Hydrogen safety

Hydrogen safety covers the safe production, handling and use of hydrogen. Hydrogen poses unique challenges due to its ease of leaking, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation. Liquid hydrogen poses additional challenges due to its increased density and the extremely low temperatures needed to keep it in liquid form.

Hydrogen is used as a feedstock in industrial processes including production of ammonia and methanol, and cooling electric generators in power stations.

NFPA 704
"fire diamond"
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chloride Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
4
0
0
The fire diamond hazard sign for both elemental hydrogen gas and its isotope deuterium.[1][2]

Summary

Hydrogen codes and standards

Hydrogen codes and standards are codes and standards (RCS) for hydrogen fuel cell vehicles, stationary fuel cell applications and portable fuel cell applications.

Additional to the codes and standards for hydrogen technology products, there are codes and standards for hydrogen safety, for the safe handling of hydrogen[3] and the storage of hydrogen.

Guidelines

The current ANSI/AIAA standard for hydrogen safety guidelines is AIAA G-095-2004, Guide to Safety of Hydrogen and Hydrogen Systems.[4] As NASA has been one of the world's largest users of hydrogen, this evolved from NASA's earlier guidelines, NSS 1740.16 (8719.16).[5] These documents cover both the risks posed by hydrogen in its different forms and how to ameliorate them.

Ignition

Mixtures

(For comparison: Deflagration limit of gasoline in air: 1.4–7.6%; of acetylene in air,[7] 2.5% to 82%)

Leaks

Liquid hydrogen

Liquid Hydrogen requires complex storage technology such as the special thermally insulated containers and requires special handling common to all cryogenic substances. This is similar to, but more severe than liquid oxygen. Even with thermally insulated containers it is difficult to keep such a low temperature, and the hydrogen will gradually leak away. (Typically it will evaporate at a rate of 1% per day.[10])

Prevention

Hydrogen collects under roofs and overhangs, where it forms an explosion hazard; any building that contains a potential source of hydrogen should have good ventilation, strong ignition suppression systems for all electric devices, and preferably be designed to have a roof that can be safely blown away from the rest of the structure in an explosion. It also enters pipes and can follow them to their destinations. Hydrogen pipes should be located above other pipes to prevent this occurrence. Hydrogen sensors allow for rapid detection of hydrogen leaks to ensure that the hydrogen can be vented and the source of the leak tracked down. As in natural gas, an odorant can be added to hydrogen sources to enable leaks to be detected by smell. While hydrogen flames can be hard to see with the naked eye, they show up readily on UV/IR flame detectors.

Incidents

Hydrogen has been portrayed in the popular press as a relatively more dangerous fuel, and hydrogen in fact has the widest explosive/ignition mix range with air of all gases except acetylene. However this is mitigated by the fact that hydrogen rapidly rises and disperses before ignition, and unless the escape is in an enclosed, unventilated area, it is unlikely to be serious.

Demonstrations have shown that a fuel fire in a hydrogen-powered vehicle can burn out completely with little damage to the vehicle, in stark contrast to the expected result in a gasoline-fueled vehicle.[11]

In a more recent event, an explosion of compressed hydrogen during delivery at the Muskingum River Coal Plant (owned and operated by AEP) caused significant damage and killed one person.[12][13] For more information on incidents involving hydrogen, visit the US DOE's Hydrogen Incident Reporting and Lessons Learned page.[14]

During the 2011 Fukushima nuclear emergency, four reactor buildings were damaged by hydrogen explosions. Exposed Zircaloy cladded fuel rods became very hot and reacted with steam, releasing hydrogen.[15][16] Safety devices that normally burn the generated hydrogen failed due to loss of electric power. To prevent further explosions, vent holes were opened in the top of the remaining reactor buildings.

See also

References

  1. ↑ http://cameochemicals.noaa.gov/chemical/8729
  2. ↑ http://cameochemicals.noaa.gov/chemical/3073
  3. ↑ HySafe Initial Guidance for Using Hydrogen in Confined Spaces. (PDF) . Retrieved on 2012-07-13.
  4. ↑ "AIAA G-095-2004, Guide to Safety of Hydrogen and Hydrogen Systems" (PDF). AIAA. Retrieved 2008-07-28.
  5. ↑ Gregory, Frederick D. (February 12, 1997). "Safety Standard for Hydrogen and Hydrogen Systems" (PDF). NASA. Retrieved 2008-05-09.
  6. ↑ Lewis, Bernard; Guenther, von Elbe (1961). Combustion, Flames and Explosions of Gases (2nd ed.). New York: Academic Press, Inc. p. 535. ISBN 978-0124467507.
  7. ↑ MSHA – Safety Hazard Information – Special Hazards of Acetylene. Msha.gov. Retrieved on 2012-07-13.
  8. ↑ http://www.arhab.org/pdfs/h2_safety_fsheet.pdf
  9. ↑ M.S. Butler, C.W. Moran, Peter B. Sunderland, R.L. Axelbaum, Limits for Hydrogen Leaks that Can Support Stable Flames, International Journal of Hydrogen Energy 34 (2009) 5174–5182.
  10. ↑ Peter Kushnir. Hydrogen As an Alternative Fuel . PB 700-00-3. Vol. 32, Issue 3, May–June 2000. almc.army.mil.
  11. ↑ "Hydrogen Car Fire Surprise". January 18, 2003. Retrieved 2008-05-09.
  12. ↑ Williams, Mark (January 8, 2007). "Ohio Power Plant Blast Kills 1, Hurts 9". Associated Press. Retrieved 2008-05-09.
  13. ↑ "Muskingum River Plant Hydrogen Explosion January 8, 2007" (PDF). American Electric Power. November 11, 2006. Archived from the original on 2008-04-09. Retrieved 2008-05-09.
  14. ↑ "Hydrogen Incident Reporting and Lessons Learned". h2incidents.org.
  15. ↑ Nuclear Fuel Behaviour in Loss-of-coolant Accident (LOCA) Conditions. Nuclear Energy Agency, OECD. 2009. p. 140. ISBN 978-92-64-99091-3.
  16. ↑ Hydrogen explosions Fukushima nuclear plant: what happened?. Hyer.eu. Retrieved on 2012-07-13.

http://www.arhab.org/pdfs/h2_safety_fsheet.pdf (PDF) Retrieved 2014-08-09

External links