The Trend Of Blending Hydrogen With Natural Gas Is Sweeping The Globe, Expanding Hydrogen Application Scenarios

Abstract: Natural gas hydrogen blending expands hydrogen's application scenarios. It not only increases the fuel value of natural gas but also leverages existing infrastructure, such as natural gas pipelines, to expand the potential for hydrogen transportation and widespread, large-scale hydrogen energy applications. It can also significantly reduce carbon dioxide emissions. While contributing to decarbonization, natural gas hydrogen blending also faces safety and cost challenges. IRENA recommends that governments urgently provide subsidies for natural gas hydrogen blending pipelines.

Hydrogen, considered to be the future star of clean energy, will become an important energy source on the energy stage.

But hydrogen is too light, 11 times lighter than the air we breathe. This characteristic makes its storage and transportation difficult, and also limits its application scenarios.

Hydrogen can generally be transported or stored in two forms: liquid and gas. When stored as a liquid, hydrogen needs to be cooled to -252.76°C at standard atmospheric pressure, which consumes a lot of energy. When stored as a gas, high-pressure containers are usually required.

These stringent requirements will undoubtedly limit the widespread use of hydrogen as an energy source. Coupled with current limitations in infrastructure and transportation methods, the high transportation and storage costs of hydrogen are a major reason why hydrogen has not been widely used in the current energy supply system.

In order to solve these difficulties and expand the application scenarios of hydrogen, people have come up with the method of "natural gas blended with hydrogen", which has laid a good foundation for expanding the scope of hydrogen energy use.

The so-called natural gas hydrogen blending refers to a mixed gas (HCNG) formed by injecting a certain proportion of hydrogen into natural gas and mixing it with natural gas. It is one of the important directions of hydrogen energy utilization.

Blending hydrogen into natural gas has multiple benefits: first, it can change the combustion characteristics of natural gas and increase its calorific value; second, it can utilize infrastructure such as natural gas pipelines to open up more possibilities for the current hydrogen transportation and the widespread and large-scale application of hydrogen energy; third, it can greatly reduce carbon dioxide emissions.

For example, according to experiments in some cities in Delhi, India, using hydrogen-rich compressed natural gas as fuel in buses, mixing about 18% of hydrogen into natural gas, can reduce carbon monoxide emissions by up to 70% and save 5% of fuel.

Because of these obvious benefits, the trend of blending natural gas with hydrogen has spread across many countries. As of May this year, countries such as the United Kingdom, the United States, Belgium, and Germany have all launched plans to blend natural gas with hydrogen.

China also has commercial projects for blending natural gas with hydrogen.

Earlier this year, the State Power Investment Corporation (SPIC) announced the official launch of its first hydrogen-blended combustion demonstration project for gas turbines, validating the feasibility of the overall solution. Adding hydrogen fuel to existing natural gas units not only effectively conserves natural gas consumption and ensures safe and stable winter heating, but also has a positive carbon reduction effect.

In addition, hydrogen gas turbines can resolve the development resistance of the gas turbine industry caused by the shortage of natural gas in my country, and are conducive to promoting the upgrading of the gas turbine high-end equipment manufacturing industry.

01 Application of natural gas blended with hydrogen

Hydrogen energy has a wide range of application modes and can be used in transportation, industry, construction and other fields. It can be used as fuel cell vehicles in the transportation field, providing clean energy or raw materials for the industrial field, and distributed power generation or cogeneration to provide electricity and heat for buildings.

Therefore, as one of the hydrogen energy utilization technologies, hydrogen-blended natural gas not only attracts much attention in pipeline transportation, but also has huge emission reduction potential in other areas mentioned above.

1/ Transportation of natural gas mixed with hydrogen

Currently, hydrogen-blended natural gas technology is widely used in pipeline transportation. Natural gas pipeline networks offer advantages such as wide coverage, high throughput, long transmission distances, and low costs. Leveraging existing natural gas transmission and distribution networks and infrastructure for hydrogen-blended transportation can achieve low-cost, large-scale hydrogen supply.

Steel exposed to hydrogen can suffer hydrogen damage, including hydrogen embrittlement, hydrogen-induced cracking, and hydrogen blistering. Furthermore, at higher temperatures and pressures, decarburization and hydrogen corrosion can occur. Hydrogen embrittlement (the phenomenon in which hydrogen atoms enter the metal lattice, causing cracks within the material) is a major safety concern in the development of hydrogen-blended natural gas pipeline transportation technology.

To solve this problem in hydrogen transportation, natural gas blended hydrogen transportation provides a good solution. The system mainly includes an in-service natural gas pipeline system, hydrogen production equipment, compression equipment, pressure reduction equipment, transportation equipment and terminal equipment.

