Heat transfer studies in an inorganic membrane reactor at pilot plant scale

The partial oxidation of butane to maleic anhydride over VPO catalyst was used to compare heat transfer in a conventional fixed bed and an inorganic membrane reactor. Three resistances to heat transfer were studied: internal resistance from the inner wall of the reactor to the fluid, heat conduction/convection across the wall and the resistance between the fluid bed and outer wall. The overall heat transfer coefficient measured in the reactor operating as a conventional fixed bed was 100 W/m2 K, which was an order of magnitude greater than that measured in the membrane reactor configuration. This large difference was attributed to the heat transfer resistance between the interior tube wall and the fluid: gas permeating across the membrane tube may have created a boundary layer thus limiting the mixing between the two fluids. Doubling the Reynolds number appeared to improve the heat transfer rate in the membrane reactor substantially, such that it approached the performance of the conventional fixed bed. Based on correlations in the literature, this large improvement in the heat transfer rate was unexpected.