Natural Gas Hydrogen Blends Research Articles

Nox Emissions Assessment of a Multi Jet Burner Operated with Premixed High Hydrogen Natural Gas Blends

Abstract Decarbonization of gas turbine combustion creates a pressing demand for new technical solutions for the combustion process. While switching to hydrogen fuels may solve the problem of carbon emissions and associated pollutants it can also lead to stability issues for swirl-stabilized combustors due to its increased reactivity. However, with jet flame burner systems, the required flashback safety can be achieved with high axial flow velocities even for premixed combustion of 100% hydrogen fuel. The development of such an engineering solution, however, requires significant effort to reach the maturity of today's swirl burners. This study examines the capacity of a premixed multi-tube jet burner to manage the chemical reactivity change over a range of volumetric blends from pure natural gas to pure hydrogen fuel. NOx emissions are measured and analyzed for atmospheric tests. The changes in emissions originate not only from altered combustion chemistry but also from changes in flame shape and turbulence intensity. To get a deeper understanding of the NOx formation process, a low-order model is designed and compared to the experimental data of technically and perfectly premixed combustion tests. Parameter variations of the low-order model are conducted to assess the influences on the NOx emission production of the multi jet burner. The information on the combustion process required for the model is obtained computationally and experimentally. Therefore, flame images are recorded and analyzed.

Assessing Hydrogen Embrittlement in Pipeline Steels for Natural Gas-Hydrogen Blends: Implications for Existing Infrastructure

Governments worldwide are actively committed to achieving their carbon emission reduction targets, and one avenue under exploration is harnessing the potential of hydrogen. Blending hydrogen with natural gas is emerging as a promising strategy to reduce carbon emissions, as it burns cleanly without emitting carbon dioxide. This blending could significantly contribute to emissions reduction in both residential and commercial settings. However, a critical challenge associated with this approach is the potential for Hydrogen Embrittlement (HE), a phenomenon wherein the mechanical properties of pipe steels degrade due to the infiltration of hydrogen atoms into the metal lattice structure. This can result in sudden and sever failures when the steel is subjected to mechanical stress. To effectively implement hydrogen-natural gas blending, it is imperative to gain a comprehensive understanding of how hydrogen affects the integrity of pipe steel. This necessitates the development of robust experimental methodologies capable of monitoring the presence and impact of hydrogen within the microstructures of steel. Key techniques employed for this assessment include microscopic observation, hydrogen permeation tests, and tensile and fatigue testing. In this study, samples from two distinct types of pipeline steels used in the natural gas distribution network underwent rigorous examination. The findings from this research indicate that charged samples exhibit a discernible decline in fatigue and tensile properties. This deterioration is attributed to embrittlement and reduced ductility stemming from the infiltration of hydrogen into the steel matrix. The extent of degradation in fatigue properties is correlated not only to the hydrogen content but also to the hydrogen permeability and diffusion rate influenced by steel’s microstructural features, with higher charging current densities indicating a more significant presence of hydrogen in the natural gas pipeline blend.

Effect of Water Injection on Combustion and Emissions Parameters of SI Engine Fuelled by Hydrogen–Natural Gas Blends

Technologies used in the transport sector have a substantial impact on air pollution and global warming. Due to the immense impact of air pollution on Earth, it is crucial to investigate novel ways to reduce emissions. One way to reduce pollution from ICE is to use alternative fuels. However, blends of alternative fuels in different proportions are known to improve some emissions’ parameters, while others remain unchanged or even worsen. It is therefore necessary to find ways of reducing all the main pollutants. For SI engines, mixtures of hydrogen and natural gas can be used as alternative fuels. The use of such fuel mixtures makes it possible to reduce CO, HC, and CO2 emissions from the engine, but the unique properties of hydrogen tend to increase NOx emissions. One way to address this challenge is to use port water injection (PWI). This paper describes studies carried out under laboratory conditions on an SI engine fuelled with CNG and CNG + H2 mixtures (H2 = 5, 10, 15% by volume) and injected with 60 and 120 mL/min of water into the engine. The tests showed that the additional water injection reduced CO and NOx emissions by about 20% and 4–5 times, respectively. But, the results also show that water injection at the rate of 120 mL/min increases fuel consumption by between 2.5% and 7% in all cases.

