Modeling and optimization of a novel membrane reformer for higher hydrocarbons

A novel circulating fast fluidized-bed membrane reformer efficiently carries out simultaneous steam and oxidative reforming of heptane over nickel catalysts. A plug-flow reactor model was developed to investigate effects of the operating parameters. The cases with palladium hydrogen membranes and/or dense perovskite oxygen membranes are investigated. The simulations show that high purity hydrogen can be efficiently produced using hydrogen membranes, which "break"the thermodynamic equilibrium barriers. The perovskite oxygen selective membranes supply oxygen along the length (or height) of the reformer for oxidative reforming of hydrocarbons, providing the heat necessary for the highly endothermic steam reforming reaction. The combination of these two membranes with the characteristics of the fast fluidization reformer makes this process not only an efficient hydrogen producer but also an energy efficient process. The fast continuous flow of catalyst makes the effect of carbon deposition on catalyst activity negligible in the novel process. Process optimization for the maximum hydrogen yield is conducted using the flexible tolerance optimization method.