Wobbe Index Research Articles

Industrial Decarbonization through Blended Combustion of Natural Gas and Hydrogen

The transition to cleaner energy sources, particularly in hard-to-abate industrial sectors, often requires the gradual integration of new technologies. Hydrogen, crucial for decarbonization, is explored as a fuel in blended combustions. Blending or replacing fuels impacts combustion stability and heat transfer rates due to differing densities. An extensive literature review examines blended combustion, focusing on hydrogen/methane mixtures. While industrial burners claim to accommodate up to 20% hydrogen, theoretical support is lacking. A novel thermodynamic analysis methodology is introduced, evaluating methane/hydrogen combustion using the Wobbe index. The findings highlight practical limitations beyond 25% hydrogen volume, necessitating a shift to “totally hydrogen” combustion. Blended combustion can be proposed as a medium-term strategy, acknowledging hydrogen’s limited penetration. Higher percentages require burner and infrastructure redesign.

Improved combustion stability of biogas at different CO2 concentrations using inhomogeneous partially premixed stratified flames

Biogas is a renewable and clean energy source that plays an important role in the current environment of low- carbon transition. If high-content CO2 in biogas can be separated, transformed, and utilized, it not only realizes high-value utilization of biogas but also promotes carbon reduction in the biogas field. To improve the combustion stability of biogas, an inhomogeneous, partially premixed stratified (IPPS) combustion model was adopted in this study. The thermal flame structure and stability were investigated for a wide range of mixture inhomogeneities, turbulence levels, CO2 concentrations, air-to-fuel velocity ratios, and combustion energies in a concentric flow slot burner (CFSB). A fine-wire thermocouple is used to resolve the thermal flame structure. The flame size was reduced by increasing the CO2 concentration and the flames became lighter blue. The flame temperature also decreased with increase in CO2 concentration. Flame stability was reduced by increasing the CO2 concentration. However, at a certain level of mixture inhomogeneity, the concentration of CO2 in the IPPS mode did not affect the stability. Accordingly, the IPPS mode of combustion should be suitable for the combustion and stabilization of biogas. This should support the design of highly stabilized biogas turbulent flames independent of CO2 concentration. The data show that the lower stability conditions are partially due to the change in fuel combustion energy, which is characterized by the Wobbe index (WI). In addition, at a certain level of mixture inhomogeneity, the effect of the WI on flame stability becomes dominant.

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.

Impact of Fuel Quality on Gas Turbine Components

Most industrial gas turbines operate with various gaseous and liquid fuels. For effective and sustainable performance, it is essential to determine the best fuel suitable for the operation of the gas power system. The heating value, Joule Thompson coefficient, dew point, Wobbe index, and other physical characteristics of the suggested fuel must be ascertained. This research explains a means of providing consistent treatment to determine the listed physical properties. It also reviews the impact that specific fuel characteristics have on the combustion process, as well as the overall operation of a gas turbine and its components.

Co-firing ammonia and hydrogen with butane under methane-equivalent calorific value and Wobbe index: Insights into transition in flame propagation and swirl flame characteristics

Fuel flexibility stands as a critical requirement for the development of combustors in future carbon-free energy systems. Carbon-free fuels including ammonia (NH3) and hydrogen (H2) are substantial supports for achieving this target, raising strong needs to counterbalance their distinct fuel thermochemical properties from methane (CH4), such as volumetric calorific value (CV) and Wobbe index (WI). In this work, butane (C4H10) which is an emerging renewable synthetic fuel is proposed to co-fire NH3 and H2 under methane-equivalent calorific value (MECV) and Wobbe index (MEWI). Laminar flame propagation of NH3/H2/C4H10 mixtures under MECV and MEWI are investigated in a cylindrical constant-volume combustion vessel. C4H10 co-firing can simultaneously tune the fuel thermochemical properties to CH4 levels and regulate the laminar flame propagation of NH3 and H2. Kinetic simulation and modeling analysis are performed to provide insights into the dominant kinetics and transition in laminar flame propagation. CV-compensated transition variables can generally well constrain the transition profiles of laminar burning velocity (LBV), while WI-compensated transition variables can linearize the transition profile from NH3 to C4H10 but meet challenges in constraining the transition profiles of H2-blending mixtures. Chemical effects are found to play the dominant role in the transition of laminar flame propagation, while thermal effects also have positive contributions. Test experiments in a gas turbine model combustor are also conducted to assess the swirl flame characteristics of NH3/H2/C4H10 mixtures under MECV and MEWI. The measured swirl flame morphologies and lean blowout limits indicate enhanced fuel reactivity and flame stability with the transition in fuel content, which is in accordance with the observed trends in LBV. Furthermore, comparison with CH4 provides a comprehensive evaluation of NH3/H2/C4H10 mixtures from the aspects of combustion characteristics and thermochemistry.

