Study of effectiveness factors with non-uniform catalyst distributions for methane steam reforming

Abstract

In the present work, three kinetic expressions for methane steam reforming with different methane and water partial pressures dependence were studied. Methane effectiveness factors were simulated for spherical uniform pellets (those customarily employed), for several temperatures and water/methane ratios (hereafter called R). It was found that all effectiveness factors decreased with temperature as expected for all the kinetics expressions studied. On the other hand, the evolution with R was strongly dependent on the kinetics analyzed, with an important change in effectiveness factors values, ranging from 30 to 400%. This implies that the most convenient active sites distribution might be dependent on R evolution throughout the reactor. Then, two MSR reactors were simulated, loaded with pelletized catalysts with uniform and eggshell in order to get uniform nomenclature active site distributions. It was found that the one loaded with eggshell in order to get uniform nomenclature pellets saves up to 30% catalysts mass with respect to the uniform catalyst distribution for the same CH4 conversion, reinforcing the importance of active sites distribution.