Research On Physical Characteristics Of Micro-proe Structures And Permeability Of Three-dimensional Dynamical Screw Pressed Vegetable Oilseed Residues

On the basis of existing studies on the one-dimensional cold pressing of vegetable oilseeds, the three-dimensional dynamical screw pressing of rapeseed and peanut kernels was studied for the physical characteristics reflected by the oilseed residues during pressing, and the following work was done:1. Based on existing pressing theories and the pressing theory previously studied by the research team, the three-dimensional dynamical screw pressing theory for vegetable oilseeds was proposed. With an understanding of the physical characteristics of vegetable oilseeds in the oil press, a corresponding mathematical model for pressing was established and solved.2. The pressure in the pressing chamber was determined by opening a hole on the cage bar of a SSYZ120/12 twin-screw oil press and installing a high temperature melt pressure sensor. An experimental stress analysis was conducted. A strain gauge was pasted onto the outer surface of the cage bar to determine the strain data for the bending deformation caused in the pressing process of the cage bar, and the stress value was obtained through calibration. This method can accurately determine the radial pressure distribution in the chamber in the pressing process of vegetable oilseeds.The relative error of rapeseed crushing and peanut press between stress high-temperature melt pressure sensor measured value and measurement method strain gauge measured were 18.85%, 11.52%.3. A scanning electron microscope, industrial computerized tomography, image-Pro Plus image analysis software were used to analyze the microstructures of rapeseed and peanut kernel residues after three-dimensional dynamical screw pressing. The experimental data were based on to establish an empirical formula for the change in the porosity of oilseed residues with the change in the pressing pressure during the three-dimensional dynamical screw pressing.4. The fractal characteristics of the pore structures of oilseed and peanut kernel residues were studied based on fractal theory. The slit island method and the box-counting method were used to calculate the fractal dimension of the pore boundary and pore size distribution of the binary image of the oilseeds residues under three-dimensional dynamical screw pressing, and the regression analysis method was used to obtain the empirical formulas for fractal dimension and pressing pressure.5. Based on Darcy’s law and the Hagen-Poiseuille equation, parameter correction was made of the maximum pore cross-sectional area for the maximum pore diameter of the Hagen-Poiseuille permeability equation to obtain the permeability fractal model of vegetable oilseed residues. The fractal principle was combined with permeability, further revealing the micro characteristics of vegetable oilseed residues under three-dimensional screw pressing.