Sciencemadness Discussion Board

Is it possible to build a DIY supercritical CO2 extractor?

Quince - 5-12-2006 at 19:05

I've seen a guy make a DIY electron microscope, so I figure anything can be done at home. Anyone heard of DIY for a supercritical CO2 extractor, or have any pointers to design information?

DrP - 6-12-2006 at 06:01

You could do it if you had an autoclave. Get the mixture right and crank up the pressure until you get the super critical fluid??

Quince - 6-12-2006 at 06:42

That just reaches the conditions. How do you actually circulate it for extraction?

roamingnome - 6-12-2006 at 12:32

This is a machine i would like to build too, but its a bit on the horizion.

Working with butane, which i still havent done well, is simmilar. That is to say, would the fluid flow simply to exspand on the other end. A heat gradient flow. Putting CO2 gas pressure on one end of the apparatus will certianly cuase a flow. The dry solid would turn liquid after 5 atm about, and shoot out of a tube into what you want to extract.

See if i can pull up some actual graphs and phase diagrams.

roamingnome - 6-12-2006 at 14:48

add to the wish list a scuba tank air compressor, gas or electric your choice....
essential for lab needs

the pressure needed is 73 ATM or 1073 PSI ..this is high but not impossibly high to obtain...

super critcal fluids have no surface tension or very little it should flow around

a_bab - 7-12-2006 at 15:17

Quince, where did you find about the electronic microscope building? If it's a website could you post it please?

Quince - 7-12-2006 at 15:46

Well, it still cost him $10000 in parts, but I'm sure the wise guys around here could do it for less.
Note that he only achieved 20000 magnification and resolution of 20 nm.

[Edited on 7-12-2006 by Quince]

Organikum - 8-12-2006 at 06:06

If I am not mistaken then a raster-tunnel microscope would be easier and cheaper to build. I believe it has been done already.

Organikum - 8-12-2006 at 07:06

A CO2 SC extractor is easy and cheap as CO2 bottles are common articles for pubs.

If recycling the CO2 is intended it gets more complicated and expensive though, but there is no need to do so as long this is not a real big scale operation.

There are two types of CO2 bottles on the market: One has only one outlet on top - this kind of bottle must be turned on top for use and the other kind has two outlets, one connected to a tube leading to the bottom of the bottle to withdraw liquid CO2. The second kind is preferred for the easier handling.

Quince - 9-12-2006 at 08:50

A scanning one has been built for about $500 I believe using piezo elements hooked up to the probe, and some simple electronics.

Quince - 9-12-2006 at 08:52

Originally posted by Organikum
A CO2 SC extractor is easy and cheap as CO2 bottles are common articles for pubs.

Organikum, you've just pointed out a source of compressed CO2. That doesn't tell me how to make an extractor.

Organikum - 9-12-2006 at 12:59

Perhaps you try the patent office?

If it is about plant material you can also just Google for butane or CO2 estraction of cannabis/marihuana.
Hint: You need a tube with a nozzle on one end. Thats so easy even stoner get it going.

[Edited on 9-12-2006 by Organikum]

Quince - 9-12-2006 at 13:04

The hell is your problem? Now you're implying I'm trying to extract drugs.
Go fuck yourself.

Organikum - 10-12-2006 at 03:24

Well I fucked myself often enough.....

I pointed you to a working simplified supercritical extraction method for plant material, the fact that it was developed for marihuana doesnt make it less valid. I did not in any way say that you want to extract drugs, but there wouldnt be anything bad with this in my eyes anyways.

The problem is solely at your side, you are a bit irritable it seems, havent you taken your medication?

Quince - 10-12-2006 at 19:34

The only CO2 I've been able to find in consumer outlets is the soda maker cartridges, which are simply too small at $1 a piece to be practical.

Magpie - 10-12-2006 at 21:30

My son brought home a 20 oz CO2 cartridge for use in paintball. With his permission I put it to a higher use in my lab. The paintball dealer even sold me a nifty stainless steel valve for a few bucks. This plus a couple brass fittings and I now have CO2 on demand. See photo below.

Building the piping system for a supercritical CO2 recirculation system doesn't seem like a real challenge, as you are only talking around 70 bar, correct? Buying a pump/compressor for this may be expensive, however.

