Hydrogen-containing Gas Mixtures Research Articles

The role of gravity and temperature on hydrogen-containing mixtures in the subsurface

A model for thermal and gravity-induced compositional grading of hydrogen-containing gas mixtures using a cubic equation of state is presented. The theoretical background of compositional gradient modeling is reviewed, and the implementation of a thermal gradient model is used to predict the compositional variation of a hydrogen-natural gas mixture for both depleted gas reservoir and salt cavern applications. We show that near-uniform gas composition versus depth is expected during the storage of hydrogen mixed with natural gas over 100 m of vertical relief. Further study into the calculation and significance of the ideal portion of the component molar enthalpy is needed to increase confidence in model implementation and application.

Managing reservoir dynamics when converting natural gas fields to underground hydrogen storage

On the path to a net-zero-carbon economy, large-scale energy storage will be an essential part of a renewable energy system. Hydrogen generated from renewable or zero-carbon sources has significant potential as an energy storage medium, by allowing for long-duration and high-capacity energy storage. At the volumes anticipated, however, underground storage systems will likely be essential. Much like the current natural gas system, underground hydrogen storage would provide a safe and cost-effective complement to smaller surface storage infrastructure. Recently, there has been significant interest in the possibility of converting existing gas storage systems to hydrogen storage, though many uncertainties exist in such a process. This paper explores the reservoir dynamics of natural gas/hydrogen gas mixtures and the resulting impacts on storage conversion and gas deliverability. Two specific topics are addressed. First, a novel viscosity model for hydrogen-containing gas mixtures is developed, which shows better agreement with experimental measurements than the widely-used Lohrenz-Bray-Clark model. Second, detailed reservoir simulations are used to investigate cost-effective injection/withdrawal strategies for converting a natural gas storage system to one that stores hydrogen/natural-gas blends. The critical role of buoyancy and gravity override is described, and recommendations are made regarding key reservoir characteristics and injection strategies for managing this behavior.

Experiment and dynamic simulation of hydrogen recovery from hydrogen-containing gas mixtures via hydrate-membrane coupling method

The recovery of hydrogen (H2) form H2-containing gas mixtures, such as petrochemical refinery tail gas, plays a important role in energy conservation and cost reduction. The hydrate-membrane coupling separation process has been demonstrated as a more efficient and energy-saving approach for H2 recovery. This study aims to achieve the synergistic matching of hydration and permeation, so as to explore the underlying mechanisms of coupling and facilitate subsequent experimental studies. In this work, an effective method was developed to calculate the gas consumption rate during the stable growth stage of hydrates. Furthermore, a dynamic matching model of the hydrate-membrane coupling mechanism was employed to simulate the variations in the separation process using infinitesimal methods. The simulations indicate that the H2 concentration of product gas and the feed gas treatment capacity of the coupling method outperform those of hydrate separation and membrane separation alone. Overall, this study provides valuable insights into an efficient and energy-saving method for H2 recovery from H2-containing gas mixtures, utilizing the hydrate-membrane coupling method. These findings hold promising prospects for practical application in the future.

Experimental and modeling on hydrate phase equilibrium conditions for hydrogen-containing gas mixtures in pure water and brines

Hydrate-based technology is considered as one of potential ways for hydrogen separation and storage. Additionally, it has been reported that injecting CO2/H2 mixture is an effective approach to the enhancement of natural gas hydrate exploitation. Hence the determination of hydrate formation conditions of hydrogen containing gas mixtures is of fundamental significance. A series of hydrate formation conditions of hydrogen-containing gas mixtures were then measured under 273.8 to 285.5 K and 2.61 to 10.52 MPa, including 3 binary (CH4 + H2) gas mixtures and 5 ternary (CH4 + CO2 + H2) gas mixtures in pure water, as well as 8 ternary (CH4 + CO2 + H2) gas mixtures in aqueous solutions of NaCl and Na2SO4. Meanwhile, a thermodynamic model for predicting hydrate formation conditions of hydrogen-containing systems were developed, in which Chen–Guo hydrate model was used to calculate the fugacities of guest species in hydrate phase and Patel–Teja equation of state was used to calculate the fugacities of guest components in gas phase and those of water in aqueous solutions. Two mixing rules, van der Waals mixing rule and Wang-Sandler mixing rule, were applied in parallel to determine the values of parameters of Patel–Teja equation of state. The overall average absolute deviation on formation pressure for 273 data points is 4.61 % when using Wang-Sandler mixing rule while it is 5.70 % when using van der Waals mixing rule. The experimental data and prediction method presented might be of significance for both exploitation of natural gas hydrate via injecting CO2/H2 mixture as well as the purification of hydrogen via forming hydrate.

