Hydrogen Blends Research Articles

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

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

Research on aerodynamic performance of centrifugal compressors for hydrogen-mixed natural gas.

Natural gas-doped hydrogen transportation has been widely used in industrial engineering. The change of the physical parameters of the conveying medium affects the working performance of the centrifugal compressor. This study aims to explore the aerodynamic performance of centrifugal compressors for hydrogen mixed natural gas, including the effects of hydrogen blending ratio (HBR) and inlet temperature on the pressure ratio and isentropic efficiency of compressors. The numerical simulation method is used and the results are compared with the experimental results to determine the reliability of the numerical simulation method. The results show that the pressure ratio decreases with the increase of HBR where the inlet temperature and rotation speed are constant. The pressure ratio and efficiency of the compressor are the highest when the conveying medium is pure natural gas (HBR = 0). The maximum pressure ratio reduction is 4.8% when the HBR is 5% and the inlet temperature is increased by 20 K. In summary, when the conveying medium of the compressor changes from pure natural gas to hydrogen-mixed natural gas, the working range and efficiency of the compressor will be reduced. Therefore, it is necessary to increase the rotation speed of the compressor or redesign the centrifugal compressor for hydrogen-mixed natural gas in order to achieve a constant flow rate at the outlet of the compressor.

Hydrogen enriched natural gas-fueled solid oxide fuel cells supported by Ni-Cu co-doping CeO2-δ catalyst-modified finger-like pore anode

Hydrogen blending in natural gas pipelines is one of the key technologies to realize the long-distance hydrogen transmission, which facilitates the large-scale hydrogen utilization. Solid oxide fuel cells can directly use hydrogen enriched natural gas (HENG, with 20 % H2) to generate electricity without separating and purifying the hydrogen, which enables the efficient conversion of hydrogen energy. In this work, finger-like pore anodes and Ni0.05Cu0.05Ce0.9O2-δ (NCCO) catalyst are prepared to address the need for anode performance and stability with hydrogen-doped natural gas fuels. The results show that NiCu@CeO2 precipitates NiCu nano-alloys on the surface after reduction treatment, which is beneficial for the anode activity. With NCCO catalyst, the maximum power densities of the single cells are 970 mW cm−2 and 700 mW cm−2 at 750 °C under wet H2 and HENG fuel atmospheres, respectively. At 750 °C, the methane conversion is as high as 46 %. More importantly, the single cell can run smoothly for 150 h, with the constant voltage (0.8 V) discharge and HENG as fuel gas. Our results confirm that the synthesized NCCO catalysts have excellent ability to catalyze CH4 and carbon resistance.

Understanding Environmental Barrier Coating Lifetimes and Performance for Industrial Gas Turbines

Abstract Hydrogen or hydrogen blend fuels are expected to replace natural gas in land-based industrial gas turbines (IGTs) to support a greener power economy. Silicon carbide (SiC) base ceramic matrix composites (CMCs) are considered for replacement of Ni-based superalloys to facilitate future efficiency improvements. SiC CMCs require environmental barrier coatings (EBCs) to mitigate volatilization from high-temperature steam, thus making the EBC lifetime critical information for identifying CMC component lifetimes. The goal of this project is to determine the maximum bond coating temperature underneath the EBC for achieving an IGT component lifetime goal of 25,000 h, which is far greater than current CMC component lifetime requirements for aeroturbine applications. To provide data for the lifetime model, laboratory testing used atmospheric plasma-sprayed rare-earth silicate EBCs on monolithic SiC substrates with an intermediate Si bond coating. Specimens exposed to 1-h thermal cycles in flowing air–steam environments and reaction kinetics were assessed from 700 °C to 1350 °C by measuring the thickness of the thermally grown silica scales. The silica growth and phase transformation appear critical in predicting EBC lifetime and several strategies have been explored to reduce the oxide growth rate and improve EBC durability at elevated temperatures. Advanced characterization using Raman spectroscopy has helped clarify this system.

