High-pressure Hydrogen Gas Research Articles

Synchronous photocatalytic benzimidazole formation and olefin reduction by magnetic separable visible-light-driven Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 Nanocomposite

A visible light-responsive magnetically separable photocatalyst Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is fabricated using vanillin as a natural junction under ultrasonic agitation. Structural, morphological, optical, thermal, and magnetic assessments of the as-prepared catalyst are carried out. The photocatalyst successfully drives the simultaneous benzimidazole formation, and olefin hydrogenation with high atom economy under blue LED light and mild conditions. The photocatalytic activity of Pd-g-C3N4-Vanillin@γ-Fe2O3-TiO2 is significantly affected by the γ-Fe2O3:TiO2 weight ratio. PL spectra revealed the effective separation of carriers in the fabricated catalyst promoting its photocatalytic activity. The action spectra using the apparent quantum efficiency (AQE) exhibited the maximum AQEs at 520 and 750 nm in which the highest performance for styrene hydrogenation is observed. The title magnetically separable heterogeneous photocatalyst provides high yields of products under perfectly safe visible light, produces low/zero waste, and avoids using an external high-pressure hydrogen gas source, harmful solvents, undesirable additives, and reducing agents rendering green conditions for chemical reactions.

Effects of hydrogen blending ratios and CO2 on hydrogen embrittlement of X65 steel in high-pressure offshore hydrogen-blended natural gas pipelines

In this study, the effects of hydrogen blending ratios and high CO2 content on hydrogen embrittlement (HE) of offshore natural gas X65 pipeline steel were investigated. In high-pressure hydrogen gas, the impact of hydrogen content on yield strength and tensile strength was minimal. However, the effect on elongation was more significant, with the area decreasing and the HE index increasing until the hydrogen-blended ratio approached 30%, at which point the HE index reached 8.94%. Introducing CO2 into high-pressure hydrogen-rich gas further increased the HE index with high CO2 content. At 40% CO2, the HE index was 2.42 times higher than in high-pressure hydrogen-blended mixtures (30% H2). Additionally, the local fracture morphology transitions from ductile to quasi-cleavage fracture with the addition of CO2 and H2.

Underground Hydrogen Storage: Comparison of High-pressure Hydrogen, Liquid Hydrogen, and Ammonia

One of the alternatives for effective storage of irregularly produced renewable energy is hydrogen energy. In order to realize a hydrogen-based society, not only environmentally friendly production of hydrogen but also effective storage is very important. Underground hydrogen storage technology is a technology that has evolved from the technology for storing natural gas underground, and includes waste gas fields, salt domes, aquifers, and rock cavities. When stored underground, hydrogen is converted into high-pressure gaseous hydrogen, liquefied hydrogen, and ammonia. Liquefied hydrogen requires extremely low storage temperatures, and ammonia is a toxic substance that requires separate handling, and energy loss occurs during the conversion process. To compensate for this, research on liquefied hydrogen, such as multilayer insulation technology, is being conducted. Ammonia has successfully extracted high-purity hydrogen by developing a membrane reactor. Ammonia toxicity can be prevented by strengthening leak detection and blocking facilities. Among these, ammonia was found to be the most suitable for underground storage in terms of economic feasibility, environment, and commercialization.

Pore coarsening mechanism during hot rolling induced by hydrogen gathering in Al-Mg alloy

A novel mechanism for pore coarsening during hot rolling was proposed that the hydrogen in the ingot, driven by non-uniform hydrostatic pressure, accumulates into the tortuous shrinkage cavities at the thickness center of the slab. High pressure hydrogen gas gradually changes the stomatal curvature and finally leads to pore coarsening.

