Ammonium Nitrate – Spontaneous Explosion?

Good morning members,

Somewhere in the back of my mind I have a memory of some research and a published article (paper?) that suggested that ammonium nitrate, if of a relatively high nitrate concentration, and if stored in large piles, can over time generate enough internal heat to cause a spontaneous explosion.  I believe the work was done following accidental explosions of ammonium nitrate in the USA and Central Europe some years ago, and I believe the results were published in our Journal.

Would someone please confirm whether I’m correct or not?  If I am, please can I have access to the relevant research and published articles?

Rob

20 answers

  1. Answered by Dr Paul James

    Hello
    Please review this article – Djerdev et al., The mechanism of the spontaneous detonation of ammonium nitrate in reactive grounds, Journal of Environmental Chemical Engineering, Volume 6, Issue 1, February 2018, Pages 281-288
    https://doi.org/10.1016/j.jece.2017.12.003
    This may be of help.

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  2. Answered by Andy morris

    Hi Rob. There is a good document on Safex April 2020. “How to assess the probability of the risk of explosion in AN storage. This reference the West Texas explosion in 2013. If you cant find it let me know and I’ll send it you. Regards Andy

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  3. Answered by Dr Paul James

    You may also want to review this article – Fu, Wang and Yan, Anatomy of Tianjin Port fire and explosion: Process and causes. Process Safety Progress, v35, 3, 216-220, 2016.
    https://doi.org/10.1002/prs.11837

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  4. Answered by Gary Smith

    In addition to Rob’s question it would also be of interest if the same hazards of AN decomposition apply to both mined and synthetic variants.

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  5. Answered by Rob Orr

    Thank you one and all – will have a look at all these articles.

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  6. Answered by GOUR CHAND SEN

    As far I know AN does not explode on its own.

    Gour Sen

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  7. Answered by Andy Oppenheimer

    Yes. I did an interview on Sky News yesterday about AN but I’m on holiday so no access to the material you mentioned

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  8. Answered by Ian MacDonald Watson

    I agree that this rings a bell. I attach an extract from the chemical description:

    Decomposition creates toxic gases containing ammonia and nitrogen oxides. The resulting nitrogen oxides will support combustion, even in the absence of other oxygen. The resulting heat and pressure from the decomposition of ammonium nitrate may build up if the reaction takes place in a confined space and the heat and gases created are not able to dissipate. As the temperature rises, the rate of decomposition increases. In a confined space, the pressure can reach dangerous levels and cause an explosion that will include the detonation of the ammonium nitrate. When dealing with a large quantity of ammonium nitrate, localized areas of high temperature may be sufficiently confined by the mass of material to initiate an explosion. The explosion of a small quantity of ammonium nitrate in a confined space (e.g., a pipe) may act as a booster charge and initiate the explosion of larger quantities (e.g., in an associated vessel).

    EPA/OSHA/ATF; Chemical Advisory: Safe Storage, Handling, and Management of Ammonium Nitrate EPA 550-S-13-001, p.6 (August 2013). Available from, as of November 21, 2013: http://www.epa.gov/oem/docs/chem/AN_advisory.pdf

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  9. Answered by Gareth Collett

    Rob, you are correct in your recollection. Ammonium nitrate can, over time, decompose to a state where the auto-ignition temperature is exceeded. The Arrhenius equation applies and with confinement, burning to detonation is the likely outcome. For large quantities in storage there are no critical diameter considerations.

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  10. Answered by Peter SHELLEY

    Hi Rob, the presence of impurities can accelerate spontaneous heating, it is known that a small amount of Potassium Permanganate can cause this effect.

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  11. Answered by Malc Ingry

    Rob

    It is all down to how it was stored.

    If it was stacked in say 1 tonne or larger bags on top of each other then it has the possibility to spontaneously combust.

    Also because of outside temperatures are high and the warehouse was not kept at a constant temperature then it’s any ones guess what would happen.

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  12. Answered by Adrian Dwyer

    This link may be useful: – especially the following abstract.

    May explode under confinement and high temperatures.

    Lewis, R.J. Sr. (ed) Sax’s Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 238
    Hazardous Substances Data Bank (HSDB)
    In the pure state it requires a combination of an initiator and a high explosive. This combination is known as a reinforced detonator. …In combination with nitro compounds, e.g., TNT, forms one of the major high explosives for military use.

    Sax, N.I. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand Reinhold, 1984., p. 2002
    Hazardous Substances Data Bank (HSDB)
    Explosions of ammonium nitrate, involving relatively small quantities, have occurred during the preparation of nitrous oxide. In these cases (e.g., an explosion in 1977), the explosions of ammonium nitrate occurred as a result of excessively high temperatures and confinement during processing.

    EPA Office of Solid Waste and Emergency Response; Explosion Hazard from Ammonium Nitrate. EPA 550-F-97-002d, p. 5 (December 1997)
    Hazardous Substances Data Bank (HSDB)
    Ammonium nitrate will not explode due to the friction and impact found in normal handling, but it can be detonated under heat and confinement or severe shock. For example, in a fire, pools of molten ammonium nitrate may be formed and if the molten mass becomes confined (eg in drains, pipes, plant or machinery) it could explode, particularly if it becomes contaminated.

    Health & Safety Executive; Explosives – Ammonium Nitrate. Available from, as of March 27, 2007: http://www.hse.gov.uk/explosives/ammonium/index.htm
    Hazardous Substances Data Bank (HSDB)
    Explosions of stored ammonium nitrate are responsible for some of the worst chemical disasters on record. Several of these incidents, including two in Germany in 1921, occurred during attempts to break up large piles of solidified or caked ammonium nitrate and ammonium sulfate mixtures using explosives. In both cases, the initial blast intended to break up solid ammonium nitrate initiated an unintended general detonation of the ammonium nitrate or ammonium sulfate mixture.

    EPA/OSHA/ATF; Chemical Advisory: Safe Storage, Handling, and Management of Ammonium Nitrate EPA 550-S-13-001, p.6 (August 2013). Available from, as of November 21, 2013: http://www.epa.gov/oem/docs/chem/AN_advisory.pdf
    Hazardous Substances Data Bank (HSDB)

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  13. Answered by Aubrey Thyer

    I did a large amount on AN storage in the past and incidents involving AN, but this does not ring a bell.
    There are certainly issues around compatibility with materials such as ammonium sulphate, and periodic concerns about interaction with hydrocarbons following fires on lorries where diesel etc were present, or even via bitumen melting and permeating into the molten AN to create a more sensitive mixture.
    Unfortunately, runaway to detonation seems quite probable in a major fire from the study of our incidents, but I’m not sure about the spontaneous explosion issue unless there were contaminants present.

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  14. Answered by Jason Burgess

    If you look at the Oppau explosion Germany 1921 under certain conditions explosions can occur but also watching the video there appears to be small precursor detonations that may have propagated to a much larger event. Is there evidence in any other munitions or explosives being stored in the warehouse?

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  15. Answered by Harry Armstrong

    Texas City disaster
    Please look this article up on Wikipedia

    Regards

    Harry Armstrong

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  16. Answered by Mark Wiltshire

    When some one founds the answer from Rob question can you send it to me please

    Cheers

    Mark W

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  17. Answered by Mark Hatt

    I am aware that AN will burn to detonation from an outside heat source if a large quantity is densely packed but I am not aware of it generating it’s own heat.

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