Decarbonisation Technology - May 2023 Issue

Figure 1 Detonation of hydrogen is entirely credible at scales representative of many scenarios where it is not for traditional hydrocarbons. This image shows a 15 m 3 hydrogen detonation conducted as a demonstration at DNV’s Research & Testing facility in Cumbria, UK Credit: DNV

how the properties of hydrogen and hydrogen derivatives affect the potential hazards  It is by far most effective (in terms of both safety and cost) if appropriate risk-reduction measures are added early in the design stage. In many instances, if addressed early, these measures can be incorporated at little (and at times no) extra cost and can result in inherently safer designs  The design intent needs to be maintained through the full lifecycle: safety measures should not degrade. Achieving all this requires an understanding of the key properties of hydrogen (and its derivatives) that affect the hazards. As hydrogen is very different to its derivatives, we need to consider those separately. Hydrogen hazards Hydrogen is a flammable, non-toxic gas in ambient conditions. The effect of its properties on hazards and hazard management is probably best understood by reference to another flammable, non-toxic gas that is widely accepted by society: natural gas (or its primary component, methane). So how do the properties of hydrogen change

the potential hazards? For hydrogen, as with natural gas, ignition of accidental releases can result in fires and explosions. Research is very active in these areas, and DNV is engaged in large-scale experimental studies at our Research & Testing facility in Cumbria, UK. Although our understanding is still developing, we know enough to recognise where to concentrate efforts with hydrogen. Table 1 summarises the differences between hydrogen and natural gas/methane in both gaseous and liquid forms. Ignition of a flammable gas cloud does not always result in an explosion. Pressure is generated when either the gas cloud is confined within an enclosure or the flame accelerates to high speed (or both). This could occur in a wide range of possible scenarios, from low-pressure leaks in domestic properties, medium-pressure leaks in hydrogen production facilities or marine applications, to high-pressure leaks from storage facilities. The severity of an explosion will depend on many factors, but in general, the more ‘reactive’ the fuel, the worse the explosion. Reactivity, in this sense, relates to how fast a flame moves through a flammable cloud. At its worst,


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