Performance of an endless-belt counter-current contactor for vapor-phase adsorption: Dispersion and residence time distribution

The residence time distribution and axial dispersion characteristics of an endless-belt countercurrent adsorbent contactor have been studied experimen tally and theoretically using, as a model system, the adsorption of CO2 fro m a N-2 carrier on a silicalite adsorbent. Expressions for the Taylor dispe rsion coefficient, and hence the height equivalent to a theoretical plate ( HETP), as a function of the gas flow rate and belt velocity have been deriv ed (from the general Aris model) and are shown to provide an approximate in dication of the system performance. However, dispersion in the experimental system is increased by mixing in the dead space within the apparatus, maki ng it difficult to test the theory quantitatively. Although diffusion of CO 2 in silicalite is rapid and the adsorbent layer is thin, the influence of mass transfer resistance is still appreciable. The experimental system (len gth of 50 cm) is shown to be equivalent to 5-10 theoretical stages (HETP 5- 10 cm), depending on flow rate and belt velocity.