The performance of a novel circulating fast fluidized bed membrane reformer (CFFBMR) is investigated using a reliable mathematical model. The removal of product hydrogen using hydrogen-permselective membranes "breaks" the thermodynamic equilibrium in the reversible system and makes it possible to operate the process at lower temperatures. The oxidative reforming of a part of the feed methane by oxygen input into the reformer using direct feed or through oxygen-permeable membranes supplies the heat needed for the highly endothermic steam reforming of methane. The combination of the exothermic oxidative reforming and endothermic steam reforming not only produces high yield hydrogen but also makes it possible to operate the CFFBMR under autothermal conditions. The novel configuration is a highly efficient hydrogen producer with minimum energy consumption. The simulation results show that the hydrogen productivity (moles of hydrogen produced per hour per m(3) of reactor) of the CFFBMR is about 8 times that in an industrial fixed bed and 112 times that in a bubbling fluidized bed membrane reformer. (C) 2003 Published by Elsevier Science B.V.