20 oz CO2 cartridge.jpg - 204kB

unionised - 11-12-2006 at 04:34

You don't really need a compressor. Connect the vessel directly to a cylinder of liquid CO2, cool it to "distill" the CO2 into the vesssel. Seal it and let it warm up. One of 3 things will happen. If you haven't got enough CO2 then you just get the vessel full of CO2 vapour. If you have too much CO2 the vessel will, quite possibly burst. Somewher in between you will get supercritical CO2.

Quince - 11-12-2006 at 05:00

unionized, that's not particularly helpful.

Finding a safety release valve appropriate for the pressure, and making joints that can withstand it on all the equipment, seem to me non-trivial tasks.

By the way, say you have your cylinder filled with supercritical CO2. Then what? How do you actually do an extraction? Also, how much CO2 is needed in general to extract say a gram of essential oils completely? Perhaps without some sort of recirculating extraction, this would be a very expensive method needing huge amounts of gas. In that case a compressor seems to be unavoidable...

[Edited on 11-12-2006 by Quince]

unionised - 11-12-2006 at 10:11

How helpful it is depends on whether or not you accept that I was just pointing out that, even without a compressor, you can quite easilly burst things while playing this game.

Quince - 11-12-2006 at 10:53

Well, so could the jar of yellowing NG that was sitting for a few months by my bedside.

unionised - 11-12-2006 at 12:33

Top ten of things not to post on a public website.
#1 I make explosives carelessly

Quince - 11-12-2006 at 12:53

I don't play around with energetic substances anymore. There're no suitable testing grounds around here. That's why I had it as long.

roamingnome - 13-12-2006 at 12:01

paintball is a versitle sport, the game itself is fun and the equipment is handy. I use 4500 psi compressed air though. The reason for a compressor is that i want to process tons of straw. the compressor needed would be large and powered by solar energy.

The fractionation of valuable wax products from wheat straw using CO2

[Edited on 13-12-2006 by roamingnome]

[Edited on 13-12-2006 by roamingnome]

building a supercritical extractor- first thoughts

chemrox - 9-3-2007 at 19:43

I want to build a supercritical extractor too. It's a future project but have given it a little thought. I got some pictures of one that a glassblower aquaintence built for an engineer who was working for a coffee company. It was a bench scale setup. It appeared to be a heavy walled stainless cylinder .. ie a pressure vessel.

As I see it there are three key components or aspects to it:

1) one has to be able to load solids into it .. a pressure tight screw seal of some kind I think

2) it needs a fluid inlet that will accomodate standard gas fittings.

3) it needs an outlet that will release the fluid quickly enough that the fluid is outside the vessel when it flashes off

I realize these parameters may be obvious to most of us and in that sense trivial. However, this is as far as I've gotten with design. I have a machinist who will make the device if we can give him exact specs.

I want to be able to handle both butane and CO2. I have no immediate plans for the CO2 side but it would be a shame not to design for it when we have free labor available to us.

The biggest problem I'm having is coming up with the outlet specs. I'd like to get an off the shelf valve or stopcock for this. Not atn all clear on where to look except the big industrial supply catalogs like Mcmann, etc.

My glassblower friend has not offered more information since we passed on buying the old prototype and since its business to him we can't ask .. or shouldn't anyway.

I'm hoping this thread will continue and brainstorming here may lead to a good solution or set of them.

Magpie - 9-3-2007 at 20:24


1) one has to be able to load solids into it .. a pressure tight screw seal of some kind I think

This statement confused me a little. At first I thought you were planning a continuous process. But it will be batch, right? You are just saying that you need a hatch or port that is resealable. This is not a big problem. The usual solution is a flanged head or port that is resealed using a gasket and bolts.


2) it needs a fluid inlet that will accomodate standard gas fittings

This is no problem at all. Use ball valves to seal off connections.


3) it needs an outlet that will release the fluid quickly enough that the fluid is outside the vessel when it flashes off

I don't understand this requirement. The fluid will not change phase until the pressure is low enough. This won't happen until it is on the downstream side of your outlet valve. For rough control a simple ball valve would be fine. For fine control a globe (or needle) valve would be used.