SYNTHESIS AND APPLICATION OF PHOSPHINITE LIGAND-CONTAINING RUTHENIUM CATALYSTS IN TRANSFER HYDROGENATION

Transfer hydrogenation (TH) is a highly significant reaction in organic chemistry, especially in the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. This method involves the transfer of hydrogen from a donor molecule to an unsaturated substrate, offering a safer and more convenient alternative to direct hydrogenation, which typically requires high-pressure hydrogen gas. TH stands out for its ability to selectively reduce multiple functional groups under milder conditions, thereby reducing the risk of overreduction or damage to sensitive functional groups. This technique is particularly valuable in asymmetric synthesis (AS), where chiral catalysts enable the production of enantiomerically pure compounds, crucial for drug development.Ruthenium complexes are particularly noteworthy for their effectiveness in asymmetric TH. Their stability and adaptability to different reaction environments make them ideal for both laboratory-scale and industrial applications. Phosphinite ligands (P(OR)R'2) are used in synthesis of complexes to improve their properties. These ligands are known for their ability to finely tune the electronic and steric properties of metal centers. The electron-donating nature of the phosphorus atom, combined with the variability in the R and R' groups, allows for significant customization of the catalyst's properties.The purpose of the work is to review up-to-date discoveries in the field of TH.The integration of phosphinite ligands into ruthenium catalysts marks a significant advancement in the field of TH. These catalysts exhibit enhanced efficiency, selectivity, and stability, proving crucial in AS. The study's exploration of various hydrogen sources, bases, and mechanisms has provided deeper insight into the process of TH.

Tensile testing in high-pressure gaseous hydrogen using the hollow specimen method

Metallic materials, predominantly steels, are the most common structural materials in the various components along the hydrogen supply chain. Ensuring their sustainable and safe use in hydrogen technologies is a key factor in the ramp-up of the hydrogen economy. This requires extensive materials qualification, however, most of the accepted; and standardized test methods for determining the influence of gaseous hydrogen on metallic materials describe complex and costly procedures that are only available to a very limited extent worldwide. The hollow specimen technique is a simple, rapid, and economical method designed to overcome the limitations of the current methods for the qualification of metallic materials under high-pressure hydrogen gas. However, this technique is not yet standardized. The TransHyDE-H2Hohlzug project is presented in this article, along with the main steps required to optimize the hollow specimen technique. This includes closing knowledge gaps related to the specimen geometry, surface quality, and gas purity in dedicated working packages, thus contributing to a comprehensive standardization of the technique for tests in high-pressure hydrogen gas.Impact statementThe hydrogen economy is considered a key solution for achieving climate neutrality in Europe, as it plays a crucial role in the decarbonization of sectors such as transport, industry, power, etc. Ensuring the safety and reliability of infrastructure is crucial for the ramp-up of the hydrogen economy. Therefore, it is necessary to meticulously study the materials and components used for infrastructure under conditions that closely resemble in-service conditions. The currently standardized methods are limited as they do not precisely replicate in-service conditions, and when they do, they are often complex, costly, and not easily accessible. This article presents the hollow specimen technique, a simple, and economical method developed to address the limitations of current standardized methods. The results from this work will contribute to the standardization of this technique for tests in high-pressure hydrogen gas. This will enable a faster evaluation of materials for hydrogen applications by industry and academia, thereby contributing to the growth of the hydrogen economy.Graphical abstract

A structural mechanics analysis on a Type IV hydrogen storage tank during refueling and discharging

High-pressure hydrogen gas, as a power generation fuel widely used in transportation, has significantly contributed to the development of hydrogen fuel cell electric vehicles. However, obvious temperature rise and drop during fast refueling and discharging cause serious safety risk to the structural stability of on-board hydrogen storage tank. The American Society of Automotive Engineers SAE J2601 and the international standard ISO 15869 strictly stipulate that the operation temperature range of hydrogen storage tank varies from −40 °C to 85 °C. In this study, a finite element mechanics model was constructed using ACP and Static Mechanical software to better understand the deformation, stress, strain, and failure modes experienced by a Type IV tank during charging and discharging. Detailed parameters such as ply angle, ply thickness, mesh generation, and boundary conditions, were extensively elucidated. The results indicate that the high temperature and pressure generated during fast fueling of the storage tanks are less likely to cause yield failure of the inner, outer layers and plug, but the stress concentration caused by low temperature and high pressure may lead to the fracture rupture of internal polyethylene materials. Aluminum alloy plug, serving as sealing devices for the tank, are most susceptible to yielding failure under coupled conditions. The mechanical load reaching the yield stress of the plug is approximately 85 MPa with the nominal working temperature of 85 °C. Additionally, the maximum stress on the outer layer can be reduced by adjusting the circumferential layer direction from 90° to 70° or by optimizing the orientation of the maximum stress layer increasing it by 110°. The present study can offer new insights into the dynamic loading behavior of the Type IV tanks during fast charging and discharging, and may provide technical references for optimization design of the tank structures.