The workflow of natural gas blended with hydrogen transportation is as follows: hydrogen is produced by electrolyzing water through a new type of renewable energy; the hydrogen is compressed and stored in a hydrogen storage device; the hydrogen that has passed through the pressure reducing device and the stabilized natural gas are mixed in a blending device with the hydrogen flow rate being injected according to the natural gas transportation volume; the natural gas is transported using natural gas pipelines and supporting facilities, and the impact of hydrogen on pipelines, valves and welds must be considered when flowing through the transportation device; finally, it is distributed to users through the terminal device.

The relationship between renewable energy and HCNG （researchgate.net）

Currently, there are no international standards and specifications specifically for hydrogen-blended natural gas pipeline transportation systems. The maximum permissible hydrogen blending ratio in natural gas quality specifications varies from country to country, as shown in the figure below (special operating conditions include: Germany, CNG filling stations not connected to the pipeline network; Lithuania, natural gas pipelines with a pressure greater than 1.6 MPa; the Netherlands, high-calorific-value coal gas). In most countries and regions, the hydrogen blending ratio does not exceed 2%, with a few setting it at 4% to 6%. Although Germany stipulates an upper limit of 10%, this ratio is significantly reduced to below 2% if the CNG filling station is connected to the pipeline network.

HCNG Market Outlook: Industry Forecast 2021-2030 （emergenresearch.com）

my country currently lacks specific standards for hydrogen pipelines. The relevant standards and specifications for natural gas pipeline transportation in my country, "Coal-to-Synthetic Natural Gas" (GB/T33445-2017) and "Quality Requirements for Gas Entering Long-Distance Natural Gas Pipelines" (GB/T 37124-2018), stipulate upper limits for the hydrogen content in mixed gases of 5% and 3%, respectively. These standards apply to coal-to-synthetic natural gas and natural gas pipeline networks, respectively. Considering the presence of hydrogen in the production process of natural gas/coal-to-natural gas, such as coke oven gas containing approximately 50% hydrogen and 30% methane by volume, hydrogen content, a key technical indicator, requires strict control to ensure safe transportation of natural gas/synthetic natural gas pipeline networks. This suggests that countries have relatively stringent requirements for hydrogen content in natural gas. Even those that have conducted demonstration and research and development work related to hydrogen-blended natural gas pipeline transportation remain cautious about the permissible hydrogen content, with the relevant standards setting upper limits of no more than 10%.

2／ Transportation

Emissions from gasoline-powered vehicles are a significant source of urban air pollution. Because hydrogen has properties distinct from natural gas, such as a faster combustion rate and a wider ignition range, blending a certain percentage of hydrogen into natural gas in engines offers advantages for energy conservation and emission reduction. This can significantly improve engine performance, combustion characteristics, and both power and emissions. Research has shown that blending 20% hydrogen with natural gas can increase engine thermal efficiency by 15%, boost fuel economy by 8%, and reduce pollutant emissions by 60% to 80%.

In shipping, LNG-powered marine engines are primarily co-fueled and dual-fuel. Because methane, which lacks C-C chains and accounts for approximately 90% of natural gas by volume, produces virtually no soot during combustion, using natural gas as a fuel ensures that ships reduce NOx and CO emissions while achieving near-zero SOx emissions. Hydrogen-blended natural gas further enhances the emissions reduction capabilities of LNG-powered engines.

Research has shown that hydrogen-blended LNG engine fuel can significantly improve carbon monoxide emissions. Since hydrogen (H2) does not contain carbon atoms, the use of hydrogen-blended fuel will effectively reduce greenhouse gas emissions; nitrogen oxide emissions do not change significantly; due to the good ignition properties of H2, hydrogen-blended natural gas burns faster, which will effectively improve the power of LNG-powered engines; hydrogen-blended fuel will make the advantages of marine LNG-powered engines more significant.

3/ Combustion (domestic gas appliances and industrial boilers)

The use of hydrogen-blended natural gas as fuel in household stoves through pipelines is also considered an effective way to improve urban gas quality and flue gas emissions. Research results show that at hydrogen blending ratios below 20% by volume, the ignition rate, flame stability, and flue gas emission performance of hydrogen-blended natural gas in household gas appliances meet all safety requirements, and flue gas emission indicators meet standard requirements. Furthermore, CO and NOx emissions decrease with increasing hydrogen volume fraction.

Research on the optimal mixing ratio of natural gas hydrogen-blended combustion technology in gas boilers shows that as the hydrogen blending ratio increases, the combustion temperature rises, the combustion reaction rate accelerates, the concentration and total emissions of soot and CO decrease, the concentration of NOX increases, but the total emissions first decrease and then increase.

4／ Power generation

In the field of hydrogen energy industrial applications, hydrogen-fired gas turbines are a key factor in achieving the goal of using renewable energy to achieve a carbon-free, hydrogen-powered society by 2050. Research has shown that this burner can achieve safe and stable combustion while meeting emission requirements when operating within a hydrogen content range of 10% to 20%.

Furthermore, Turkish researchers conducted a study on the impact of a 20% hydrogen-blended natural gas system on a real-world photovoltaic system. The results showed that hydrogen-blended natural gas increased the system's power by 14.28%, reduced the system's capacity usage, and reduced the house's carbon footprint by 67.5%.