ТЕОРЕТИКО-ПРИКЛАДНІ ЗАСАДИ ЕКОНОМІЧНОЇ ОЦІНКИ ЯКІСНИХ ХАРАКТЕРИСТИК ПРИРОДНОГО ГАЗУ

The article examines the theoretical and applied foundations for the economic evaluation of natural gas quality characteristics, significantly impacting its efficient utilization and cost for consumers. The relevance stems from natural gas's importance as an energy source. The authors analyze classical (comparative price method, cost analysis) and modern (risk analysis, economic-mathematical modeling) methods for assessing gas quality. Key influencing factors are identified: competition level, government regulation, gas usage type, and technological equipment level. The principles outlined include determining quality indicators and their interrelationships; the impact of characteristics on efficiency across industries; evaluation methods considering extraction, transportation, and processing costs; pricing scenario modeling; and analysis of regulation and market mechanisms. The necessity of an integrated approach for decision-making regarding efficient use of varying gas qualities is substantiated. Emphasis is placed on analyzing quality indicators (calorific value, density, Wobbe index, component content) and their interrelationships based on real data. Investigating the impact of characteristics on the efficiency of use in industry, energy, and the municipal sector is crucial. Calculating the economic efficiency of using varying quality gas in these sectors, considering preparation, transportation, and processing costs, is essential. The development of methodological approaches for the economic evaluation of quality indicators, considering extraction, transportation, and processing costs, is underscored. Modeling pricing scenarios for varying quality gas and assessing the impact on consumer costs is vital. Building economic-mathematical models for demand/supply forecasting and simulating market operation with different pricing schemes is recommended. The analysis of the impact of changing quality parameters on consumer costs due to changes in extraction, transportation, and gas preparation is emphasized. The analysis of regulation and market pricing mechanisms for varying quality gas is highlighted. Developing recommendations for authorities, companies, and enterprises to optimize the use of varying quality gas for maximum efficiency and cost reduction is important. A comprehensive approach combining theoretical developments and applied research will form the foundation for management decisions on the efficient use of varying gas qualities.

Numerical simulation and performance analysis of solar hydrogen production using anion exchange membrane electrolyzer and blending with natural gas

Hydrogen production using solar energy and blending in a natural gas pipeline is a cost-effective alternative to hydrogen storage and transmission that leads to lower CO2 emissions caused by the energy infrastructure. In this paper, energy, exergy, and Exergoeconomic analyses of a solar hydrogen production system and its blending with natural gas in a city gate station of Isfahan city are performed in three days with minimum, average, and maximum solar irradiations. The system includes photovoltaic arrays, anion exchange membrane electrolyzer cells (AEMECs), a hydrogen compressor, and a system blending. The AEMEC is used due to its less expensive catalysts, non-acidic electrolyte, and high efficiency at high pressures. A three-dimensional numerical model is developed to determine the AEMEC’s polarization curve, accurately. The results show that with increasing solar irradiation and decreasing ambient temperature, the maximum power of the PV increases and the energy and exergy efficiency of the PV decreases. By increasing the injection of hydrogen into natural gas from 1% to 10% vol., the lower heating value of the fuel and the Wobbe Index decrease by 6% and 1.55%, respectively. By injection of 10% vol. hydrogen gas into natural gas compared to the case of using natural gas without hydrogen, the exergy cost of natural gas blended with hydrogen increases by 5.9%. Considering the environmental benefits of using hydrogen in combination with natural gas, including the reduction of greenhouse gases, and the fact that blending hydrogen up to 10% vol. with natural gas does not require any change in urban gas supply facilities, this process is feasible. In the case of using high-pressure AEMEC and removing the compressor to produce hydrogen at high pressure, the exergy cost of high-pressure hydrogen reduces by 29.3%.

