# Mathematical Modeling of Screw Press Configuration for Processing Safflower Oil
## 3 Results and Discussion
### Dependence of Oil Content of Saffflower on Screw Rotation Speed and Diaphragm Gap  
Saffflower seeds used for the experimental studies were preliminarily peeled. After finishing the separation of the husk from the kernel, the total protein and lipid fraction of the safflower seed was removed and subjected to pressing. Preliminary separation of the husks from the kernel helps to increase the oil content of the processed oil raw materials [38,39]. The raw material is cleared of low-oil-bearing components and the relative oil content in it increases.  
At the same time, the productivity of the technological equipment increases, because the working volume of machines and devices are not loaded with ballast low-oil-bearing material--the husks. Oil quality increases, because when the husks are removed, husk lipids rich in waves and wax-like substances do not enter the oil [40]. Their presence in oil deteriorates its commodity appearance; a suspension or \"grid\" of small wax crystals appears, which can be removed due to the chemical inertness of waves as a result of the long oil treatment.  
The removal of husks is necessary to simplify the process of pressing, as the mechanical strength of the husks compared to the kernel is quite high and their presence causes not only intense wear and tear of the working bodies of the machines but also reduces the efficiency of their operation [41,42]. However, determining the husk content in the main mass of the product is of great importance in the pressing process. To increase the oil yield, it is possible to use the husk when adding it to the main mass of the product. The presence of husks in the peeled safflower kernels reduces the plasticity of safflower, improves its structure, serves as a drainage factor in oil separation, and helps to reduce the amount of grease in safflower [43,44].  
Oil flowability is related to its viscosity and its ability to crack under plastic deformation, that is, to its elasticity modulus [45,46]. The optimal content of the husk in the seed kernels reduces its plastic properties and improves its composition. Before adding the husks to the oil, it was milled. In the next stage, we analyzed the dependences of the oil content on the velocities and diaphragm gap during the pressing of safflower oil.  
Figure 12: Change of rheological characteristics depending on oil content (\(\varphi\)) and temperature (\(t\)) of safflower cake: (**a**) yield stress; (**b**) plastic viscosity; and (**c**) rate of structure destruction.  
According to Figure 13, the highest value of the oil yield index is determined at a diaphragm gap equal to \(\delta\) = 1.0 mm. As the velocity increases, the difference between the diaphragm gap and the change in oiliness can be noticed. This can be explained by the deterioration of the pressing process under the effect of the incomplete separation of oil because of high velocities (\(\omega\) = 6.8 rad/s, \(\omega\) = 7.3 rad/s) and the highest percentage of husk in the cleaned kernels of safflower seeds N\({}_{3}\) = 10%, N\({}_{4}\) = 15%. The presence of the highest amount of husks, due to their high porosity, in contact with oil can intensively absorb it, and then very strongly retain it (oiled) [47; 48]. As a result, oil losses in production are increased, respectively; this parameter is not optimal.  
From the graph, it is visible that the highest value of oil yield is reached at the diaphragm gap equal to \(\delta\) = 1.0 mm. Analysis of graphic dependences revealed that the optimum content of husk in the cleaned kernels of safflower seeds was N\({}_{2}\) = 5% at the speed \(\omega\) = 6.2 rad/s, which provides the minimum residual oil content and, therefore, the maximum oil yield.  
Figure 13: Dependence of safflower oil content on the diaphragm gap and screw rotation speed. N—husk content.