Combined Experimental and Numerical Investigation of Linear Driving Force Kinetics in Small Activated Carbon Beds

Abstract

A numerical model has been developed with the intention of better understanding the relationship between flow characteristics and adsorption behavior in small activated carbon beds. The model uses the Dubinin–Radushkevich adsorption isotherm with Linear Driving Force kinetics and has been validated against experimental data for the breakthrough of cyclohexane. Simulations have been carried out varying the inlet flow rate and the adsorption kinetic constant. The adsorption behavior has been analyzed by assessing the furthest point into the bed that a threshold concentration of a contaminant could be seen in the vapor phase. It was seen in all cases that the adsorption was a two-stage process with a rapid initial penetration into a certain bed depth followed by a relatively slow gradual progression of the front through the bed over time. The initial distance penetrated into the bed has been seen to be inversely proportional to the kinetic constant, the same trend as predicted from a plug flow mass balance analysis. The rate of steady front advancement after this showed a slight tendency to increase with decreasing adsorption kinetics, compared to the expected plug flow speed.