Introduction

Experimental methodology and modeling approach

Results and discussion

Conclusions

References

Abstract

The novel paradigm of distributed energy production foresees the production of hydrogen from methane and biomasses in small plants, which may take advantage from membrane-based processes. By means of a modeling approach, this paper compares the energy efficiency of two membrane-based processes to produce H2 from methane steam reforming. The two-step process (TS) envisages a high temperature classical reactor and a following WGS stage in a membrane reactor, while the alternative process uses a simple packed-bed membrane reactor (MR). Both processes show a general increase of H2 production and energy efficiency with the pressure and a maximum energy efficiency for S/C of 4, while the increase of the space velocity reduces the performances of the MR. The results show that the TS process performs better than the studied MR and that the maximum energy efficiency of both processes is between 30 and 40%. A comparison with the literature shows that the TS process may achieve similar performances respect to an intensified MR.

Introduction

Following the Paris Agreement (2015), the EU energy policy for next decades till 2050 is focused on security, efficiency and diversification of energy sources in order to cut down the CO2 emissions. Such strategy encourages the use of renewable or low-emission energy sources and also implies the distributed generation of energy [1]. To obtain such targets, the wide use of H2 as an energy vector for different kind of civil final energy uses is foreseen [2,3]. However, so far, such strategy is hindered by the lack of a proper distribution infrastructure [3,4] therefore a solution may be to produce H2 in distributed facilities. Hydrogen can be produced from diverse renewable sources: generally, from renewable energy via water electrolysis, which allows using H2 as energy storage mean [4e8], but also from methane or ethanol via steam reforming; such last processes may be CO2-neutral if the fuels come from biomasses (e.g. bio-methane, bio-ethanol) [9e12]. The purity of H2 generated by steam reforming reactions depends on both the technology used and on the considered feed stocks, therefore a separation step could be required to recover hydrogen from a gas mixture containing also CO2, CO, N2 or water vapor with the desired purity [6,13].