Numerical simulation of toluene adsorption on activated carbon in a technical column in low concentration range

Abstract

This paper deals with the modeling of toluene adsorption in a technical column of activated carbon in a low concentration range (2.6 to 3.4 · 10-3 kg/m3), which is usual for environmental applications. It is also concerned with methods of numerical solutions of the nonlinear partial differential equations (PDE), a modified control volume method was used to determine the PDE. Three nonequilibrium isotherm models are developed to describe mass transfer in a fixed bed of activated carbon (Degussa WS-4). The important parts of this paper are the simulation of the maldistribution of concentration and loading of the pollutant in the technical column, as a result of the flow velocity maldistribution and the study of the mass transfer mechanisms in a technical fixed bed. It is found that in a low concentration range, toluene adsorption in a fixed bed of activated carbon (Degussa WS-4) is an external rate-controlled process, thus surface diffusion cannot be neglected. The calculated results are in good agreement with the experimental ones. The measured effect of an earlier breakthrough near the wall-near zone has been calculated using the model.