Unsteady convective diffusion in an annular catalytic reactor

Abstract

A theoretical treatment of transient dispersion in an annular reactor with catalytic walls is developed. From fundamental considerations, a dispersion equation with time-variable coefficients is derived for the average solute concentration. These coefficients reach asymptotic constant values for large time and results are derived to show their explicit dependence on the system parameters, especially, the kinetic ones. The results show that, in general, in interphase transport systems such as the present one, all the three coefficients in the dispersion equation should be fitted simultaneously to experimental data. However, in contrast to the tubular geometry, it is found that for certain ranges of radius ratios, the dispersion coefficient in the annulus is insensitive to wide variations in the reaction rate parameter; the exchange and convection coefficients still remain sensitive under these conditions thereby making the annulus an attractive geometry for the experimental determination of kinetic parameters. A procedure is suggested for such determination.