Accelerated corrosion by nitrate-reducing bacteria and gaseous hydrogen permeation of X80 steel

Effects of hydrogen gas and Nitrate-Reducing Bacteria (NRB) on the corrosion and hydrogen permeation dynamics of X80 steel in simulated pipeline condensate water was investigated. Weight-loss analysis and electrochemical tests show a direct correlation between NRB-induced corrosion of X80 steel and the presence of hydrogen gas, particularly evident with escalating hydrogen blending ratios. Notably, corrosion primarily manifested through the formation of localized pitting, exhibiting a positive correlation with hydrogen blending ratios. Furthermore, the hydrogen permeating results show there is a synergistic enhancement of hydrogen permeating facilitated by the coexistence of hydrogen gas and NRB. Quantitative assessments of hydrogen permeability parameters highlighted significant amplifications in hydrogen diffusion flux (J) and apparent hydrogen concentration (Capp) under the combined influence of hydrogen and NRB, underscoring the complex interplay between these factors.

Multi-period operation of integrated electricity and gas systems with hydrogen blending considering gas composition dynamics

Green hydrogen from renewable sources can be blended with natural gas and serves as a potentially feasible measure for contributing to the net zero energy sector. The time-varying nature of hydrogen injection, influenced by stochastic renewable generations, can result in fluctuations in gas concentrations in the entire network. It poses a potential threat to the secure regulation of integrated electricity and gas systems (IEGS). For managing the operating condition and guaranteeing the security of IEGS during operation, a multi-period operation framework with alternative gas (e.g., hydrogen) blending is developed. First, a convex gas security range is derived using the Dutton method. Then, the multi-period operation framework is devised to mitigate the impacts of alternative gas injection on gas security over the entire operational period. Both the dynamics from gas composition and gas flow are modelled, accurately describing the real-time travel of alternative gas concentrations. The dynamics in the gas mixture properties (e.g., relative density) are fully revealed with time-varying gas concentrations. To tackle the high non-convexities in the optimization problem, second-order-cone relaxation is well-tailored and firstly used in the case of varying gas compositions, making the motion equations and advective transport equations more tractable. An advanced second-order-cone sequential programming is devised to drive the relaxation tight more efficiently. Finally, our operation strategy is illustrated in IEEE and Belgium Electricity and Gas Systems. Results indicate that hydrogen concentrations take about 12.5 h to travel from the injection point to the end of the pipeline route in the Belgium gas system. By incorporating this unique characteristic into the model, operational scheduling and dispatch in IEGS can be more practical when integrating hydrogen in the future.

Modeling and assessment of hydrogen-blended natural gas releases from buried pipeline

Blending hydrogen into natural gas pipelines for transportation reduces costs but increases safety risks. The main objective of this work is to explore the evolution of leakage hazards in hydrogen-blended natural gas pipelines and quantify these risks. To achieve this, multi-stage coupling numerical models are developed to explore the leakage hazards in hydrogen-blended natural gas transportation. The results show that the proposed model accurately predicts leakage rates of hydrogen-blended natural gas pipelines in various soil types. The gas diffusion pattern shifts from spherical to hemispherical, with the hazardous volume increasing linearly overall. The influence of pressure on leakage is amplified in the soil, while the impact of the leakage aperture is diminished. Although increasing the hydrogen blending ratio reduces the leakage rate, it also enhances the hazard evolution. Burial depth primarily affects alarm time, while an increase in leakage angle within 90–180° significantly delays the hazard evolution. Moreover, higher soil resistance not only mitigates the leakage diffusion but also reduces the pressure differential. The leakage aperture exhibits the highest correlation with the hazard evolution.