Catalytic Decomposition of Hydrazine and Hydrazine Derivatives to Produce Hydrogen-Containing Gas Mixtures: A Review

Catalytic Decomposition of Hydrazine and Hydrazine Derivatives to Produce Hydrogen-Containing Gas Mixtures: A Review

Revealing the effect of plasma-chemical treatment of propane-butane fuel on the environmental characteristics of the internal combustion engine

One of the key problems of modern engine construction is the improvement of environmental performance while ensuring a competitive price of produced engines. This is achieved using state-of-the-art control systems, expensive fuel equipment, and complex exhaust gas neutralization systems. The search for ways to improve the environmental performance of transport engines without significant complication of their structure is a priority area of modern research. Plasma chemical treatment of gas makes it possible to reduce the level of harmful substances in exhaust gases by 1.5‒4 times relative to operation on propane-butane without processing. This paper considers the possibility of using a plasma dynamic stabilization technique and conducting an electric discharge without contact with metal electrodes for the implementation of endothermic reactions whose implementation requires energy from an external source. During test experiments, volt-ampere characteristics of the system with needle electrodes were established, the distance between which was 2‒5 mm at different feed pressures of propane-butane gas mixture (75 % propane and 25 % butane). At the outlet of the plasma-chemical reactor, a hydrogen-containing gas mixture is obtained, which is subsequently supplied to the combustion chamber through the regular gas fuel system of the engine. Next, when such a gas mixture burns in the combustion chamber, hydrogen acts as a catalyst for chemical reactions, which reduces the thickness of the flame extinguishing front, increases the speed and completeness of combustion of the gas mixture. Based on the results of comparative motor studies, it was found that plasma-chemical treatment of propane-butane has almost no influence on the effective efficiency of the engine and specific fuel consumption. It should also be noted that the use of plasma-chemical reactors on board a vehicle allows them to be integrated into regular gas fuel engine systems with minimal changes in their structure, which has almost no effect on the mass-size indicators and maintenance conditions of the gas fuel system

Directional separation of hydrogen-containing gas mixture by hydrate-membrane coupling method

Recovery of hydrogen (H 2 ) from H 2 -containing gas mixtures has great significance for energy conservation, cost reduction and benefit increase. However, the common separation methods have the ubiquitous problem due to phase equilibrium principle and results in the conflict between H 2 concentration and H 2 recovery rate in the product gas. Consequently, an innovative conception of hydrate-membrane coupling approach is proposed in this work. In the separation process, hydration and membrane permeation two separation driving forces coexist to achieve the aim of strengthening mass transfer kinetics. H 2 and non-H 2 components (hydrocarbons) are synchronously and directionally selected by membrane and hydrate to improve different phase compositions. Therefore, the gas in feed side could keep relatively high two separation driving forces (H 2 fugacity and hydrocarbons fugacity). The results show that the coupling method could synchronously increase both the concentration and the recovery rate of H 2 in the product gas. At the same time, the volume and concentration of the hydrocarbons in hydrate both increases effectively. It indicates that hydrate and membrane separation methods support each other in the separation process. The hydrate-membrane coupling method fundamentally solves the issue of the decreasing driving force resulting from single separation method and phase equilibrium relationship. Fig. 1 . The schematic diagram of directional separation of H 2 -containing gas mixture using hydrate-membrane coupling method. (a) Before separation. (b) After separation. • We proposed a coupling separation mechanism based on coexistence of two mass transfer processes. • Hydrate-membrane coupling method was used to directionally separate H 2 -containing gas mixture. • The coupling separation method could synchronously increase the concentration and recovery of H 2 . • Coupling separation method breaks through the constraint of single phase equilibrium relation.

