Hydrogen Blending

This paper presents the results of increasing the hydrogen concentration in natural gas distributed within the territory of the Slovak Republic. The range of hydrogen concentrations in the mathematical model is considered to be from 0 to 100 vol.% for the resulting combustion products temperature and heating value and for the scientific assessment of the environmental and economic implications. From a technical perspective it is feasible to consider enriching natural gas with hydrogen up to a level of 20% within the Slovak Republic. CO2 emissions are estimated to be reduced by 3.76 tons for every 1 TJ of energy at an operational cost of EUR 10000 at current hydrogen prices.

Methane is a significant contributor to anthropogenic greenhouse gas emissions. Blending hydrogen with natural gas in existing networks presents a promising strategy to reduce these emissions and support the transition to a carbon-neutral energy system. However hydrogen’s potential for atmospheric release raises safety and environmental concerns necessitating an assessment of its impact on methane emissions and leakage behavior. This study introduces a methodology for estimating how fugitive emissions change when a natural gas network is shifted to a 10% hydrogen blend by combining analytical flowrate models with data from sampled leaks across a natural gas network. The methodology involves developing conversion factors based on existing methane emission rates to predict corresponding hydrogen emissions across different sections of the network including mainlines service lines and facilities. Our findings reveal that while the overall volumetric emission rates increase by 5.67% on the mainlines and 3.04% on the service lines primarily due to hydrogen’s lower density methane emissions decrease by 5.95% on the mainlines and 8.28% on the service lines. However when considering the impact of a 10% hydrogen blend on the Global Warming Potential the net reduction in greenhouse gas emissions is 5.37% for the mainlines and 7.72% for the service lines. This work bridges the gap between research on hydrogen leakage and network readiness which traditionally focuses on safety and environmental sustainability studies on methane emission.

The ability for existing burners to operate safely and efficiently on hydrogen-blended fuels is a primary concern for the many industries looking to adopt hydrogen as an alternative fuel. This study investigates the efficacy of increasing fuel injector diameter as a simple modification strategy to extend the hydrogen-blending limits before flashback. The collateral effects of this modification are quantified with respect to a set of key performance criteria. The results show that the unmodified burner can sustain up to 50 vol% hydrogen addition before flashback. Increasing the fuel injector diameter reduces primary aeration allowing for stable operation on up to 100% hydrogen. The flame length visibility and radiant heat transfer properties are all increased as a result of the reduced air entrainment with a trade-off reported for NOx emissions where in addition to the effects of hydrogen reducing air entrainment further increases NOx emissions.

In order to study the flow blending and transporting process of hydrogen that injects into the natural gas pipelines a three-dimensional T-pipe blending model is established and the flow characteristics are investigated systematically by the large eddy simulation (LES). Firstly the mathematical formulation of hydrogen-methane blending process is provided and the LES method is introduced and validated by a benchmark gas blending model having experimental data. Subsequently the T-pipe blending model is presented and the effects of key parameters such as the velocity of main pipe hydrogen blending ratio diameter of hydrogen injection pipeline diameter of main pipe and operating pressure on the hydrogen-methane blending process are studied systematically. The results show that under certain conditions the gas mixture will be stratified downstream of the blending point with hydrogen at the top of the pipeline and methane at the bottom of the pipeline. For the no-stratified scenarios the distance required for uniformly mixing downstream the injection point increases when the hydrogen mixing ratio decreases the diameter of the hydrogen injection pipe and the main pipe increase. Finally based on the numerical results the underlying physics of the stratification phenomenon during the blending process are explored and an indicator for stratification is proposed using the ratio between the Reynolds numbers of the natural gas and hydrogen.

The primary methods for hydrogen transportation include gaseous storage and transport liquid hydrogen storage and transport via organic liquid carriers. Among these pipeline transportation offers the lowest cost and the greatest potential for large-scale long-distance transport. Although the construction and operation costs of dedicated hydrogen pipelines are relatively high blending hydrogen into existing natural gas networks presents a viable alternative. This approach allows hydrogen to be transported to the end-users where it can be either separated for use or directly combusted thereby reducing hydrogen transport costs. This study based on the GERG-2008 equation of state conducts experimental tests on the compressibility factor of hydrogen-doped natural gas mixtures across a temperature range of −10 ◦C to 110 ◦C and a pressure range of 2 to 12 MPa with hydrogen blending ratios of 5% 10% 20% 30% and 40%. The results indicate that the hydrogen blending ratio temperature and pressure significantly affect the compressibility factor particularly under low-temperature and high-pressure conditions where an increase in the hydrogen blending ratio leads to a notable rise in the compressibility factor. These findings have substantial implications for the practical design of hydrogen-enriched natural gas pipelines as changes in the compressibility factor directly impact pipeline operational parameters compressor characteristics and other system performance aspects. Specifically the introduction of hydrogen alters the compressibility factor of the transported medium thereby affecting the pipeline’s flowability and compressibility which are crucial for optimizing and applying the performance of hydrogen-enriched natural gas in transportation channels. The research outcomes provide valuable insights for understanding combustion reactions adjusting pipeline operational parameters and compressor performance characteristics facilitating more precise decision-making in the design and operation of hydrogen-enriched natural gas pipelines.

The increasing demand for energy and the urgent need to reduce carbon emissions have positioned hydrogen as a promising alternative. This review paper explores the potential of hydrogen blending in natural gas pipelines focusing on the compatibility of pipeline materials and the associated safety challenges. Hydrogen blending can significantly reduce carbon emissions from homes and industries as demonstrated by various projects in Canada and globally. However the introduction of hydrogen into natural gas pipelines poses risks such as hydrogenassisted materials degradation which can compromise the integrity of pipeline materials. This study reviews the effects of hydrogen on the mechanical properties of both vintage and modern pipeline steels cast iron copper aluminum stainless steel as well as plastics elastomers and odorants that compose an active natural gas pipeline network. The review highlights the need for updated codes and standards to ensure safe operation and discusses the implications of hydrogen on material selection design and safety considerations. Overall this manuscript aims to provide a comprehensive resource on the current state of pipeline materials in the context of hydrogen blending emphasizing the importance of further research to address the gaps in current knowledge and to develop robust guidelines for the integration of hydrogen into existing natural gas infrastructure.