Fuel blend combustion for decarbonization

The utilization of fossil fuels is currently transforming to low-carbon or zero-carbon fuels, which is one of the solutions to global warming. Hydrogen and ammonia are regarded as promising zero-carbon fuels in power supply and transportation scenarios but the availability of hydrogen and their distinctly different chemical activity constrain their large-scale direct utilizations. Fuel blends with physical and chemical complementary are considered as the effective approaches in the utilization of hydrogen and ammonia because no significant modification to the existing end-user infrastructures is needed. This paper reports recent progress in the fundamental combustion behaviors of fuel blends, focusing on hydrogen-hydrocarbon blends and ammonia-hydrocarbon blends. Firstly, laminar flame behaviors, auto- and forced-ignition characteristics, and pollutant emissions of binary fuels containing hydrogen are reviewed, all of which are supplemented with a discussion on the governing hydrogen-enriched combustion chemistry. Subsequently, the hydrogen-enriched flame responses to the flow conditions are discussed, including the turbulent burning velocity and statistical structures, the flashback swirl flames, thermoacoustic instabilities, and the jet ignition characteristics; Furthermore, with the increasing concern over ammonia as a zero carbon fuel and its extremely weak reactivity, recent progress on combustion of fuel blends containing ammonia are also reviewed. The fundamental combustion chemistry studies including laminar burning velocity, the ignition delay times data collection, as well as the attempts for chemical kinetic modeling development for fuel blend with ammonia are presented. The literature reported ammonia containing blends of turbulent flame characteristics are presented. Finally, from an engineering point of view, examples using hydrogen blends in practical internal combustion engines and in gas turbines are introduced, including the topic of engine efficiency performance and pollutant emissions and different combustors for gas turbines. It is suggested that fuel blends with hydrogen or ammonia that potentially monitors the overall reactivity will be one realistic solution to de-carbonization, on the basis of current transportation and power generation systems.

Development of a Novel Correlation for Laminar Burning Velocity in Iso-Octane and Hydrogen Blends

Development of a Novel Correlation for Laminar Burning Velocity in Iso-Octane and Hydrogen Blends

Effects of hydrogen enrichment on the performance and emission characteristics of a diesel engine with the addition of Syzygium cumini (Jamun) biodiesel

ABSTRACT Biofuel made from Syzygium cumini, often known as Jamun, has the potential to be a low-cost, sustainable, and emission-free alternative. In this work, we experimentally explore the performance of a compression ignition (CI) engine that burns a blend of hydrogen and biodiesel. Hydrogen is pumped into the air intake manifold by means of a hydrogen gaseous supplement that, when exposed to atmospheric conditions, co-combusts with a pilot flame ignited by Jamun oil. To investigate the impact of hydrogen supplementation on performance and exhaust emission, a variety of hydrogen–Jamun fuel mixture proportions are provided to the engine. The research demonstrates that adding hydrogen improves the thermal efficiency (5%) of diesel engines whereas lowering specific energy fuel consumption (4%) at fixed Jamun flow rates. The gas emission data demonstrates that when hydrogen (HC) emission (12%) supplements decreases, NOx emission (10%) increases somewhat but opacity (8%) increases significantly. The experiment demonstrates that hydrogen and Jamun duel fuel in compression ignition engines burn smoothly.

Mathematical modeling for hydrogen blending in natural gas pipelines moving towards industrial decarbonization: Economic feasibility and CO2 reduction analysis

Hydrogen blending has proved to be a promising alternative to reduce CO2 emissions in current applications such as the industrial sector in which natural gas is the fuel source since it can mitigate GHG emissions and help to reach nation’s goal of decarbonization. This study explored the feasibility of different hydrogen blend compositions going from 1% to 30% hydrogen content (by volume) by computational simulations to determine the best performance of the system considering real operating conditions from Central Plant at UC Irvine. This work also performed an economic analysis as part of the implementation plan. It was determined that a blend of 19% H2 content could be implemented without any major renovation of utility infrastructure based on the operating conditions and change in the properties of the mixture. An addition of 30% H2 can reduce around 11% of the emissions produced by pure natural gas. This is equivalent to 1422 kg of CO2 in 1 h. It is evident that the higher the H2 content, the better the CO2 benefits that would be produced, but for the actual application of higher hydrogen content, there is a need for a better understanding of the effects of hydrogen in the current natural gas pipeline. Based on the CO2 savings, it was determined that a 30% blending of hydrogen may save about 22.2% of the economic cost compared to natural gas.

Towards hydrogen gas turbine engines aviation: A review of production, infrastructure, storage, aircraft design and combustion technologies

