Abstract
Hydrogen is the most abundant element on earth, being a low polluting and high efficiency fuel that can be used for various applications, such as power generation, heating or transportation. As a reaction to climate change, authorities are working for determining the most promising applications for hydrogen, one of the best examples of crossborder initiative being the IPCEI (Important Project of Common European Interest) on Hydrogen, under development at EU level. Given the large interest for future uses of hydrogen, special safety measures have to be implemented for avoiding potential accidents. If hydrogen is stored and used under pressure, accidental leaks from pressure vessels may result in fires or explosions. Worldwide, researchers are investigating possible accidents generated by hydrogen leaks. Special attention is granted to the atmospheric dispersion after the release, so that to avoid fires or explosions. The use of consequence modelling software within safety and risk studies has shown its’ utility worldwide. In this paper, there are modelled the consequences of the accidental release and atmospheric dispersion of hydrogen from a pressure tank, using state-of-the-art QRA software. The simulation methodology used in this paper uses the “leak” model for carrying out discharge calculations. This model calculates the release rate and state of the gas after its expansion to atmospheric pressure. Accidental release of hydrogen is modelled by taking into account the process and meteorological conditions and the properties of the release point. Simulation results can be used further for land use planning, or may be used for establishing proper protection measures for surrounding facilities. In this work, we analysed two possible accident scenarios which may occur at an imaginary hydrogen refuelling station, accidents caused by the leaks of the pressure vessel, with diameters of 10 and 20 mm, for a pressure tank filled with hydrogen at 35 MPa / 70 MPa. Process Hazard Analysis Software Tool 8.4 has been used for assessing the effects of the scenarios and for evaluating the hazardous extent around the analysed installation. Accident simulation results have shown that the leak size has an important effect on the flammable/explosive ranges. Also, the jet fire’s influence distance is strongly influenced by the pressure and actual size of the accidental release.
Highlights
There is currently widespread interest in hydrogen and the role it may play as the fuel of choice for the clean fuel-cell vehicles of the future
It has wider explosion limits (4 to 75.6%), low ignition energy, very high burning velocity and susceptibility to detonation. These properties suggest that hydrogen presents different safety challenges than other hydrocarbon fuels. These unique features of hydrogen have been safely managed on an industrial scale for many years but, in a retail environment for refuelling hydrogen powered vehicles, industrial safety measures would be inappropriate and the proximity of the public unavoidable [1]
Hydrogen refuelling stations must be as safe as gasoline stations
Summary
There is currently widespread interest in hydrogen and the role it may play as the fuel of choice for the clean fuel-cell vehicles of the future. Hydrogen is a light gas and has higher diffusion coefficient which means that hydrogen has higher tendency to go upwards and mix quickly with air (because of higher diffusion coefficient) in comparison to other hydrocarbons It has wider explosion limits (4 to 75.6%), low ignition energy, very high burning velocity and susceptibility to detonation. These properties suggest that hydrogen presents different safety challenges than other hydrocarbon fuels. As an important infrastructure in the application of hydrogen fuel cell vehicles, hydrogen refuelling stations have received extensive attention for their safety. This paper uses Phast software to simulate the hydrogen dispersion distance and jet fire radiation in case of a hydrogen refuelling station under certain accident conditions. For several failure scenarios “effect” distances are calculated for car filling at 35 MPa and 70 MPa
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