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not_important
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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.
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Magpie
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Sauron
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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.
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MARXYZ
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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.
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contrived
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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?
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MagicJigPipe
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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)?
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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-jeffB
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| Quote: | 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:
http://www.coleparmer.com/catalog/0506_pdf/c-0764.pdf
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.
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not_important
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It looks like a proper manufacturing setup can do better:
| Quote: | 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. |
http://www.dryiceinfo.com/mfn.htm
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trilobite
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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:
| Quote: | | 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]
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crystalXclear
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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
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spirocycle
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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
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dAp
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hope this helps
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Morgan
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Supercritical CO2 caffeine extraction (negative result -- more work needed)
http://www.youtube.com/watch?v=Y_N3-Lnfn_A
A close look at supercritical carbon dioxide CO2
http://www.youtube.com/watch?v=-gCTKteN5Y4&feature=relmf...
Effect of long-term high pressure CO2 on acrylic
http://www.youtube.com/watch?v=70znrkiHfpA&feature=relmf...
[Edited on 23-1-2012 by Morgan]
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Mr. Wizard
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They use supercritical CO2 in dry cleaning.
http://en.wikipedia.org/wiki/Supercritical_carbon_dioxide
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.
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GreenD
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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.
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gordonliu
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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 $10,000 you can purchase a full functional, tunable/controllable, properly designed commercial system.
and to save me the trouble:
no dispensary sells supercritical CO2 extracted oil. there are dispensaries (and vendors) that sell CO2 (pressurized liquid) extracted oil.
those are different. CO2 becomes liquid when pressurized above atmospheric pressure. it is NOT a supercritical fluid....
your CO2 tank on your paintball gun? the CO2 tank used to carbonate beverages at a restaurant?
that is a LIQUID. Remember, we are talking about a COMPLETELY different phase. Supercritical fluid.
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AirCowPeaCock
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According to wiki " specifically, it behaves as a supercritical fluid above its critical temperature (31.1 °C) and critical pressure (72.9 atm/7.39
MPa), expanding to fill its container like a gas but with a density like that of a liquid.". Though I find this gas-like a liquid explanation,
'stupid', at best. I don't think you would need to spend 10,000 dollars on a commercially viable SCF CO2 extractor, but its not going to be pocket
change. Mind you that if you look at the 'close look at super critical co2' YouTube video, pressures and temperatures necessary to produce SCF co2
were achieved for pocket change and some equipment. I think you could make a decent SCF co2 extractor for, say, 250$ if you have access to equipment
and someone who has some knowledge in this stuff.
BOLD
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GreenD
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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.
Procedure:
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]
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magnus454
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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
History is repeating itself.
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PhysicsBiochemstatistic
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Benchtop Supercritical CO2 Extractor
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.)
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Wizzard
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See Ben's device. Works, to boot!
http://benkrasnow.blogspot.com/2011/09/close-look-at-supercr...
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johansen
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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.
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encipher
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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.
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watson.fawkes
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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?
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tetrahedron
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sodastream CO2
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.
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