This study explores the potential of hydrogen gas turbine engines for sustainable aviation, with a particular focus on their development for low subsonic to transonic flight regimes. Hydrogen offers notable advantages, including zero CO2 emissions and high energy density. However, its widespread adoption is prevented by significant challenges in production, infrastructure, storage, aircraft design, and combustion technology. The limited availability of green hydrogen – the global production totaled only 127 kt in 2023, with 76% produced in China - raises concerns about the feasibility of a rapid shift to hydrogen-powered general aviation. Despite numerous pledges for hydrogen adoption in the Western world, major aircraft manufacturers have primarily engaged in marketing activities rather than substantial product innovation. To date, the only hydrogen aircraft demonstrator from this century is the 2012 Boeing Phantom Eye, which utilized modified hydrogen internal combustion engines rather than a gas turbine engine. The only hydrogen aircraft demonstrator with a gas turbine engine was the 1988 hybrid Tupolev Tu-155 which coupled one hydrogen gas turbine engine to other two jet fuel engines. This paper evaluates the current state of hydrogen gas turbine technology, comparing its combustion characteristics with traditional jet fuels and examining various NOx emission control techniques. It also investigates the potential of micro-mix lean combustion and staged combustion to achieve efficient and low-emission hydrogen combustion in gas turbines. Given the more extensive experience with terrestrial gas turbines compared to their aeronautical counterparts, the review includes insights from terrestrial power generation applications. Additionally, it considers hythane - a blend of hydrogen and natural gas - as a transitional solution for significantly reducing CO2 emissions while progressing towards net-zero targets. The review underscores the urgent need for advancements in green hydrogen production, technology, and infrastructure to overcome existing barriers and enable a more sustainable aviation future powered by hydrogen. Importantly, the review emphasizes the need to move beyond mere virtue signaling and make tangible progress toward a hydrogen economy.

Simulation of gas mixture dynamics in a pipeline network using explicit staggered-grid discretization

We develop an explicit staggered finite difference discretization scheme for simulating the transport of highly heterogeneous gas mixtures through pipeline networks. This study is motivated by the proposed blending of hydrogen into natural gas pipelines to reduce end use carbon emissions while using existing pipeline systems throughout their planned lifetimes. Our computational method accommodates an arbitrary number of constituent gases with very different physical properties that may be injected into a network with significant spatiotemporal variation. In this setting, the gas flow physics are highly location- and time- dependent, so that local composition and nodal mixing must be accounted for. The resulting conservation laws are formulated in terms of pressure, partial densities and flows, and volumetric and mass fractions of the constituents. We include non-ideal equations of state that employ linear approximations of gas compressibility factors, so that the pressure dynamics propagate locally according to a variable wave speed that depends on mixture composition and density. We derive compatibility relationships for network edge boundary values that are more complex than for a homogeneous gas. The simulation method is evaluated on initial boundary value problems for a single pipe and a small network, is cross-validated with a lumped element simulation, and used to demonstrate a local monitoring and control policy for maintaining allowable concentration levels.

Impact of Diluents on Flame Stability With Blends of Natural Gas and Hydrogen

Abstract Two potential decarbonization pathways for natural gas (NG)-fueled gas turbine engines include blending hydrogen (H2) into NG and postcombustion carbon capture. H2 blending changes several combustion properties, including flame speed and stretch sensitivity. The use of post-combustion carbon capture systems is typically facilitated by the implementation of exhaust gas recirculation (EGR), where exhaust gases are injected into the inlet of the engine, increasing carbon dioxide (CO2) concentration at the outlet and, hence, increasing the efficiency of carbon capture technologies. In this work, we explore the impact of H2 blending and EGR on the stability of a swirl-stabilized, central-piloted flame. Mixtures of NG and H2 are tested at a range of different diluent compositions, with oxygen varied from 21% to 15% by volume in the oxidizer. In all cases, a constant adiabatic flame temperature is maintained to mimic the operation of a gas turbine at a given turbine inlet temperature. A variable-length combustor is used for testing, where combustor length is varied to understand the dynamic stability characteristics of the system. Results show that EGR and H2 work in opposition to each other, where higher levels of EGR result in poor flame holding and higher levels of H2 result in better flame holding. Increasing H2 generally increases the amplitude of thermoacoustic instability at each condition, a result of the change in flame position in this particular combustor. Importantly, H2 can be added to NG to improve flame holding without significantly decreasing CO2 levels in the products, showing that H2 blending can be a method for counteracting combustor operability issues that arise from high levels of EGR necessary to improve the efficiency of typical carbon capture systems.

