BREAKTHROUGH CURVES FOR FIXED-BED ADSORBERS - QUASI-LOGNORMAL DISTRIBUTION APPROXIMATION

The quasi-lognormal distribution (Q-LND) approximation was used to pre dict breakthrough curves in fixed-bed adsorbers for a linear adsorptio n system with axial dispersion, external film diffusion resistance, an d intraparticle diffusion resistance for slab; cylindrical-, and spher ical-particle geometries. The exact solution and parabolic profile app roximation were also obtained for different particle geometries. Numer ical results show that the Q-LND approximation is a simple and handy s olution. It predicts breakthrough curves with an accuracy comparable t o the parabolic-profile approximation over a wide range of parameters; compared with the fatter, it only takes less than one hundredth the c omputation time and does not have a convergence problem in numerical c alculations. A criterion for the applicability of the Q-LND approximat ion is suggested. The effect of particle geometries on the breakthroug h curves is discussed. A criterion is also provided for the Q-LND appr oximation to explore the conditions where one should consider this eff ect on breakthrough curves.