Hydrogen Embrittlement Detection Technology Using Nondestructive Testing for Realizing a Hydrogen Society.

Crack detection in high-pressure hydrogen gas components, such as pipes, is crucial for ensuring the safety and reliability of hydrogen infrastructure. This study conducts the nondestructive testing of crack propagation in steel piping under cyclic compressive loads in the presence of hydrogen in the material. The specimens were hydrogen-precharged through immersion in a 20 mass% ammonium thiocyanate solution at 40 °C for 72 h. The crack growth rate in hydrogen-precharged specimens was approximately 10 times faster than that in uncharged specimens, with cracks propagating from the inner to outer surfaces of the pipe. The fracture surface morphology differed significantly, with flat surfaces in hydrogen-precharged materials and convex or concave surfaces in uncharged materials. Eddy current and hammering tests revealed differences in the presence of large cracks between the two materials. By contrast, hammering tests revealed differences in the presence of a half size crack between the two materials. These findings highlight the effect of hydrogen precharging on crack propagation in steel piping and underscore the importance of early detection methods.

Study on low cycle fatigue properties of Cr-Mo steel in 50 MPa gaseous hydrogen

At present, a lack of fatigue design curves for Cr-Mo steel in high-pressure gaseous hydrogen worldwide impedes the use of the design fatigue curve (S-N curve) evaluation for vessel fatigue design, necessitating reliance on fracture mechanics methods related to the initial crack size. In this study, strain-controlled fatigue tests with a strain ratio of −1 were carried out in 50 MPa gaseous hydrogen to study the low cycle fatigue properties of Cr-Mo steel. Results indicate that hydrogen reduces the fatigue life of 4130X under high strain amplitudes. Under 0.5 % strain amplitude, different from characteristics of ductile fracture in air, the fracture in 50 MPa gaseous hydrogen showed quasi-cleavage and intergranular fracture characteristics. Based on the test results, the S-N curve in 50 MPa gaseous hydrogen was obtained with fatigue life safety factor 20 and stress amplitude safety factor 2. The S-N curve in 50 MPa gaseous hydrogen is under the curve in KD-320.2 M of the 2023 ASME Boiler & Pressure Vessel Code VIII-3, which does not consider the effect of hydrogen, when the number of cycles to failure is less than 1×106. This indicates that the fatigue life calculated by the S-N curve in KD-320.2 M cannot ensure that 50 MPa high-pressure hydrogen storage vessels avoid fatigue failure under high stress amplitudes.

Experimental Study on the Influence of Ignition Position on the Overpressure of Hydrogen Jet Flame.

The accidental leakage of hydrogen poses a significant barrier to the widespread adoption and development of hydrogen energy due to the potential risks of fire, explosion, and jet fire hazards. Experimental investigations have been conducted on the process of jet fires formed by igniting hydrogen jet streams after accidental releases in scenarios such as high-pressure hydrogen gas storage tanks and hydrogen transmission pipelines. These experiments utilized a release pipe with a diameter of 10 mm and a length of 0.75 m, along with three pressure sensors, to study the influence of release pressure and ignition position on jet flame overpressure and flame propagation. Extensive tests at 1.5 MPa yielded a hydrogen flammability map containing two nonflammable zones and one flammable zone, along with a graph illustrating the relationship between overpressure and ignition points. Furthermore, experiments conducted at ignition positions of 0.05, 0.5 and 1.0 m under release pressures ranging from 6 to 10 MPa revealed that release pressure had no significant effect, while ignition position notably influenced the waveform and peak of the shockwave. Additionally, a peak shockwave reaching 30 kPa was observed at the downstream of the pipe outlet when ignited at 0.05 m, far exceeding the threshold of 24 kPa associated with fatalities. This research aims to provide valuable insights for safety design and protection distance considerations in scenarios involving hydrogen release and ignition.

