
A.A. Salamatin
Estimation of Axial Dispersion Effect on the Supercritical Fluid Extraction from Bidisperse Packed Beds
General masterequations of mathematical model for supercritical fluid extraction
are derived within the framework of the continuum mechanics approach. The shrinking
core concept is used to describe the masstransfer on the solidliquid interface. The
complete system of macroscopic differential mass balance equations is reduced to a
onedimensional approximation and accounts for the axial dispersion effect. Correlation
formulas available in literature are used to calculate the axial dispersion coefficient
for the conditions of supercritical CO_{2} filtration. The effect of axial dispersion onto
the characteristics of macroscopic process is analyzed for the typical laboratoryscale
extraction conditions in the framework of the suggested model. The numerical simulations
demonstrate that the difference between the values of current mass of accumulated
extract calculated in terms of the complete approach, which accounts for the axial
dispersion, and the one related to the simplified model (in which the axial dispersion
is neglected) is less than 10 %. The same comparison is made for the outlet
concentrations of the target compounds; the difference reaches 200%.
Key words: supercritical fluid extraction, oil crop, polydisperse packed bed, convective diffusion, dispersion number
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