A design study on a flat membrane-reactor stack for on-site hydrogen production

Hydrogen stations face limited accessibility in remote areas despite the increasing demand for fuel cell electric vehicles. On-site hydrogen production using the liquid-fuel infrastructure can improve the accessibility of the stations. This concept integrates a pressurized steam reformer (SR) and a catalytic membrane reactor (MR) to produce high-purity hydrogen. This study builds a stack of scaled-up MRs and extends the stack size to accommodate 45 reactors to design a compact system that produces hydrogen sufficiently and effectively. We compare the performance of two configurations, U-type and Z-type, where the inlet and outlet face the same and different directions, respectively. We also widen the two primary retentate tubes of the stack. With its fixed conditions, this study reveals that performance converges past a particular retentate-tube diameter and declines past a certain number of reactors, with the Z-type outperforming the U-type. These findings are explained by the pressure distribution within the stack, along with the inlet flow rate and the permeation rate of each reactor. Our final Z-type stack demonstrates 99.0 % of the permeation of the individual reactors. The insights from this research provide a valuable methodology for designing large-scale MRs in future studies.