Article,
Diffusion coefficients in bidisperse porous structures
Chemical Engineering Science, (1988)
Abstract
On the basis of theoretical analysis the reason for experimentally
observed differences in effective diffusion coefficients in porous
media when stationary and nonstationary methods are applied to the
measurements has been explained. It has been shown that these differences
appear as a function of the porous structure of the media and are
especially significant for bidisperse porous pellets. In order to
verify the theoretical conclusions effective diffusion coefficients
were measured for five different porous pellets, one monodisperse
and four bidisperse structures using the dynamic membrane method.
The experimental results fully confirm the theoretical conclusion
that the diffusion coefficients estimated from the zero and first
moments of the response curves should be identical and thus equal
to those obtained in the stationary methods. For all bidisperse structures
considered values of diffusion coefficients estimated from the second
moments on the basis of the formula for the monodisperse structure
are lower than the diffusion coefficients estimated from the zero
and first moments, thus fully supporting the theoretical conclusions.
