Natural Gas Mixtures Research Articles

Characterization of a Novel Additive Manufacturing Micromix Nozzle Burning Methane to Hydrogen

Abstract As the energy landscape transitions to low/zero-carbon fuels, gas turbine manufacturers are targeting fuel flexible operation with natural gas, syngas, and hydrogen-enriched mixtures. Having a single geometry that can support the different fuel blends requested by clients can accelerate the transition to cleaner energy generation and mitigate the environmental impact of gas turbines. Toward this goal, micromix combustion technology has received significant interest, and when coupled with additive manufacturing, novel injector geometries with unique configurations may be capable of stabilizing premixed, partially-premixed, and diffusion flames using fuel mixtures ranging from pure methane to pure hydrogen. In this work, a preliminary investigation of this micromix concept is performed in the Atmospheric Combustion Rig at the National Research Council (NRC) Canada. Flame stability maps are obtained for fuel lean mixtures of H2/CH4 ranging from 0/100, 70/30, 90/10, to 100/0%, by volume. Multiple flame shapes are observed depending on the fuel mixture and combustion mode selected. Particle image velocimetry (PIV), OH, and acetone planar laser-induced fluorescence (PLIF), and acoustic measurements provide additional insights into the combustion process of these novel burners to better understand the stability mechanisms. The quality of the fuel–air mixing from the premixed and micromix injectors is assessed using acetone as a tracer for the fuel, while simultaneous OH-PLIF measurements provide an indication of the postflame regions in the flow. Acoustic measurements complete the current dataset and provide combustion dynamics maps measuring the normalized pressure amplitudes and identifying the dominant frequencies. The preliminary characterization of this additive manufacturing (AM) micromix nozzle shows promising fuel flexibility with wide stability margins and low combustion dynamics for this single nozzle burner.

Effect of Predisolved Natural Gas on CO2 Solubility in Water With Various Salinities at Reservoir Conditions

Dissolution of CO2 in saline waters is considered one of three main CO2 trapping mechanisms, along with structural/stratigraphic trapping and mineralization. CO2 can dissolve in fresh/saline water under typical reservoir pressure and temperatures. Its solubility is dependent on pressure, temperature, and salinity. CO2 solubility studies typically consider saline water or fresh water as a liquid without any predissolved gases. The reality is formation water may contain appreciable dissolved gases for all pressure and temperature conditions. An example of gas-water ratio (GWR) can be ~1 scf/stb for formation water in an oil reservoir and ~5 to 6 scf/stb for a deep saline aquifer. Therefore, it is essential to quantify the effect of brine salinity on CO2 solubility in “live” saline waters. Just as “live” oil denotes reservoir oil that contains solution gas, we define “live” brine as saline water that includes dissolved gases. Conversely, “dead” brine refers to saline water devoid of any dissolved gas content. Two sets of experiments were conducted under typical reservoir conditions. The first set of experiments evaluated the CO2 solubility in live formation water. The second set of experiments evaluated how variation in the live brine salinity affected CO2 solubility. These experiments involved 1) synthesis of the brine, 2) synthesis of natural gas mixture, 3) recombination of live formation water with a natural gas mixture and transfer into a high-pressure and high-temperature pressure-volume-temperature (PVT) visual cell, 4) CO2 addition to the PVT cell, and 5) bubblepoint pressure determination within the PVT cell. The results showed that CO2 solubility in live formation water is significantly less than that in “dead” water under reservoir conditions. In addition, the brine salinity affects CO2 solubility in live formation water by further reducing CO2 solubility with increasing live brine salinity. As the brine salinity increases, very little CO2 can be dissolved in the live brine once it reaches a certain solubility. An understanding of CO2 dissolution in live saline water is essential for future CCUS evaluation and execution.

