Research On Pore Structure And Permeability Of Oil Cake Based On Fractal Geometry

The fractal characteristics of pore structures and the effects of pressing pressure on the pore structures of oil cakes were investigated using oil cakes (dehulled rapeseed cakes, sesame cakes and peanut cakes) formed under uniaxial compression as objects of study. The microstructures of oil cakes under different pressing pressures were measured by using scanning electronic microscope and Image-pro image analyzer. Fractal dimensions of pore section edges and pore size distributions were measured by the slit island process. The empirical formulas of fractal dimensions of pore section edges and pore size distributions as functions of pressing pressure were developed by regression analysis. A fractal permeability for predicting the permeability of oil cakes was developed based on fractal theory integrating Hagen—Poiseulle equation and Darcy law .The fractal permeability model was found to be a function of tortuosity fractal dimension, pore area fractal dimension and the structure parameters of oil cakes. The results showed that the fractal feature of the pore in oil cakes was remarkable, the higher the fractal dimension value, the more irregular the pore section edges ; the fractal dimension increased with the increase of pressing pressure, the linear equations of fractal dimensions as functions of pressing pressures were satisfyingly obtained. The predicted permeability is compared with the available experimental data, and good agreement is found between the present model predictions and available experimental data.