Fatigue investigations of elastomers developed for high-pressure hydrogen gas environments

Hydrogen possesses many characteristics to be an ideal candidate as a more sustainable energy carrier, especially for the transport sector. For a proper optimization of this abundant resource, hydrogen needs to be compressed, and stored in high-pressure conditions, which demands improvement in technology and the development of appropriate materials. In this context, elastomeric sealing components play a critical role and they need to withstand harsh working conditions, for example, high-pressure, wide temperature range, cyclic exposure conditions, etc. In this work, eight different grades designed for this application were analyzed in terms of fatigue behavior and long-term performance. This was verified through fatigue crack growth experiments, the energy dissipation, and temperature increase during crack propagation were analyzed and correlated with micro-structural differences of materials. Furthermore, the materials were investigated at large and small deformations through uniaxial tensile tests and Dynamic Mechanical Analysis (DMA), respectively. It was found that only with the addition of a coupling agent can silica-filled NBR have properties similar to carbon black (CB) filled NBR, despite a reduction in both fatigue strength and energy dissipation. Coupling agents also involved an increase in bound rubber. Regarding CB-filled compounds, with peroxide crosslinking a reduction in fatigue strength was found, while no effect on the quantity of bound rubber was observed. Increased CB content in NBR grades led to decreased fatigue resistance and higher energy dissipation; higher bound rubber content was found as well. Also for EPDM grades, increased CB content resulted in reduced fatigue resistance. Despite an increase in energy dissipation, the content of bounded rubber was the same even with higher CB content.

Study on the mechanical properties of X80 pipeline steel under pre-charged high-pressure gaseous hydrogen

Hydrogen embrittlement (HE) is a significant challenge to the safe operation of hydrogen-blended natural gas pipelines. The mechanical properties of X80 steel were studied after H2 pre-charging followed by mechanical properties tests and fracture morphologies observation. Results indicated that the hydrogen saturation time of X80 steel was roughly 48 h. H2 pre-charging induced a decline in strength, plasticity, and fatigue properties, while hydrogen-assisted fatigue crack growth occurred during the early stage of fatigue crack growth rate tests. Additionally, the fracture morphologies transited from primary microvoid coalescence to a mixed mode characterized by ductile dimples and quasi-cleavage planes with increasing hydrogen. The HE susceptibility increased with increasing hydrogen partial pressure and decreasing loading frequency, but there existed a critical value (6 × 10−7 s−1) for the strain rate effect on the HE susceptibility. Under H2 pre-charging conditions, the predominant HE mechanism was the hydrogen-enhanced local plasticity (HELP) mediated hydrogen-enhanced decohesion (HEDE) mechanism.

Experimental and molecular dynamics study of the hydrogen embrittlement behavior of X52 steel: Analysis of abnormal hydrogen embrittlement susceptibility

The hydrogen embrittlement (HE) susceptibility of the X52 pipeline steels in simulated hydrogen-blended natural gas (HBNG) environments were investigated with a combination of in situ high-pressure gaseous hydrogen permeation tests, slow strain rate tensile (SSRT) tests and molecular dynamics simulation, the results were compared with the X80 steel. The HE susceptibility of the X52 steel was found higher than that of the X80 steel. The mechanism of the two steels showing different HE susceptibility was analyzed from a point of permeation parameters and molecular dynamics simulation. The results showed that the X52 steel contained more impurity elements and a larger grain size, leading to a higher hydrogen solubility and a microstructure with lower HE resistance. This study suggests that the steel microstructure and the hydrogen permeation property are crucial for the understanding and prediction of the HE susceptibility of the steels.

