Dynamic Simulation of an Autothermal Methane Reformer

A dynamic autothermal methane reformer model has been developed and tested for the production of a hydrogen- and carbon monoxide-rich syngas. This study looks at potential advantages and disadvantages of an autothermal reformer, both operating in stand-alone mode and in conjunction with a high temperature fuel cell stack. The model uses a conservation of moles as the fundamental continuity relationship, and applies basic energy conservation equations to simulate both the gas and the catalyst bed energies. Chemical kinetic expressions using empirical constants for the Arrhenius rate terms that describe steam reformation of methane and partial oxidation of methane are simultaneously solved to provide an accurate picture of the reaction dynamics. This paper presents dynamic responses of reformer outlet temperature, hydrogen mole fraction, reaction rates and methane conversion to the perturbation of the reformer inlet variables of steam-to-carbon ratio, oxygen-to-carbon ratio and inlet gas temperature. Also explored is the concept of catalyst “light-off,” where there is found to be a lower temperature limit above which catalyst activity is substantially increased.