Design and Costs Analysis of Hydrogen Refuelling Stations Based on Different Hydrogen Sources and Plant Configurations

In this study, the authors present a techno-economic assessment of on-site hydrogen refuelling stations (450 kg/day of H2) based on different hydrogen sources and production technologies. Green ammonia, biogas, and water have been considered as hydrogen sources while cracking, autothermal reforming, and electrolysis have been selected as the hydrogen production technologies. The electric energy requirements of the hydrogen refuelling stations (HRSs) are internally satisfied using the fuel cell technology as power units for ammonia and biogas-based configurations and the PV grid-connected power plant for the water-based one. The hydrogen purification, where necessary, is performed by means of a Palladium-based membrane unit. Finally, the same hydrogen compression, storage, and distribution section are considered for all configurations. The sizing and the energy analysis of the proposed configurations have been carried out by simulation models adequately developed. Moreover, the economic feasibility has been performed by applying the life cycle cost analysis. The ammonia-based configurations are the best solutions in terms of hydrogen production energy efficiency (>71%, LHV) as well as from the economic point of view, showing a levelized cost of hydrogen (LCOH) in the range of 6.28 EUR/kg to 6.89 EUR/kg, a profitability index greater than 3.5, and a Discounted Pay Back Time less than five years.

Characterization of Pd60Cu40 Composite Membrane Prepared by a Reverse Build-Up Method for Hydrogen Purification

A thin Pd-based H2-permeable membrane is required to produce high-purity H2 with high efficiency. In this study, a porous Ni-supported Pd60Cu40 composite H2-permeable membrane was developed using a reverse build-up method to produce economical H2 purification. The thickness of the Pd60Cu40 alloy layer produced by the improved membrane production process reached 1.0 μm; it was thinner than the layer obtained in a previous study (3.7 μm). The membrane was characterized by scanning electron microscope, inductively coupled plasma optical emission spectrometer, H2 permeation test, and Auger microprobe analysis. The permeation tests were performed at 300–320 °C and 50–100 kPa with H2 introduced from the primary side. The H2 permeation flux was stable up to ~320 °C. The n-value was determined to be 1.0. The H2 permeance of the membrane was 2.70 × 10−6 mol m−2 s−1 Pa−1.0 at 320 °C, after 30 h, similar to those of other 2.2-µm-thick and 3.7-µm-thick Pd60Cu40 composite membranes, suggesting that the adsorption and dissociation reaction processes on the PdCu alloy surface were rate-limiting. The Pd cost of the membrane was estimated to be ~1/30 of the Pd cost of the pure Pd60Cu40 membrane.

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H2/CO2, H2/C2H6, and H2/C3H8, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies.

Assessment of Sieverts Law Assumptions and ‘n’ Values in Palladium Membranes: Experimental and Theoretical Analyses

Palladium and palladium alloy membranes are superior materials for hydrogen purification, removal, or reaction processes. Sieverts’ Law suggests that the flux of hydrogen through such membranes is proportional to the difference between the feed and permeate side partial pressures, each raised to the 0.5 power (n = 0.5). Sieverts’ Law is widely applied in analyzing the steady state hydrogen permeation through Pd-based membranes, even in some cases where the assumptions made in deriving Sieverts’ Law do not apply. Often permeation data are fit to the model allowing the pressure exponent (n) to vary. This study experimentally assessed the validity of Sieverts’ Law as hydrogen was separated from other gases and theoretically modelled the effects of pressure and temperature on the assumptions and hence the accuracy of the 0.5-power law even with pure hydrogen feed. Hydrogen fluxes through Pd and Pd-Ag alloy foils from feed mixtures (5–83% helium in hydrogen; 473–573 K; with and without a sweep gas) were measured to study the effect of concentration polarization (CP) on hydrogen permeance and the applicability of Sieverts’ Law under such conditions. Concentration polarization was found to dominate hydrogen transport under some experimental conditions, particularly when feed concentrations of hydrogen were low. All mixture feed experiments showed deviation from Sieverts’ Law. For example, the hydrogen flux through Pd foil was found to be proportional to the partial pressure difference (n ≈ 1) rather than being proportional to the difference in the square root of the partial pressures (n = 0.5), as suggested by Sieverts’ Law, indicating the high degree of concentration polarization. A theoretical model accounting for Langmuir adsorption with temperature dependent adsorption equilibrium coefficient was made and used to assess the effect of varying feed pressure from 1–136 atm at fixed temperature, and of varying temperature from 298 to 1273 K at fixed pressure. Adsorption effects, which dominate at high pressure and at low temperature, result in pressure exponents (n) values less than 0.5. With better understanding of the transport steps, a qualitative analysis of literature (n) values of 0.5, 0.5 < n < 1, and n > 1, was conducted suggesting the role of each condition or step on the hydrogen transport based on the empirically fit exponent value.

Biphenyl Hydrogenation with Syngas for Hydrogen Purification and Transportation: Performance of Dispersed Catalytic Systems Based on Transition Metal Sulfides

The feasibility of biphenyl hydrogenation with syngas for hydrogen purification and binding with the aim of its transportation was demonstrated. Specific features of the hydrogenation of biphenyl as a promising organic hydrogen carrier using unsupported Ni–Mo sulfide catalysts were studied. In particular, the influence of temperature, reaction time, presence of water in the system, and Н2/СО gas mixture composition on the substrate conversion and selectivity with respect to products was examined. The highest conversion and the maximal hydrogen uptake are reached at 380°С in 6–8 h. The dispersed catalysts are active in biphenyl hydrogenation at the CO concentration in the Н2/СО gas mixture of up to 50 vol %, and H2O can act in this case as an in situ hydrogen source owing to the occurrence of the water-gas shift reaction.