The role of ammonia as an alternative fuel by mixing it into natural gas and satisfying the gas quality requirements

AbstractAmmonia as a carbon‐free e‐fuel has a good potential as a future energy vector to contribute to reducing greenhouse gas emissions. By mixing it into natural gas (NG), the carbon dioxide emissions are decreased when the mixture is burnt. To study the change in the gas properties of different NG compositions with and without added hydrogen, 0–20 mol% ammonia was mixed and various parameters were calculated. The results show that a higher content of ammonia decreases the compression factor, lower heating value, and Wobbe index (WI). Depending on the gas composition the relative density is either increasing, for NGs containing a high level of methane and/or hydrogen, or decreasing, for gases with larger quantities of higher hydrocarbons and/or inert gases. NGs with added hydrogen are more impacted by addition of ammonia, where the relative density can be improved by mixing the gas with ammonia to satisfy the gas quality requirements. However, taking the WI limits into account, more ammonia can be added into a NG without any hydrogen compared to one with hydrogen. The addition of ammonia into NG is possible considering the gas quality parameters, even in the case when the gas contains some hydrogen.

Thermodynamic performance study of large-scale industrial gas turbine with methane/ammonia/hydrogen blended fuels

The fuel interchangeability range without any modifications was proposed within 5% of Wobbe index (WI) by the gas turbine manufacturers. The system modifications, especially in combustor, are needed with the out-of-range 5% of WI. In this study, the thermodynamic performances were studied with the fuels exceeding 5% of WI, the focused fuel compositions were ammonia and hydrogen for eco-friendly power generation and carbon neutrality. A performance analysis was conducted for a J-class gas turbine wherein ammonia and hydrogen were mixed with conventional liquefied natural gas (LNG) fuel. The maximum mixable ratio of ammonia is 76%, and fuels with higher mixable ratio cannot achieve a high turbine inlet temperature (1873 K). 100% hydrogen can be used with stable operation if the flame stability is guaranteed by developing a new combustor with conventional compressor and turbines. Environmental–economic analysis was also conducted to study the effect of carbon-neutral fuel on air pollution. Mixing hydrogen is a highly effective method to reduce the air pollutant tax; however, mixing ammonia is not suitable for decreasing air pollutants. As ammonia emits enormous NOx, an after-treatment system is required to use ammonia as a carbon-neutral fuel.

Recent progresses in H2NG blends use downstream Power-to-Gas policies application: An overview over the last decade

This paper attempts to give a broad overview on technologies progress status, effects, perspectives, and issues associated to H2NG widespread applications. It deepens and completes the content of previous reviews by including hitherto unreviewed aspects as far as possible. To do so, a holistic approach has been used by surveying technical, energy, environmental, economic and safety issues related to the hydrogen mixtures’ use. This review aims to provide support for a broader understanding of the problem, starting from the simple list of mixtures properties up to their impact on both NG pipelines and end-use devices. Hydrogen injection affects several blend characteristics and gas network parameters. Mixing limits are also related to Wobbe index variations and safety aspects due to the flashback risk. Numerous works have shown that hydrogen fractions of 10% allow parameters to be kept within acceptable ranges, and up to 20% are not related to significant risks.

Life cycle emission and cost assessment for LNG-retrofitted vessels: the risk and sensitivity analyses under fuel property and load variations

