Addressing Risk in Hydrogen-Natural Gas Blends

Growing global momentum for novel decarbonization strategies has prompted utilities and gas producers to explore the blending of hydrogen into natural gas pipelines — a method that could lower their carbon footprint. In their article "Blended natural gas/hydrogen fuel gas systems: An evaluation of risk," published in Process Safety Progress, Exponent's Alfonso Ibarreta, Achim Wechsung, Ryan Hart, Trey Morrison, and Nicholas Reding present an in-depth hazard analysis of natural gas and hydrogen mixtures to inform safe implementation practices.

In their study, the authors used integral modeling and computational fluid dynamics (CFD) to evaluate the consequences of accidental releases from blended fuel gas systems. Their research focused on three primary hazards: jet fire thermal radiation, flammable vapor dispersion, and explosion overpressure.

Results indicate that increasing hydrogen concentration in a natural gas blend results in a moderate reduction in the proximity of jet fire hazard thresholds, moderately increases the flammable vapor hazard zones due to hydrogen's lower density, and significantly increases explosion overpressure distances — by over 300% in some scenarios. The comparative analysis between PHAST and CFD tools further highlights that conservative modeling assumptions can introduce practical constraints for facility design and operation.

This evaluation underscores the importance of multidimensional risk assessments when transitioning existing infrastructure to accommodate hydrogen blends. These findings serve as guidance for utility and energy companies seeking to reduce risks and comply with regulatory requirements during the conversion to blended fuel gas systems. As the industry moves toward lower-carbon solutions, expanding risk models to incorporate both consequence and probability will be essential to address safety in natural gas and hydrogen distribution networks.

From the publication: "As fuel gas production and utility industries look to minimize the risks associated with the conversion of existing infrastructure networks from natural gas to hydrogen blending, it is important to expand single-dimension evaluation into a full-risk model that incorporates an assessment of both consequence and application-specific probability."