Supercritical CO2 Extraction
Using supercritical CO2 fluid as the extraction agent, the component to be separated is extracted from the liquid or solid material under conditions near the critical temperature and critical pressure.
Using the characteristics of supercritical fluids, under high-density conditions (low temperature, high pressure), the required components are dissolved, and then the conditions are changed to separate the extracted components from the extractant under low-density conditions.
Features of Supercritical Fluid Extraction
- Process conditions are easy to control
- Solvents are less prone to contamination
- Suitable for heat sensitive or easily oxidized ingredients
- High voltage equipment required
Selection Conditions for Supercritical Fluids
- The operating temperature is close to the critical temperature
- The extractant is chemically similar to the components to be separated.
Six Notes on the Operation of Supercritical CO2 Extraction Machine
Notes 1: The pressure of the CO2 bottle
When performing supercritical CO2 extraction in winter, due to the influence of temperature, the pressure of the CO2 bottle drops, generally between 4~5Mpa. In order to maintain normal operation, a heating device is required, or the indoor greenhouse is kept elevated. When the pressure of the CO2 cylinder reaches 6Mpa, it can be used.
Notes 2: Expansion valve and refrigeration
Pay attention to the blockage accident of the expansion valve, so that the refrigeration cannot meet the required requirements, which can be judged by the change of the pressure gauge (especially the pressure drop, which is lower than the normal value).
Notes 3: Co-solvent corrosion problems
Pay attention to the corrosion problem of cosolvents. Stainless steel materials have different degrees of corrosion in the supercritical state, including localized corrosion, among which pitting corrosion (also known as pitting corrosion) is the most serious.
Notes 4: water blockage
When the phenomenon of “water blockage” occurs, it should be stopped first, and it is best to use nitrogen to purge the coil. If there is no nitrogen, the frozen liquid can also be released, and the water vapor can be discharged out of the tube by heating.
Notes 5: cleaning CO2 tubes
When the supercritical CO2 extraction machine is shut down for a long time, it is necessary to add a CO2 cleaning line with a modifier (ethanol) to prevent some biomass from sticking to the pipe wall and causing a blockage. When replacing the extracted biomass, also clean the pipes and the CO2 extraction machine.
Notes 6: Adopt new technology equipment
In order to prevent the extraction dead zone in the extract, vortex supercritical CO2 extraction can be used, which overcomes the shortcomings of the previous CO2 extraction machines. The comprehensive and effective contact between the CO2 fluid and the biomass accelerates the CO2 extraction speed, prevents the extraction dead zone, and improves the extraction efficiency of the CO2 extraction process.