(119c) Blended Natural Gas / Hydrogen Fuel Gas Systems: An Evaluation of Risk

The addition of renewably produced (“green”) hydrogen to existing natural gas pipeline systems presents an effective means of transmitting energy with a reduced overall carbon footprint while also granting end users access to federal monetary incentives, a product of recent climate legislation.

Although the concept of a blended hydrogen/natural gas infrastructure is not new, it presents a host of engineering challenges that merit attention before being put into practice. In consideration of dissimilarities in diffusivity through materials and gases and combustion characteristics between natural gas and hydrogen, safe implementation demands a comprehensive assessment of risks involved, including material durability, integrity management, pipeline steel embrittlement and cracking, and elastomeric seals with increased likelihood for gas mixture permeation.

In this paper, a hazard analysis considering the effects of loss of containment for several blend composition scenarios (0-20% H₂ by volume) is undertaken that specifically considers blast front overpressure, flammable gas dispersion, and emission capacity for fixed leak sizes. Offering stark contrast on computational robustness between empirical and ‘first principles’ models, this investigation applies analytical techniques to evaluate the consequence of potential gas release behavior through jet fire and mixture flammability simulation. The work described takes aim to identify and quantify the hazard severity and degree of risk associated with system retrofit for hydrogen blending within existing natural gas distribution networks.