Techno-economic assessment of membrane reactor technologies for pure hydrogen production for fuel cell vehicle fleets

In the evolution toward a "carbon-neutral" energy economy, among the most promising solutions for replacing today's greenhouse gas (GHG)-emitting vehicles is the use of hydrogen as an energy carrier. In the pathway toward a future infrastructure based on renewable energy sources, a medium-term step would rely on the use of fossil fuels for on-site production of hydrogen, feeding small fleets of fuel cell vehicles. Great interest is on natural gas as a primary source because of its high hydrogen/carbon ratio. State of the art technology for the production of hydrogen from natural gas includes a series of reacting steps typically involving steam reforming (at 800 C or above), a water-gas shift reactor, and a final purification of hydrogen through pressure swing adsorption (PSA). An alternative that has been the subject of growing interest is the use of thin (2-50 μm thick) Pd-alloy materials as hydrogen perm-selective membranes for the embedded extraction of pure hydrogen from the chemical reactor; this system is usually known as the "membrane reactor". This paper studies the adoption of palladium-based membrane reactor technologies for pure hydrogen production from natural gas. In particular, three system layouts are analyzed and compared to the traditional option: (i) autothermal reforming membrane reactor, (ii) steam reforming membrane reactor (externally heated), and (iii) water-gas shift membrane reactor downstream of a steam reformer. The comparison is made in terms of performances and techno-economic considerations for the design of compact systems for on-site production of hydrogen at filling stations. The systems are designed for 50 m3/h (1766 cfh) of hydrogen, which corresponds to refilling 25 vehicles a day with 4 kg of hydrogen (approximately 418 km driving range on fuel cell vehicles with a 70 MPa storage tank).