), but they are more expensive than Liebig-type condensers. This one on eBay is pretty cheap, though.

If you go with a Liebig condenser (assuming you've worked out the issues with cooling), all you'll need is the "distillation" flask, a simple still head, a recieving vessel, and the condenser. That's going to be the most inexpensive route.

As far as the product recovery goes, "lab spoons" like this are fairly effective at getting stuff out of round-bottom flasks. How gooey are you expecting the oils to be? If they're destined to be redissolved into something, it might be worth it to just go ahead and rinse the flask out with alcohol or oil or whatever the goo will be ending up in anyway.
GlobalVillageIdiot (author)  Mongpoovian4 years ago
I was originally thinking of a coolant (I have some experience with liquid cooling computers), but thinking about it, you're right about the dewar condenser. This wall simplify things a lot for now. And I can get more 'creative' once the basic set-up is working.

It's great to finally meet someone who really knows what they're talking about (you've probably noticed that I don't).

the "distillation" flask
a simple still head
a recieving vessel
and the condenser

This is what I would use with the dewar condenser as well?

I think the lab spoons should do the trick. The end product will be comparable to honey.

Initially, that'll be the end of the process, but I might add additional refining or clarifying later on.
Here's how I'd set up the dewar apparatus.

The blue flask contains the butane/oil essential mixture. That's attached to the top of the dewar condenser (red) by a length of rubber tubing. The red liquid indicates where the cooling bath material would go.

As the butane evaporates, it'll condense on the dewar condenser and drip into the receiving flask beneath it, which would also need to be cooled. For safety, the receiving flask should be vented in case the temperature rises and increases the pressure inside the apparatus. I've used a three-neck flask for collection, but any flask that can be vented (two-neck or side-arm/schlenk flask) would work.

Hope this is helpful!
Dewar Setup.JPG
GlobalVillageIdiot (author)  Mongpoovian4 years ago
Yes, this is very helpful! I'm really seeing how this all fits together now.

I have a set of plans for a PVC tube (going to use some material other than PVC) where butane is forced in one end, through the plant material, then a filter and out the other into an evaporation plate.

If I use a two-neck flask for the first flask, with that tube connected to one neck and a butane line connected to that.

Then, at the other end I would just need a way to pump the liquid butane into a canister (initially it'll probably be a different canister than the first one to make it easier, but I'm still working on this part).

Thank you!

Now all I have to do is figure out what I need to pump butane (all the systems I'm finding so far are large industrial, but I'm working on it). Anyone have advice on the end of it?

Thanks
The setup would be a little different with the dewar condenser. It's hard to describe in words; I'll set something up in the lab and take some pictures.
 It might be easier to remove the butane using pressure, I think it's around 30 psi it'll be liquid at room temperature, unless being mixed with air changes that dynamic a lot...
NachoMahma4 years ago
.  Capture the vapor, then chill and/or compress (butane vapor pressure chart).
.  Butane is flammable and explosive. Also a suffocation and frostbite hazard.
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