The particle size of the material has a dual effect on the extraction.
On the one hand, the finer the material, the more mass transfer area is increased, and the mass transfer distance and mass transfer resistance are reduced, which is beneficial to the extraction.
On the other hand, if the material is too fine, it is easily compacted under high pressure, increasing the mass transfer resistance without Conducive to extraction. Due to the high content of grape seed oil, it is generally easy to use about 40 mesh.
Supercritical CO2 fluids have good mass transfer characteristics. Increasing the pressure will not only increase the density of CO2 but also reduce the distance between molecules.
At lower temperatures, the extraction rate of grape seed oil gradually increases with increasing pressure, but when the pressure is too high, the extraction rate increases slowly.
Because of the high density of CO2 under high pressure, the compressibility is small, and the increase of pressure has little effect on the solubility of the substance.
At the same time, high pressure will increase the investment and operating costs of the equipment. Therefore, it is more appropriate to select 28Mpa for extraction from all aspects.
On the one hand, the elevated temperature increases the diffusion coefficient of the substance, so that the solubility increases, which is beneficial to the extraction.
On the other hand, since the extraction temperature is an important factor affecting the density of the supercritical CO2 fluid when the temperature rises, the CO2 is lowered.
The density of the material reduces the solubility of the substance, which is not conducive to extraction; in addition, the increase in temperature also degrades the quality of the product.
Therefore, the extraction temperature should not be too high.
At 28Mpa, the extraction rate of grape seed oil decreased with the increase of temperature, but the extraction rate increased slowly at the specified temperature of 35 °C; when the pressure was less than or equal to 28Mpa, the temperature was below 35 °C, and the extraction rate increased with temperature, and rise.
For the effect of combined pressure and temperature, the optimum temperature for extraction should be 35 °C.
The supercritical CO2 extraction process is divided into three stages: the initial stage of extraction, the stage of conversion, and the final stage of extraction.
In the initial stage of extraction, the contact time of the substance with CO2 is small, and the amount of material per unit time is less; as the extraction time is extended, the extraction stage is gradually increased; the final stage of extraction is due to the low content of the extracted material in the material.
In addition, the amount of extraction per unit time is reduced. The results show that at 35 ° C, 28 Mpa, the extraction rate is gradually increased below 80 minutes; the extraction rate below 80 minutes is close to the level and no longer increases.
Therefore, the time for extracting grape seed oil from supercritical CO2 fluid should be 80 minutes.
The CO2 extraction method of grape seed oil
- Accurate weighing of crushed grape seeds of a certain size is placed in the extracting kettle. The filling volume is about 60% of the kettle volume. Then the extracting kettle is fixed in the heating furnace and the safety door is closed. Make sure the safety door does not open at will until the extraction process is over. Check that the valves on the extractor are closed.
- Connect the mainframe power supply, the power supply of the constant temperature circulating system, and the power supply of the air compressor respectively to check whether the equipment is working properly. 3. Open the intake valve so that liquid carbon dioxide enters the extraction system through the siphon.
- Open the temperature control switch of the heating furnace and the exhaust valve respectively, and set the extraction temperature and the exhaust valve temperature on the temperature control panel;
- When the kettle temperature reaches the set value and stabilizes, the system pressure will be adjusted to the set value. Keep the exhaust valve closed and start the static extraction process.
- Open the discharge valve after the static extraction and start the dynamic extraction process. Adjust the opening and closing degree of the exhaust valve to control the exhaust gas velocity of carbon dioxide. Supercritical fluid with product expands through throttle after pressure reducing valve releases grape seed oil, and turns into atmospheric CO2 gas. The discharge velocity is measured by a float flowmeter.
- The product is collected in the weighing tube. The quality of grape seed oil was accurately weighed after extraction.
CO2 extraction process
- Pulverization degree: 40 mesh
- Extraction pressure:28Mpa
- Extraction temperature:35 °C
- Extraction time:80 minutes