There are various energy efficiency and emission reduction regulations enforced by the national and international maritime authorities for the shipping industry to adopt greener technologies. In this light, LNG-fueled vessels can be a promising alternative for ocean going diesel operated ships. It will be more beneficial if the price of LNG is lower than diesel to make that an economically viable fuel. Otherwise, there are concerns over the emission/economic considerations under the cost-benefit analyses of such fuels during their lifetimes with the initial investment risk for the technology, related infrastructure including fueling facilities and technology retrofitting processes.This study is an attempt to address the respective emission, energy, and cost concerns of LNG as a possible greener fuel with innovative dual-fuel engines within the SeaTech H2020 project (seatech2020. eu) initiative. The fuel life cycle of LNG in two scenarios of fuel property modification and load management for the cost analysis is considered. The life cycle assessment (LCA) section is designed to compare typical diesel and LNG fuels with selected short and deep-sea ship routes. Moreover, it is found that the effect of the ship travel distance on the amount of emissions is not significant when compared with the respective ratio. The life cycle cost assessment (LCCA) indicated that the fuel quality is more influential than the load variations in ship navigation. A 39% GHG emission reduction and up to a 22% fuel efficiency can be achieved under more optimal operational conditions by replacing LNG with diesel. The results also showed that the feasibility of using good quality LNG (higher Wobbe Index) instead of poor diesel characteristics in a selected ship is guaranteed within 30% of the sensitivity range. The fuel consumption variations under different engine loads (50% max to 85% min) can decrease the payback period from 6-years to 4-years as per the LCCA.

Effects of hydrogen content on laminar burning velocity and Markstein length in outwardly propagating spherical SNG–air premixed flames

As the hydrogen content of the five synthetic natural gas (SNG) fuels fixed with the Wobbe index increases, the unstretched laminar burning velocity and Markstein length also increase. For the addition of hydrogen to natural gas pipelines, an experiment was conducted using up to 19% hydrogen gas (SNG H19). By comparing the error rates with the measured laminar burning velocities and the four reaction mechanisms, Aramco 2.0 was selected as the optimized mechanism for the SNG mixtures. The unstretched laminar burning velocities were compared with those of Aramco 2.0 for SNG–air premixed flames under elevated pressures up to 0.5 MPa for equivalence ratios (ϕ) of 0.7–1.4. The results showed that the measured laminar burning velocities were consistent with the numerical values under lean and stoichiometric conditions; however, the deviations increased under rich conditions as the hydrogen content increased. The laminar burning velocities estimated using the four mixing laws were evaluated under elevated pressure and rich conditions. Consequently, the results predicted by mass-fraction mixing and Q/k models were in good agreement with the measured values. The Markstein length decreases linearly as the hydrogen content increases, but all Markstein lengths are positive; therefore, no instability occurs in the SNG–air premixed flames. The measured Markstein lengths were compared with the theoretical Markstein lengths and reasonably traced well to the isothermal surface at 600 K. When the hydrogen content reaches up to SNG H19, the theoretical Markstein lengths overpredict the results, except for ϕ values of 0.7 and 1.4.

Gas Quality Impact on Gas Engine Performance: Case of an Indonesia Natural Gas Station

This research was conducted to find a correlation between changes in the variable composition of the natural gas fuel in gas engine generators, and the occurrence of a unit shutdown at a natural gas distribution facility in South Sumatra-Indonesia. The analysis is carried out by investigating the trend of changes in gas composition parameters, and simulation using the Methane Number Calculator application. The results obtained from the research results, in Changes in the composition of fuel gas cause changes in the methane number, Low Heating Value (LHV), High Heating Value (HHV), and Wobbe index (WI), which may indicate engine trouble and cause a unit shutdown. Several options of solutions can be carried out as discussions to solve problems that occur in the gas engine generator at the natural gas distribution facility

