Towards a Thermal Optimization of a Methane/Steam Reforming Reactor

Plug-flow reactors are very common in methane/steam reforming applications. Their operation presents many challenges, such as a strong dependence on temperature and inlet composition distribution. The strong endothermic steam reforming reaction might result in a temperature drop at the inlet of the reactor. The strong non-uniform temperature distribution due to an endothermic chemical reaction can have tremendous consequences on the operation of the reactor, such as catalyst degradation, undesired side reactions and thermal stresses. One of the possibilities to avoid such unfavorable conditions and control thermal circumstances inside the reforming reactor is to use it as a fuel processor in the solid oxide fuel cell (SOFC) system. The heat generated by exothermic electrochemical SOFC reactions can support the endothermic reforming reaction. Furthermore, the thermal effects of electrochemical reactions help to shape the uniform temperature distribution. To examine thermal management issues, a detailed modeling and corresponding numerical analyses of the phenomena occurring inside the internal reforming system is required. This paper presents experimental and numerical studies on the methane/steam reforming process inside a plug-flow reactor. Measurements including different thermal boundary conditions, the fuel flow rate and the steam-to-methane ratios were performed. The reforming rate equation derived from experimental data was used in the numerical model to predict gas composition and temperature distribution along the steam reforming reactor. Finally, an attempt was made to control the temperature distribution by adopting locally controlled heating zones and non-uniform catalyst density distributions.