02 The "trend" of natural gas blending with hydrogen has swept many countries

In-depth research into the application of hydrogen blending in natural gas began after 2000. In the context of carbon neutrality, governments around the world are actively promoting natural gas hydrogen blending projects as a means of exploring hydrogen energy applications. As of early 2019, according to IEA data, 37 demonstration projects were underway in various countries to study hydrogen blending in natural gas networks.

UK: In January 2020, the UK demonstration project HyDeploy officially commenced operations. This is the UK's first pilot project to inject hydrogen into natural gas for use in homes and businesses. The project will inject up to 20% hydrogen into Keele University's existing natural gas network, supplying 100 homes and 30 academic buildings. The project successfully obtained HSE approval in 2018 to conduct experiments at Keele University using a 20% hydrogen blend, currently the highest hydrogen blending ratio in Europe.

Italy: In April 2019, Italian company Snam launched a natural gas hydrogen blending project in southern Italy, supplying a 5% hydrogen-enriched gas mixture to two industrial companies in the region. By the end of 2019, Snam doubled the project's hydrogen blending capacity to 10%, meaning it will inject 7 billion cubic meters of hydrogen into the pipeline annually.

Germany: In August 2019, Avacon, a subsidiary of German utility company E.ON, announced plans to increase the hydrogen blending ratio in its natural gas pipeline network to 20%. Furthermore, the German Association of Natural Gas Network Operators (FNB Gas) has stated that hydrogen is suitable for development in Germany, given its relatively well-developed natural gas infrastructure. The association urged the government to gradually increase the proportion of hydrogen in the natural gas pipeline network, for example, from 1% in 2021 to 10% in 2030.

Spain: On May 22, 2022, Nortegas, Spain's second-largest natural gas distributor, launched the H2SAREA project, Spain's first national demonstration project to inject green hydrogen into an existing natural gas network. The company will inject hydrogen into its existing pipeline infrastructure of over 8,000 kilometers, aiming to consolidate hydrogen as a lever for economic decarbonization in Spain's residential, industrial, and mobility markets.

China: The State Power Investment Corporation's natural gas pipeline hydrogen blending demonstration project, undertaken by Liaoning Chaoyang Yanshan Lake Power Generation Co., Ltd., has entered the pilot phase. Upon successful completion of the pilot, a production line capable of producing 1,000 cubic meters per hour will be constructed. Currently, a production line capable of producing 10 cubic meters per hour of hydrogen has been established. The project utilizes water electrolysis to produce hydrogen, which is then compressed, stored, and blended into natural gas pipelines. Following the pilot, a standard for natural gas hydrogen blending will be issued, filling a domestic gap and promoting the commercialization of natural gas hydrogen blending projects. On December 15, 2021, the Inner Mongolia Science and Technology Major Project, "Key Technology Research and Development and Demonstration Application of Hydrogen-Blended Natural Gas Internal Combustion Engines," was officially launched. This project will provide technical support for breakthroughs in key technologies, core component development, prototype development, and engineering applications for hydrogen-blended natural gas (HCHG) internal combustion engines in my country.

03 Future Development of Natural Gas Blended with Hydrogen

While hydrogen blending of natural gas contributes to decarbonization, it also faces challenges in safety and cost control. In terms of transportation, hydrogen blending increases the risk of gas leakage, combustion, and explosion. The degree of danger increases with increasing hydrogen concentration. The consequences of leakage need to be analyzed based on the specific leakage environment.

However, there are also views that the diffusion coefficient of hydrogen in the air is much greater than that of natural gas, so it is less likely to cause aggregation after diffusion, thereby reducing the danger.

In civilian combustion, when hydrogen is added to natural gas, the gas composition changes, altering combustion conditions. This can affect burner performance and even cause malfunction and flashback, posing safety risks. In industrial applications, due to the high diversity of industrial burners, the maximum hydrogen content varies across different burner types, making it difficult to draw general conclusions about the impact of hydrogen addition to natural gas, nor is it possible to establish a unified standard for hydrogen concentration.

Furthermore, several industry organizations have further stated that the current production cost of hydrogen is still significantly higher than that of natural gas. Governments and businesses need to carefully consider the economics before promoting the large-scale blending of natural gas with hydrogen. According to the International Renewable Energy Agency (IRENA), blending 20% hydrogen only reduces greenhouse gas emissions by approximately 7% compared to using natural gas alone. However, the cost of supplying hydrogen-blended natural gas is significantly higher than using natural gas alone.

IRENA also points out that due to its high costs, natural gas hydrogen blending faces competition from other carbon reduction methods, such as carbon capture and storage (CCS). Given the rapid market development of CCS, the cost will soon drop below $200 per ton, which will put significant pressure on natural gas hydrogen blending. Therefore, IRENA recommends that governments provide subsidies for natural gas hydrogen blending pipelines as soon as possible.