Studies on the safe application techniques of high-pressure hydrogen gas

Abstract Hydrogen is expected to be a clean next-generation energy source. Although hydrogen technologies such as FCVs have already reached the practical stage, hydrogen energy has not yet been fully utilized. One of the reasons for this may be that many people feel that hydrogen gas is dangerous. Now the development of safe technologies such as hydrogen storage materials is progressing. However, hydrogen is still stored and used as high-pressure gas in FCVs and supply stations. Hydrogen gas is certainly highly flammable and explosive. However, it can be used as safely as any other fuel, when it is properly managed and operated. To popularize the use of hydrogen energy, it is very important to correctly recognize the properties of hydrogen gas and take appropriate safety measures. In this paper, analysis of past hydrogen gas accidents, simulations of gas flow during the leak accident, damage of structures caused by explosion tests, and effective safety measures technologies for these accidents will be shown.

Effects of structure parameter and material property on thermal performance of on-board hydrogen storage tanks during fast refueling

As a power generation fuel, high-pressure hydrogen gas is widely used in transportation, and significantly contributed to development of hydrogen fuel cell electric vehicles. However, obvious temperature rise generated during fast refueling causes serious safety risk to reliable operation of fuel cell stacks. Therefore, it is necessary to conduct in-depth research on fast filling process. Based on safety reasons, the SAE J2601/ISO 15869 strictly regulates the maximum temperature limit of 85 °C in specifications for refueling hydrogen gas tanks. In this study, a 70 MPa, Type IV on-board hydrogen storage tank is adopted as the research object, and a 2-dimensional axisymmetric numerical model is established to study the temperature rise of the vapor within storage tanks during fast refueling. The Realizable k-ε turbulence model is employed to simulate high intensity turbulent fluctuation during fast filling. Considering the compressibility of vapor, the state of equation for real hydrogen gas is used by obtaining fluid thermodynamic properties from the National Institute of Standards and Technology database. Three groups of fast filling experiments are selected to validate the developed numerical model. The comparison result shows that the numerical model has good prediction ability on hydrogen fast refueling. The final mass average temperature differences between numerical results and experimental data are 2.6 K, 4.3 K, and 0.03 K, respectively. Based on the developed numerical model, the influences of structure parameters and material properties on the temperature rise of hydrogen storage tanks are investigated. The results indicate that the inlet diameter and wall thickness of the inner and outer layers of the storage tank have weaken impacts on the temperature rise during rapid charging, with the maximum temperature differences of 1.8 K, 0.74 K, and 0.54 K, respectively. Due to the influence of heat capacity, the material properties of different layers exhibit a similar variation trend. This work can deepen researchers' understanding of the temperature rise of on-board hydrogen storage tanks during fast filling, and provide technical references for the structural optimal design of tanks and rapid refueling at hydrogen stations.

The study of the crystallinity effect on the structural change of nylon 11 exposed to high-pressure hydrogen gas

This study was specifically focused on how different degrees of crystallinity affect the structural changes in crystalline polymers when exposed to high-pressure hydrogen gas. Four nylon 11 samples with different crystallinities were prepared and subsequently exposed to 90 MPa hydrogen gas for one day, followed by rapid decompression.The differences in structure before and immediately after exposure, as well as the structural recovery process over approximately several days, were investigated mainly by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). For all nylon 11 samples, the WAXD results indicated increased crystallinity due to exposure, while the SAXS results indicated void formation during the depressurization process. The SAXS results also indicated that the voids gradually shrank with time after decompression and that the time dependence of shrinkage was strongly correlated with crystallinity.

Hydrogen diffusivity, uptake and embrittlement of solution annealed and cold deformed austenitic stainless steel 1.4435 at hydrogen pressures up to 1000 bar and 200 °C

Austenitic stainless steel 1.4435, a candidate material for high-pressure tubing for hydrogen applications, was investigated in two different stages of cold deformation (0 and 27 %) regarding its hydrogen embrittlement tendency. The determination of effective diffusion coefficients revealed slightly increased diffusion kinetics at 60°C for the cold-reduced material (8.0 · 10−15 m²/s) compared to the solution annealed one (5.0 · 10−15 m²/s). High-pressure gaseous hydrogen charging shows no differences regarding the degree of cold deformation with a maximum hydrogen concentration of 112 wt.-ppm. Furthermore, a significant ductility loss expressed by the ratio of the reduction of area was observed.

