In recent years, many research activities have been carried out on effective use of natural gas. The first step for this process, however, is converting natural gas to synthesis gas (syngas). Natural gas reforming process by means of a reformer furnace is commonly used for syngas and hydrogen production. In this paper a windows-based software, RIPI-RefSim, is introduced. By using rigorous heat, mass, kinetic and thermodynamic models as well as taking into account the effect of catalyst shape, the software has been developed in order to provide reformer furnace simulation for syngas and hydrogen production. RIPI-RetSim can be used in three different modes (rating, simulation and design) and provides a detailed understanding of furnace performance, product characteristics, temperature, reaction rates and pressure drop profiles, effect of catalyst shape, and so on. (C) 2007 Elsevier Ltd. All rights reserved.