Experimental study of the performance of a SI-engine fueled with hydrogen-natural gas mixtures

Green hydrogen has become more attractive as a fuel for engines to reduce greenhouse gas emissions. By mixing it with natural gas (NG), the modification work on the engine can be minimized but the carbon dioxide emissions from combustion can still be decreased. In this paper, an experimental study was accomplished to investigate the performance of a spark-ignition engine fueled with hydrogen-natural gas blends by either keeping a constant ignition timing or changing it. Up to 25 mol-% hydrogen was mixed into natural gases with different compositions and the methane number and Wobbe index were calculated and compared to the requirements set by Euromot. The results show that up to 15 mol-% hydrogen can be blended into NG to meet the limits of Euromot. However, when 25 mol-% hydrogen was mixed into NG the methane number varied between 56 and 64 depending on the gas composition. This would most likely cause knock for a mixture consisting of higher hydrocarbons but during the executed tests knock was never a problem. Furthermore, it was detected that the methane number alone cannot tell the knock tendency of a gas in a certain engine and an additional condition is needed such as the hydrogen level. An adjusted ignition timing was also preferable compared to a constant one to keep the engine component temperature at a moderate level.

Метод визначення коефіцієнта стиснення газоводневої суміші з використанням регресійного рівняння та алгоритму штучної нейронної мережі

Метод визначення коефіцієнта стиснення газоводневої суміші з використанням регресійного рівняння та алгоритму штучної нейронної мережі

Techno-Economic Analysis of Hydrogen–Natural Gas Blended Fuels for 400 MW Combined Cycle Power Plants (CCPPs)

Various research and development activities are being conducted to use hydrogen, an environmentally friendly fuel, to achieve carbon neutrality. Using natural gas–hydrogen blends has advantages such as the usage of traditional combined cycle power plant (CCPP) technology and existing natural gas piping infrastructure. Therefore, we conducted CCPP process modeling and economic analysis based on natural gas–hydrogen blends. For process analysis, we developed a process model for a 400 MW natural gas CCPP using ASPEN HYSYS and confirmed an error within the 1% range through operation data validation. For economic analysis, we comparatively reviewed the levelized cost of electricity (LCOE) of CCPPs using hydrogen blended up to 0.5 mole fraction. For LCOE sensitivity analysis, we used fuel cost, capital expenditures, capacity factor, and power generation as variables. LCOE is 109.15 KRW/kWh when the hydrogen fuel price is 2000 KRW/kg and the hydrogen mole fraction is increased to 0.5, a 5% increase from the 103.9 KRW/kWh of CCPPs that use only natural gas. Economic feasibility at the level of 100% natural gas CCPPs is possible by reducing capital expenditures (CAPEX) by at least 20%, but net output should be increased by at least 5% (20.47 MW) when considering only performance improvement.

Performance Evaluation of an Anode-Supported Solid Oxide Fuel Cell Short-Stack Operating with Different Hydrogen-Natural Gas Blends as Stationary Combined Heat and Power System

One of the most promising characteristics of Solid Oxide Fuel Cells (SOFCs) is the possibility to process a wide variety of fuels with high electrical efficiencies, when compared to other types of fuel cells. Considering the prospected transition of the Natural Gas (NG) grid to hydrogen to decarbonize the gas sector, SOFCs could play a crucial role as efficient and clean stationary Combined Heat and Power (CHP) systems.In this work a 15-cell SOFC short-stack (Anode Supported, cell area 121 cm2) has been analysed experimentally under different compositions resembling possible short-, medium- and long-term gas grid scenarios (100% NG, 67%H2 blend in NG and 100%H2) which have been obtained by a preliminary system-level simulation which takes into account operating conditions of the stack and fine-tuning of the system parameters (e.g. Recirculation Rate RR, once through Fuel Utilization FUot, global Fuel Utilization FUtot) to optimize the overall system-level efficiency. Several tests were run at different temperatures (640-710 °C), Fuel Utilization (FU, 50%-70%) and at current loading (15-30 A - part/full load), characterizing in detail the stack response from an electrochemical (polarization curves and short-term stability tests) and chemical conversion point of view (gas chromatographic analyses in OCV and under load), as well as mapping its performances in stationary conditions (output power and stack-level efficiency). The conversion efficiency has been assessed in detail with different approaches at both stack and cell level, considering both once-through (stack-level) and total (system) FU rates.After having confirmed that the stack performances in reference testing conditions are fully aligned to the stack manufacturer data, confirming the test bench setup validity, the foreseen testing campaign has been carried out showing compatibility of the SOFC stack in the investigated conditions. The results show that from a pure performance point of view the 100%H2 composition obtains highest voltage and power at nominal conditions due to losses of the reformate compositions due to lower OCV values and kinetic behaviour of the chemical reaction chains. Instead, from an efficiency point of view the reformate conditions obtain higher stack-level efficiency (72.02% for the 67%H2+NG; 69.45% for the 100%NG) respect to the 100%H2 compositions (68.61%) due to the lower input fuel calorific value. The comparison of the different efficiency definitions provides further insight on the process and system level. By comparing reference testing conditions before and after the testing campaign it is possible to confirm that no significant degradation has occurred at global stack level in all the compositions. Figure 1

