Subcritical fluid extraction (SFE) uses subcritical fluid as extractant. In a closed, oxygen-free, low-pressure pressure pressure vessel, according to the principle of similar solubility of organic matter, through the molecular diffusion process of extraction material and extractant in the soaking process, the fat soluble components in solid material are transferred to liquid extractant, Finally, a new extraction and separation technology of the target product was obtained. Compared with other separation methods, subcritical fluid extraction has many advantages, such as non-toxic, harmless, environmental protection, non pollution, non thermal processing, non destruction and non oxidation of the active components of the extract, large capacity, large-scale industrial production, energy saving, low operation cost, and easy separation from the product.
Subcritical extraction equipment has been serialized, from the daily processing of raw materials from 1~100 tons of complete equipment has been very mature, 60 tons / day equipment located in Anyang City, Henan Province is the key demonstration plant of the State Economic and Trade Commission, has been in operation for 15 years, processing more than 100,000 tons of raw materials, processing dozens of raw materials
Commonly Seen Extraction Solvent
When extraction solvents such as propane, butane, high purity isobutane (R600a), 1,1,1,2-tetrafluoroethane (R134a), dimethyl ether (DME) are present in a subcritical fluid state, the molecular diffusion properties are enhanced. Those solvents' mass transfer rate is accelerated, and the permeability and solvency for the non-polar, medium-weak, and highly polar substances of the natural products are significantly improved.
The boiling point of the solvent suitable for subcritical extraction is lower than the ambient temperature around us. Generally, the boiling point is below 0ºC, and the liquefaction pressure at 20ºC is below 0.8 MPa (gauge pressure).
The subcritical solvents used in industrial applications are butane and propane initially. Then comes success with dimethyl ether, tetrafluoroethane (R134a), liquid ammonia, sulfur hexafluoride, dichlorodifluoromethane (freon R12), and chlorodifluoromethane (Solvents such as Freon R22). Because of the difference in the polarity of these solvents, they can be used to extract different target products in applications.
subcritical low temperature extraction Flow chart
Common Subcritical Fluids Physical and chemical properties
| Propane | butane | dimthylether | Tetrafluoroethane | Liquid Ammonia |
Molecular Formula | C3H8 | C4H10 | CH3OCH3 | CH2FCF3 | NH3 |
Molecular Weight | 44 | 58 | | 102 | 17 |
Boiling Point ºC | -42 | -0.5 | -24.9 | -26.2 | -33.4 |
Pressure Mpa at 20ºC | 0.83 | 0.23 | 0.533 | 0.6 | 0.88 |
Critical Temp ºC | 95.7 | 152.8 | 129 | 101.1 | 132.3 |
Critical Pressure MPa | 4.4 | 3.6 | 5.32 | 4.07 | 11.3 |
Liquid Density: kg/L at 25ºC | 0.49 | 0.57 | 0.66 | 1.2 | 0.61 |
Gas Density: kg/m 25ºC | 20.15 | 6.18 | | | 0.6 |
Dielectric Constant | 1.69 | 1.78 | 5.02 | | 16.9 |
Latent Heat of Vaporization KJ/kg at 30ºC | 329 | 358 | 410 | 216 | 1369 |
Explosion Limit | 2.3%~9.5% | 1.9%~8.5% | 3.5%~27% | non-inflammable | 16%~25% |
Toxicity LC50(mg/m3) | minor | minor 680 | 308000 | non-toxic | 1390 |
Appearance | colorless, odor | colorless, odor | colorless, odor | colorless, odorless | colorless, pungent odor |
Low temperature extraction technology mainly solves the problems of traditional extraction process, such as high temperature, decomposition of extraction solution, more impurities, loss of a large number of effective components, large amount of solvent and high concentration cost;
At the same time, the low-temperature extraction technology changes the original traditional static percolation process into dynamic percolation mode, which speeds up the percolation extraction time and reduces the traditional 8-10 times amount of solvent to 4-5 times.
The low-temperature extraction equipment is applied to the extraction process of various plants, Chinese herbal medicines, fruits, animal drugs and food additives at room temperature.
Low temperature extraction equipment is suitable for normal pressure and normal temperature extraction, Soxhlet extraction, dynamic thermal reflux extraction, plant essential oil extraction and vacuum concentration of extraction solution in traditional Chinese medicine, health products, biopharmaceutical, cosmetics, food and other industries.
