Nonuniform Channels in Adsorbent Monoliths

A model is introduced to account for nonuniform channel geometries in monolithic adsorbents. Based on nonisothermal operation, fully developed parabolic flow and the full three-dimensional convection-diffusion equation, the model is applied to the adsorption of dichloromethane from an air stream flowing through a binder-less activated carbon monolith. The equilibrium parameters and the effective diffusion coefficient for adsorption are obtained independently from gravimetric adsorption experiments. The nonuniform channel model is capable of predicting breakthrough curves as a function of feed gas flow rates up to dimensionless breakthrough concentrations of about 0.4-0.6, depending on the feed flow rate. Even though the variation of effective diffusion coefficient with both concentration and temperature has been tested, successful prediction over the whole range of concentration may require the incorporation of further aspects relating to the anisotropic nature of the carbon. (C) 2010 American Institute of Chemical Engineers AIChE J, 57: 1163-1172, 2011