Conceptual Solution of the Green PV – Hydrogen Complex on the Existing Infrastructure of the Thermal Power Plant “Morava”

The paper presents the concept of replacing the existing thermal power plant Morava with facilities for the production, storage and combustion of green hydrogen. The facilities for the production of hydrogen would consist of an electrolyzer and a photovoltaic power plant, which is planned at the existing ash pit within the Morava thermal power plant. Hydrogen storage systems would also be part of the existing thermal power plant complex. The production of electricity would be carried out in a thermal power plant with a gas turbine powered by a mixture of hydrogen and natural gas, which would be built and connected to the power system at the site of the existing 110 kV substation. It would also be foreseen to use thermal energy that would serve for heating the households near the thermal power plant. Such a complex would enable the existing infrastructure of the Morava thermal power plant to be reoriented to the production of manageable green energy.

Permeability measurement theory in case of natural gas and natural gas-hydrogen mixture

Green hydrogen, using renewable electricity that breaks down water molecules into hydrogen and oxygen, holds great promise for meeting global energy demand while contributing to climate policy goals. Interest in green hydrogen production technologies has increased considerably. This is because the potential uses of hydrogen cover many sectors, including power generation, manufacturing processes in steel and cement production, fuel cells for electric vehicles, and power grid stabilization. One possible use of green hydrogen is to blend it with natural gas and deliver it to end-users using existing natural gas pipeline storage and networks, thereby increasing performance and reducing emissions. In the case of underground storage of a hydrogen natural gas mixture, it is important to assess its impact on the reservoir beforehand, which rock permeability studies can do. This article deals with the theory of rock permeability testing for natural gas and natural gas-hydrogen mixtures.

Evaluation of an integrated electric power generation system with natural gas engines operating in dual mode through heat recovery with thermoelectric devices for hydrogen production

In the present investigation, an environmental, thermal, economic, and social analysis of an integrated system is carried out, which has as its function the production of hydrogen through the recovery of residual thermal energy from exhaust gases. The proposed integrated system consists of a thermoelectric generator and a hydrogen production bench based on the water electrolysis process. For the development of the research, an internal combustion engine fueled with natural gas was used, operating under four load conditions (25%, 50%, 75%, and 100%). From the environmental assessment, it is demonstrated that the implementation of the integrated system allows a decrease of 12.30%, 6.26%, and 7.90% in CO, CO2, and HC emissions. However, the addition of hydrogen causes a 9.9% increase in NOx emissions. Additionally, the implementation of the integrated system allows a 4.9% decrease in brake specific fuel consumption and a 4.9% increase in engine thermal efficiency. The improvement in engine thermal performance contributes to the 7% reduction in engine operating costs. On the other hand, it demonstrates an 8.7% reduction in the environmental and social impact cost and a 9% reduction in the ecological cost. Additionally, the integrated system minimizes the cost of environmental and social impact, as well as the ecological cost of polluting gases CO, CO2, and HC. The mixture of natural gas and hydrogen allows for a 4.70% and 7.59% increase in pressure and maximum heat release rate. In general, the proposed integrated system is a way to harness the thermal energy of exhaust gases for hydrogen production. In this way, it is possible to obtain an auxiliary fuel that improves the efficiency of the combustion process of the natural gas engine. This allows for minimizing energy losses in self-generation activities in Colombia, achieving better energy management and a reduction in operating costs.

A comparative study between Helmholtz and entropy scaling approaches for viscosity of natural gas mixtures based on the GERG-2008 equation of state

A comparative study between Helmholtz and entropy scaling approaches for viscosity of natural gas mixtures based on the GERG-2008 equation of state

Semi-industrial-scale silicalite-1 membranes for n-butane/methane separation

The semi-industrial-scale tubular silicalite-1 membranes with a thickness of 8.4–8.9 µm were prepared and used for the separation of n-butane/methane mixture for the first time. The membranes remained highly [h0h] oriented. The effects of temperature, pressure and feed flow rate (Reynold numbers) on the separation performance for the 6-cm-long and 50-cm-long membranes were investigated. Separation stability of the semi-industrial-scale tubular silicalite-1 membrane was studied. The short silicalite-1 membranes displayed the highest n-butane/methane separation factor of 935 among the literature data so far and a permeance of n-butane of 0.5 × 10−8 mol/(m2 s Pa) at 243 K. Two long silicalite-1 membranes showed n-butane permeances of 3.1 × 10−8 and 1.9 × 10−8 mol/(m2 s Pa) and n-butane/methane separation factors of 72 and 110 at 298 K in the 10/90 mol% n-butane/methane mixture, respectively. The results displayed that silicalite-1 membranes have great potential application for removal of n-butane from natural gas mixtures.

