6YL series screw oil press, its oil extraction process can be divided into three stages, namely feeding (pre-pressing) section, main pressing section (oil outlet section), and cake forming section (heavy pressure and draining section).

BTMA company–6YL series screw oil press

Feeding section: The crushed material starts to be squeezed tightly in the feeding section, air and a small amount of moisture are discharged, plastic deformation occurs to form “muffins”, and oil begins to come out. Oil with high oil content begins to produce oil during the feed compression stage.

Main pressing section: This stage is the stage in which high pressure and large amount of oil are discharged. At this time, due to the rapid and regular reduction of the space volume of the press chamber, the press material is strongly squeezed, and the material particles begin to combine, and the press material becomes a continuous porous substance in the press chamber and is no longer loose, and a large amount of oil is discharged. At the same time, the press material Also due to the interruption of the screw, the scraping force of the press chamber, and the shearing effect of the edges and corners of the press cage, the speed difference displacement, fracture, and mixing of the material layer will be caused, so that the oil passage will be continuously opened, which is conducive to quickly draining the oil.

Cake-making section: The extruded material has formed a tile-shaped cake in the cake-forming section, which is pushed forward almost as a whole, which also produces a large compression resistance. At this time, the compressibility of the tile cake is not great, but it still needs to Keep the pressure high so that the oil can drain without being sucked back. Finally, the tile-shaped cake discharged from the oil press will increase in volume due to elastic expansion.

Studies have shown that a large amount of oil is squeezed out in the first half of the press chamber of the oil press during the pressing process, that is, in the area of the feed section and the main pressing section, which can be obtained from the length of the screw shaft. The change characteristics of the residual oil rate were confirmed. Of course, the oil discharge distributed axially in the press chamber will vary with the oil content of the press material and the structure of the press, but the general hope is that it will appear in the main press section, and the structural design or fabrication is improper. It will cause the oil discharge position to move backward or advance.

During the oil pressing process, the oil content of the cake embryo along the radial layers is different, and the oil content of the inner surface layer is higher than that of the outer surface layer. Decrease the note as the mouth of the pie goes. However, the residual oil rate in the radial layer of the cake discharged outside the machine is just the opposite, that is, the residual oil in the outer layer of the cake is higher than that in the inner layer.

On the one hand,the occurrence of this phenomenon can be considered to be due to the structural characteristics of the screw press: on the one hand, the one-way oil discharge of the cake embryo in the press chamber will inevitably make the oil passage along the surface of the screw shaft longer and difficult to discharge;

On the other hand,the material layer in the front part of the feeding section and the pressing section is thicker, which is easy to produce a gradient of oil content. In the later stage of pressing, the pressed material is compressed and thinned, and at the same time, the water evaporation intensity near the surface of the screw shaft is higher than that of the inner wall of the press cage, so that the grease in the pores of the squeezed material particles is squeezed out.