Edible oil solvent extracting is a chemical unit operation called Extraction, which is divided into liquid-liquid extraction and solid-liquid extraction. The former is the use of substances in 2 mutually insoluble (or slightly soluble) solvent solubility or distribution coefficient of the difference, so that the substance from one solvent to another solvent transfer method, the latter is the use of solvents in solid materials to separate a component of the method, also known as leaching. Leaching can be divided into physical leaching, chemical leaching, and bacterial leaching. Physical leaching is a simple solute dissolution process, the solvent used are water, alcohol, or other organic solvents. Chemical leaching is used to treat minerals, commonly used acid, alkali, and some salts of aqueous solutions, through a chemical reaction, the dissolution of certain components. Bacterial leaching is used to treat certain sulfide metal ores, relying on the oxidation of bacteria to transform insoluble sulfides into soluble sulfates and transferred them into the leaching solution. Extraction is widely used in botany, pharmacology, microbiology, aquatic products processing, agricultural products processing, and other disciplines in the extraction and identification of chemical components, but also in metallurgical processes, petroleum refining process is also widely used. The process of “solvent extraction” has different Chinese names in different disciplines, for example, the extraction of chemical components in botany is called “solvent extraction” (“Botanical Terminology”, second edition), chemical engineering is called “solvent extraction” (“chemical engineering terminology” first edition), etc. In the oil industry, the use of solvent commercial hexane or No. 6 solvent oil to extract the oil in the oil method, known as leaching. Leaching method (solvent extraction) oil production is the most widely used oil production method in the world today, is a common safety and health, scientific and advanced oil production process at home and abroad. The extracting process, the solvent hexane, and grease and leaching material billet (soybean germ flakes, puffed soybeans, rapeseed cake, etc.) does not have a chemical reaction, is only a simple solute penetration, diffusion process, so the leaching method of oil production is a physical process. The main factors affecting the solvent extracting efficiency are:
Solvent extraction temperature has a great impact on the leaching rate. Increase the extracting temperature, the viscosity of the oil and solvent is reduced, the molecular thermal movement is enhanced, thus increasing the leaching rate. The higher the working temperature of the leach, the faster the mixed oil through the cell wall, the faster the intracellular mixed oil and the surrounding mixed oil to reach equilibrium. However, if the leaching temperature is too high, it will cause an increase in the amount of vaporized solvent in the extractors, a higher pressure, an increase in solvent loss in production, and an increase in the amount of non-oil substances in the leached gross oil. In balancing leaching efficiency with safety and environmental issues, it is best to operate the extractor at 61-62°C close to the solvent boiling point. Proper suction of the incoming leach material and insulation of the conveying equipment are essential for good leaching results.
(2) Solvent or mixed oil permeability to the material layer mixed oil.
Permeability refers to the rate at which the mixed oil on the surface of the leached material diffuses into the oil body within the cells of the oil material. Solvent or mixed oil penetration of the oil is expressed in terms of the volume or weight of solvent or mixed oil flowing through each square meter of the material blank surface per hour. The greater the amount of penetration, the higher the penetration rate of solvent or mixed oil through the material layer, the stronger the convection-diffusion, the smaller the thickness of the interface layer, and so that the concentration difference between the oil inside and outside the billet increases, molecular diffusion is enhanced, which is conducive to the increase in leaching rate. The key to the leach design is to minimize the permeation time at all levels of leaching. Material embryo preparation has a greater impact on the permeation rate of the oil mixture: puffed soybean material: 41 m3/h/m2 or 1.4 m/min rapeseed cake: 25 m3/h/m2 or 0.8 m/min under the permeable cake 0.38 mm soybean flakes: 19.5 m3/h/m2 or 0.6 m/min soybean flakes
(3) Solvent Extracting Time
Solvent extracting time should ensure that the oil molecules have enough time to diffuse into the solvent. However, with the extension of the leaching time, the reduction of meal residual oil has been very slow, and the leaching of non-triglyceride content of the gross oil increases, the leaching equipment processing capacity is also reduced accordingly. In actual production, to ensure that the amount of residual oil in the meal meets the target, as short as possible to shorten the leaching time, increase the number of counter-current leaching levels close to equilibrium, can shorten the total leaching time required.
(4) Preparation of solvent extraction material
Thickness determines the time required for each leaching level of the oil mixture in the cells and the surrounding oil mixture concentration close to equilibrium. Different oilseeds and different pretreatment methods before leaching have a significant impact on the leaching time:
puffed soybean: 4 min/stage
rapeseed cake: 8 min/stage
0.38 mm soybean flakes: 5 min/stage
0.30 mm soybean flakes: 4 min/stage
The height of the material layer in the extractor has an impact on the utilization of the leaching equipment and the leaching effect. Generally speaking, the material layer to improve, the same leaching equipment to improve the production capacity, while the material layer of mixed oil from the filtering effect is also good, the mixture of oil containing meal froth reduced, the mixture of oil concentration is also higher. However, the material layer is too high, the solvent and mixed oil penetration, drip dry performance will be affected.
(5) Surface Water
The material embryo surface covered with water will prevent the mixed oil penetration into the appearance of water particles, thus preventing the leaching of oil. Excess moisture in the air surrounding the flakes, puffed material or pre-pressed cake being transported to the extractors can condense on the surface of the particles, causing moisture to be present on the surface of the leached material.
(6) Wet meal with solvent
Wet meal with solvent refers to the solvent content in the extracted meal after the extracting separation of the mixed oil. Drainage time, the height of the material layer, mixed oil permeability, the leach grate opening area all affect the wet meal solubility. Inappropriately sized extractors, the extracted meal solubility is between 26-30%.
At present, the extractors commonly used in the oil industry are divided into Rotocel Extractor, Drag Chain Extractor, crawler type, and so on according to their structural features and operation methods. With proper selection, pre-treatment/pre-pressing of the billet, and proper operation of the leaching process, all of these extractors can achieve the desired leaching efficiency, the main difference being the size of the investment, floor space, and maintenance costs.
As a professional edible oil solvent equipment supplier, Chemsta is ready to help you solve any problems in production, you can contact us at any time, Chemsta engineers are at your service.