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.

Effect of degraded environmental conditions on the service behavior of a X65 pipeline steel not designed for hydrogen transport

With the international drive to deploy green energies and decarbonized intermediates in the place of fossil fuel sources, a large number of developed countries are actively preparing for a future where hydrogen plays a strategic role as an energy storage medium. Producing and using hydrogen requires the rapid expansion of a dedicated, economically viable industrial sector. Nevertheless, questions on how to safely store, transport and distribute hydrogen remain an important priority today. In countries with existing natural gas transport grids, the possibility to retrofit these networks to store and transport hydrogen-natural gas blends is being studied.A key challenge is to evaluate how pressurized H2 would interact with steel structures with regards structural embrittlement of the latter, with a view to exploiting existing transport infrastructures for storage and transport applications. In this work, we evaluate the H2-performance of a non-hydrogen service ×65 pipeline steel. The cracking susceptibility of this steel grade has been evaluated at 100 bar H2 using slow strain rate testing, Constant strain testing and fracture toughness measurements. Accompanying hydrogen permeation tests under pressure provide diffusion data and elucidate the discussion. Exposures were carried out in dry or wet H2 and with or without H2S contamination at levels representative of biogas. The results underline that the impact of dry or wet hydrogen on this grade are moderate. The presence of traces of H2S together with humidity could risk seriously degrading the mechanical performance of the ×65 steel grade.

Performance Evaluation of an Anode-Supported Solid Oxide Fuel Cell Short-Stack Operating with Different Hydrogen-Natural Gas Blends as Stationary Combined Heat and Power System

In the perspective of the transition of gas grids towards hydrogen/natural gas blends or even pure hydrogen, Solid Oxide Fuel Cells “SOFC” could play a crucial role as efficient and clean stationary Combined Heat and Power (CHP) systems, flexibly operating on different feedstocks. A SOFC short stack is analyzed experimentally under different fuel gas compositions which emulate different gas grid transition scenarios. The testing campaign is defined with the aid of a preliminary system-level simulation which assesses system architecture and operating strategy (off-gas recirculation, external reforming, etc.). Experimental tests (polarization curves and performance/efficiency maps) are run in different operating conditions in terms of fuel utilization, current loading and temperature in three gas composition scenarios. Experimental results show that – albeit the highest voltage/power is obtained with the 100%H2 scenario – the efficiency may be higher with 100%NG and blend scenarios, due to the lower energy content of the input fuel.

An experimental study on the environmental impact of hydrogen and natural gas blend burning

In this study, an experimental investigation is conducted to analyze the effect of adding hydrogen into natural gas on emissions and the burning performance of the obtained blends. Natural gas alone and natural gas-hydrogen blends are burned in identical gas stoves, and the emitted CO, CO2, and NOx are measured. The base case with natural gas only is compared with the natural gas and hydrogen blends (including hydrogen additions of 10%, 20% and 30% volumetrically). The experimental results show that the combustion efficiency increases from 39.32% to 44.4% by enhancing the hydrogen blending ratio from 0 to 0.3. While CO2 and CO emissions are reduced with rising the hydrogen ratio in the blend, NOx emissions have a fluctuating trend. Moreover, a life cycle analysis is performed to determine the environmental impact of the considered blending scenarios. With the blending ratio of 0.3 hydrogen by volume, global warming potential decreases from 6.233 to 6.123 kg CO2 equivalents per kg blend, and acidification potential reduces from 0.0507 to 0.04928 kg SO2 equivalents per kg blend in comparison with natural gas. On the other hand, human toxicity, abiotic depletion, and ozone depletion potentials per kg blend show slight augmentation from 5.30 to 5.52 kg 1,4-dichlorobenzene (DCB) eq., 0.0000107 to 0.00005921 kg SB eq., and 3.17 × 10−8 to 5.38 × 10−8 kg CFC-11 eq., respectively.