Extraction of sustainable and low-emission hydrogen from hydrogen-blended natural gas driven by multi-product sequential separation

Blending hydrogen in natural gas, taking advantage of the readily available pipeline transportation, is considered as a highly promising means of sustainable hydrogen deployment on a vast scale. However, re-obtaining hydrogen from the mixture for end users via conventional separation technologies could pose practical challenges both energetically and economically, due primarily to the relatively low blending ratio (<30 vol%). In contrast to the commonly adopted pressure swing adsorption (PSA) separation, we propose a thermochemical approach of deriving hydrogen with synergistic capture of CO2 by steam reforming of the mixture to tackle such challenges. The process is simulated by a two-dimensional model validated by experimental data. Three typical scenarios with hydrogen blending ratios of 0–30 vol% are investigated in the operating temperature range of 300–400 °C and natural gas pipeline pressure of ≤ 40 bar. Results show that in all scenarios the amount of hydrogen recovered can exceed the amount of renewable hydrogen initially blended and additional hydrogen could be contributed thermochemically, all at relatively low energy cost. Thermochemical methods increase the partial pressure of target products, reducing separation energy and increasing yield. For the typical 10 vol% blending ratio (widely adopted), when considering the separation of hydrogen at the end user and compressing the separated off-gas before transporting it to the next end user, the hydrogen separation cost, after counterbalancing with the revenue from carbon dioxide, is only 1.33$/kgH2 with the new approach. This corresponds to a decrease by over 70.2 % as compared with that of the PSA separation cost (4.45$/kgH2). The captured CO2 in its high-purity form helps to reduce the final cost of hydrogen by a maximum of 0.33$/kgH2. The new route shows great potential for integrated hydrogen production, hydrogen purification and carbon capture for the promotion of renewable energy, green hydrogen and related technologies.

9E heavy-duty gas turbine ammonia-hydrogen mixture combustion characteristics and NOx emission characteristics research

In this study, we used the numerical simulation tool FLUENT to numerically simulate the combustion of ammonia-hydrogen fuel in the combustion chamber of a 9E heavy-duty gas turbine, and analysed the effects of different hydrogen blending ratios on the stability of ammonia combustion and NOx emissions. We found that an increase in the hydrogen mixing ratio in the fuel during the ammonia-hydrogen mixture combustion process contributes to the reduction of NOx emissions and has a positive effect on combustion stability.

Effects of hydrogen addition on ignition characteristics and engine performance of ammonia-hydrogen blended fuel: A kinetic analysis

To investigate the effects of hydrogen addition on the ignition characteristics and engine performance of ammonia-hydrogen fuel, a reaction kinetics mechanism suitable for high-pressure engine conditions was proposed. The study explores the influence of hydrogen blending ratios on the ignition delay time (IDT) of ammonia-hydrogen fuel, revealing the sensitive reactions and evolution characteristics of reaction pathways during the ignition process of ammonia-hydrogen fuel promoted by hydrogen. The study also investigates the impact of hydrogen blending ratios on the engine performance of ammonia-hydrogen fuel. The results show that the IDT of ammonia significantly decreases with increasing hydrogen blending ratios and temperature. The addition of hydrogen to ammonia significantly lowers the autoignition temperature boundary of the mixture. Under low-temperature and low-pressure conditions, ammonia, which would not ignite originally, ignites due to the addition of hydrogen. The addition of hydrogen shifts the sensitive reactions of the mixture from NH3 and NH2-related reactions to H2/O2-related reactions, without altering the reaction pathway of ammonia, only changing the pathway flux of components such as NH2, H2NN, H2NO, and HONO. In a spark-ignition (SI) engine, maintaining the total fuel heat value and ignition timing constant, an increase in hydrogen blending ratio significantly raises the peak cylinder pressure. However, due to the forward movement of the heat release process, the power performance of engine experiences varying degrees of reduction. Therefore, it is necessary to delay the ignition timing of engine with the increase in hydrogen blending ratio, moving the combustion center beyond the top dead center (TDC). Furthermore, increasing the hydrogen concentration in the blend significantly raises the temperature and pressure during the engine combustion process, leading to an increase in the concentration of thermal NOX in the emissions.

Analysis of Leakage and Diffusion Characteristics and Hazard Range Determination of Buried Hydrogen-Blended Natural Gas Pipeline Based on CFD.

