Hydrogen production via oxidative steam reforming of ethanol in a dense tubular membrane reactor (DMR) is sequentially simulated with ASPEN PLUS. The DMR is divided into multi-sub-reactors, and the Gibbs free energy minimization sub-model in ASPEN PLUS is employed to simulate the oxidative steam reforming of ethanol process in the subreactors. A FORTRAN sub-routine is integrated into ASPEN PLUS to simulate the oxygen permeation through membranes in the sub-separators. The simulation result indicates that there is an optimal length of the tubular membrane reactor at the operating temperature and steam-to-ethanol (H(2)O/EtOH) ratio, under which hydrogen and carbon monoxide formation reach their maxima. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.