Start-up behavior and the ignition limit of passive hydrogen recombiners with various catalytic elements

The paper gives the results of experiments aimed to study start-up characteristics and the ignition limit of recombiners containing two various types of catalysts, namely ceramic rods and high porosity cell material. Both types of catalysts were produced by Redkino Catalyst Company. Experiments were carried out using a 15 m3 BM-P chamber located at the FSUE “RFNC-VNIITF named after Academ. E.I. Zababakhin” test site. The recombiner was tested in a homogeneous hydrogencontaining gas mixture under the quasi-stationary conditions with a stepwise increase in hydrogen concentration.Experimental results demonstrated that similar physical processes were observed for both types of catalysts. The recombiner was shown to start up when natural convection flow was activated through its case. Ignition was proved to be caused not only by a heated catalyst, but also by particles escaping from catalytic surface due to spallation and thus decreasing the ignition limit from 10% down to 5%.

Measurement and Prediction of Hydrate Phase Equilibrium Conditions for Hydrogen-Containing Gas Mixtures in Pure Water and Brines

Measurement and Prediction of Hydrate Phase Equilibrium Conditions for Hydrogen-Containing Gas Mixtures in Pure Water and Brines

Hydrogen-methanol SOFCs for transport

The physico - chemical analysis of the energy efficiency of the installation with high-temperature fuel cells (SOFC) operating on the hydrogen-containing gas mixture (synthesis gas) obtained in the catalytic process directly in the car from liquid fuel - methanol. The resulting energy is used for an electric vehicle engine. The electrical efficiency of the installation is 42.1%, which for energy efficiency corresponds to the level of the best modern internal combustion engines.

A Two-Model Complex for Research into the Process of Adsorption Obtaining Hydrogen from Natural Gas Steam Reforming Products

The problem of approximation of kinetic models of adsorption by equilibrium models with fictitious coefficients of linear isotherms is set and solved. A complex of two mathematical models of the hydrogen adsorption process and an algorithm for calculating model equations has been developed. Numerical studies of the adsorption process of a multicomponent hydrogen-containing gas mixture have been carried out.

The effect of the catalytic layer composition on the hydrogen permeability of assymetric tantalum-based membranes

The paper offers the measuring results for hydrogen permeability of the membranes made of 40 μm thick tantalum foil covered with a metallic film with different thicknesses on one side. The measurements were performed when the membranes were in contact with a commercial argon and hydrogen gases mixed at the ratio of 1/5 at an overpressure of 500 kPa and at 580-585°C. It is shown that films of Mo, Re, W, Cu, Co, and Ni metals deposited on the tantalum membrane surface from the side facing a hydrogen-containing gas mixture increase its hydrogen permeability. The effect degree of these metals increases in the specified row from left to right. The effect on the hydrogen permeability of tantalum membranes, comparable to and superior to the deposition of a Pd film, exerts the deposition of Cu, Co, and Ni films. It is explained by the high hydrogen permeability level of these metals and the catalytic activity of their surface that results in intense hydrogen dissociation. The value of the hydrogen permeability of the membranes naturally increases with a thickness decrease of metallic films, however, it is obvious that this behavior is not linear. The hydrogen permeability of membranes with Cu, Co, and Ni films decreases over time, that is explained by the oxygen segregation at the Ta membrane/film interface, as well as by the processes on the membrane surface in contact with the gas mixture. The nature of these processes should be studies since the lower oxides of these metals are reduced by hydrogen at this temperature.

