Solvent extraction is a method of making oil by using the principle of extraction to select an organic solvent which can dissolve oil and make it contact with pretreated oil by soaking or spraying to dissolve the oil and fat in the oil. This method makes the solvent and the oil it dissolves into a solution called a mixture. Using the different boiling point of the selected solvent and the oil, evaporation, and stripping of the mixed oil were carried out, and the solvent was evaporated, leaving the oil to obtain the crude oil. The steamed solvent vapor is recovered by condensation and recycled.
Solvent extraction is an advanced method of extracting oil, which is generally recognized in the world. In summary, it has the following advantages:
- Low residual oil in meal
In crushing oil production, because the pretreatment process can not completely destroy the oil cells, protein denaturation can not be very thorough; the temperature of the crushing chamber can not be very high, and the pressure of the crushing chamber can not be very high. Therefore, it is impossible to extract oil by pressing method, and the residual oil rate of pressed cake is still high. For example, the residual oil rate of cake obtained by ZX 18 oil press is 5%-8%. In contrast, the residual oil rate of a leached meal can be controlled below 1% by solvent extraction, either directly or pre-press leaching.
- Good quality of the meal
Compared with the crushing process, in the production of the leaching process, the denaturation degree of protein in a solid material is smaller and the quality of the meal is better due to the lower operating temperature of the related processes. It is very beneficial to feed the value of the meal or to extract vegetable protein from a meal.
- Low production cost
Compared with the crushing process, the production line used in the leaching process is generally complete, mechanized and easy to realize automation. Secondly, the leaching workshop has fewer operators and low labor intensity. Moreover, the energy consumption of the leaching process should be lower accordingly. Therefore, the production cost of leaching oil is low.
- Potential hazards caused by the use of solvents
At present, the solvent used in the leaching process is mainly hydrocarbon compounds. Hexane is the main component of light gasoline used in the current domestic leaching process. These solvents are flammable and explosive and have a strong stimulating effect on the human nervous system. For example, when the vapor concentration of light gasoline in the air reaches 1.20%-7.50%, it will explode in the event of a fire; when the vapor concentration reaches 30-40 mg/l, it will be lethal in direct contact with people.
For these shortcomings of solvents, as long as we strictly implement the “Fire Safety Code for Leaching Oil Plant”, strictly abide by the operating rules, and keep a high degree of vigilance, accidents will generally not occur.
- The quality of leached crude oil is slightly poor.
The solubility of organic solvents is very strong. It can not only dissolve oils but also dissolve some pigments and lipids in oils. Mixed with oils, the color of oils becomes darker and the impurities increase. In this way, the quality of leached crude oil is worse than crushed crude oil, and the refining rate is lower. At the same time, the workload of the refining process will be increased accordingly.
- Investment needs to be increased
Because the solvent used in the immersion production process is flammable and explosive and harmful to the human body, the fire hazard category of the building in the production workshop should be Class A, and the minimum fire resistance grade should reach Class II. The workshop equipment should be grounded, the electrical appliances used should be explosion-proof, and the workshop should be equipped with lightning arresters. In addition, the equipment and pipes in the workshop need to be tightly sealed, and so on. In this way, the construction of the whole leaching workshop will increase the total investment.