I still think your biggest problem will be recirculation. There are pumps that can do this big is your budget? :o

not_important - 9-3-2007 at 21:50

Magpie is right, the outlet requirement sounds bogus. Quickly releasing the SCF will drop pressure in the extraction vessel, which could result in some of the product dropping out while still in the extractor. Rapid release of pressure could also drag some of the solids out along with your product.

The typical process runs the SCF at process pressures through a pipe to a expansion vessel, where it is released through a nozzle at the top of the expansion unit. Because the SCF will get cold as it expands, the expansion vessel is usually heated to maintain temperatures high enough to avoid the working fluid forming a condensed phase. The escaping gas is lead through a cyclonic separator and then through some very fine filters and recompressed back into the storage tanks. Heat generated by the compression may be used to warm the expansion vessel.

Magpie - 9-3-2007 at 23:36

I really know nothing about SCFs or their use in extraction. Nor have I ever seen an extractor, or even a schematic for one.

I have just imagined that one could be constructed using a pressure vessel holding a porous basket. The basket would hold a solid material containing a CO2 soluble component. The CO2 would then be continuously recirculated through the basket using a pump, thereby dissolving the soluble component. The CO2 would then be removed from the solute by evaporation.

Sauron - 10-3-2007 at 02:49

The liquid-CO2 removing tube described above is properly called a dip tube in the compressed-gas jargon.

I use a cylinder like that with a dip tube and a relatively cheap gadget to make dry ice snow (rather than the usual half kg cylindrical blocks) for dry ice-acetone baths and dry ice-ethanol baths. The widget that does this trick is about $150 and a whole lot cheaper than the machines from same company that makes the solid dry ice blocks.

No clue as to how to build a SCF extractor for CO2, sorry.

MARXYZ - 10-3-2007 at 22:08

I am not to up on specs for compressed gas cylinders. But couldn't the top valve be removed, and solid inserted. Replace the top valve securely. Begin pressurizing from a larger high compression cylinder of CO2. If your target is say 1500 psi and 60 degree centigrade, pressurize to say 1000 psi, and heat cylinder to temperature of 60 degree. There is some amount of psi coupled with heat to reach the targeted matrix. If unable to mathematically predict this point, trial and error with a pressure gage and thermometer should eventually lead to this matrix or the mathematical formula.

As for circulation, simply rotating tank slowly in liquid heat bath might work. After designated time, attach some kind of sturdy filter on the top valve, turn upside down, and slowly open valve to push liquid through filter into whatever.

Just brainstorming. Safety, fittings, and filter must receive most rigorous attention. Any thoughts toward details would be most helpful.

contrived - 11-3-2007 at 22:44

You said it was a bench scale project. I assume recirculation won't be an immediate issue or will it? Is it supposed to be a model for an industrial sclaeup?

MagicJigPipe - 24-2-2008 at 08:36

Sauron, is dry ice not available in your area? Or is it just cheaper to make dry ice in this way? It seems like it would be considering no refridgeration is necessary and storage/transportation is much easier and cheaper.

This is intriguing. I am interested in this device if it is, in fact, cheaper to make solid CO2 "snow" in this way.

How much CO2 is wasted through evaporation (cooling the rest of the CO2 to it's freezing point)?

-jeffB - 25-2-2008 at 07:46

Originally posted by MagicJigPipe
This is intriguing. I am interested in this device if it is, in fact, cheaper to make solid CO2 "snow" in this way.

How much CO2 is wasted through evaporation (cooling the rest of the CO2 to it's freezing point)?

I was looking at such devices a while back. As I recall, the big-block machines yielded 9-10 lb of dry ice from a 50 lb cylinder. I can't find figures for the "Frigimat Junior" bag-collector type, but I have the impression that efficiency is 10% or less -- 1kg of CO2 would yield maybe 100g of dry ice snow. Things go slightly better if you chill the CO2 cylinder.

