Techno-economic analysis for the design of membrane reactors in a small-scale biogas-to-hydrogen plant

Pd-based membranes are a key-component to obtain high-purity hydrogen from gaseous mixtures. They can be integrated in reactors called Membrane Reactors (MR), where the selective removal of reaction products allows to circumvent equilibrium limitations of traditional reactors. MRs for hydrogen production from methane reforming have been already investigated in literature, where they showed potentialities in small-scale biogas plants. However, analyses have typically been performed fixing many operating conditions and geometrical parameters, while only investigating few of them. It is therefore difficult to generalize the conclusions and to have a clear overview of the process behaviour. This article proves that MR performance can be summarized in generalized performance charts, where it is possible to characterize the reactor and the overall MR-based system only based on the membrane area it contains, for each set of temperatures, pressures, feed composition, catalyst amount and steam-carbon-ratio. From techno-economic analysis, it turned out that LCOH is 6.81 €/kg for a system with 100 kg/day of hydrogen production at 20 bar, reaching 7.49 €/kg if compressed up to 700 bar. System performance have been compared with a traditional reactor followed by a PSA (LCOH = 7.31 €/kg), showing that MR-based solution outperforms benchmark for its higher capacity to separate hydrogen. A sensitivity analysis assessed the influence of major uncertain costs.