The application of reverse flow reactors to endothermic reactions

Abstract

The concept of the reverse flow reactor traditionally used for mildly exothermic reactions has been extended to endothermic reactions and applied to the dehydrogenation of ethylbenzene. Periodic alternation of a reactant and a regenerating medium countercurrently over a fixed bed of catalyst in endothermic processes can be shown to result in higher conversions than traditional non-periodic systems. With this configuration several new process parameters are introduced such as total cycle time and the ratio of countercurrent flows. By judicious choice of operating conditions the hottest point of the reactor can be placed at the exit of the reactant stream allowing for much more favourable equilibriums and outlet conversions than if it were the coldest spot in the reactor as is common in steady-state processes. Two types of modeling are utilized. The first employs a technique which assumes that the switching is so rapid that the temperature distribution in the catalyst is in time independent steady-state. This high switching frequency model is compared against a more complicated time dependent dynamic model which traditionally is employed in reverse flow systems. Results for the first model are shown to be the limiting case of the dynamic model with fast switching. The models show significant conversion improvement with respect to existing steady state processes.