Here's a relevant page from the Cole-Parmer catalog:

I seem to remember a do-it-yourself column somewhere that talked about just using a CO2 cylinder (presumably with a dip tube), a standard valve, and a pillowcase.

not_important - 25-2-2008 at 07:53

It looks like a proper manufacturing setup can do better:
About 46% of the gas will freeze into dry ice snow. The rest of the C02 gas, 54%, is released
For a low cost alternative to making dry ice blocks you can even make dry ice snow yourself with a CO2 tank. Although it is not very efficient, just open the hose into a burlap bag, and then pack the dry ice snow into a container.

trilobite - 3-4-2008 at 16:45

Why do you people insist on some sort of recirculation mechanism? It seems many of you haven't understood what supercritical means in this case. Wikipedia says:

A supercritical fluid is any substance at a temperature and pressure above its thermodynamic critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid.

In other words, above both the critical temperature and pressure there is only one phase which fills the whole vessel in addition to the material to be extracted. You'll just have to keep the temperature and pressure above those limits. I suppose the possibility of extracts crashing out of the fluid inside the vessel on expansion could be a problem. In that case maybe filling and purging multiple times could work. Another possibility is simply to keep the pressure and temperature higher than the critical point by some margin during the extraction.

The PVC pipe used to extract cannabis with butane is nowhere near supercritical extraction. It works because the butane cools on expansion and eventually you have a stream of liquid butane running trough the material to be extracted. You could as well use petroleum ether or hexane, but evaporating it wouldn't be as easy and there wouldn't be any pressure to push the solvent through the pipe. Why isn't it supercritical? How could you get a supercritical phase out of a gas bottle without heating or compressing? After all, a gas bottle containing two phases is not supercritical to begin with.

[Edited on 4/4/2008 by trilobite]

crystalXclear - 3-1-2011 at 04:52

As a possible point of interest, I have tried the butane extraction (copper pipe) that is used with cannabis on ground black pepper With (what looked like) good results. I just rolled up some of that 1/4"-1/2" thick,white nylon(?) fiberous packaging material with the ground pepper down the middle (like rolling a joint), rolled it up tight to get it in the tube, and after taping it up and filling it with a small can of butane, collected a quantity of the resulting oil. Nothing fancy & some product gained. It smelt like & looked like the very same oil from a solvent extract. No testing equipment available but eye's & nose, so it may only have been one of the fractions of the pepper oil, but which one remains a mystery.
Also, with all the interest in the extraction of pse from pills,and extraction of other goodies from pills,might this work?. XtalClear

spirocycle - 9-1-2011 at 10:37

It seems that some people here don't know the difference between a supercritical fluid and a liquid. butane extractions are liquid extractions, and SC CO2 extractions are, well, supercritical.
the SCF will act like a mix of liquid and gas almost. With comparable density to a liquid, but will fill its container like a gas. You cant gravity filter a SCF, you need to pump it

hope this helps

dAp - 22-1-2012 at 22:38

attachment.jpg - 59kB

Morgan - 22-1-2012 at 23:04

Supercritical CO2 caffeine extraction (negative result -- more work needed)

A close look at supercritical carbon dioxide CO2

Effect of long-term high pressure CO2 on acrylic

[Edited on 23-1-2012 by Morgan]

Mr. Wizard - 22-1-2012 at 23:05

They use supercritical CO2 in dry cleaning.

Most bars and beverage dispensers are fed by tanks of CO2 that contain supercritical fluids on a summer day. When I fill smaller CO2 tanks from larger ones, I have to wait for a cool day to get liquid to transfer. I guess it would work without the fluid being a liquid, but I can hear the liquid moving better. I use regular small diameter steel plumbing pipe and brass adapters. You can tell when a tank is supercritical because it doesn't slosh when you tip or shake them, but the liquid will. I can't tip the big tanks, but the small beer keg ones can allow it without much trouble.

GreenD - 26-1-2012 at 14:07

The hell are you guys talking about. CO2 extractions are really easy.

You can do it with a centrifuge tube...

Put in dry ice, screw on cap. Certain caps are rated for ~15atm or so, so they open at that psi. I extracted about 60% clove oil from cloves doing this.

To do it on a larger scale, a back of the envelope sketch:

Pressure cooker, large grate, funnel (like a mechanics funnel)
Put funnel in - as you normally would use a funnel. Fill funnel with extraction medium (I'm thinking solids here) - plug bottom with cotton. Place grate over funnel, put dry ice on grate, put cap on. You should have a pressure meter and a release valve.

