Process

Extraction process

The extraction process using supercritical CO₂ consists of the following three major process steps:

• Extraction process

• Separation of solvent (CO₂) from extract

• Solvent make-up (recovery, purification of solvent…)

The liquid CO₂ is usually supplied from a corresponding buffer tank where CO₂ is present at its boiling point. The conditions of the buffer tank are usually at approx. 60bar and 22 ° C. In the first step the CO₂ is cooled down before feeding it to the CO₂ pump which pressurizes the CO₂ up to extraction pressure and is responsible for feeding the desired amount of CO₂ to the extractors. The cooling before the pump prevents possible cavitation inside the pump since the compression of CO₂ induces heat thus partly evaporating the liquid CO₂. After the pressurization, the CO₂ is pre-heated before conveying it to the corresponding extractor. In this high pressure vessel the product is charged inside a corresponding handling basket and the CO₂ flows through the product material. The solubility of certain compounds in the CO₂ cause these organic components to dissolve in the CO₂ and the loaded CO₂-mixture is conveyed to the depressurization valve which keeps the pressure inside the extractor at a constant level. After the relaxation of the CO₂ / extract mixture is routed through a pre-heater and is introduced into a separator. Since the solubility is strongly dependent on pressure and temperature of the CO₂ the extract can be separated inside the separator since the pressure of the CO₂ is lower than in the extractor. Depending on the actual product, several separation steps can be realized allowing a frationation of the extract by using different pressures and temperatures. The CO₂ can be recovered to the buffer tank using a condenser which recombines the gaseous CO₂ thus optimizing the loss of solvent.