Study of the efficiency of monolithic activated carbon adsorption units.

Although the use of activated carbons as a purification step in the treatment of gaseous effluents from industrial plants is a well established technique, when large volumes of gas need to be treated pressure drop limitations may arise from the use of conventional adsorption beds. For these applications the conformation of the adsorption bed as honeycomb monoliths with high activated carbon content take advantage of the almost null pressure drop of these open channel structures and significantly improves the handling characteristics. In this study a commercial activated carbon was conformed as a ceramic monolith using a natural magnesium silicate as the agglomerating agent. The adsorption studies employed ortho-dichlorobenzene (o-DCB) as a probe molecule, since it can be considered as representing approximately half a molecule of tetra-chloro-dibenzene-dioxin (TCDD) the most toxic isomer of the dioxin family. It has been shown that the dynamic adsorption capacity of these units at 30 degrees C was equivalent to the micropore volume. However, in industrial applications the adsorption step should take place at higher temperatures so that the gases exiting from the chimney rise rapidly into the upper atmosphere. Thus, the adsorption capacities of these units were determined over a range of temperatures from 30 degrees C to 150 degrees C at linear gas velocities between 0.3m.s(-1) to 2m.s(-1). The effects of variation in the monolith geometry: overall length versus gas linear velocity, on the dynamic adsorption capacity were studied in order to predict the optimum monolith dimensions depending on the gas flow to be treated.