Experiments, modeling and scaling-up of membrane reactors for hydrogen production via steam methane reforming

Abstract

Steam methane reforming (SMR), which is endothermic and equilibrium-limited, is an important reaction in syngas production and in hydrogen generation for hydrogen economy. To improve SMR, a process intensification concept using membrane walled reactors is explored in detail here. The simultaneous removal of hydrogen shifts the equilibrium, allowing higher conversion to be realized than in traditional mode without product removal. The paper provides experimental data on kinetics using Ni/Al2O3 catalyst and kinetic models. The membrane permeability is also measured and fitted with Sievert’s law. Using these data, we develop three-dimensional models in the COMSOL Multiphysics platform which include momentum and energy balances, along with multicomponent diffusion effects. Using these detailed models, the paper proposes scale-up strategies. A monolith arrangement with provision for simultaneous heat supply and hydrogen removal is suggested and modeled in detail. The optimum geometric arrangement for the suggested design is examined, and recommendations are made for the proposed reactor design. The design providing the best effectiveness of membrane utilization has a surface area-to-reactor volume ratio of 255 m2/m3—which can be shown to be related to the product of Damkohler and Peclet numbers being close to unity, indicating that the hydrogen production rate matches to permeation.