Applications in Extraction and Purification

Physical properties of supercritical fluid carbon dioxide

• The density is similar to that of a liquid, and offers higher dissolving capability for various substances.
• Because the viscosity is similar to that of a gas and the diffusion coefficient is larger than that of a liquid, substance extraction is faster.

Supercritical carbon dioxide physical property reference

Features of technique for using supercritical carbon dioxide

• Because only a slight change of pressure/temperature brings about a significant change in solubility, use of supercritical carbon dioxide enables a highly efficient isolation of components to be extracted.
• This solvent can be reused, which means a lower operating cost.
• It is possible to use carbon dioxide as a chemically inactive solvent.
  • As this solvent can be manipulated at room temperature, it makes handling heat-vulnerable substances easy and safe.
  • As this solvent is not organic, it can safely be used in food processing.
  • This solvent is both relatively cheap and easy to handle.

Supercritical fluid extraction/purification process

Because supercritical fluids allow for strict control of the dissolving action and transportability, they can be used to extract, separate or purify both usable and unusable substances. The process can also be adapted to the quantity of material to be processed, or to the form of the material (liquid or solid).

1. In-batch material loading format: this approach is adopted when the quantity of material to be processed is small, regardless of whether the material is liquid or solid. Loading and discharge of the material are carried out by a high-pressure batch extractor, with the opening and closing of the lid automated and the feeding of the supercritical fluid continuous.
   Figure 1 shows the process flow, while Photos 1 and 2 show the supercritical fluid batch extraction device and the vessel with its automatically opening and closing lid.
   [Application examples] Extraction of odorants or colorants; removal of pesticides from ginseng extract or powder.
   
   
   Fig.1 Schematic flow of supercritical fluid extraction process
   
   Photo 1 Supercritical fluid extraction device (Extraction vessel: 150)
   
   Photo 2 Supercritical fluid extraction device (Extraction vessel: 390)
   
   
2. Continuous feed format: This approach is adopted when the material is in liquid form and the quantity to be processed is large. The material is fed in continuously by means of a pump. The discharge of the processed material is also continuous.
   Shown in Photo 3 is a pilot plant for the purification/concentration processing of a crude ethanol solution.
   [Application examples] Removal of impurities from a crude ethanol solution; conversion of azeotropic mixtures such as an ethanol aqueous solution into absolute alcohol.
   
   
   Photo 3 Pilot plant with continuous material feeding;
   for concentration of crude ethanol solutions