supercritical co2 extraction - diy community?

Rating and testing are different. A ASME tank tested to 9000 psi, would be rated at 3000 psi. Here is the experiments that we performed:

15.24 DIY SCFE CO2 - GrayWolf's Lair (graywolfslair.com)

Ostensibly, using heat instead of pumps will expose your material to a more wider pressure/temperature curve. Even if you heat the CO2 in a separate tank, as soon as you start transferring to the process tank, the pressure will fall.

Fadedawg said:

Rating and testing are different. A ASME tank tested to 9000 psi, would be rated at 3000 psi. Here is the experiments that we performed:

15.24 DIY SCFE CO2 - GrayWolf's Lair (graywolfslair.com)

Ostensibly, using heat instead of pumps will expose your material to a more wider pressure/temperature curve. Even if you heat the CO2 in a separate tank, as soon as you start transferring to the process tank, the pressure will fall.

Click to expand...

Yes, thank you. Now that I take a closer look the aluminum CO2 tank has a service pressure of 1,800psi, and a 3,000psi pressure test. Whereas the carbon fiber tank has working pressure of 4,500psi, a pressure test at 7,250psi, and a minimum burst pressure of 15,000psi. (Those are rounded, it actually has 30 mpa, 50 mpa, and 102mpa)

Yea, without a pump to regulate the pressure it will be unavoidable to lose pressure throughout the process. Maybe after I get this up and running I will run some tests doing shorter cycles with larger tanks to minimalize the pressure difference. (As in using only 4# of C02 from a 20# tank)

Fadedawg do you know anything about solenoid Valves? I want to use one to let out bursts of the liquid CO2 into the collection vessel for depressurization. But I am having trouble understanding how they are rated for pressure. I can't find any that mention pressure above 145psi, but a few of those mentioned wog 1000. Do solenoid Valves have two different pressure ratings for different things?

WOG means water, oil, and gas service.

Check out "high pressure solenoid valves" for higher ratings. IE: high-pressure solenoids | McMaster-Carr

Fadedawg said:

WOG means water, oil, and gas service.

Check out "high pressure solenoid valves" for higher ratings. IE: high-pressure solenoids | McMaster-Carr

Click to expand...

Thank you, I was able to find one with ease thanks to your link.

@Fadedawg

I'm back with another question! It's been awhile, I got a couple 6,000psi 316 stainless steel pressure vessels. After that I turned my time, attention, and effort elsewhere, and have recently revisited this topic. I'm pretty clear on what I need to get for the pressure vessels, so expect updates on that in the future. What brought me here today are the 8g-45g "rechargeable" CO2 cartridges. I mentioned wanting to use these in earlier posts, but was unable to find a way to get active flow through one. The issue being the bottom fill port has female M5-0.5 unf threading, which is rather limiting. So I gave up on the active flow. Opting instead for a passive system that is charged either through packing the vessel with dry ice(which is easy given the cartridge unscrew at the center), or filling from a CO2 tank with a CGA320 to NPT 1/4 Adapter. The CO2 cartridge is threaded for UNF 3/8-24 male and the needle valve needed for slow decompression is threaded for NPT 1/4 female. I was only able to find one company(XS Scuba) that sells a stainless steel adapter, and it doesn't come with much for details. It also doesn't include a sealing washer or o-ring. Which brings me to my question:

What type of material is best suited to CO2 extractions both subcritical and supercritical in the 600psi-1,300psi, and the 21°C-35°C range?

I already have all the parts either in my possession or on the way, including some seals. I will be testing it out within a half month.

Thanks for all your help this far!

PTFE works but isn't highly resilient. Have you checked out FEP encapsulated O-rings?

Fadedawg said:

PTFE works but isn't highly resilient. Have you checked out FEP encapsulated O-rings?

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No, I hadn't checked out FEP. I ordered both nitrile o-rings, and nylon flat washers. Which are at the lower end of resiliency, but are also very cheap and replaceable.

I was looking at getting some EPR, or EPDM ones, but I was having some trouble finding the right size(admittedly I didn't look for long). FEP looks ideal if I want some longer lasting seals.

Thank you once again! Your advice has been invaluable along my journey. I will update with results of my test run soon.

Alright, back with an update.

I ran a few test, all of which had less than desirable results. I ran into sealing issues each time, almost entirely due to having trouble getting a good grip on a smooth CO2 cartridge. I also broke my pressure guage on the first run, so never actually saw what pressure I got up to on the third attempt when I only had a very slow leak, and held some amount of pressure for 4 hours until I manually released pressure. I'm waiting for a CO2 tank to use for filling the cartridge as opposed to the dry ice. I can only get powdered dry ice nearby, and it makes filling akward.( I could use a funnel). More updates at a later date.

Test 1 - lost pressure within a half hour, not sure where.
Test 2- I wasn't able to get the CO2 cartridge sealed all the way until I got a vice grip. There was a failure with the o-ring causing all pressure to be lost within a minute.
Test 3 - used the vice grip to completely seal the CO2 cartridge, held unorganized pressure for a little over 4 hours, only had small bubbles escaping from one connection at a 1-2 second interval. I did not submerge the material basket in the liquid CO2 fully, and did not rotate the chamber hardly at all. The needle valve stuck when opening, and there was a good burst released which very apparently contained some amount of the aromatic components. The rest of the de pressurizing took about 5 minutes, and no visible oil could be seen inside the cartridge, but it did have the same aroma even after the material basket was removed.