What are the factors affecting edible oil solvent extraction process?

The edible oil solvent extraction process is a kind of solid-liquid extraction. Because of different substances have different solubilities, using solvent can separate the different components of solid oil materials. 

The general edible oil solvent extraction process is as follows: First, the oil seeds after expanding are sent into leaching device. Second, using 6 # solvent oil (n-hexane) to spray onto puffing material, after soaking for a while, the oil inside the puffing material will be dissolved in solvent, and then flow out mixed oil. Third, the mixed oil is boiled and vaporized according to different boiling points of the different substances in mixed oil, so that the solvent and the oil are separated. And the solvent vapor is condensed and recycled after cooling. At last, the dross contains a certain amount of solvent, which can be obtained after dissolving and drying. The volatile solvent vapor in the process of dissolution and drying is also condensed and recycled after cooling.

 

 
Edible oil solvent extraction process flow chart
 

There are ten factors affecting edible oil solvent extraction process:

1. The properties of the puffing material

Take cotton seed for example, before extraction, cottonseed is expected by the flaking, steaming and frying, and extrusion so that the cellular structure of cottonseed is maximum destruction, which can reduce the resistance of oil out of the cell proliferation and improve the efficiency of extraction.

There are four points we should pay attention to:

a. Puffing material particle size should be smaller, but the powder content should not be too high. Generally we require the puffing material’s powder content should be 4% or less (30 mesh). And the surface area of puffing material is as large as possible accordingly require material grain unit weight, which can increase the extraction efficiency.

b. The expansion material should have sufficient and uniform permeability, that is, the more pores in the material, the better.

c. Puffing material to solvent and mixed oil adsorption ability is as small as possible. At the same time, the amount of cotton-shell in the puffing material should not be more than 10%, because the shell in the material embryo can absorb a lot of grease and increase the residual oil in the meal.

d. The puffing material should have certain strength and cannot be foamed by the solvent, which requires the quality assurance in the process of steaming and frying and puffing, so as to make the pasting powder as mushy as possible to enhance the strength of the puffing material.

2. The thickness of the puffing material embryo

In the process of embryo rolling, the thicker the slice is, the longer the extraction time is required, which is not conducive to improving the production efficiency and often increases the amount of residual oil in the meal. Therefore, in the process of embryo rolling, we require the thickness of embryo to be 0.25 -- 0.3mm, but not too thin. Otherwise, the puffing material embryo has no strength, which will affect the extraction effect.

3. The controlling of extraction temperature

In edible oil solvent extraction process, the raw material temperature determined according to the distillation process of the solvent is called "extraction temperature".In principle, the higher the extraction temperature is, the less residual oil in the meal. However, the extraction temperature by the solvent boiling point 6 (initial boiling point 60 ℃, 98% distillate temperature 90 ℃), the extraction temperature should be controlled in 50 to 55 ℃ for good. In general, the extraction temperature should be lower than the solvent boiling point 8-10 ℃.

4. The moisture content of the puffing material embryo

In edible oil solvent extraction process, the moisture content of puffing material embryo can’t be too high, or which can influence the dissolution of solvent to oil, also affect the penetration of solvent to material embryo. Besides, before it reacts with the solvent, the material embryo absorbs water and expands into clumps, causing the phenomenon of "bridging" and "short-circuiting" when spraying the solvent. Therefore, please make sure the moisture content of the puffing material is less than or equal to 8%. If the moisture content of the puffing material embryo is too low, the puffing will become difficult, resulting in high powder degree.

5. The permeability of solvent and mixed oil

Continuous edible oil extraction process is mixing solvent and the puffing material embryo quickly, and quickly leave to contact with another group of new puffing material embryo, which makes the oil in the puffing material embryo dissolved as soon as possible to the solvent, and the oil content in solvent will become more and more. Therefore, it is important to accelerate the number of solvent and mixed oil permeable embryos in unit time to improve the extraction effect.

Technically, the permeability is calculated based on how many kilograms the solvent or the mixture of oil flows through the surface of the material embryo in 1 hour and 1 square meter. If the permeability is less than 10.000kg/h·m2, the extraction time should be relatively prolonged, thus reducing the production capacity of the leaching device.

6. The thickness of the leaching layer

As long as the puffing material structure strength high, not easy to be crushed or bubble material layer thicker, the thicker material layer can increase the capacity of the extractor. At the same time, in the same solvent ratio, material layer is thicker, the material layer on the surface of can contact with more solvent, and improve the efficiency of extraction. The material layer thickness of the crawler type leaching device used by us can reach 1000mm.

7. The concentration of the mixed oil

In our extractor, puffing material and solvent is counter-current flow direction. The new entrants to extractor of puffing material mixed with thick oil contact, and soon the hydrolysis of contact with the new fill into pure solvents, which not only can get thicker the mixture of oil, but also minimize the residual oil in the meal. Currently, our blend concentration is required to be between 24 and 28 percent.
 

The loop type extractor in installation process

8. The time of edible oil solvent extraction process

Leaching time is counted from embryo material into to out of the extractor. The length of the leaching time should be according to the type of the extractor, and too long or too short are both not appropriate. We use the caterpillar extractor, including feeding, leaching, drain. The leaching time is about 100 min, and the shortest time is not less than 80 min.

9. The ratio of solvent

Solvent ratio is the ratio of the weight of the leached material embryo to the solvent used in unit time. To ensure the residual oil rate of the meal is less than 0.5%, the solvent ratio should be 1:0.8-1.4.

10. The way to spraying and draining of solvent

Our extraction method is:

Material embryo -- percolation extraction -- drain off -- percolation extraction -- drain off -- the meal

4-7 times spray can minimize the residual oil in the meal.
 

To sum up, whether edible oil solvent extraction process can proceed smoothly and achieve the desired effect depends on many factors, which are complex and interplay. Therefore, we should dialectically grasp and analyze these factors in production to improve our efficiency of edible oil solvent extraction process, reduce leaching time and reduce residual oil in the dregs. If you are interested in our edible oil solvent extraction plant, welcome to inquiry and visit!