The invariability of water-soluble protein was more than 95%, residual oil was less than 1%, and residual solubility was less than 50ppm; Low temperature extraction technology mainly solves the problems of traditional extraction process, such as high temperature, decomposition of extraction solution, more impurities, loss of a large number of effective components, large amount of solvent and high concentration cost;
Low temperature extraction equipment will be used in the production of precious oil "liquefied petroleum gas extraction technology"
This principle of avocado oil extraction machine utilizes sub-critical solvent for the first extraction process that is known as counter-current extraction. The process involves treating of pretreated seeds with propane and butane, which are classified as liquefied sub critical solvents. The end product from extractor are extracted oil meal and mixture fluid. The mixture fluid yields to gassified solvent as a result of solvent gasification whereby the fluid is subjected to vacuum evaporation at normal temperature. A fresh recycling session is done after the gasified solvent is condensed or liquefied. The basis of utilizing the sub-critical low temperature extraction technology of our avocado oil extraction machine is that the boiling point of these solvent is below 0°C. When under low temperature and normal pressure condition, the soluble fatty acids and other active components within the raw material and solvents has the propriety of dissolvability. That is how this low temperature extraction machinery get the target products. The processes in this method are achieved with normal temperature and pressures, avoiding damages to the thermal sensitivity of final oils. Our latest prickly pear seed oil extraction machine and moringa seed oil extraction machine also adopts this efficient low temperature extraction method.
Animal fat oil extraction methods | Pros | Cons |
Pressing | - low investment
- simple extraction process
| - low extraction rate
- a big loss of raw material
- unsuitable for scale production
|
Cooking | simple and small investment extraction equipment | - low quality animal fat oil
- can't extraction the fat composition that can be combined with the protein
|
Traditional Solvent disllation extraction | - low investment cost
- suitable for small or large scale animal fat oil production
| - high solvent residues
- easy to pollute
|
Supercritical Extraction | - high quality animal fat oil
| - highest investment cost
- highest requirements for extraction equipment
- only suitable for small scale aniamal fat oil processing
|
Sub-critical Biological Extraction | - largely extract the active components within fishes
- energy-saving extraction process
- lower investment cost
- high quality animal fat oil
- suitable for small or large scale oil production
| - newly emerging technology for fat oil
|
The advantages of subcritical low temperature extraction technology are as follows:
1. The quality of the extracted cake is good and the original heat sensitive substances are not destroyed, which can further develop plant protein;
2. The solvent consumption is low, and the solvent consumption per ton of raw material is less than 8 kg;
3. No steam is needed, only 90 ºC hot water is enough. Compared with No. 6 solvent, 70% of thermal energy can be saved;
4. There is no "three wastes pollution" in production, which belongs to environmental protection engineering.
5. Extraction at room temperature, desolvation at low temperature (less than 40 ºC), no damage of heat sensitive substances in oil and meal after extraction, high yield of pigment in extract, bright color, it is an ideal process for extraction of precious oil, plant protein and natural pigment;
6. Small investment and low production cost (compared with CO2 equipment);
7. Subcritical fluid has a wide range of sources and low price. This solvent is available in all oilfields and refineries, and its price is lower than that of No. 6 solvent;
8. Low pressure and high safety (working pressure 0.3mpa-1.0mpa);
9. The production scale is large, and the processing capacity of a complete set of extraction equipment can reach 0.1t-200t/d.
Low temperature extraction technology mainly solves the problems of traditional extraction process, such as high temperature, decomposition of extraction solution, more impurities, loss of a large number of effective components, large amount of solvent and high concentration cost;
At the same time, the low-temperature extraction technology changes the original traditional static percolation process into dynamic percolation mode, which speeds up the percolation extraction time and reduces the traditional 8-10 times amount of solvent to 4-5 times.
The low-temperature extraction equipment is applied to the extraction process of various plants, Chinese herbal medicines, fruits, animal drugs and food additives at room temperature.
Low temperature extraction equipment is suitable for normal pressure and normal temperature extraction, Soxhlet extraction, dynamic thermal reflux extraction, plant essential oil extraction and vacuum concentration of extraction solution in traditional Chinese medicine, health products, biopharmaceutical, cosmetics, food and other industries.
The invariability of water-soluble protein was more than 95%, residual oil was less than 1%, and residual solubility was less than 50ppm; Low temperature extraction technology mainly solves the problems of traditional extraction process, such as high temperature, decomposition of extraction solution, more impurities, loss of a large number of effective components, large amount of solvent and high concentration cost;
Low temperature extraction equipment will be used in the production of precious oil "liquefied petroleum gas extraction technology"
This principle of avocado oil extraction machine utilizes sub-critical solvent for the first extraction process that is known as counter-current extraction. The process involves treating of pretreated seeds with propane and butane, which are classified as liquefied sub critical solvents. The end product from extractor are extracted oil meal and mixture fluid. The mixture fluid yields to gassified solvent as a result of solvent gasification whereby the fluid is subjected to vacuum evaporation at normal temperature. A fresh recycling session is done after the gasified solvent is condensed or liquefied. The basis of utilizing the sub-critical low temperature extraction technology of our avocado oil extraction machine is that the boiling point of these solvent is below 0°C. When under low temperature and normal pressure condition, the soluble fatty acids and other active components within the raw material and solvents has the propriety of dissolvability. That is how this low temperature extraction machinery get the target products. The processes in this method are achieved with normal temperature and pressures, avoiding damages to the thermal sensitivity of final oils. Our latest prickly pear seed oil extraction machine and moringa seed oil extraction machine also adopts this efficient low temperature extraction method.