Modeling transient transport through a fixed bed: Comparative study of phenomenological models with and without hydrodynamic dispersion

Abstract

Numerous publications on the transport of pollutants in a fixed bed, in particular in the treatment of waters still use two-parameter models: a capacity parameter measuring the delay of the breakthrough curve (CP) and a transfer kinetics parameter to translate the dispersion observed (Thomas model and Yoon-Nelson model), The authors totally neglect the role of the hydrodynamic dispersion which however largely contributes to the spread of the curves and thus the adjustments made on the analyzed breakthrough curves are invalid, Using three examples involving fixed beds of homogeneous adsorbent beads or sand, one of Lin et al [2013] with biochar-alginate grains (diameter 2.0 mm), the following from Jang et al. [2018] with resin beads (diameter 0.8 mm), and the last of our own work with a clay-limestone quartz sand of mean diameter 0.4 mm (Benaouag et al., 2018) we analyzed the validity of these models, For this we used as reference model a model with 4 parameters (Mixers in Cascade with Exchange) taking into account hydrodynamic dispersion, linear sharing and first-order mass transfer kinetics.