Injecting hydrogen into natural gas pipelines is an economical and efficient method of hydrogen transportation. However, the addition of hydrogen leads to significant hydrogen corrosion and embrittlement in the pipelines, especially in harsh and concealed underground conditions, where leak accidents are frequent and difficult to detect. This Article uses Le Chatelier's Principle to determine the hazardous range of hydrogen-blended natural gas (HBNG) by employing numerical simulation, it examines the gas leakage and diffusion characteristics before and after hydrogen injection as well as under different hydrogen blending ratio (HBR). Additionally, considering the density of the mixed gas, a prediction model for the diffusion hazard range of hydrogen-mixed natural gas is established based on multivariate regression theory. The results show that after a leakage occurs in HBNG the diffusion range in soil is wider compared to methane, with higher corresponding pressure and velocity values. Moreover, as the HBR increases, the farthest danger range (FDR) of the HBNG also increases. When the leakage of the buried HBNG pipeline occurs for 1 min, the difference in FDR between HBR 25% and HBR 5% is 0.005 m. After 30 min, this difference increases to 0.019 m, indicating that with longer leakage duration, the potential explosion risk resulting from increased HBR becomes greater. Factors such as pipeline pressure increase, larger leak hole size, and decreased burial depth all contribute to an increase in FDR, with pipeline pressure change having the greatest impact and burial depth change having the smallest impact. The maximum error of the predicted model for the diffusion hazard range of hydrogen-mixed natural gas is 9.385%, and the average error is 2.376%, demonstrating the accuracy of the prediction results. This study provides guidance for monitoring underground hydrogen-blended natural gas pipeline leaks, offers a basis for determining the repair range of pipelines, and ensures the safe transportation of hydrogen-mixed natural gas pipelines.

Investigating the explosive characteristics of hydrogen/ n-butane blended fuel: Experimental and kinetic insights

Investigating the explosive characteristics of H2/n-C4H10 mixtures is crucial for the safe utilization of this blended fuel. Our study focused on varying equivalent ratios and hydrogen blending ratios within a closed 20-L spherical explosion vessel. Additionally, the microscopic kinetics of the reactions were analyzed through chemical reaction simulation. Our findings indicate that the most violent explosion occurred at an equivalent ratio of 1.2. Increasing hydrogen content intensified combustion reactions, reducing flame thickness and inducing cellular structures along the flame front. This escalation also increased explosion pressure, flame temperature, and flame propagation speed, elevating explosion risk. Moreover, the equilibrium molar fraction of O2 and CO2 decreased while that of H2O increased with higher hydrogen blending ratios. Correspondingly, the heat release rate and generation rates of H•, O•, and OH• radicals increased. Notably, the peak time of C2H4 and CH4 consumption rates preceded. Additionally, R5: O2 + H• = O• + OH• and R978: C4H10 + H• = SC4H9 + H2 represented crucial promoting and inhibiting steps, respectively. These insights deepen our understanding of the explosion mechanism of H2/n-C4H10 mixtures, providing a theoretical basis for designing safer protective measures and evaluating explosion risks in industrial production.

A novel static mixer for blending hydrogen into natural gas pipelines

A novel static mixer is designed specifically to blend hydrogen into natural gas pipelines, and its effectiveness is validated by numerical simulation method. Firstly, the structural model of the proposed static mixer model for hydrogen-methane blending is introduced, and the evaluation indicators are defined. Secondly, the computational fluid dynamic model for the mixing process is established based on the Large Eddy Simulation(LES) method, and the accuracy of the numerical results is validated against the experimental data of a benchmark gas mixing model. Subsequently, using LES, effects structural parameters (angle and height of trapezoidal baffle, number of mixing elements, and spacing and installation distance of mixing elements) and flow parameters (main flow velocity and hydrogen blending ratio) on the mixing homogeneity and pressure drop of the static mixer are investigated systematically to explore the optimal design and operational conditions. The numerical results showed that the static mixer can significantly improve the mixing efficiency of hydrogen and natural gas with acceptable pressure loss. In the range of flow conditions concerned, a best performance of mixing could be obtained by installing the mixer at a distance of 3D (D is the diameter of the natural gas pipeline) downstream the blending point, setting the spacing between mixing elements as 1D and employing four mixing elements. Finally, the underlying physics of mass transportation are analyzed based on the vortex structures generated by the mixer.