Experimental and modeling study of ignition delay times of natural gas with CO2 dilution

Pressurized oxy-fuel combustion has attracted considerable attention as an efficient technology with lower emissions. Natural gas, which primarily consists of methane, ethane, and propane, is a widely used fossil fuel owing to its safety and low cost. The auto-ignition of 90 %methane/9 %ethane/1 %propane mixture diluted in CO2 or N2 were investigated using a shock tube at temperatures of 1280–1645 K, pressures of 2 and 10 bar, and equivalence ratios of 0.5–2.0 in this study. An updated model named OXY-NG can accurately predict the ignition delay times, species yields, and laminar flame speeds of natural gas mixtures in oxy-fuel and air combustion modes. The ignition delay times increased as the equivalence ratios increased related to the recombination of CH3 radicals at 2 bar but decreased as the equivalence ratios increased owing to reactions involving HO2 at 250 bar. The diluent CO2 has inhibitory effects on ignition compared with N2, and these effects were minor under high pressure and fuel-rich conditions when diluted in CO2. The effects on natural gas mixture ignition owing to chemical and physical properties of CO2 are discussed in detail.

Examination of the effect on the engine of diesel-nanoparticle mixture with natural gas addition

Diesel engines have a broader application area and have a significant share in the transportation sector. Although there are restrictions on producing within the scope of emission standards, diesel fuel will remain important in heavy-duty vehicles for some time. Therefore, studies continue for environmentally friendly combustion and low emissions in diesel fuel. This paper reveals the results of using nanoparticle fuel with natural gas (NG) on diesel engine emissions and performance. In the experiments, the motor load was adjusted from no to full load by increasing it at 25% intervals. Three different diesel-nanoparticle blends containing 25 ppm, 50 ppm and 75 ppm carbon nanotube (CNT) were prepared and each of these blends was tested both with and without NG. In light of the test results, it has been seen that the D75ppmCNT + NG mixture is the best fuel mixture compared to both diesel and nanoparticle-added diesel since it provides the highest value in brake thermal efficiency (BTE) and the lowest value in brake specific fuel consumption (BSFC) at full load conditions. In the case of using a D75ppmCNT mixture, around 29% decrease in BSFC and about 28% increase in BTE were observed according to the diesel fuel use. In terms of emissions, when NG is added to the D + CNT fuel mixtures, there is an increment in CO and HC emissions and a slight reduction in NOx emissions at low and medium load.

Storage of a mixture of natural gas and hydrogen in underground gas reservoirs

In accordance with the document of the Ministry of Industry and Trade – Hydrogen Strategy of the Czech Republic, it can be expected that in the coming years, pressure will be exerted to inject hydrogen into the gas infrastructure, which is currently used mainly for natural gas. Injection of hydrogen into natural gas can have an effect not only on the transport and distribution system, but also on the storage of this mixture in underground reservoirs in CR. This article aims to describe the issue of storing a mixture of hydrogen and natural gas in underground reservoirs. In particular, the effect on the storage capacity and on the overall integrity of the reservoir, problems with the embrittlement of the metal parts of the probes, the effect on the rubber seal. The paper therefore describes not only the effects on the storage of a mixture of hydrogen and natural gas, but also on the devices that are located on surface technologies. The results of studies from foreign literature demonstrate that the addition of 10-15% by volume of hydrogen to natural gas will have a minimal effect on the operation of the underground reservoir. The storage of a mixture of hydrogen and natural gas in the Czech Republic is currently a much-discussed topic, also regarding the experience with the storage of town gas (which contained a high proportion of hydrogen) in the Lobodice aquifer type underground gas storage.

