A close look at supercritical carbon dioxide CO2

I built a pressure vessel from aluminum and acrylic, and filled it by placing pieces of dry ice inside. The dry ice melts under high pressure, and forms a liquid and gas phase. When the vessel is heated, the CO2 becomes supercritical -- meaning the liquid and gas phases merge together into a new phase that has properties of a gas, but the density of a liquid.

Supercritical CO2 is a good solvent, and is used for decaffeinating coffee, dry cleaning clothes, and other situations where avoiding a hydrocarbon solvent is desirable for environmental or health reasons.

If you have a suggestion for what I should do with the supercritical CO2, please leave a comment.

CO2 can be liquefied in plastic bottle preforms:
http://www.youtube.com/watch?v=8AN_XMcD3yI
It may be important to open the container before all of the solid melts. When there is still some solid CO2 present, the pressure will be close to the triple point. Once the solid completely melts, the pressure will increase quickly to about 750 psi depending on the ambient temp. I really doubt those plastic containers could hold 750 psi.

My first look at supercritical fluids:
http://www.youtube.com/watch?v=yBRdBrnIlTQ

Another youtuber interested in supercritical CO2:
http://www.youtube.com/watch?v=GEr3NxsPTOA

Added engineering recap and formulas:
http://benkrasnow.blogspot.com/2011/09/close-look-at-supercritical-carbon.html

Category:

Science & Technology

Tags:

• supercritical
• co2
• carbon dioxide
• fluid
• supercritical fluid
• phase transition
• pressure vessel
• acrylic
• aluminum

[vusiliyK]

I would love to see you extract caffeine. This is awesome.

[bkraz333]

@vusiliyK I did. Check out my channel. I can't post a URL in the comments.

[icenh]

how can you get scco2 at 750 psi, while the critical pressure is around 1000~1100 psi?

[bkraz333]

@icenh At 750 psi, the CO2 is not supercritical. It is a liquid and a gas. As the temperature and pressure rises, the two phases merge together into a supercritical fluid, as shown in the video.

[icenh]

@bkraz333 Thanks for the clarification. Can you please tell me about the pressure of the fluid (inside the pressure vessel that you made) in the supercritical phase?

Also I found that the surface of PMMA (acrylic) "reacts" (a physical reaction rather than chemical) with SCCO2 while it is placed inside a supercritical environment for a longer time (2-3 hrs). Have you ever faced anything similar to this?

[bkraz333]

@icenh Yes, the acrylic wasn't happy about holding regular high-pressure CO2. See my latest video.

[masteranza]

Most interesting channel on whole youtube.

[Films4You]

That's a lot of dangerous pressure, take care :)

[Tmaker197812]

be careful with that ... it can cut off your fingers due to fatigue cracks ...

[fusionfreak2009]

for coffee beans a 10,000 psi pressure is needed along with a high pressure water blast to strip the caffine from the beans. how about making some pop rocks, or carbonated smoothies that spit these dioxide gysers everywhere?

[bbrown6799]

I wish you were my neighbor. I'd always be at your house working on crazy projects like this with you!

[JimmyFarina97]

now open it

[portblock]

Just curios, if you put dry ice in there, like you did, there is also, air, a lot of it, perhaps a vacume, pump all air out, then I trounce co2?

[purplemutantas]

Super critical CO2 is also used for making extracts of kava kava. The kava paste sold by iamshaman is made this way. I am sure you could do other plant extracts as well.

[AsymptoteInverse]

Fantastic video, and a fine-looking pressure vessel! As you say in your video description, it probably isn't possible to hold CO2 at the triple point in a plastic container for very long, but I now have first-hand experience that says you can do it in a *glass* container.

[finalio]

For EOR purposes we use CO2 at super-critical conditions and we get around 5-15% incremental oil recovery