Potential hazards of indoor use of hydrogen
André Vagner Gaathaug, Knut Vågsæther and Dag Bjerketvedt
Department of Process, Energy and Environmental Technology, University of South-Eastern Norway
The usage of hydrogen as an energy carrier has a large potential both economically, environmentally and technologically. The safety aspect of such usage is also a concern for many applications, since hydrogen has a wide flammability limit (from 4% to 75% hydrogen in air) and has a lower ignition energy compared to traditional hydrocarbon fuels. Outdoor use of hydrogen is considered safer than indoor use, since the light gas will usually be dispersed if the leak is unignited. The indoor use of hydrogen poses potential hazards, and some of them will be addressed in this presentation.
Hydrogen is often stored at high pressure (70 MPa) and a leakage will result in a momentum driven jet release. If the jet is ignited, there will be a jet flame which is potentially hazardous. If the jet is not ignited and the release is indoor, there will be a mixture of hydrogen and air under the ceiling of the compartment. The propagation of such a cloud is driven by buoyancy and it is diluted as it propagates away from the source.
Ignition of a combustible cloud of hydrogen in air can lead to explosions and dangerous overpressures. Even small amounts of hydrogen released in closed compartments can lead to destructive overpressures. Hydrogen and air mixtures can explode in two different modes. One mode is the subsonic deflagration, while the other is the supersonic detonation.