Supercritical fluid is a high-density fluid above the critical temperature and critical pressure. It is neither a gas nor a liquid, but has properties between those of a gas and a liquid, and is characterized by having solvent properties. When a fluid is in a supercritical state, its density is close to that of a liquid, and changes significantly with changes in fluid pressure and temperature, while the solubility of a solute in a supercritical fluid increases with the increase in the density of the supercritical fluid. Supercritical extraction is carried out using this property of supercritical fluids.
Supercritical CO2 fluid extraction technology is a new type of separation technology in modern chemical separations, with the characteristics of fast mass transfer rate, strong penetration ability, high extraction efficiency and low operating temperature. This technology has been widely used in the pharmaceutical, food, chemical and other industries.
Supercritical CO2 extraction devices can be used for extracting materials (solids and liquids) at high pressure and appropriate temperature under the condition of separator replacement, so that soluble materials can decompose the target product during the extraction and separation process.
The supercritical fluid extraction process is carried out under high pressure and is mostly intermittent operation. The materials in the extraction kettle need to be frequently replaced and frequently opened for cleaning. Therefore, the characteristics of the supercritical fluid extraction process determine that the extraction kettle needs to adopt a quick-opening sealing structure. The extraction kettle is subjected to high pressure, and the quality of the steel used determines the limit of the maximum working pressure it can withstand.
Advantages and characteristics of supercritical extraction technology
- The extraction process can be completed at near room temperature, which is suitable for extracting and separating some components that are sensitive to heat, easy to oxidize and decompose, and destroyed.
- At normal pressure and room temperature, the extractant is a gas, and it is relatively easy to separate from the residual phase and the extraction group after extraction.
- Under ideal process conditions, the extracted components can be almost completely extracted, thereby improving the yield of the product and the utilization rate of resources.
- The extraction process is simple and pollution-free, and the supercritical fluid after separation can be recycled after refining.
- In supercritical carbon dioxide extraction, the extracted substance can be precipitated by reducing the pressure or increasing the temperature, and no repeated extraction operations are required. Therefore, supercritical carbon dioxide extraction has a relatively simple process.
Conclusion
Supercritical CO2 fluid extraction is a separation and extraction technology that is highly valued at home and abroad. It has many advantages and characteristics. Supercritical fluid extraction technology has broad application prospects in the food, chemical, and pharmaceutical industries, and also shows new vitality in the separation of high value-added products.
It can be said that at present, SFE has been designed and optimized in an all-round way, just like other more mature unit operations. This also shows from one aspect that the practicality of SFE is receiving more and more attention.