An existing hydrogen plant is simulated using a rigorous model for the steam reformer, shift converters, CO2 absorber using DGA (Diglycolamine) and the Methanator. The CO2 absorber using DGA along with the methanator modeled in this work replace the PSA (pressure swing adsorption) system used in other studies, making the current study unique in this respect. A close agreement is observed between the results of the modeling and industrial data from the hydrogen plant of the Tehran refinery. Thereafter, an adaptation of the non-dominated sorting genetic algorithm is employed to perform a multi-objective optimization. Simultaneous maximization of the hydrogen product and export steam flow rates are considered as two objective functions. For the design configuration considered in this study, sets of Pareto-optimal operating conditions are obtained. (C) 2010 Elsevier Ltd. All rights reserved.