Effects of stress concentration on the mechanical properties of X70 in high-pressure hydrogen-containing gas mixtures

This study aims to investigate the mechanical properties of X70 pipeline steel under the synergistic influence of hydrogen and stress concentration. Slow strain rate tensile tests and low-cycle fatigue tests were performed on the specimens with different stress concentration factors (Kt) in 10 MPa nitrogen/hydrogen mixtures. Results show that the degradation degree of the ductility and fatigue life of X70 steel induced by hydrogen increases with the increase of Kt, and as the hydrogen partial pressure in mixtures increases, the influence of Kt on hydrogen-induced degradation increases as well. In addition, finite element analysis was performed via a modified hydrogen diffusion/plasticity coupled model to study the effect of Kt on hydrogen distribution in the specimens, which can influence the mechanical properties of X70. The maximum hydrogen concentration consistently appears at the notch tip of the specimen and increases with the increase of Kt, which is proposed to be one of the reasons for the severe hydrogen embrittlement of the specimens with large Kt. As the axial tensile force on the specimen increases, the maximum hydrogen concentration at the notch tip begins to be dominated by hydrogen in the normal interstitial lattice sites and, subsequently, in the trapping sites.

Моделирование и исследование динамики адсорбционного разделения синтез-газа и концентрирования водорода

On the basis of the Dubinin theory of micropore volume filling, a mathematical model of dynamics of pressure swing adsorption processes for synthesis gas separation has been developed. The model takes into consideration the influence of the processes of mass and heat transfer in gas and solid phases on the kinetics of diffusion transfer of adsorbate (carbon dioxide, carbon monoxide, hydrogen) in the adsorbent layer and accounts for all devices included in the process diagram (adsorber, compressor, vacuum pump, valves, throttle, receiver). Numerical studies of the process of separation of synthesis gas and concentration of hydrogen in a four-adsorber unit with granulated zeolite adsorbent 13X were carried out by methods of mathematical modeling: the influence of disturbing influences (composition and temperature of the initial hydrogen-containing gas mixture), regime parameters (cycle duration, pressure at the compressor outlet, pressure at the vacuum pump inlet, backflow coefficient) and design parameters (length of the adsorbent bulk layer and inner diameter of the adsorber) on the purity of the product hydrogen, its recovery rate and productivity of the unit were studied. The most dangerous disturbances and the most effective regime parameters of pressure swing adsorption process of synthesis gas separation were determined. It is established that the increase of temperature from 298 to 323 K and decrease of hydrogen concentration from 68 to 48 % (vol.) in initial gas mixture result in ~10 % lower efficiency of the unit due to the decrease of product hydrogen recovery rate. Practical recommendations on effective choice of operation regimes of an adsorption unit to ensure the achievement of required purity of product hydrogen at the level of 99.99 % (vol.), regardless of the impact of disturbances are formulated.

Potential Applications of Layered Double Hydroxides in Membrane-Based Separation and Anti-Corrosion

Layered double hydroxides (LDHs) are representative of inorganic layered compounds consisting of positively charged brucite-like sheets and charge compensating anions located in interlayer galleries. The high length-to-width ratio, uniform gallery height, flexible chemical compositions, active surface functionality and unique calcination properties of LDHs have inspired us to explore their potentials in gas separation. In the presentation we demonstrated that LDHs not only enabled to effectively separate hydrogen-containing gas mixtures relying on the uniform interlayer galleries, but also could serve as efficient perch, active heterogeneous nucleation center and qualified single metal source of MOF crystals for the preparation of high performance MOF membranes. In addition, potential applications of LDHs in anti-corrosion were further explored. Relying on the dense in-plane structure of LDHs, preferentially c-oriented NiAl-CO3 LDH coatings were prepared showing excellent anti-corrosion performance. In addition, well-intergrown MOF coatings exhibiting excellent anti-corrosion performance could be in situ grown on Al substrates further by simple solvothermal treatment of ZnAl-CO3 LDH buffer layers. To sum up, full utilization of both microstructural and physicochemical properties of LDHs had greatly expanded their potential applications in membrane-based separation and anti-corrosion.

Effect of the Hydrogen Concentration on the Pd/n-InP Schottky Diode Photocurrent

The variation rate of the short-circuit photocurrent of Pd/n-InP Schottky diodes is studied as a function of the presence of hydrogen in a gas mixture with H2 concentrations of 1–100 vol %. It is shown that upon the simultaneous exposure of the Schottky diode to a hydrogen-containing gas mixture and to light (λ = 0.9 μm), the hydrogen concentration in the gas mixture and the Pd/n-InP diode photocurrent variation rate are related exponentially. The Schottky-diode response rate to the presence of hydrogen in the gas mixture increases with the illumination intensity.