Prospects for the Development of Reference Materials of the Wobbe Index

The thermophysical properties of gaseous fuel, including the calorific value and the Wobbe index, are one of its main properties for industrial use. The correctness of measurements of the volumetric energy of gas combustion is currently ensured by using sets of certified reference materials of the lowest volumetric energy of combustion based on pure gases: hydrogen, methane, ethane and propane GSO 11662–2020 / GSO 11665–2020 and gaseous mixtures GSO 11904–2022 / GSO 11907–2022 with metrological traceability to GET 16–2018. However, it becomes necessary to measure the gas relative density to air with established traceability to GET 18–2014 when determining the Wobbe index.The purpose of this research is to improve the accuracy of the pycnometer method for measuring the density of gases for further development and creation of metrological assurance in the field of measuring the Wobbe index.In the course of the research, an analysis of existing methods for determining the gas density was performed, as a result of which the pycnometer method set forth in GOST 17310–2002, GOST 34721–2021 was taken as the basis for the developed method. The uncertainty budget of gas density measurements was estimated using the pycnometer method. It has been established that the mass determination of the gas under study makes the greatest contribution to the total uncertainty. It was decided to increase the internal volume of the pycnometer and use a modified method for determining its volume to minimize the uncertainty.An imitator of a pycnometer with an increased volume was manufactured in an original design to solve the task of developing a modified pycnometer method for measuring the gas density. A gravimetrically produced gaseous mixture of the following composition was chosen for testing the developed method: CO2 – 40.22 mol. %, CH4 – rest.The theoretical significance of the results obtained lies in approbation of a modified pycnometer method to improve the measurement accuracy of such a gaseous fuel property as the Wobbe index. In the process of developing a modified pycnometer method, the measurement algorithm was tested, the density values of the studied gas were obtained, and the uncertainty budget of density measurements was estimated.The practical significance of the results of this research will expand the possibility of establishing metrological characteristics during the metrological assurance of Wobbe index analyzers, as well as apply the developed method in future accuracy control of the measurement results of the gas relative density to air.

Effects of Wobbe Index on the Combustion and Emission Characteristics of a Natural Gas/Diesel RCCI Engine

Abstract Due to energy shortage and environmental problems, the application of natural gas in internal combustion engine has attracted extensive attention. Therefore, diesel pilot ignition natural gas engine is a promising technology. However, the different sources of natural gas lead to the change in composition, which has a great impact on engine combustion and emission. In this study, the relationship between Wobbe index (WI) and swirl ratio (SR) of six different natural gas mixtures was studied by numerical simulation method. Besides, reactivity controlled compression ignition (RCCI) combustion strategy was evaluated. The results showed that increasing the WI increased the in-cylinder pressure and temperature, increased the ignition delay, and shortened the combustion duration, the gross indicated efficiency (GIE) of the six gases exceeded 50%. In addition, the increase of WI increased the nitrogen oxide (NOx) emissions and reduced the hydrocarbon (HC) and carbon monoxide (CO) emissions. Moreover, the peak pressure rise rate (PPRR) increased with the rise of WI, which may lead to engine knock. The results also showed that the increase of SR increased the in-cylinder pressure and temperature and improved the PPRR. When the SR was 0.7 and the WI was 51.7, the combustion and emission performance of the RCCI engine was relatively better.

Substitution of Natural Gas by Biomethane: Operational Aspects in Industrial Equipment

Global gas markets are changing as natural gas (NG) is replaced by biomethane. Biomethane is produced by upgrading biogas, which can have a molar concentration of methane to over 98%. This renewable energy has been injected into the pipeline networks of NG, which offers the possibility to increase its usage in industrial and residential applications. However, the expectation of the increase in biomethane proportion on the NG grids could increase the fluctuations on the composition of the NG–biomethane mixture in amplitude and frequency. In this context, the injection of biomethane into the existing network of NG raises a discussion about the extent to which variations in gas quality will occur and what permissible limits should exist, as variations in combustion characteristics can affect the operation of the combustion processes, with consequences for consumers, distributors and gas producers. This study describes a gas quality analysis with regard to the use of biomethane in industrial equipment, mixed or not mixed with NG, taking into account the indicators for gas interchangeability and provides a discussion on the necessary gas quality level to be achieved or maintained for efficient combustion in equipment originally designed to operate with NG. NG and biomethane real data collected for 92 consecutive days in 2022 and provided by two different companies in Brazil were used for this study. It is shown that the maximum deviation of the Wobbe Index (WI) of 5%, which is allowed for industrial plants, does not work for the operation of furnaces at temperatures of 1200 °C or more. In addition, it is shown that the WI, as defined in relation to the calorific value of the fuel, may allow inappropriate substitution of fuel gases, which is likely to reduce the range of blending of biomethane in NG pipelines. The results can be assessed to analyze how the addition of biomethane to NG grids will impact the WI and the equipment operation parameters such as the air-to-gas ratio, products-to-gas ratio, adiabatic flame temperature and furnace temperature.

