A steady-state, one-dimensional mathematical model for a multifunctional reactor with in situ adsorption for ammonia synthesis is developed. The model represents integrated ammonia catalytic equilibrium reaction with ammonia adsorption in a co-current gas-flowing solids-fixed bed reactor (GFSFBR). The model was used for simulating the performance of an industrial-scale reactor, which confirmed that the reactant conversion is significantly higher in the multifunctional reactor in comparison to the conventional reactor under optimal conditions. The analysis of the simulation results shows that the conversion in the GFSFBR stays higher than those in the classical reactor even if much lower temperatures and pressures are used. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.