In practice the commercial instruments provide options to either vent or recycle the CO2. With sufficient depressurization, CO2 (in gaseous form) loses its ability to dissolve any extracted compounds and obtained almost as good as "clean" CO2. This recycled CO2 is continuously collected in a pressure-bottle from where the CO2 pump draws CO2 to re-pressurize. This pressure bottle is also fed with clean CO2 to make-up for the losses of CO2 from the system during collection and other venting.

There are sometimes carry-over issues but in most cases that do not lead to any significant concern. For that reason, CO2 is recycled mostly for pilot-scale operations or beyond so that any carry-over should not pose any problems.   

I also know, that in this case where the CO2 is as a SCF loaded with extracted compounds, as Abhijit says, after the depressurization is recirculated into the pressurizing system to liquify. Sometimes the Co2 is stripped, to get rid of any carry over phenomena. Otherwise it can also be purged.

Ok thank you Abhijit and Nico for these helpful answers.

Hello all,

I use the CO2 supercritical pilote for plant extraction but I have a problem when i change the raw material form one to another.

how can i clean the pilote when i am going to extract a new raw material(there is always a residue and the smell is very strong)

I am wondering if there is anyone can help me with this.

Thank you in advance for your help

yes, I tried with ethanol. But , I still have the same problem. I always smell the odor of plants (very strong )