- Oil pretreatment. Camellia seeds → shelling → crushing → sieving (12 mesh) → weighing → loading.
- Extraction process. The experimental device is a 10L supercritical CO2 extraction device.
- Production process design:
After the carbon dioxide is released from the steel cylinder, it enters the cooling device. After the high-pressure pump obtains the pressure, it can enter the extraction kettle together with it. After the extraction is completed, the obtained substance enters the separation kettle I to complete the pressure reduction, thereby obtaining camellia seed oil. The gas will enter the separation tank II again for further use.
- Determination of oil content. Soxhlet extraction method.
- Determination of camellia seed oil oil color. Lovibond colorimetry.
- The formula for calculating the oil extraction rate. Oil output rate (%) = extract weight / raw material weight × 100%.
- The calculation formula of oil extraction efficiency. Oil output efficiency (%) = oil output rate / total grease content × 100%.
Results and analysis
Influence of feed volume on oil yield
If the degree of pulverization is specific, the amount of feed is directly related to the extraction concentration. Excessive feeding amount will cause accumulation of raw materials, which is not conducive to the flow of carbon dioxide, resulting in uneven airflow in the entire device, which will instead result in low extraction concentration.
When the amount of carbon dioxide is determined to be constant, increasing the amount of feed will result in a decrease in the flow rate per unit of raw material, thereby reducing the extraction concentration. Make the relevant device to complete the extraction smoothly, thereby reducing the efficiency of the equipment.
The dehulled tea seed kernel used in the experiment contained 36.5% oil. When the input amount of camellia seed powder was added to 80 kg, the extraction concentration became lower, indicating that 70 kg reached the peak.
The oil output rate at this time is 35.8%, which is more than 10% higher than the traditional hydraulic pressing oil rate (with 70kg of tea seed kernels used for hydraulic pressing, the oil output is 17.5 kg, and the oil output rate is 25%).
Effect of Extraction Pressure on the Oil Yield of Camellia Seed Oil
The size of the extraction pressure will directly affect the critical state of the extract. Generally speaking, the extraction pressure is positively correlated with the extraction concentration.
Because the pressure in the device increases, the unit quantity of carbon dioxide will increase, which will increase the density, and the density of carbon dioxide is positively correlated with the solubility of the extract. The increase in the density of carbon dioxide means that the rate of transfer between molecules increases, and the rate of mass transfer between solutes and solvents increases, thereby accelerating dissolution.
The increase in extraction pressure will also increase the rate of oil output. From the experimental results, it is found that when the extraction pressure reaches 40 MPa, the extraction work only takes 90 minutes. Therefore, it is best to set the extraction pressure at 35-40 MPa.
Effect of extraction temperature on oil yield
The extraction temperature has a certain relationship with the degree and speed of the oil dissolving in carbon dioxide. When the extraction temperature is 30-40 ℃, there is a direct proportional relationship between the two. The extraction temperature has a direct effect on the quality of the oil. Generally speaking, , The higher the extraction temperature, the more turbid the extracted oil, but if the temperature is too low, the oil yield will decrease.
The extraction concentration is positively correlated with temperature, but the degree of change is not large, and the degree of turbidity is also increasing. It is finally determined that 30 ℃ is the best value.
Effect of extraction time on oil yield
It can be seen from Table 2 and Table 3 that when the extraction pressure reaches 40 MPa, when the extraction time is less than 90 minutes, the extraction efficiency will increase, and 90 minutes is the critical value of extraction.
When the extraction pressure is between 35 -40 MPa, and when it exceeds 120 min, the extraction speed will be temporarily slow, so the best extraction time is set at 90 ～ 120 min.
Effect of separation pressure and temperature on extraction
When the feed is transferred from the extraction kettle to the separation kettle, the pressure decreases and the temperature increases, and the solubility of the oil in carbon dioxide will become smaller. At this time, the camellia seed oil will be separated from the separation kettle I, so you must choose a suitable separation pressure and Temperature value.
Through experiments, it is found that the pressure of separation kettle I is 8-11 MPa and the temperature is 55-75 ℃, and the quality and net value of the extracted camellia seed oil are the best.
The camellia seed oil in a supercritical state was heated up at a high temperature of 280 ℃. The color of the camellia seed oil became heavier and no flocs were produced.
Moreover, the unreasonable test parameters will result in aggravation of impurities in the oil. When the extracted oil with more impurities is used for the heating experiment at 280 ℃, there is no precipitate, that is, the heating experiment still meets the national standard of first-class oil.
It can be seen that for the camellia seed oil extracted by supercritical fluid, the other processes can be cancelled except for the fine filtration.
The process of using CO2 supercritical extraction of camellia seeds to produce camellia seed oil is feasible. The experimental research determined that the more suitable process conditions are:
The extraction pressure is 35-40 MPa, the extraction temperature is 30 ℃, the pressure of the separation vessel I is 8-11 MPa, the temperature is 55-75 ℃, the temperature of the separation vessel II is 25-40 ℃, the feed volume is 70 kg, and the extraction time is 90-120 min.