A hybrid reaction system of catalytic methane steam reforming (MSR) and in situ non-catalytic removal Of CO2 by the carbonation of CaO to CaCO3 in a moving bed reactor where reforming catalyst and CaO-based CO2 acceptor in pellets move co-currently with gaseous reactants has been simulated through a mathematical model. The model has been developed at non-isothermal, non-adiabatic, and non-isobaric operating conditions assuming that the rate of the CaO carbonation in a local zone of the reactor bed is governed by kinetic limitation or by the CO2 limitation in bulk gas phase. The effects of major operating parameters such as the feed rates of CaO and CH4, and the reactor bed temperature on steady-state behavior of the hybrid reaction in a moving bed reactor have been determined. It was revealed that the feed rate of CaO for a given feed rate of CH4 should be optimized in order to maximize the utilization degree of CaO carbonated through the reactor while producing the reformed gas in the possible lowest concentration Of CO2 at a given temperature of reaction. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.