The pressure for supercritical processing is often 10 MPa or higher. Since it is difficult to continuously feed solids into a high-pressure vessel, batch processing is used. To facilitate batch processing, the pressure vessel is equipped with a rapid lid opening/closing mechanism as shown in the picture. This makes it easy to load and unload materials to be processed. Normally, multiple pressure vessels are installed. The reason is that the alternative use of these pressure vessels enables continuous operation of carbon dioxide supply and recovery, which is economical.