Nanosized Au Catalysts Supported on Mg(OH)<sub>2</sub>-CeO<sub>2</sub> for Preferential Oxidation of CO in Hydrogen Stream

Preferential oxidation of carbon monoxide in the presence of hydrogen (PROX) is a promising method to remove CO from a hydrogen-containing gas mixture. Nanosized gold catalyst supported on CeO2 and modified with Mg(OH)2 was used for preferential oxidation of carbon monoxide in hydrogen-rich stream in this study. Mg(OH)2 was added on CeO2 by incipient-wetness impregnation. Au was loaded on Mg(OH)2-CeO2 by deposition-precipitation method. PROX reaction was carried out in a continuous flow, fixed bed reactor. CO/O2 feed ratio was fixed at 1 to magnify the difference of various catalysts. The catalysts were characterized by N2 sorption, TEM, HR-TEM and XPS. Mg(OH)2 formed a thin layer on the surface of CeO2. CeO2 was in the crystalline phase and Mg(OH)2 was amorphous. Au particles were homogeneously dispersed on the support with a size of 2 - 5 nm. Using CeO2 as a support could increase the dispersion of Mg(OH)2 and thus increase the interaction between Au and Mg(OH)2. Adding Mg(OH)2 on Au/CeO2 could suppress H2 oxidation and therefore increase CO oxidation activity.

Влияние концентрации водорода на фототок диодов Шоттки Pd/n-InP

AbstractThe variation rate of the short-circuit photocurrent of Pd/ n -InP Schottky diodes is studied as a function of the presence of hydrogen in a gas mixture with H_2 concentrations of 1–100 vol %. It is shown that upon the simultaneous exposure of the Schottky diode to a hydrogen-containing gas mixture and to light (λ = 0.9 μm), the hydrogen concentration in the gas mixture and the Pd/ n -InP diode photocurrent variation rate are related exponentially. The Schottky-diode response rate to the presence of hydrogen in the gas mixture increases with the illumination intensity.

Computational Fluid Dynamics Modeling of Combustion of Synthetic Fuel of Thermochemical Heat Recuperation Systems

CFD modeling of the combustion of synthetic fuel formed in the systems of thermochemical recuperation of waste flue gas heat due to steam methane reforming was performed using the ANSYS Fluent software. Scientific justification and validation of the physicomathematical approaches involved the ANSYS Fluent for the problems of modeling the combustion of multicomponent hydrogen-containing gas mixtures. Numerical results were validated against experimental data. A visual comparison of the flame contours obtained by burning syngas at Reynolds numbers of 600, 800, and 1000 was performed. In all cases there is obvious convergence of the results. Change in the temperature of the fuel–air mixture at the entrance to the combustion chamber was found to have no significant effect on the temperature of the combustion products. The obtained results are of practical importance for the design of burner units of high-temperature plants with thermochemical heat recuperation.

Sieving of Hydrogen-Containing Gas Mixtures with Tetrahydrofuran Hydrate

Using the different diffusion rates of gas mixture components in hydrate crystals is a promising new method for the separation of gas mixtures. The diffusion behavior of hydrogen (H2), methane (CH4), and carbon dioxide (CO2) in tetrahydrofuran (THF) hydrate was investigated experimentally by exposing a THF hydrate layer to H2, H2 + CH4, or H2 + CO2 gas or gas mixtures and monitoring the penetration of the molecules into the hydrate by Raman spectra. The experimental results demonstrate that only H2 molecules can penetrate the entire 5 mm thick hydrate layer, while the THF hydrate is resistant to CH4 and CO2 molecules on the experimental time scale employed. The minimum partial pressure for H2 to diffuse through the THF layer is 2.9 MPa, and the diffusion coefficient of H2 in the THF hydrate layer was determined to be 6.1 × 10–12 m2/s via time-resolved Raman collection. This is the first observation of the sieving behavior of a massive hydrate layer toward different gas molecules. This work also suggests t...