Extraction from a solid with a bidisperse porous structure

A mathematical model is proposed for the process of extraction from a semi-infinite solid containing the pores of two types: large pores that extend to the surface and small pores that are connected to large pores. Effective transport coefficients in two types of pores are assumed to be different. The dependence of the flux of an extractant through the surface of the solid on time is found using the method of fractional differentiation. Theoretical results are compared with experimental data on the kinetics of the extraction of the target components from raw vegetable materials in apparatuses with an intensive hydrodynamic mode.