A comparison of vintage and modern X65 pipeline steel using hollow specimen technique for in-situ hydrogen testing

The transition toward a hydrogen-based economy requires a widespread transport and distribution network, and repurposed natural gas pipelines are a viable option. An assessment of the hydrogen-induced degradation of pipeline steels is needed to inject H2 gas into the existing infrastructure safely. The conservative and standardized method consists of in-situ tensile tests in an autoclave filled with high-pressure hydrogen gas. A proposed alternative method involves using a hollow specimen as containment volume and applying the gas pressure in the inner cavity. This technique has lower costs and shorter test preparation time but is not standardized yet. This study aims to evaluate and compare the tensile properties of API 5L X65 pipeline steel in two states: vintage and modern. The influence of the surface roughness is investigated through parallel tests with drilled and reamed specimens. Hydrogen tests are compared with reference tests in an inert environment. A significant hydrogen-induced decrease in tensile properties is observed, and no significant difference between vintage and modern X65 can be drawn. The reduction in tensile properties is more significant in specimens with higher inner surface roughness. The evaluation of surface conditions appears crucial when assessing the HE susceptibility of hydrogen transport and storage equipment.

Real-time energy management strategy of the hydrogen-coupled microgrid based on Informer model prediction results and deep reinforcement learning

Abstract Microgrids (MG) powered by emerging distributed energy resources (DERs) are increasingly pivotal in driving the decarbonization of the power system. Due to the uncertainty of renewable energy sources, electricity generated from wind and solar is typically stored, either in batteries or in the form of high-pressure hydrogen gas within hydrogen storage tanks to meet the refuelling requirements of fuel cell vehicles (FCVs). For FCVs, the substantial operational expenses associated with hydrogen refuelling stations pose a significant barrier to their widespread adoption, with a notable portion of these costs attributed to hydrogen transportation. To address this challenge, this paper employs the Informer model based on a transformer for day-ahead prediction of photovoltaic power generation, as well as load demand forecasting. Subsequently, the Twin-delayed deep deterministic (TD3) policy gradient algorithm is used for real-time energy management of the microgrid. While ensuring that the State of Charge (SOC) remains above 45% daily to meet future hydrogen demands, the MG pursues an optimal strategy to minimize the total daily cost, including electricity procurement, carbon emissions and equipment degradation. Compared to outcomes derived from rule-based approaches, the algorithm introduced in this paper minimizes solar waste and equipment degradation, facilitating hydrogen production during low-cost electricity periods and enhancing economic feasibility.

Numerical Simulation and Consequence Analysis of Full-Scale Jet Fires for Pipelines Transporting Pure Hydrogen or Hydrogen Blended with Natural Gas

The use of existing natural gas pipelines for the transport of hydrogen/natural gas mixtures can achieve large-scale, long-distance and low-cost hydrogen transportation. A jet fire induced by the leakage of high-pressure pure hydrogen and hydrogen-blended natural gas pipelines may pose a severe threat to life and property. Based on the Abel–Nobel equation of state and a notional nozzle model, an equivalent pipe leakage model is established to simulate high-pressure pipeline gas leakage jet fire accidents. Large-scale high-pressure hydrogen and natural gas/hydrogen mixture jet fires are simulated, showing the jet impingement process and obtaining an accurate and effective simulation framework. This framework is validated by comparing the simulated and experimental measured results of flame height, flame appearance and thermal radiation. Several combustion models are compared, and the simulated data show that the non-premixed chemical equilibrium combustion model is superior to other combustion models. The influence of the pipe pressure and the hydrogen blending ratio on the consequences of natural gas/hydrogen mixture pipeline leakage jet fire accidents is explored. It is found that when the hydrogen blending ratio is lower than 22%, the increase in the hydrogen blending ratio has little effect on the decrease in the thermal radiation hazard distance.