The fluidized-bed membrane reactor for steam methane reforming: model verification and parametric study

Abstract

A new approach is presented for the modelling of a fluidized-bed membrane reactor (FBMR). The model considers the two-phase nature of the fluidized-bed reactor system and the parallel reactions taking place in stream methane reforming, as well as selective permeation through the walls of membrane tubes immersed in the bed. The model is based on the two-phase bubbling bed model with allowance for some gas flow in the dense phase. Plug flow is assumed for the combined sweep gas and permeating hydrogen flowing through the membrane tubes. Freeboard non-isothermal effects and reactions are also taken into account. The coupled differential equations for the fluidized bed and membrane tubes are solved numerically. The model is in very good agreement with experimental data, both with and without permeation, obtained in a pilot-scale reactor system. Parametric investigations demonstrate the effect of key operating variables and design parameters over a wide range. The model is also tested for its sensitivity to changes in hydrodynamic parameters. Increasing the permeation of hydrogen through the membrane tubes is of key importance in achieving high methane conversions and in minimizing adverse reactions in the freeboard region. Hydrodynamic and kinetic properties have limited influence for the conditions studied.