With respect to the reference case, different runs were carried out to explore the
potentiality of the system to generate hydrogen. This was accomplished by
performing 6 more runs where for a given inlet temperature, the mass flow rates
of reactants on both sides of the reactor was progressively increased. The results
are reported in Table 6 and show that it is possible to increase the hydrogen
productivity by properly changing reactants flow rates and or compositions. In
particular, in the first three runs the mass flow rates of the reactants were
increased, doubling from the first to the second and from the second to the third.
Results reported in the Table make evident that the total amount of produced
hydrogen (ṀH2) increases but the trade off is a corresponding decrease of the
methane conversion on both combustion and reforming sides. The fourth run was
carried out with the same inlet molar methane flow rates as the third run but
changing the oxygen fed to the combustion channel from 1.4 to 0.84. In other
words from the third to the fourth run in Table 6 the combustible mixture
composition changes from 40% excess oxygen to 16% defect oxygen. This, as can
be evinced from the form of equation (4), leads to raise the catalytic combustion
rate. As a result XCH4-co, XCH4-sr, Tmax and the total molar flow rate of hydrogen
produced (ṀH2) increase (the latter by a factor 1.27). Further increases of the flow
rates of all the reactants by factors 1.5, 2.5 and 3.12 (in runs 5, 6 and 7 in Table 6,
respectively) with respect to those employed in run 4 lead to decreases of the
methane conversions on both sides of the reactor although ṀH2 increases up to
48% with respect to run 4 (compare rows 4th and 7th). Once again, data in Table 6
show that it is possible to increase the hydrogen production but the trade off is a
corresponding decrease of the methane conversion on both combustion and
reforming sides.