What is supercritical CO2?

     CO2 is a gas at standard condition. When the pressure exceeds 0.54MPa, CO2 is liquified below the temperature on the vapor pressure curve. However, the vapor pressure curve disappears above the critical point (7.38MPa and 31.1C) and this condition was called 'supercritical fluid'. Supercritical CO2 has the properties both the liquid (high solubility) and the gas (high diffusivity). Because supercritical carbon dioxide has a low dielectric constant and properties similar to organic solvents, it is used for purposes such as extraction and cleaning. The properties such as solubility can be easily controlled by changing the pressure and temperature. This is one of the advantages of organic solvent extraction.

    What can be done by supercritical CO2?    

The most common use of supercritical carbon dioxide is extraction. For example, extraction of lycopene (tomatoes), astaxanthin (Haematococcus algae), and various active ingredients from herbal medicines. Similarly, removal of specific components is also possible. The caffeine extraction from coffee beans by supercritical CO2 is widely practiced. Supercritical CO2 can also be used for dry cleaning, cleaning of semiconductor wafer without damages due to surface tension, dying to fibers, and injection of flame retardants into porous materials such as wood.

    Supercritical CO2 extraction process    

Organic solvent extraction requires drying process(removal of organic solvent), waste liquid treatment, fire protection, deodorization, and heating for evaporation. The supercritical CO2 as a solvent can be easily evaporate by decompression and the CO2 gas is non-toxic and non-flammable. From these points, supercritical CO2 is applied to a wide range of fields such as functional foods, pharmaceuticals, removal of harmful substances, various cleaning, and other production of functional substances.

    Process flow in mass production    

For large-scale extraction system, CO2 is recycles as shown in the figure. High pressure CO2 is fed from the CO2 storage via the cooler by the CO2 pump. Then the CO2 is heated to supercritical condition and pushed to the extractor. The extractor contains the raw material to be extracted. As the raw materials are continuously exposed to the CO2 flow, chemical compounds gradually dissolve. Entrainers are sometimes added to increase extraction efficiency. Subsequently, CO2 is send to the separator and depressurized. The solubility of compounds decreases as decreases the pressure in the separator. Thus the components can be separated. The CO2 returns to the CO2 storage again through the cooler.

Our products

Supercritical CO2 is hydrophobic and can dissolve many organic compounds. The solubility of an organic compounds strongly depend on the pressure and temperature. This controllability is advantageous over organic solvent extraction.

We have CO2 extraction apparatuses for several scale such as lab scale, pilot plant, and commercial plant as follows.

  Lab scale (skeleton type) Lab scale (multi-use type) Pilot plant Commercial plant
Volume (L) Extractor 0.4 0.16 30 250
Separator 0.21 0.1 15 60x2
Pressure (MPa) Extractor 25 30 50 50
Separator 5 7 6.5 20/6
Temperature (C) Extractor 65 120 80 80
Separator r.t. r.t. 80 65/32
CO2 flow rate (kg/H) 4.5 3.5 200 600

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