The supercritical extraction process is mainly composed of two parts: the extraction stage and the separation stage.
- In the extraction stage, the supercritical fluid extracts the desired components from the raw material;
- In the separation stage, by changing a certain parameter, the extraction component is separated from the supercritical CO2 fluid component, and the extraction agent is recycled.
Three typical supercritical CO2 extraction processes
According to different separation methods, the supercritical CO2 extraction process can be divided into three categories, namely isothermal pressure-swing process, isobaric temperature-swing process, and isothermal isobaric adsorption process.
Classification comparison of supercritical fluid extraction technology process equipment
|Isobaric temperature change||Extraction and separation are carried out under the same pressure. After the extraction is completed, the temperature is raised through heat exchange. Under the stable pressure of CO2 fluid, the dissolving power decreases with the increase of temperature, and the solute is precipitated.||Compression consumes relatively little energy||Affects heat-sensitive materials||Propane deasphalting|
|Isothermal pressure change||Extraction and separation are carried out at the same temperature, and after the extraction is completed, it passes through a throttling and depressurizing electrostatic separator. Due to the pressure drop, the dissolving ability of the CO2 fluid to the extract gradually decreases, and the extract is separated and separated||Since there is no temperature change, the operation is simple, and it can realize the extraction of high boiling point, heat sensitive, and easily oxidized substances close to normal temperature||High pressure, large investment, and high energy consumption||Extraction of supercritical hops|
|Constant temperature and pressure||Operated under constant temperature and pressure, the operation of this equipment requires special adsorbents such as ion exchange resins, activated carbon, etc. for the separation of extracts, for exchange and adsorption, generally used to remove harmful substances||It is always in a supercritical state during operation, so it is very energy-saving||Need special adsorbent||Water Absorption of Supercritical Extraction of Caffeine|
Supercritical constant temperature and pressure reduction extraction process
The supercritical constant temperature and pressure-reducing extraction process is to use the difference in the extraction capacity of supercritical fluid under different pressures and to separate the solute from the supercritical fluid by changing the pressure.
The so-called constant temperature means that the temperature of the fluid in the extractor and the separator is basically the same. This is the most convenient process. First, the extractant reaches the supercritical state through the compressor, and then the supercritical P₂ fluid enters the extractor and mixes with the raw materials for supercritical extraction. After the solute is extracted, the supercritical fluid passes through the pressure-reducing valve, and the pressure drops, the density decreases, and the solubility decreases. Thereby the solute and solvent are separated in the separator. Then compress the extractant to reach a supercritical state and repeat the above extraction-separation steps until the predetermined extraction rate is reached.
Supercritical constant pressure and temperature rise extraction process
The supercritical constant pressure and heating extraction process uses the solubility difference of substances in supercritical fluid at different temperatures and separates the solute from the supercritical fluid by changing the temperature. The so-called equal pressure means that the pressure of the fluid in the extractor and the separator is substantially the same. The supercritical fluid that has extracted the solute is heated to separate the solute from the solvent, the solute is taken out from the bottom of the separator, and the extractant is compressed and temperature-regulated for recycling.
Supercritical isothermal and isobaric adsorption process
The supercritical isothermal and isobaric adsorption process is to place an adsorbent that only absorbs the solute but not the extractant in the separator. The solute is separated from the extractant due to being adsorbed in the separator, and the extractant is recycled after being shrunk.
Supercritical isothermal and isobaric adsorption is a process used in supercritical fluid extraction, where a solute is adsorbed onto a solid adsorbent material in a supercritical fluid. In this process, the pressure and temperature are kept constant, while the adsorbent material is exposed to the supercritical fluid, allowing the solute to be adsorbed onto the surface of the adsorbent.
3 main steps
- Loading: The adsorbent material is loaded into a column, and the supercritical fluid is introduced into the column. The pressure and temperature are maintained at a constant level throughout the process.
- Adsorption: As the supercritical fluid flows through the column, the solute in the fluid is adsorbed onto the surface of the adsorbent material. The adsorption process is isothermal and isobaric, meaning that the temperature and pressure are kept constant, which allows for accurate control of the adsorption process.
- Desorption: Once the adsorption process is complete, the column is depressurized, allowing the solute to be desorbed from the adsorbent material. The desorption process can be performed by reducing the pressure, increasing the temperature, or using a different solvent to elute the solute.
The supercritical isothermal and isobaric adsorption process has several advantages over traditional adsorption methods. One advantage is that the process is more efficient, as the supercritical fluid can penetrate deep into the adsorbent material, allowing for better solute adsorption. The process is also more selective, as the supercritical fluid can be tuned to specific conditions to selectively adsorb certain solutes.
Additionally, the process is environmentally friendly, as supercritical fluids are non-toxic and non-flammable, and can be easily recycled, reducing waste and pollution. Overall, the supercritical isothermal and isobaric adsorption process is an efficient and environmentally friendly method for separating and purifying solutes from a variety of matrices.
Supercritical CO2 Fluid Extraction
Supercritical Fluid Extraction (SFE) is a technology that uses supercritical fluid to extract substances. It is often used to extract medicinal ingredients from natural plants, extract nutrients from food, and extract organic substances from chemicals.
The following is a typical process of supercritical extraction:
- Pretreatment: The materials to be extracted (such as plants, food, chemical raw materials, etc.) are subjected to pretreatment operations such as crushing and drying to improve extraction efficiency.
- Packing material loading: the pretreated material to be extracted is loaded into the extractor, usually using a pressurized vessel or a tubular reactor.
- Adding solvent: Add supercritical fluid as a solvent to the extractor, generally using carbon dioxide (CO2).
- Extraction: Under certain temperature and pressure conditions, the supercritical fluid is fully contacted with the material to be extracted, so that the target component is dissolved from the material into the supercritical fluid.
- Separation: Make the supercritical fluid into a gaseous state by adjusting the temperature and pressure of the solution to separate the target components.
- Recycling: Purify and recycle the recovered supercritical fluid.
It should be noted that the specific supercritical CO2 extraction process will be affected by many factors, such as the nature of the material to be extracted, the type and parameters of the extractor, etc., so the above process is for reference only. In practical applications, process design and parameter optimization need to be carried out according to specific conditions to improve extraction efficiency and product quality.