Doesn't seem too difficult to me.

gordonliu - 7-2-2012 at 19:05

This thread is hilarious.

its basically a dead thread that was started by people who knew what they were talking about and taken over by stoners trying to make something better than BHO.

suffice it to say:

no. you can't extract THC using supercritical CO2 using a glass or home depot copper extraction tube. neither can you use that commercially sold stainless steel tube with the legs.

you need very strong, very very thick walled stainless steel cylinders capable of holding at the very least 73 atmospheres of pressure.

sorry to say, but 73 atmospheres is beyond the realm of even commercial scuba diving equipment....

you could probably build one for $3,500 to $5,000, including lots of custom/contracted work.

but for $7,500 to $10,000 you can purchase a full functional, tunable/controllable, properly designed commercial system.

and to save me the trouble:

no dispensary sells supercritical CO2 extracted oil. there are dispensaries (and vendors) that sell CO2 (pressurized liquid) extracted oil.

those are different. CO2 becomes liquid when pressurized above atmospheric pressure. it is NOT a supercritical fluid....

your CO2 tank on your paintball gun? the CO2 tank used to carbonate beverages at a restaurant?

that is a LIQUID. Remember, we are talking about a COMPLETELY different phase. Supercritical fluid.

AirCowPeaCock - 7-2-2012 at 20:18

According to wiki " specifically, it behaves as a supercritical fluid above its critical temperature (31.1 °C) and critical pressure (72.9 atm/7.39 MPa), expanding to fill its container like a gas but with a density like that of a liquid.". Though I find this gas-like a liquid explanation, 'stupid', at best. I don't think you would need to spend 10,000 dollars on a commercially viable SCF CO2 extractor, but its not going to be pocket change. Mind you that if you look at the 'close look at super critical co2' YouTube video, pressures and temperatures necessary to produce SCF co2 were achieved for pocket change and some equipment. I think you could make a decent SCF co2 extractor for, say, 250$ if you have access to equipment and someone who has some knowledge in this stuff.

GreenD - 8-2-2012 at 07:43

You can extract with CO2 at justa few atms - I was unaware that it officially became SC CO2 at 73ATM, 31.1°C.

Like I've said - I've extracted clove oil with a centrifuge tube and dry ice.

Ain't as scary as you think it is, and it doesn't need to be more than a few ATMS.

Centrifuge tube, screw cap.

To the tube is first placed a small cotton ball/glass wool (1cm). On which is placed the organic matter (2-4cm). Above that is placed a pinky-nail sized chunk of dry ice.

Hold in your hands. It won't bite.

tah dah.

This is extremely easy to scale up, and SC CO2 is not needed (as defined earlier) this is simply liquid CO2. The extraction is so efficient, and dry ice is cheap & plentiful.

Have at it. Worse case scenario your cap flies off and gets deflected by your GOGGLES.

[Edited on 8-2-2012 by GreenD]

[Edited on 8-2-2012 by GreenD]

magnus454 - 13-3-2012 at 20:02

I live just south of Houston, TX. The FOLGERS Coffee plant just off of downtown does it all day long to coffee. My thoughts,

Build it with a high alloy aluminum
as for the compressor, I don't know where you are going to get a cryogenic class compressor for cheap other than salvage yards

Benchtop Supercritical CO2 Extractor

PhysicsBiochemstatistic - 3-8-2012 at 12:57

I have reviewed some of this post, and the available commercial equipment, and see a community looking for a solution.

I have constructed a home CO2 extractor that had a net cost of about $800 to build. The sample volume is 1L, and the equipment is glass and stainless steel.

The only energy needed is to run some simple equipment like a water pump.

The CO2 is recycled on a continuous loop, and scale up is easy, but of course costs increase exponentially with size.

I have performed several extractions on items like: rose petals, coffee beans, freeway soil, and cactus.

Some Notes: Supercritical CO2 is NOT an ideal solution for all extractions, and upon reviewing industry standards (i.e. decaffeinating coffee, pharmaceutical) the use of supercritical rather than liquid CO2 is not based on necessity, but based on the level of understanding the design engineers are capable of.

