Hydrogen Blending

A transient pipeline flow model with gas composition tracking is solved for studying the operation of a natural gas pipeline under nonisothermal flow conditions in a hydrogen injection scenario. Two approaches to high-resolution pipeline flow modeling based on the WENO scheme are presented and compared with the implicit finite difference method. The high-resolution models are capable of capturing fast fluid transients and tracking the step changes in the composition of the transported mixture. The implicit method assumes the decoupling of the flow model components in order to enhance calculation efficiency. The validation of the composition tracking results against actual gas transmission pipeline indicates that both models exhibit good prediction performance with normalized root mean square errors of 0.406% and 1.48% respectively. Under nonisothermal flow conditions the prediction response of the reduced model against a high-resolution flow model with respect to the mass and energy linepack is at most 3.20%.

The weather-dependent nature of renewable energy production has led to periodic overproduction making hydrogen production a practical solution for storing excess energy. In addition to conventional storage methods such as physical tanks or chemical bonding using the existing natural gas network as a storage medium has also proven to be effective. Households can play a role in this process as well. The purpose of these experiments is to evaluate the parameters of a household heating device currently in use but not initially designed for hydrogen operation. The appliance used in the tests has a closed combustion chamber with a natural draft induced by a density difference which is a common type. The tests were conducted at nominal load with a mix of 0–40 V/V% hydrogen and natural gas; no flashbacks or other issues occurred. As the hydrogen ratio increased from 0 to 40 V/V% the input heat decreased from 3.9 kW to 3.4 kW. The NOx concentration in the flue gas dropped from 26.2 ppm to 14.2 ppm and the CO2 content decreased from 4.5 V/V% to 3.4 V/V%. However the CO con centration slightly increased from 40.0 ppm to 44.1 ppm. Despite these changes efficiency remained stable fluctuating between 86.9% and 87.0%. The internal flame cone height was 3.27 mm when using natural gas but reduced sharply to just 0.38 mm when using 62 V/V% hydrogen. In addition to the fact that the article examines a group of devices that has been rarely investigated but is also widely distributed it also provides valuable experience for other experiments since the experiments were carried out with a higher hydrogen ratio compared to previous works.

Blending hydrogen in existing natural gas pipelines compromises steel integrity because it increases fatigue crack growth promotes subcritical cracking and decreases fracture toughness. In this regard several laboratories reported that the fracture toughness measured in a hydrogen containing gaseous atmosphere KIH can be 50% or less than KIC the fracture toughness measured in air. From a pipeline integrity perspective fracture mechanics predicts that injecting hydrogen in a natural gas pipeline decreases the failure pressure and the size of the critical flaw at a given pressure level. For a pipeline with a given flaw size as shown in this work the effect of hydrogen embrittlement (HE) in the predicted failure pressure is largest when failure occurs by brittle fracture. The HE effect on failure pressure diminishes with a decreasing crack size or increasing fracture toughness. The safety margin after a successful hydrostatic test is reduced and therefore the time between hydrotests should be decreased. In this work all those effects were quantified using a crack assessment methodology (level 2 API 579-ASME FFS) considering literature values for KIH and KIC reported for an API 5L X52 pipeline steel. To characterize different scenarios various crack sizes were assumed including a small crack with a size close to the detection limit of current in-line inspection techniques and a larger crack that represents the largest crack size that could survive a hydrotest to 100% of the steel specified minimum yield stress. The implications of a smaller failure pressure and smaller critical crack size on pipeline integrity are discussed in this paper.

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.