Research on the hydrogen injection strategy of a turbulent jet ignition (TJI) rotary engine fueled with natural gas/hydrogen blends

Natural gas/hydrogen blends (NGHB) fuel is considered as one of the ideal alternative fuels for the rotary engine (RE), which can effectively reduce the carbon emissions of RE. Additionally, applying turbulent jet ignition (TJI) mode to RE can significantly increase the combustion rate. The purpose of this study is to numerically investigate the influence of hydrogen injection position (HIP) and hydrogen injection timing (HIT) on the in-cylinder mixture formation, flame propagation and NOx emission of a TJI hydrogen direct injection plus natural gas port injection RE. Therefore, in this paper, a test bench and a 3D dynamic simulation model of the turbulent jet ignition rotary engine (TJI-RE) fueled with NGHB were respectively established. Moreover, the reliability of the 3D simulation model was verified by experimental data. Furthermore, based on the established 3D model, the fuel distribution and flame propagation in the cylinder under different HIPs and HITs were calculated. The results indicated that the HIP and HIT could change the hydrogen distribution by altering the impact position, impact angle, and the strength of vortexes in the cylinder. To improve the flame propagation speed, more hydrogen should be distributed in the pre-chamber. Additionally, a higher concentration of hydrogen in the cylinder should be maintained above the jet orifice. This was not only conducive to the rapid formation of the initial fire core in the pre-chamber, but also significantly improved the combustion rate of the in-cylinder mixture. Compared with other hydrogen injection strategies, the hydrogen injection strategy by using the HIP at the middle of the cylinder block and the HIT of 190oCA(BTDC) could obtained the highest peak value of in-cylinder pressure and the highest NOx emission.

Greenhouse gas reduction potential and cost-effectiveness of economy-wide hydrogen-natural gas blending for energy end uses

North American and European jurisdictions are considering repurposing natural gas infrastructure to deliver a lower carbon blend of natural gas and hydrogen; this paper evaluates the greenhouse gas reduction potential and cost-effectiveness of the repurposing. The analysis uses a bottom-up economy-wide energy-systems model of an emission-intensive jurisdiction, Alberta, Canada, to evaluate 576 long-term scenarios from 2026 to 2050. Many scenarios were included to give the analysis broad international applicability and differ by sector, hydrogen blending intensity, carbon policy, and hydrogen infrastructure development. Twelve hydrogen production technologies are compared in a long-term greenhouse gas and cost analysis, including advanced technologies. Autothermal reforming with carbon capture provides both lower-carbon and lower-cost hydrogen compared to most other technologies in most futures, even with high fugitive natural gas production emissions. Using hydrogen-natural gas blends for end-use energy applications eliminates 1–2% of economy-wide GHG emissions and marginal GHG abatement costs become negative at carbon prices over $300/tonne. The findings are useful for stakeholders expanding the international low-carbon hydrogen economy and governments engaged in formulating decarbonization policies and are considering hydrogen as an option.

Study to Adapt Industrial Gas Turbines for Significant and Viable CO2 Emissions Reduction

Abstract Gas turbines have been a significant part of energy production and transportation for decades and should continue indefinitely. As the world evaluates the best approaches to achieve net-zero greenhouse gas emissions in the world by 2050, while also meeting energy demand, the industrial gas turbine will remain part of that solution with a variety of adaptations. Current (2021) global temperature rise from preindustrial levels is at about 1.2 °C and increasing at a significant rate. The Paris Agreement's objective is to mitigate this rise to 1.5 °C to stem climatic catastrophes and change. Adapting industrial gas turbines for lower CO2 emissions and carbon capture will be incentivized as the pricing authority on CO2 emissions will continue to increase throughout the world. Using the vast existing natural gas infrastructure, post combustion carbon capture adapting to pure hydrogen or hydrogen/natural gas blends, and other augmented solutions will yield substantial GHG reductions that could be implemented on industrial gas turbines. This paper presents the performance impact of adapting the industrial gas turbines for cost-effective carbon capture and using fuels with lower carbon content, such as hydrogen and hydrogen-natural gas blends. As a part of the discussion, the options of either transporting hydrogen to a power plant or transporting natural gas to said power plant and compressing and transporting captured CO2 back to a sequestration site, are evaluated, and supported with simulation data. Lastly, various configurations and mitigations that minimize carbon intensity are discussed and assessed through a simplified techno-economic analysis showing thresholds where industrial gas turbines remain viable in a clean energy future. Industrial gas turbines are needed for growing energy demand and to complement the growing deployment of clean and safe renewable energy sources.