As a chemist and physicist, I have found data and demonstrated that liquid CO2 is more "tunable", has a lower cost of ownership, and requires less skilled staff to operate.

As such I designed my solution with layman operators in mind.

This process could be automated, but again cost is typically 2x to 4x for automation.

I am thinking about manufacturing my solution, and providing it to a larger community.

Is there sufficient interest to manufacture and sell this product at <$5K? (ideally cheaper but I don't know all the factors in this market yet.)

Wizzard - 3-8-2012 at 19:15

See Ben's device. Works, to boot!

johansen - 10-8-2012 at 12:25

funny you mention that PhysicsBiochemstatistic , on my birthday.

steel, welding rods, stainless steel tubing, 10% silver braze is relatively cheap.
glass to metal seals aren't.

i would think the price could be well under 5K.

encipher - 29-9-2012 at 12:47

Lots of misinformation going around on this thread, so I felt compelled to comment.

For example:
"...and upon reviewing industry standards (i.e. decaffeinating coffee, pharmaceutical) the use of supercritical rather than liquid CO2 is not based on necessity"

That is incorrect. The reason ScCO2 is used instead of LCO2 IS necessity. You see, the real benefit of supercritical CO2 is the ability to tailor the solvent power by varying the temperature/pressure. See the image below:

Thus, by choosing the appropriate conditions, you can increase the solubility of a particular component. So in the case of decaffeinating coffee, you want to maximize caffeine solubility while minimizing flavor loss. It would be utterly stupid to design a system to use ScCO2 unnecessarily because of the added cost of high T/P.

You can also perform LCO2 extractions, but again, in order to achieve higher densities you will end up venturing into the supercritical region.

If there is genuine interest in reviving this discussion I would love to share what I can - much of my work is deals with fluid phase equilibria.

watson.fawkes - 2-10-2012 at 07:13

Quote: Originally posted by encipher  
You see, the real benefit of supercritical CO2 is the ability to tailor the solvent power by varying the temperature/pressure. See the image below: [...]
Thus, by choosing the appropriate conditions, you can increase the solubility of a particular component.
That diagram is density vs. pressure, with isothermal lines. How does that relate to solubility?

sodastream CO2

tetrahedron - 2-10-2012 at 07:36

how about this: fill an empty sodastream CO2 tank with dry ice and 'herb' (see youtube videos on the procedure, careful not to exceed the pressure rating), put the valve back into place, let sit for a while at room temp, then discharge it slowly in the sodastream machine to recover the product as a deposit on the bottle.

S.C. Wack - 2-10-2012 at 13:11

Little dissolves in liquid CO2 at room temp. If you could just add chunks of dry ice, you'd be able to buy such a system, or read about it in the journals.

IIRC the coffee is extracted while wet with water. It's done because it's "green", no one wants tolucoffee.

tetrahedron - 2-10-2012 at 17:53

caffeine alone is dangerous enough =D

encipher - 3-10-2012 at 02:47

Quote: Originally posted by watson.fawkes  
Quote: Originally posted by encipher  
You see, the real benefit of supercritical CO2 is the ability to tailor the solvent power by varying the temperature/pressure. See the image below: [...]
Thus, by choosing the appropriate conditions, you can increase the solubility of a particular component.
That diagram is density vs. pressure, with isothermal lines. How does that relate to solubility?

It shows the ability to change the T&P to regulate density, which regulates the solvent power of a supercritical fluid. The solvent strength of a supercritical fluid increases dramatically when it's compressed to liquid-like densities.

This is important because the difference between ScCO2 and LCO2 at the same density is the fact that ScCO2 has like one or two orders of magnitude higher diffusivity (read: gas-like) and the same applies for lower viscosity, while having zero surface tension. Hence the appeal of supercritical extractions.

Of course there are situations were even these properties present no real benefit versus a traditional solvent. It depends on the application.

co2extractor - 13-3-2015 at 07:28

Yes it is possible, it is very practicle, and very promising technology for now. Co2 is used because its supercritical temperature and pressure is relatively low at 31C and 73 atmosphere is easily achieved. Anyone w a pressure vessel rated at least 1073psi can do the extraction.