On the explosion characteristics of natural gas with hydrogen and inert gas additions

In this work, the explosion limits of three different natural gas mixtures (with various proportions of methane (CH4), ethane (C2H6), and propane (C3H8)) have been investigated numerically based on detailed chemical kinetics. Furthermore, a comprehensive investigation of the effects of hydrogen (H2) and inert gas (N2, CO2) addition on the explosive properties of natural gas has been carried out. The results indicate that the C3H8 components have a dominant effect on the explosion limits of natural gas. The addition of high-hydrocarbons in natural gas can significantly reduce the auto-ignition temperature, shorten the ignition delay time, and enhance the explosion risk of the mixture. Furthermore, the negative temperature coefficient (NTC) response of natural gas in the second explosion limit gradually disappears, and changes to the Z-curve response with the addition of H2. However, the explosion tendency of the mixture is reduced with the addition of H2 under normal to high-pressure conditions. In addition, with the increase of inert gas (N2, CO2), the explosion limits of the mixtures shift upwards to a higher-pressure region, which significantly reduces the explosion tendency. Nevertheless, the explosion propensity of the mixture increases significantly under low-pressure conditions when the mixture contains hydrogen. To elucidate the critical control reactions and determine their synergistic effects, sensitivity analyses under different conditions are performed. Finally, the interaction of different fuels in natural gas mixtures is further summarized by analyzing the explosion limits of single-component, binary-component, and multi-component mixtures of hydrogen to propane. This paper provides an important guidance for the development of natural gas with high safety, low risk, and low pollution.

BACKGROUND FOR THE USE OF HYDROGEN IN UKRAINE IN THE ENERGY AND AUTOMOTIVE SECTORS

Based on the global trends, the article substantiates the place of hydrogen and hydrogen technologies in the further decarbonisation of the energy sector and road transport in Ukraine. The variety of methods of production, transportation and storage, and the use of hydrogen of different purity require complex trade-offs between the cost of the technology and the amount of possible emissions of harmful substances into the environment at all related stages of application of these technologies. Hydrogen fuels and hydrogen technologies should be positioned as one of the areas of energy transition of economic sectors to decarbonisation, which will lead to the development of climate-neutral technologies. Traditional reciprocating internal combustion engines (ICE) can be upgraded to run on purely hydrogen fuel, but this requires the use of new materials due to the high specific energy intensity of hydrogen. The combustion of hydrogen in ICE combustion chambers is hindered by nitrogen oxide (NOX) emission restrictions. A possible option is to use a mixture of hydrogen and natural gas or to upgrade dual-fuel internal combustion engines. This is the most realistic option for Ukraine at this point. In light of the decarbonisation process, the main advantage of fuel cells (FC) is the absence of hydrocarbon combustion and, accordingly, the ability to reduce air pollution with the greenhouse gas CO2. Existing FC can operate not only on hydrogen but also on natural gas. In the energy sector, hydrogen technologies compete not with traditional methods of generating heat and electricity, but with bioenergy, heat pumps, and technologies for capturing and storing carbon and its oxides. In the automotive sector, hydrogen technologies compete with liquid and gaseous biofuels, electric vehicles and hybrids with internal combustion engines and batteries. The potential application of hydrogen technologies for decarbonisation processes will only be unlocked once a hydrogen market and the relevant infrastructure are in place. The segment and price of hydrogen technologies depend on by the method of production process chosen, as well as the infrastructure components, including storage, transportation and fuelling stations. The safe operation and implementation of hydrogen technologies in Ukraine requires qualified engineering staff. The training of such specialists for the energy and transport sectors can be taken on by universities by universities in the speciality 142 – energy engineering.

Time-varying mechanism of fluid-structure interaction vibration effects and dynamic characteristics of the cross-over pipeline when the medium flows

The time-varying mechanism of fluid-structure interaction (FSI) vibration effects and dynamic characteristics of the cross-over pipeline with the flowing of the crude and natural gas mixture two-phase medium were revealed in this study. An active fluid finite element method (FEM) model was built for the medium that exhibited a volume ratio 1:1 and flowed through the pipeline under a velocity of 2 m/s. The standard turbulence κ-ε model was modified by incorporating the flow velocity and pressure fluctuation changes with the floating of the medium. The pipeline's FSI vibration effects and the pipeline-crossing system's dynamic characteristics were determined and then analyzed. As indicated by the research results, the medium was affected by frictional damping at the pipeline wall and energy transfer losses at the phase interface, such that irregular flow regimes were generated (i.e., slug flow and wavy flow). The flow velocity was further reduced in the 280 s, and the intervals between pressure fluctuations gradually increased. The FSI vibration effects in the middle section of the cross-over pipeline were significant, with a peak displacement response reaching 45.7538 mm while the medium flow. Notable differences and complex changes were identified in the acceleration response among the monitoring sections of the first and second spanning sections. The dynamic properties of the pipeline-crossing system changed significantly with time. The natural frequencies of the 1st to 7th modes decreased with time.In contrast, the natural frequencies of the 8th to 12th modes tended to decline with complex time-varying characteristics more notably. The methods in the respective direction exhibited time-varying characteristics. Specifically, their relative proportions of the effective mass ratio varied with time. As the research concludes, The research concludes that the flowing mechanical behavior can be more accurately expressed by modifying the standard κ-ε turbulence model using the medium's velocity changes and pressure fluctuation curves. This study can lay a theoretical foundation for gaining insights into the time-varying mechanism of the FSI vibration effects and dynamic characteristics in the cross-over pipeline.

Hydrogen–Natural Gas Mix—A Viable Perspective for Environment and Society

The increase in demand, and thus the need to lower its price, has kept C-based fuels as the main source. In this context, the use of oil and gas has led to increased climate change, resulting in greenhouse gases. The high percentage of eissions, over 40%, is due to the production of electricity, heat, or/and energy transport. This is the main reason for global warming and the extreme and increasingly common climate change occurrences, with all of nature being affected. Due to this reason, in more and more countries, there is an increased interest in renewable energies from sustainable sources, with a particular emphasis on decarbonisation. One of the energies analysed for decarbonisation that will play a role in future energy systems is hydrogen. The development of hydrogen–natural gas mixtures is a major challenge in the field of energy and fuel technology. This article aims to highlight the major challenges associated with researching hydrogen–natural gas blends. Meeting this challenge requires a comprehensive research and development effort, including exploring appropriate blending techniques, optimising performance, addressing infrastructure requirements, and considering regulatory considerations. Overcoming this challenge will enable the full potential of hydrogen–natural gas blends to be realised as a clean and sustainable energy source. This will contribute to the global transition to a greener and more sustainable future. Several international, European, and Romanian studies, projects, and legislative problems are being analysed. The mix between H2 and natural gas decreases fugitive emissions. In contrast, using hydrogen increases the risk of fire more than using natural gas because hydrogen is a light gas that easily escapes and ignites at almost any concentration in the air.

Ignition delay times of C1–C7 natural gas blends in the intermediate and high temperature regimes: Experiment and correlation

This study presents new ignition delay time data for two multi-component natural gas (NG) blends composed of C1–C7n-alkanes with methane as the major component. New experimental data were recorded using a high-pressure shock tube (HPST) at reflected shock pressures (p5) of 10–30 bar, at temperatures (T5) in the range 770–1480 K, and at equivalence ratios (φ) of 0.5–1.5 in ‘air’. The current results together with published rapid compression machine (RCM) measurements show that higher concentrations of larger molecular weight n-alkanes in the NG blends increase fuel reactivity by more than an order of magnitude with mixtures that have ∼18.75% of C3–C5 components compared to mixtures that have ∼44.4% of C3–C7 components at temperatures below 1000 K. On the contrary, at higher temperatures the effect of increasing reactivity is reduced. NUIGMech1.2 is used to simulate the conditions studied and shows good agreement with the experimental ignition delay time data. A correlation equation is developed through regression analyses using NUIGMech1.2 to predict ignition delay times for a wide range of C1–C7 NG mixtures, in the pressure range 10–50 bar, at temperatures in the range 950–2000 K, and at φ = 0.3–3.0 in air. The proposed correlation expression that employs a traditional Arrhenius form is successfully validated against the new experimental data as well as previously published HPST experimental data.

Controlled ignition of low-carbon gas-engine fuels based on natural gas and hydrogen: process kinetics

The potential wide use of environmentally friendly low-carbon gas fuel based on natural gas, hydrogen, their mixtures, and syngas in power generation and transport requires detailed information about the kinetics of ignition of these gases at temperatures below 1000 K, at which fuel ignition occurs in internal combustion engines (ICEs) and gas turbines. The same temperature range is also important for monitoring the storage and transportation conditions of these fuels. Although there are quite a few studies addressing the ignition of classical gas fuels such as methane or hydrogen, there is an obvious lack of works dealing with real natural gases and gas mixtures. Furthermore, even for methane and hydrogen, data on the ignition at high temperatures (T > 1000 K), which have been mainly gained by the shock-wave method for highly diluted mixtures, are at variance with the kinetic estimations for real conditions of operating with them or their use in ICEs. Considering the ignition characteristics at T < 1000 K is also important for syngas, the largest-scale base product of gas chemistry and the main industrial source of hydrogen. The pronounced discrepancies between the extrapolation of the results obtained for high-temperature ignition to lower temperatures and the results of kinetic modelling of these processes make it necessary to analyze their causes. This review addresses new experimental results on the ignition of methane–alkane and methane–hydrogen mixtures (real gas fuels) and kinetic modelling of these processes, which reveal significant changes in the ignition behaviour at T < 1000 K. These changes in the ignition process upon the variation of the temperature, pressure, and composition of the mixture are related to significant changes in the methane and hydrogen oxidation mechanisms in this temperature range. They are mainly caused by changes in the kinetics and, hence, the role of peroxide compounds and radicals in methane and hydrogen oxidation following temperature and pressure variation. The established features bring about the question of the adequacy of the existing criteria for assessing the knock resistance of gas engine fuels, primarily those containing hydrogen, when they are used in ICEs, and for assessing their explosiveness and measures taken for their safe handling. The review considers the possible methods for improving the knock characteristics of natural and associated gases to meet the requirements of power equipment manufacturers.<br> The bibliography includes 128 references.

Multi-functional Flow Assurance Chemicals: Corrosion and Kinetic Hydrate Inhibition from Maleic Anhydride:N-Vinyl Caprolactam Copolymers and Synergists

Water-based flow assurance issues include corrosion, scale, and gas hydrate formation. Chemical solutions to mitigate these issues usually require separate inhibitors, which sometimes can lead to compatibility difficulties. Herein, we report studies on maleic-based copolymers to combat hydrate and corrosion with a view to optimizing for scale inhibition also. The product of maleic anhydride:N-vinyl caprolactam copolymer reacted with 3-dibutylaminopropylamine (MA:VCap-DBAPA) and its amine oxide derivative (MA:VCap-DBAPA-AO) were the kinetic hydrate inhibitor (KHI) polymers investigated. Due to limited CO2 corrosion inhibition (CI) by the polymers alone, various oxygen-, sulfur-, and nitrogen-based additives were screened for improved CO2 CI and possible KHI synergy. KHI performance screening tests were conducted under high pressure with a structure II-forming natural gas mixture in steel rocking cells using the slow (1 °C/h) constant cooling method. CO2 corrosion inhibition was measured by linear polarization resistance in a stirred 1 L CO2 bubble test apparatus using C1018 steel coupons and 3.6 wt % brine at 20.5 °C. Several sulfur-based additives improved the CI efficiency of the maleic polymers, especially butyl thioglycolate and 2-aminoethanethiol, without a negative effect on the KHI performance. For example, 2500 ppm MA:VCap-DBAPA plus 1000 ppm butyl thioglycolate gave an average hydrate onset temperature (To) of 4.4 °C (12.7 °C below the To for no additive) and 99.7% CI efficiency. In contrast to a classic fatty acid imidazoline surfactant corrosion inhibitor, butyl thioglycolate was also found to greatly enhance the CI efficiency of industrial KHIs, poly(N-vinyl caprolactam) (PVCap) and N-vinyl pyrrolidone:N-vinyl caprolactam copolymer, with no antagonism to the KHI performance of the polymer. In addition, butyl thioglycolate boosted the KHI performance of PVCap. The use of small synergists such as butyl thioglycolate avoids the use of classical surfactant corrosion inhibitors which can lead to tighter emulsions and poor overboard oil-in-water quality.

Polymer materials for solving actual problems of membrane gas

Membrane gas separation using polymeric membranes is one of rapidly developing energy-conserving technologies. This review describes the scope of membrane gas separation problems and demonstrates the relevance of membrane methods for their solution. The basic concepts and regularities of diffusion gas transfer and principles and characteristics of membrane gas separation are considered. The main physicochemical approaches to the selection of membrane materials considering both the properties of the gas–polymer system and the structure and physical properties of polymers are discussed. The considered issues are combined within a common approach to substantiate the choice of both existing commercial polymers and advanced polymeric materials to address important gas separation problems such as separation of air components; carbon dioxide, hydrogen and helium recovery from natural and industrial gas mixtures; and separation of a nitrogen and methane mixture. The avenues of development of the membrane materials science to solve each of the mentioned problems of membrane gas separation are demonstrated. The review is intended for specialists in the synthesis and physics of polymers for planning the research and assessing the applicability of polymeric materials for various practical gas separation problems and for specialists in the membrane materials science and membrane technology. <br> The bibliography includes 165 references.

Deblending and purification of hydrogen from natural gas mixtures using the electrochemical hydrogen pump

This work evaluates the use of Electrochemical Hydrogen Pumps (EHPs) for H2 deblending from natural gas (NG) grids for use in H2 refuelling stations which need to meet the high ISO 14687-2019-D purity standards. Concentrations of 20, 50 and 80% H2 in either CH4 or NG were tested at current densities of 0.2 and 0.3 A cm−2. Moreover, the impact of adding O2 and O2/O3 bleeds to the inlet EHP feeds were investigated for their effectiveness in mitigating poisoning of the EHP catalysts. The CH4 concentration requirement of <100 μmol mol−1 was met using NG at 0.3 A cm−2 (20–80% H2) or with 80% H2 at 0.2 A cm−2; however, the CO2 limit of <2 μmol mol−1 could not be met, due to the high permeability of CO2 in Nafion®. Moreover, the other hydrocarbon concentrations limit of <2 μmol mol−1 could be met when operating with 80% H2 in NG at 0.3 A cm−2. Additionally, the EHP demonstrated low energy consumption, particularly at 0.2 A cm−2 ranging from 3.5 to 12.5 kWh kgH2−1.

Inhibiting effect of a composite formulation of kinetic and thermodynamic inhibitors for gas hydrate formation in high water cut oil–water emulsion

AbstractIn oil and gas exploitation and transportation, it is essential to avoid hydrate blockage in the wellbores and pipelines. Using kinetic inhibitors in composite with thermodynamic inhibitors can reduce the operational expenditure for oil and gas pipelines under high water content conditions. The phase equilibria of pure water natural gas system, oil–water natural gas system, and oil–water monoethylene glycol (MEG) natural gas system were first investigated by experiments and combined with software predictions in this study. The results showed that both mineral oil and MEG shifted the phase equilibrium of the system to high‐pressure and low‐temperature directions. The oil phase increased the effective temperature range of the compounding inhibitor. Then the hydrate inhibition performance and natural gas hydrate generation characteristics of the composite formulation of Luvicap 55w and MEG in oil–water emulsions and natural gas mixtures were investigated. With the increased subcooling, the induction time decreased sharply, and the gas consumption increased. The induction time increased with increasing MEG concentration, which verified the synergistic effect of MEG in oil–water emulsion for Luvicap 55w. The hydrate generation characteristics did not change much with increasing Luvicap concentration at the same temperature. In contrast, the hydrate induction time rose from 142.8 to &gt;3500 min as the MEG concentration increased from 10 to 20 wt%.