Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

SFE CO2 Supercritical Extraction questions

  1. Mar 1, 2005 #1
    Can someone possibly give me some links or info which, in more detail will explain the mechanics and process of SFE CO2 extraction? Something beyond the ' CO2 is heated to 31 C at 74 bars' . I assume the unit is charged with the extraction media, charged with liquid CO2, brought to 74 bars with the 'extracts' going over to the separator, at reduced pressure via a PRV. Then I assume the separator is isolated and the pressured CO2 is either released or recovered. Anyone else have more info/details?

    Thanks .....Spiff
  2. jcsd
  3. Mar 2, 2005 #2
    Well I am working on producing some aerogels and in order to this I am currently building an autoclave. I need the autoclave to do a solvent exchange of the alcohol in the gel to CO2. Basically, you take the gel and place it in the autoclave, then fill it with liquid CO2, then drain it out, and repeat until all the alcohol has been removed. Then you fill the autoclave up with CO2 and begin heating the autoclave. As the temperature rises, so does the pressure. The CO2 wants to be a gas at higher temperature, but higher pressur keeps it a liquid. Once the CO2 hits its critical point of 1071 psi and 31 ºC, it becomes what is known as a supercritical fluid. This substance is very cool looking, because it has properties of both a liquid and a gas. You then slightly open a valve in the top of the autoclave to slowly drain out the CO2 while maintaining a high temperature. Eventually all the CO2 has left and you can depressurize the vessel and remove the aerogel.

    Now I am not sure if this helps at all, but basically, the CO2 just hits a critical point where it can no longer be defined as a gas or a liquid, and it can leave the pores of a gel without damaging the bonds..
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook