High Hydrogen Content Research Articles

Study of thermal effects in ammonia-fueled solid oxide fuel cells

Ammonia is regarded as a promising alternative to hydrogen because of its high hydrogen content, ease of transportation and storage, and other favorable properties. However, in ammonia-fueled solid oxide fuel cell (SOFC), the intense heat absorption and excretion of ammonia decomposition and electrochemical reactions can lead to inhomogeneous temperatures inside the cell, which restricts long-life operation. For this reason, a three-dimensional tubular solid oxide fuel cell thermo-electrochemical model is established to explore the thermal characteristics when using ammonia as the fuel. The errors between the power density and voltage obtained from the numerical model and the experimental data in the literature are less than 5 %, which proves the accuracy of the model in this paper. Further parametric simulations reveal that the electrochemical performance and heat production rate are strongly affected by the operating voltage. And a peak power density of 66.4 mW/cm2 is obtained at an operating voltage of 0.45 V. Additionally, increasing the inlet temperature and increasing the fuel flow rate are beneficial for improving cell efficiency, although achieving temperature uniformity remains a challenge. The ammonia pre-reforming degree can be adjusted to effectively improve the temperature distribution uniformity within the cell and improve its internal heat balance. The maximum temperature difference in 96 % pre-reformed SOFC is only 22 K, while it reaches 167 K in direct ammonia SOFC. The temperature and electrochemical performance laws revealed in this study provide a theoretical basis for the optimization of ammonia-fueled SOFC.

Highly air-stable magnesium hydrides encapsulated by nitrogen-doped graphene nanospheres with favorable hydrogen storage kinetics

Severe surface oxidation and sluggish kinetic rates of Mg hydrides (MGHs) are the main bottlenecks for their industrial applications. Herein, we present a strategy to simultaneously tackle these problems. The nano-size MGHs were encapsulated in nitrogen-doped graphene nanospheres (NGNSs) via a facile wet-chemical method. This configuration not only prevented the MGHs from oxidation when exposed to air even after a long duration, but also stimulated faster kinetic rates of hydrogen absorption and desorption owing to the nano-size effect of MGHs and the unique electronic structure of NGNSs. As a result, MGHs of ca. 20 nm were coated by a few layered NGNSs to form MGH@NGNSs nanocomposite. A high hydrogen absorption capacity of 6.5 wt% was achieved at 200 °C within 0.4 h, with a releasing hydrogen capacity of 5.5 wt% at 300 °C within 0.5 h, indicating that this composite has obtained remarkably hydrogen storage performance. Density Functional Theory (DFT) based calculations suggested that the hydrogen adsorption/desorption kinetics were significantly fast at the interface of Mg surface and NGNSs with pyridinic configuration. This strategy paves a way for the development of high-performance Mg-based hydrogen storage materials for industrial applications.

Effects of oxygen loading on the red-luminescence of non-bridging oxygen hole centers in γ-irradiated silica glasses

Ultra-high purity Corning 7980 and Corning 7979 silica glasses, respectively with high and low contents of hydroxyl and hydrogen, were specifically selected to investigate the effects of O2 loading on the 1.9 eV red luminescence of the gamma-ray induced non-bridging oxygen hole center (NBOHC), whose luminescence intensity is beneficial not only to predict the laser damage of silica but also to the targeted improvements in the preparation-treatment processes of silica. The UV trasmittance spectra, the UV excitation spectra, the visible emission spectra and the red emission lifetime decay curves were determined for these two types of the gamma-ray irradiated silica glasses before and after O2 loading. The content ratios of Si dangling bond (Si-E′) to NBOHC in silica glasses before and after O2 loading are estimated. The formation precursors and other related defects for NBOHC, such as Si-E′, Si-O-Si bond, Si-O-H bond, peroxy radical and linkage, oxygen-deficient centers ODC(I) and ODC(II), etc, are discussed. The bandwidths of the excitation and emission spectra before and after O2 loading are compared at the lower energy side of the spectra. The average emission lifetimes and especially the decay curves of the red luminescence before and after O2 loading are analyzed. There appear two types of NBOHCs with and without neighbouring hydrogen interaction at room temperature, respectively corresponding to the shorter and longer lifetime components. After O2 loading, the shorter lifetime component disappears and becomes the longer one, indicating that the hydrogen-bonded NBOHC is altered into the non-bonded. It is suggested that the analysis of the shorter and longer lifetime components of the red luminescence can be utilized in the laser damage prediction as well as the preparation and treatment processes of silica.

Recyclable ammonia uptake of CuCl2/graphite composite adsorbents with high adsorption capacity

Ammonia is considered a good hydrogen storage material due to its advantages of high hydrogen content density. At the same time, the characteristic of efficient heat transfer of ammonia makes it develop rapidly in many energy industries. However, unutilized NH3 can cause corrosion and poisoning, therefore, NH3 must be captured in time. Metal chloride is a green, efficient and sustainably utilized material for NH3 adsorption and capture. In this paper, a novel composite adsorbent was proposed by loading graphite to CuCl2 to enhance the NH3 adsorption·NH3 adsorption–desorption experiments of composite adsorbents were performed on the fixed bed. The results showed that the optimal loading of graphite on CuCl2 was 20 wt% and the optimal adsorption temperature was 25 ℃. The optimal adsorption of CuCl2-G (20) was 0.64 g NH3/g adsorbent. Moreover, the composite adsorbents showed good stability in NH3 adsorption properties during long-term cycling. The cumulative NH3 adsorption capacity of CuCl2-G (20) in the 10 cycles was up to 5.8 g NH3/g adsorbent, which was 0.07 g NH3/g adsorbent higher than that of CuCl2. Notably, all graphite-loaded composite adsorbents showed a stronger NH3 adsorption capacity than a single CuCl2 in the 2nd and subsequent cycles. Thus, CuCl2-G (20) is a promising adsorbent with potential application in the removal and enrichment of excess NH3 produced in industrial processes.

Analysis of Mechanical Properties of Welded Joint Metal from TPP Steam Piping after Its Operational Degradation and Hydrogenation.

In this paper, the mechanical properties of various zones of the welded joints of a heat-resistant steel 15Kh1M1F in different states (in the initial state, after an operation on the main steam piping of a thermal power plant (TPP) for 23 years) were determined, and the fracture surfaces were analyzed using scanning electron microscopy (SEM) images. The effect of hydrogen electrolytic charging on mechanical behavior and fracture mechanism was also studied. The long-term operation of welds resulted in a higher degradation degree of the weld metal compared to the base one, indicated by the deterioration of mechanical properties: decrease in hardness, strength characteristics, and reduction in area, which was accompanied by an atypical increase in elongation at fracture. All studied zones of the operated welded joints were characterized by higher hydrogen content, 2.5-3 times higher than that in the initial state. Additional hydrogen charging of the weld joint metal led to a decrease in the strength and ductility characteristics, more significantly for the operated weld compared with the non-operated one. This justified the possibility of using short-term tests of hydrogenated WM in the air to assess the degree of its damage during operation on a steam piping.

Effects of ignition position and hydrogen concentration on the flame propagation characteristics of hydrogen–air deflagration

In this study, the effects of hydrogen concentration and ignition position on the flame propagation characteristics of hydrogen–air deflagration in a pipe were investigated using a visual explosion propagation system. The change laws of propagation characteristics were analyzed at the microscopic level using free radical spectroscopy. The results indicated that the hydrogen flame had a lower velocity but higher explosion temperature and pressure under central ignition than under bottom ignition. However, the effect of ignition position weakened at higher hydrogen concentrations. As the hydrogen concentration was increased from 13 to 17 vol%, the differences in the maximum flame velocity, maximum temperature, and maximum pressure between central and bottom ignition decreased from 60.4%, 25.3%, and 17.8%, respectively, to 24.9%, 1.1%, and 4.6%, respectively. In addition, the maximum relative intensity and duration of the OH· spectral peak were more than 14% lower and shorter, respectively, under central ignition than under bottom ignition. As the hydrogen concentration was increased, the OH· spectral peak appeared earlier, the duration of this peak was shortened, and the explosion reaction was accelerated. OH· was consumed in the explosion reaction, which resulted in the release of heat; thus, the temperature and explosion pressure increased.

Stability of industrial gallium-doped Czochralski silicon PERC cells and wafers

The carrier lifetime stability of gallium-doped silicon wafers and performance stability of industrial PERC solar cells produced from sister wafers were investigated under four different illumination conditions and temperatures. The seven investigated materials feature a resistivity variation of 0.4–1.0 Ωcm and lifetime samples were processed to create high hydrogen content (with PECVD SiNx) or low hydrogen content (with ALD Al2O3 or HfO2). Our results confirm that the material itself is prone to light and elevated temperature induced degradation (LeTID), however experiments on PERC cells produced utilising the same silicon material indicate that the production process can successfully suppress LeTID. In contrast to earlier studies, we observe only small levels of degradation at the cell level, with some showing an improvement in cell parameters under LeTID testing conditions. Our results indicate that LeTID is not necessarily a major issue for the performance of modern passivated emitter and rear cells made from gallium-doped silicon substrates.

Colourless distributed combustion effects on a pre‐mixed coke oven gas flame

AbstractFuels consisting of high hydrogen concentration can be consumed under colourless distributed combustion (CDC) to suppress flashback tendency in premixed conditions. Higher NOX challenges can also be overcome through CDC. For those purposes, coke oven gas was consumed under CDC within the scope of this study. To achieve CDC, or diluents were introduced into the oxidizer so that oxygen concentration in the oxidizer would be decreased from 21% O2 to its lean blow‐off limits. Excess air ratios were determined as λ = 1.2 and λ = 1.5 along with a thermal power of 10 kW under premixed conditions. A commercial computational fluid dynamics code was used to predict temperature distribution and , CO, and emissions. 162‐step reactions created with GRI‐Mech 3.0 chemical kinetics was integrated to the eddy dissipation concept combustion model. The temperature and profiles predicted were compared with the experimental results. Consistency was achieved at ~95% for temperature profiles, and almost 100% for profiles between the measured and the predicted ones. According to the results, it is concluded that a more homogeneous temperature distribution with the ~21% decrease in the maximum temperature was observed, and there was about 96% decrease in level. It was also demonstrated that using as a diluent is more effective in terms of temperature distribution over the combustor and reduction, while dilution with is more effective in terms about 70% in decrease on CO.

Integration of a Microchannel Reactor in a CECE Process for H2 Removal from the O2 Stream Produced by the H2 Generator

A hydrogen generator is used in the combined electrolysis catalytic exchange process (CECE) for low-level tritiated water detritiation as a source of H2 (Q2) for the liquid-phase catalytic exchange column(s) within the process. To produce H2, the H2 generator employs an electrolytic process for H2O splitting into H2 and O2, resulting two streams: a hydrogen stream and an oxygen stream. During the detritiation of water, tritium is accumulated in the H2 generator in the form of tritiated water, and the effluent streams (hydrogen and oxygen) show in time an increased tritium concentration in the form of both tritiated water vapors and gas, which need to be recovered. The traditional methods for recovery present a risk of explosion due to the high concentration of hydrogen in oxygen (above 3%, while the explosion limit is 1%). In order to minimize this risk, a microchannel reactor with platinated channels has been developed and tested for the oxidation of tritiated hydrogen from the O2 electrolyzer stream in view of its recovery in a scrubber column and returned as tritiated water to the process. The reactor has been coupled to an electrolyzer and tested with regard to the operating temperature. It has been found that it reaches the highest oxidation efficiency of hydrogen when operated at 200°C. The design of the equipment is presented together with the results of the tests done with the equipment integrated in the CECE process.

CFD study of flameless combustion in a real industrial reheating furnace considering different H[formula omitted]/NG blends as fuel

On the path towards decarbonisation of the steel industry, the use of H2/NG blends in furnaces, where high temperatures are needed, is one of the alternatives that needs to be carefully studied. The present paper shows the CFD study carried out for a full-scale reheating furnace burner case. The real operating conditions as well as experimental measurements provided by the furnace operator were used to validate the results and reduce simulation uncertainties. The burner under consideration (2.5 MW) works in flameless mode with natural gas and preheated air (813 K). Starting from this point, another three fuel blends with volumetric percentages of 23% (also known as G222), 50% and 75% of H2 in natural gas were considered. For this purpose, the open source CFD code OpenFOAM was used, where the novel NE-EDC turbulence-chemistry interaction model was implemented, which has already been successfully validated specifically for flameless combustion in a furnace. The implementation incorporated an enhanced approach for calculating the chemical time-scale, coupled with a specific post-processing solver to predict NOx emissions. The study analyses the relative impact of the considered fuel blends on NOx formation and flameless regime. The modelling results demonstrated the burner’s capability to operate efficiently with high concentrations of hydrogen, maintaining flameless regime in all cases. This condition ensured uniform temperature distributions and low levels of NOx emissions, reaching a maximum value of 86 mg/m3. These results indicated the proper functionality of the existing natural gas-based burner with H2/NG blends, which was the primary requirement for the conversion process.

Acceptorless dehydrogenation of ethanol by Ru(II) complexes with tridentate Schiff-base ligands

Hydrogen, often hailed as the purest form of energy, is renowned worldwide for its exceptional energy density, renewability, and pivotal role in driving sustainable societal progress. However, safe, efficient, and cost-effective storage of hydrogen remains a significant challenge. Ethanol, as a liquid organic hydrogen carrier (LOHC), offers a notable solution with its high hydrogen content, eco-friendliness, and cost efficiency. In this work, hydrogen production by acceptorless dehydrogenation of ethanol (ADE) catalyzed by two new Ru(II) complexes (C1 and C2) with Schiff-base ligands was explored. Under optimized conditions, these catalysts produced respectable turnover numbers (TONs) of 19,398 and 31,965, respectively, comparing favorably with other homogeneous catalysts in the same capacity. Notably, the hydrogen gas produced is free of any CO, which is critical for the hydrogen-based fuel-cell application. Ethyl acetate, the byproduct of this process, can be recycled for other purposes. A mechanism possibly responsible for the observed catalysis was proposed based on an intermediate identified by the mass spectroscopic analysis of the reaction mixture.

Hydrogen production by aqueous phase reforming over stable La-promoted Ni-based hydrotalcite catalysts

Methanol, a common product of biomass pyrolysis or gasification, contains a high hydrogen content and serves as a valuable feedstock for hydrogen production through catalytic aqueous phase reforming (APR). However, poor hydrothermal stability of metal oxides support of the APR catalyst in liquid phase presents a challenge for the continuous and effective production of H2 over Ni-based hydrotalcite catalysts. A series of La-promoted NiMgAl hydrotalcite catalysts were prepared and their hydrogen production performances during methanol APR were evaluated. Promoted 5La–NiMgAl catalyst shows superior methanol APR reactivity due to the higher concentration of medium-strength basic sites than unpromoted catalyst. The La species adsorbs CO2 to form LaCO3OH and maintains La–NiMgAl catalyst structural integrity, which limits Ni leaching during reaction and promotes catalyst stability.

Transformation of struvite from wastewater to a hydrogen fuel storage compound ammonia borane.

Ammonia borane (NH3BH3) is a carrier of hydrogen gas that is known as a carbon-free renewable energy source. A high hydrogen content of ammonia borane and its stability in air at ambient temperatures make it a valuable molecule for its potential use as a hydrogen storage compound. In this study, we investigate a new approach for synthesizing ammonia borane using wastewater-derived ammonia source. Wastewater recycling has always been a global interest towards sustainability. In addition to reclaiming the water, recycling nutrients in wastewater is a topic of interest. Nutrients such as nitrogen, magnesium, and phosphorous are readily recovered from wastewater as struvite (NH4MgPO4·6H2O). This new process involves converting urine into struvite, and then reacting struvite with alkali borohydrides to produce a high-purity ammonia borane. The use of mild reaction conditions without extensive purification process, together with high purity ammonia borane product make this process a desirable course of action for recycling the nitrogen waste. In the course of moving towards a sustainable environment, the energy and wastewater industries will benefit from this combined process of nitrogen removal from wastewater to generate a renewable carbon-free energy molecule.

Experimental study of microwave processing of pine nut shells into a high-calorie gas: main results and physicochemical features

Involving biomass in the energy sector is a way to replace fossil fuels with renewable and CO2-neutral raw materials, reducing the negative impact on the environment. The energy application of agro-industrial waste is of particular interest, allowing one not only to obtain biofuel, but also to utilize by-products. The present work considers pine nut shells from a candy factory in relation to microwave processing into solid and gaseous fuels. The aim is to study the features of pine nut shells microwave pyrolysis, including the initiation mechanism and process behaviour, as well as the composition and characteristics of the resulting products. The study included experimentation in combination with application of high-speed video recording of the process and gas analysis, study of dielectric characteristics of raw materials, proximate and ultimate analysis of the obtained solid and gaseous products. At microwave pyrolysis, the conversion degree into liquid and gaseous products (76.9%) is much higher than, for example, at slow fixed bed pyrolysis (65.5%). The radiation absorption by the sample is nonlinear throughout the process and increases during the organic part degradation with the appearance of liquid and gaseous products. The gas obtained at microwave processing has a low ballast (share of CO2=3.5%) and a high hydrogen content (share of H2=19.3%) that results in a high heat of combustion (21.8 MJ·m-3), which is probably connected with interaction of pyrogenetic water and fuel carbon during plasma-chemical reactions.

Clathrate metal superhydrides under high-pressure conditions: enroute to room-temperature superconductivity.

Room-temperature superconductivity has been a long-held dream of mankind and a focus of considerable interest in the research field of superconductivity. Significant progress has recently been achieved in hydrogen-based superconductors found in superhydrides (hydrides with unexpectedly high hydrogen contents) that are stabilized under high-pressure conditions and are not capturable at ambient conditions. Of particular interest is the discovery of a class of best-ever-known superconductors in clathrate metal superhydrides that hold the record for high superconductivity (e.g.T c = 250-260K for LaH10) among known superconductors and have great promise to be those that realize the long-sought room-temperature superconductivity. In these peculiar clathrate superhydrides, hydrogen forms unusual 'clathrate' cages containing encaged metal atoms, of which such a kind was first reported in a calcium hexa-superhydride (CaH6) showing a measured high T c of 215K under a pressure of 170GPa. In this review, we aim to offer an overview of the current status of research progress on the clathrate metal superhydride superconductors, discuss the superconducting mechanism and highlight the key features (e.g.structure motifs, bonding features, electronic structure, etc.) that govern the high-temperature superconductivity. Future research direction along this line to find room-temperature superconductors will be discussed.

Mechanistic and microkinetic insights into the stability and activity of Ni3In catalyst for dry methane reforming

Dry methane reforming (DMR) reaction has garnered significant attention for its potential in consuming CO2 for environmental sustainability, as well as utilizing CH4 as a fossil resource with the highest hydrogen content. In-depth understanding the reaction mechanism with microkinetic modeling is essential for suppressing coke deposition and improving the stability of Ni catalysts. This study investigates the reaction intermediates and pathways of DMR on Ni3In alloy, which has been previously identified by theoretical high-throughput screening and experimental results as having improved resistance to carbon accumulation. Energetic profiles, determined through density functional theory calculations, reveal that the Ni3In catalyst exhibits an increased formation barrier for C* and lower adsorption strength compared to pure Ni catalyst. Microkinetic analysis using the CatMAP package demonstrates significantly lower carbon coverage on Ni3In than Ni catalysts. Importantly, the dissociation of CO2 plays a critical role in influencing the rate of CO formation, particularly at higher reaction temperatures. Furthermore, through flux analysis, we have identified the main reaction pathways for CO formation and highlighted the multiple pathways for oxidizing carbon-containing species to suppress carbon deposition on Ni3In catalyst. These findings not only provide theoretical support for the experimental stability of Ni-In catalysts but also offer valuable insights for the rational design of other Ni-based bimetallic catalysts employed in DMR reactions.

Ultra-Low Loading of Gold on Nickel Foam for Nitrogen Electrochemistry

Ammonia (NH3) is widely used in various fields, and it is also considered a promising carbon free energy carrier, due to its high hydrogen content. The nitrogen reduction reaction (NRR), which converts nitrogen into ammonia by using protons from water as the hydrogen source, is receiving a lot of attention, since effective process optimization would make it possible to overcome the Haber–Bosch method. In this study, we used a solution-based approach to obtain functionalized porous Ni foam substrates with a small amount of gold (<0.1 mg cm−1). We investigated several deposition conditions and obtained different morphologies. The electrochemical performance of various catalysts on the hydrogen evolution reaction (HER) and NRR has been characterized. The ammonia production yield was determined by chronoamperometry experiments at several potentials, and the results showed a maximum ammonia yield rate of 20 µg h−1 mgcat−1 and a Faradaic efficiency of 5.22%. This study demonstrates the potential of gold-based catalysts for sustainable ammonia production and highlights the importance of optimizing deposition conditions to improve the selectivity toward HER.

A parametric study on hydrogen production by fluidized bed co-gasification of biomass and waste plastics

This paper presents a parametric study on hydrogen production potential from biomass and waste plastics via fluidized bed co-gasification technique by using different gasifying agents such as steam, air and CO2. In this regard, a new Aspen Plus model representing this process was developed. For this purpose, first, a comparative feedstock selection between several materials was performed, ultimately identifying the cotton husk (CH) and high-density polyethylene (HDPE) mixture as the most promising choice. Secondly, the study focused on steam co-gasification of CH with HDPE to assess the impact of various factors, including plastic content in feedstock, temperature, steam to feedstock ratio (S/F), and the introduction of gasifying agents, namely air and CO2, next to steam. The analysis mainly examined the influence of these parameters on the composition of syngas, calorific value, and the hydrogen production. Accordingly, it was determined that an increase in plastic content and S/F ratio resulted in higher hydrogen concentration in the syngas, and the maximum quantity of H2 with 1189.3 Nm3/ton feed was produced at 900 °C. In addition, co-utilization of air or CO2 with steam as a gasifying agent deteriorated the system performance regarding H2 yield. Thus, it is expected that the model developed will contribute to the researchers, investors, engineers and policy maker working on the gasification technology for hydrogen production.

New coefficients of the weighted-sum-of-gray-gases model for gas radiation characteristics of hydrogen/natural gas blends combustion

To achieve carbon neutrality, hydrogen/natural gas blends are gaining momentum as a clean low-carbon fuel for the future. In order to accurately carry out the CFD numerical simulation of hydrogen/natural gas blends combustion, it is imperative to establish a precise model for gas radiation characteristics. The existing weighted-sum-of-gray-gases model (WSGGM) is not suitable for high hydrogen content fuels, such as hydrogen/natural gas blends. Hence, new coefficients of WSGGM is formulated specifically for the combustion of hydrogen/natural gas blends, drawing upon the groundwork established by the statistical narrow-band model (SNB model). This model is specifically designed to be applicable within the ambient pressures, encompassing the temperature regime of 400–2500 K, a path-length range of 0.001–60 m, and a hydrogen blending ratio of 20%–70%. The radiative heat transfer characteristics of the sum of the molar fraction of H2O and CO2 at 0.9, 0.6, and 0.3 were studied according to application conditions. The WSGGM is implemented to compute the radiative heat transfer in non-isothermal and non-homogeneous gas mixtures. When compared to the benchmark model, the deviation of the wall heat flux does not surpass 5.20%. The results demonstrate the excellent adaptability of the WSGG coefficients in simulating the radiative heat transfer during hydrogen/natural gas blends combustion.

Flame evolution and pressure dynamics of methane-hydrogen-air explosion in a horizontal rectangular duct

This work is aimed at exploring flame evolution and pressure dynamics of methane-hydrogen-air explosion experimentally and numerically by changing equivalence ratio and hydrogen content. For the flame evolution, the smooth distortion vanishes at equivalence ratio of Ф = 1.4, the prominent cellular structure and distorted tulip flame start to form with increasing hydrogen content. For the pressure dynamics, as the equivalence ratio increases, both maximum explosion overpressure and maximum pressure rise rate increase and then decrease, and both of them continue to increase with increasing hydrogen content. H + O2 = O + OH is the main elementary reaction with positive effect on the laminar burning velocity. The main elementary reactions with negative effects are H + O2(+M) = HO2(+M) and CH3 + H(+M) = CH4(+M). H radical always dominates on the rich side or the lean, stoichiometric side with high hydrogen content. As the hydrogen content increases, the main oxidation pathways of CH4 undergoes the transfer from CH4 → CH2(S) → CH2 → CO to CH4 → CH2(S) → CH2 → CH → CO → CO2. The research results are helpful to improve combustion efficiency of internal combustion engine and ensure process safety of hydrogen doped natural gas pipeline transportation.