Large-scale long-distance land-based hydrogen transportation systems: A comparative techno-economic and greenhouse gas emission assessment

Interest in hydrogen as an energy carrier is growing as countries look to reduce greenhouse gas (GHG) emissions in hard-to-abate sectors. Previous works have focused on hydrogen production, well-to-wheel analysis of fuel cell vehicles, and vehicle refuelling costs and emissions. These studies use high-level estimates for the hydrogen transportation systems that lack sufficient granularity for techno-economic and GHG emissions analysis. In this work, we assess and compare the unit costs and emission footprints (direct and indirect) of 32 systems for hydrogen transportation. Process-based models were used to examine the transportation of pure hydrogen (hydrogen pipeline and truck transport of gaseous and liquified hydrogen), hydrogen-natural gas blends (pipeline), ammonia (pipeline), and liquid organic hydrogen carriers (pipeline and rail). We used sensitivity and uncertainty analyses to determine the parameters impacting the cost and emission estimates. At 1000 km, the pure hydrogen pipelines have a levelized cost of $0.66/kg H2 and a GHG footprint of 595 gCO2eq/kg H2. At 1000 km, ammonia, liquid organic hydrogen carrier, and truck transport scenarios are more than twice as expensive as pure hydrogen pipeline and hythane, and more than 1.5 times as expensive at 3000 km. The GHG emission footprints of pure hydrogen pipeline transport and ammonia transport are comparable, whereas all other transport systems are more than twice as high. These results may be informative for government agencies developing policies around clean hydrogen internationally.

The potential of the natural gas grid to accommodate hydrogen as an energy vector in transition towards a fully renewable energy system

The temporal and geographical availability of renewable energy sources is highly variable, which imposes the importance of correct choices for energy storage and energy transport systems. This paper presents a smart strategy to utilize the natural gas distribution grid to transport and store the hydrogen. The goal is twofold: evaluating the capacity limits of the grid to accommodate “green hydrogen” for preset increasing shares of renewable energy sources (RESs) and determining at the same time the optimal mix of wind, photovoltaic (PV), biomethane and power-to-gas systems that minimizes the investment and operation costs. To this end, the energy supply system of an entire country is modelled and optimized considering the real characteristics and pressure levels of the gas grid, which is assumed to be the only storage mechanism of green hydrogen. The operational concept is to fill up the gas grid with hydrogen during the day and with natural gas during the night while always consuming the natural gas-hydrogen blend. Green hydrogen is generated by electrolysers powered by PVs, wind turbines and biomethane power systems. Results of the optimizations showed that: i) as long as the share of RES does not exceed 20%, there is no need to use the gas grid as RES storage system, ii) from 20 to 50% of RES share the gas grid receives the surplus of electricity in the peaks that would be necessary to “complete” the dispatchability of RES electricity, iii) above 50%, the excess of electricity in the peaks has to be used to generate the thermal energy required by the consumers. The gas grid can be used as unique renewable energy carrier and storage system up to 65% of RES share.

Hydrate phase equilibrium of hydrogen-natural gas blends: Experimental study and thermodynamic modeling

Blending hydrogen (H2) into natural gas pipelines has become an effective way to transport H2 on a large scale. Due to the difference in properties between H2 and natural gas, the natural gas hydrate (NGH) phase equilibrium will be changed after blending H2, which influences the flow assurance in pipelines. In this work, hydrate phase equilibrium for CH4 + H2, CH4 + C2H6 + H2, and CH4 + C2H6 + C3H8 + H2 multicomponent systems had been measured at a temperature range from 274.24 K to 289.59 K by the isochoric pressure-search method. The results show the inhibition effect on CH4 hydrate formation of blending H2 to 20% is a little better than the 5.0 wt.%CH3OH solution. In addition, the Chen–Guo model was adopted to predict hydrogen-natural gas blends (HNGB) hydrates formation conditions, and model results have a good agreement with the experimental data. Average enthalpies of HNGB hydrates dissociation were also calculated utilizing the Clausius-Clapeyron equation, which was in the range of 68.02 kJ/mol and 90.17 kJ/mol. These studies provide basic data for flow assurance when transporting HNGB in pipelines.

