An Enhanced Sherwood Number to Model the Hydrogen Transport in Membrane Steam Reformers

It is well known that membrane reactors are inherently two-dimensional systems in which species concentrations vary as a consequence of both the reaction and permeation across the membrane, which occurs in the direction perpendicular to that of the main gas flow. Recently, an expression for an enhanced Sherwood number was developed to describe the hydrogen concentration gradients arising in methane steam-reforming membrane reactors as a consequence of the combined effect of hydrogen production, dispersion, and permeation. Here, the analysis is developed in further detail with the aim of (i) assessing the validity of the simplifying assumptions made when developing the 1D model and (ii) identifying the operating conditions under which it is possible to employ the 1D model with the enhanced Sherwood number.

Syngas production plus reducing carbon dioxide emission using dry reforming of methane: utilizing low-cost Ni-based catalysts

Applicability of using Dry Reforming of Methane (DRM) using low-cost Ni-based catalysts instead of Conventional Steam Reformers (CSR) to producing syngas simultaneously with reducing the emission of carbon dioxide was studied. In order to achieving this goal, a multi-tubular recuperative thermally coupled reactor which consists of two-concentric-tubes has been designed (Thermally Coupled Tri- and Dry Reformer [TCTDR]). By employing parameters of an industrial scale CSR, two proposed configuration (DRM with fired-furnace and Tri-Reforming of Methane (TRM) instead of fired-furnace (TCTDR)) was simulated. A mathematical heterogeneous model was used to simulate proposed reactors and analyses were carried out based on methane conversion, hydrogen yield and molar flow rate of syngas for each reactor. The results displayed methane conversion of DRM with fired-furnace was 35.29% and 31.44% for Ni–K/CeO2–Al2O3 and Ni/La2O3 catalysts, respectively, in comparison to 26.5% in CSR. Methane conversion in TCTDR reached to 16.98% by Ni/La2O3 catalyst and 88.05% by NiO–Mg/Ce–ZrO2/Al2O3 catalyst in TRM side. Also, it was 15.88% using Ni–K/CeO2–Al2O3 catalyst in the DRM side and 88.36% using NiO–Mg/Ce–ZrO2/Al2O3 catalyst in TRM side of TCTDR. Finally, the effect of different amounts of supplying energy on the performance of DRM with fired-furnace was studied, and positive results in reducing the energy consumption were observed.