Supercritical CO2 fluid extraction has the characteristics of fast mass transfer rate, strong penetrating ability, high extraction efficiency, and low operating temperature, and has become one of the most effective methods to obtain high-quality products.
What is a supercritical CO2 extraction machine?
The supercritical CO2 fluid extraction equipment is used for supercritical CO2 extraction. The supercritical fluid extraction machine is mainly composed of a freezing part, a pressurizing part, an extraction part, a separation part, and a recovery part, but according to the different production processes and fluid media, The configuration of the device is also different.
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The main extraction process of the CO2 extraction machine consists of two parts: CO2 extraction and separation vessels.
In the CO2 extraction machine, at a specific temperature and pressure, the raw material is brought into contact with the supercritical CO2 fluid, and when the dynamic balance of the material components between the gas and liquid is reached, the temperature and pressure are adjusted to separate the extraction product from the supercritical CO2 fluid. Complete the whole process of supercritical extraction.
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Supercritical CO2 extraction technology has been successfully used in medicine, food, chemical, and other industries, but in the production process, the following problems should be prevented:
Four important considerations
Important considerations 1#: Temperature monitoring
To prevent the temperature control instrument temperature control operation stable time is too long, and the fluctuation range is large. Since the temperature-measuring thermocouple sensor on the temperature controller is installed on the upper part of the CO2 extraction vessel and the CO2 extraction separator vessels, it is greatly affected by the ambient temperature.
In practical applications, the sensor should be directly inserted into the hot water tank, so as to solve this problem well.
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Important considerations 2#: “Water Blocking” Phenomenon During CO2 Extraction
There is a “water block” phenomenon. In the application of supercritical CO2 extraction, since there is more or less water in the raw material, the CO2 in the separator after extraction usually carries a part of the water, and the CO2 containing a part of the water will freeze into ice when it is refrigerated and liquefied, causing the pipeline to block.
This phenomenon is called the “water blocking” phenomenon, also known as the “ice blocking” phenomenon.
Before the circulating CO2 gas enters the refrigerator, a dehydrator is set in the process flow, and a dehydrating agent such as silica gel or anhydrous CaCl2 is added to the dehydrator. It can also be transformed on the basis of the original purifier, and the purifier can be transformed into two parts, the upper part is a desiccant such as silica gel or anhydrous CaC2, and the lower part is a packing made of dense stainless steel, with a small hole in the middle. Stainless steel plates are separated.
Important considerations 1#: Blockage of CO2 extraction pipeline
The solid material in the extraction kettle should not be too fine. In the CO2 extraction process, the solid material is too fine to be carried out of the material basket by CO2 fluid, causing the blockage of the pipeline and reducing the mass transfer rate. The solution is to add loose and uniform stainless steel fillers in the extraction kettle to reduce the diffusion resistance of the material layer, thereby increasing the mass transfer rate, and effectively avoiding the channeling phenomenon (that is, the route with low CO2 fluid resistance passes through the material layer. , forming many pinholes, resulting in significantly uneven extraction).
Important considerations 4#: CO2 fractionation
Supercritical CO2 extraction and CO2 fractionation technology are combined. Because the CO2 fractionation tower is high and the pipe diameter of the segmented circulating heating water introduced into the fractionation tower is long, it is necessary to add thermal insulation materials outside.
6 tips for using a supercritical CO2 extraction machine
- 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.
- 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).
- 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.
- 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.
- 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.
- 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.
Read More: CO2 Extraction Pumps