Assessment of natural gas/hydrogen blends as an alternative fuel for industrial heat treatment furnaces

The present study investigates the application of natural gas/hydrogen blends as an alternative fuel for industrial heat treatment furnaces and their economic potential for decreasing carbon dioxide emissions in this field of application. Doing so, a detailed technological analysis of several influencing parameters on the heating system was performed as well as a consideration of furnace heating technology challenges. Starting with an evaluation of the main thermophysical properties of the blends and their corresponding flue gases, requirements for the heating systems were identified. Potential ways of decreasing flue gas losses and increasing the heat transfer are shown. In the radiant tube application, an increased overall combustion efficiency of about 1.2% was measured at 40 vol% hydrogen in the fuel gas. Influences on the air to gas ratio control system of the furnace is a further important point, which was considered in this study. Two commonly used control systems were evaluated concerning their capabilities to regulate the gas flow rates of blends with varying hydrogen contents and combustion properties, such as Wobbe Index. This is important, since it shows the capability to retrofit existing furnaces. Two types of burners were tested with different natural gas/hydrogen blends. This includes an open jet burner with air-staged and flameless combustion operation modes. A recuperative burner for radiant tube application was considered as well in these tests. Doing so, the nitrogen oxide formation of both systems under different operating conditions and different fuel blends were evaluated. An increase by about 10% at air-staged combustion and about 100% at flameless combustion was measured by a hydrogen content of 40 vol% in comparison to pure natural gas firing. Finally, the additional fuel costs of natural gas hydrogen blends and different cases are presented in an economic analysis. The driving force for the use of hydrogen as a fuel is the price of the CO2 certificates, which are considered in the analysis at a current price of 25.2 €/t CO2.

Critical hydrogen concentration of hydrogen-natural gas blends in clathrate hydrates for blue hydrogen storage

The so-called blue hydrogen production process, integrates conventional fossil fuel-based production methods with carbon capture and storage technologies. This combination reduces total CO2 emissions, compared to conventional grey fossil-fuel-based hydrogen production, and can be implemented more rapidly than renewable energy-based water-splitting green hydrogen production. Recently, hydrogen-natural gas blends (HNGB) have been proposed as a practical near-term option, because the blended H2 can be transported through existing natural gas pipelines. Clathrate hydrates could be a feasible way to store the HNGB in intermediate fuelling stations. In this study, we investigated and determined the critical hydrogen concentration (CHC) of HNGB hydrates and their formation kinetic patterns. The results suggest that including natural gas components (e.g., CH4 and C2H6) significantly affects the level of H2 occupation in the structural cages of the clathrate hydrates. Multiple hydrogen molecules were observed to occupy both small and large cages in all cases. Specifically, up to two and four H2 molecules occupied small and large cages, respectively, of the synthesized clathrate hydrate, which exhibited a critical H2 concentration when the feed gas ratio of CH4, C2H6, and H2 was 27:3:70 mol%. The kinetic properties were also determined for designing clathrate-based HNGB storage media. These findings provide practical insights for developing clathrate hydrate-based HNGB storage media and transportation systems in the near future.

Computational Fluid Dynamics (CFD) Transient Pressure and Temperature Simulation of a Natural Gas– Hydrogen Gas Blend Transportation Pipeline

The need for a CFD exploratory investigation into the possible effect of hydrogen injection into existing natural gas pipeline network, was the driver for this study. Recent technical feasibility reports on transporting a blend of both gases (JIR, 2019), did not mention if a study was done to rule out the possible effect of natural gas-hydrogen blend on hydrate formation in a hydrate-prone gas pipeline. A CFD model of 0.0508m and 10m length, with a mesh size of 20,000 elements was developed and simulated using ANSYS Fluent version R19.3. Hydrogen concentration by volume of 5%, 10%, 15% and 20% were simulated at velocities of 5m/s and 10m/s. The results indicated that increasing the volume concentration of hydrogen gas in the blend led to a reduction of downstream temperature. Again, the force on the inner wall decreased as the volume of hydrogen injected increased. The inference was that the reduction in temperature could lead to hydrates formation, whereas the reduction in exerted force on the pipe wall by the fluid could suggest a reduction in turbulence. However, this study was exploratory in nature and it is recommended that a detailed experimental study be carried out to clearly define the hydraulic and thermal behavior of a pipeline transporting a natural gas-hydrogen blend under various subcooling temperatures.