Pd-based membrane steam reformers: A simulation study of reactor performance

Steam reforming of natural gas is the main process for the production of hydrogen and synthesis gas needed in the chemical industry as reactants for the manufacturing of important products, mainly ammonia and methanol. Moreover, the development of fuel cell technology in many application fields (stationary and automotive) will increase in the next years the need of industrial quantities of pure hydrogen.This increasing demand is stimulating the development of new technologies for producing large amounts of hydrogen at low cost. The most promising process is based on the integration of ultra-selective membranes in steam reforming reactor, removing continuously hydrogen from reaction environment and preventing equilibrium conditions to be achieved.In this work the integrated membrane methane steam reformer performance is evaluated by a bi-dimensional non-isothermal non-isobaric model and a comparison with the traditional reformer varying the gas mixture residence time and the wall temperature is made. Results obtained attest the remarkable improvement in the steam reforming reactor by integrating the selective membrane: if a long residence time is imposed (50 kgcat s/mol), the methane conversion is more than doubled in respect to the traditional technology. On the other hand, the increase of the wall temperature improves the performance of both the traditional and the membrane reactor. However, selective membranes have a stringent technological threshold (T<823 K) which limits the thermal level accepted inside the reactor.