2. Liquefied gases as extraction solvents

The use of liquefied gases in a process that can be easily transposed to industrial scale involves a number of selection criteria linked to technical considerations. In particular, the following two thermodynamic criteria are essential for industrial use:

• a boiling temperature at atmospheric pressure of between -30°C and ambient temperature (+20°C), to enable the gas to be condensed at temperatures reasonably achievable on an industrial scale;

• a steam pressure of less than 10 bar at ambient temperature, to limit the investment cost of pressure equipment.

These criteria make it possible to select a limited number of solvents (table