Transcritical co2 pulverization

A method for comminution of solid materials, the method comprising:

• introducing solid materials into a first pressure vessel;
• providing a working fluid in the first pressure vessel at an operating pressure and an operating temperature;
• allowing the working fluid to permeate into the solid materials;
• rapidly expanding the working fluid to thereby create fractured solid materials from the solid materials;
• and
• after rapidly expanding the working fluid and before removing the fractured solid materials from the first pressure vessel:
• increasing the pressure of the working fluid in the first pressure vessel to the operating pressure;
• and
• rapidly expanding the working fluid to further fracture the fractured solid materials;
• wherein increasing the pressure of the working fluid to the operating pressure comprises injecting working fluid recaptured in a second pressure vessel into the first pressure vessel, wherein the recaptured working fluid was recaptured during a step of rapidly expanding the working fluid.