Assessing Differences of Ignited H2 and Hydrocarbon Vent Releases: Design Considerations and Safety Risks

Hydrogen has been increasingly studied and applied in the energy and maritime industries, whether for heating, electricity, or as a fuel itself. However, in the absence of specific requirements for the design of ships using hydrogen as a fuel, the alternative for these projects is to demonstrate the safety level equivalence with ships using conventional fuels, the so-called “Alternative Design” approach. With the expanded applications and the already well consolidated knowledge from the oil and gas industry, some hazards might be underpredicted. The current paper studies the different vent requirements for LNG and hydrogen gases and the potential risks associated in case of an accidental ignition leading to a jet fire. The radiation modeling is assessed using DNV PHAST software, utilizing the recently implemented Miller formulation. The consequence modeling performed of the radiated heat indicates that the minimum vent height requirement is deemed one of the most critical parameters one should take into consideration for the hydrogen vents design. The radiation levels can pose severe hazards to personnel close to an ignited hydrogen vent designed with the inappropriate height. The findings also indicate that there is a significant difference in the heat flux to which one could be exposed for these two distinct gases; for LNG, the lower heat of combustion plays an important role to justify the less intense radiation magnitude. In conclusion, although experiences from the traditional hydrocarbon industry can be greatly useful for hydrogen projects, it is critical to keep in mind the differences between these chemical compounds and properly assess the risks, in terms of frequency and consequences, of the application of hydrogen, including the accidental scenario of an ignited vent leading to a jet fire.