FEATURES OF THE USE OF LIQUEFIED PETROLEUM GAS AS A RESERVE AND ALTERNATIVE FUEL AT COAL-BASED CHP PLANTS

The paper analyzes the main properties of liquefied petroleum gas and the peculiarities of its energy use compared to natural gas, including taking into account the specifics of the operation of pulverized coal boiler units of the CHP. The advantages of liquefied petroleum gas compared to heavy fuel oil are shown and a comparative economic assessment of their use is given. It is shown that interchangeability with natural gas is ensured by mixing the vaporized liquefied petroleum gas with air to form a homogeneous mixture — synthetic natural gas, which can be directly used in burners as a direct substitute for natural gas without changes in the composition of the equipment and in the design of the boiler burners. The calculation is presented of the permissible limits of the air fraction for liquefied petroleum gas of different composition according to the criterion of the Wobbe Index correspondence of synthetic natural gas and natural gas. Technical solutions are proposed for the use of liquefied petroleum gas as a reserve and alternative fuel at coal-fired combined heat and power plants in the event of damage of gas supply networks, which provide reliable and economical feeding of a coal-fired boiler unit with synthetic natural gas in such fundamentally different modes as coal jet “lighting” with low consumption and pressure of synthetic natural gas and ignition or emergency operation at a load of 25 % with high consumption and increased synthetic natural gas pressure, with the possibility of switching from natural gas to liquefied petroleum gas and vice versa. Bibl. 17, Fig. 3, Tab. 5.

Impact of Hydrogen on Natural Gas Compositions to Meet Engine Gas Quality Requirements

To meet the target of reducing greenhouse gas emissions, hydrogen as a carbon-free fuel is expected to play a major role in future energy supplies. A challenge with hydrogen is its low density and volumetric energy value, meaning that large tanks are needed to store and transport it. By injecting hydrogen into the natural gas network, the transportation issue could be solved if the hydrogen–natural gas mixture satisfies the grid gas quality requirements set by legislation and standards. The end consumers usually have stricter limitations on the gas quality than the grid, where Euromot, the European association of internal combustion engine manufacturers, has specific requirements on the parameters: the methane number and Wobbe index. This paper analyses how much hydrogen can be added into the natural gas grid to fulfil Euromot’s requirements. An average gas composition was calculated based on the most common ones in Europe in 2021, and the results show that 13.4% hydrogen can be mixed with a gas consisting of 95.1% methane, 3.2% ethane, 0.7% propane, 0.3% butane, 0.3% carbon dioxide, and 0.5% nitrogen. The suggested gas composition indicates for engine manufacturers how much hydrogen can be added into the gas to be suitable for their engines.

Interchangeability analysis from natural gas to natural gas/hydrogen mixtures: The wobbe index as a first approximation

Interchangeability analysis from natural gas to natural gas/hydrogen mixtures: The wobbe index as a first approximation

Interchangeability of Hydrogen Injection in Zhejiang Natural Gas Pipelines as a Means to Achieve Carbon Neutrality

The blending of hydrogen gas into natural gas pipelines is an effective way of achieving the goal of carbon neutrality. Due to the large differences in the calorific values of natural gas from different sources, the calorific value of natural gas after mixing with hydrogen may not meet the quality requirements of natural gas, and the quality of natural gas entering long-distance natural gas and urban gas pipelines also has different requirements. Therefore, it is necessary to study the effect of multiple gas sources and different pipe network types on the differences in the calorific values of natural gas following hydrogen admixing. In this regard, this study aimed to determine the quality requirements and proportions of hydrogen-mixed gas in natural gas pipelines at home and abroad, and systematically determined the quality requirements for natural gas entering both long-distance natural gas and urban gas pipelines in combination with national standards. Taking the real calorific values of the gas supply cycle of seven atmospheric sources as an example, the calorific and Wobbe Index values for different hydrogen admixture ratios in a one-year cycle were calculated. The results showed that under the requirement of natural gas interchangeability, there were great differences in the proportions of natural gas mixed with hydrogen from different gas sources. When determining the proportion of hydrogen mixed with natural gas, both the factors of different gas sources and the factors of the gas supply cycle should be considered.