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Topic: AZF Explosion  (Read 2650 times)

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Offline zenorin

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AZF Explosion
« on: June 16, 2018, 05:01:51 PM »
Hello,

I am working on a project about the AZF explosion in school. I am required to find the reaction that occurred, but I can't seem to find it. I know it involves ammonium nitrate, but I can't find the second reactant. If someone would take their time to find what I am looking, I would be very thankful.

Thanks in advance.

Offline Borek

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Re: AZF Explosion
« Reply #1 on: June 16, 2018, 06:30:05 PM »
There is no other reactant, just the decomposition.
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Offline zenorin

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Re: AZF Explosion
« Reply #2 on: June 16, 2018, 07:12:13 PM »
Are you certain? I visited a few websites and it said the reaction involved chlorine... But it wasn't specific :/

Offline Enthalpy

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Re: AZF Explosion
« Reply #3 on: June 18, 2018, 08:50:25 AM »
Pure ammonium nitrate detonates but it needs some initiator, which can be a big enough deflagration (=slower than detonation) of ammonitrate if mixed with some fuel. So a limited amount of some fuel somewhere on ammonitrate suffices to detonate everything just with an ignition source.
https://en.wikipedia.org/wiki/Ammonium_nitrate#Explosives
check also the MSDS (=Material Safety Data Sheet)

An other initiator class just sensitizes ammonitrate, and hypochlorite (=bleach) is a known example. Not chlorine, which is a gas. It has been cited as a possible cause at AZF. Though, tainting ammonitrate with anything, and certainly with bleach, is not what you can expect from workers at an ammonitrate plant who know their job.

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A part of the story is little known. On that same day in Toulouse, few kilometres and seconds apart, SNPE's plant producing hydrazines for Ariane exploded too. Probabilities speak against a coincidence. Alternately, both plants can have been attacked (this was little after the Twin Towers). Or the explosion at one plant damaged the other.
http://www.usinenouvelle.com/article/proces-azf-faut-il-aller-voir-du-cote-de-l-armee.162919
fun: usinenouvelle sends to a different article now, but never mind, I append the original one here under. Replace the extension txt by htm.
http://www.sudouest.fr/2012/08/29/azf-la-these-officiel-le-remise-en-cause-806412-4697.php

Hydrazines are very toxic, and building such a plant within the already existing neighbourhood was a criminal negligence that has not been investigated by the Justice.

The linked newspapers tell about 10t of UDMH had leaked. This would have had catastrophic sanitary consequences for the inhabitants. One SNPE worker died in the following explosion. While UDMH ignites very easily, possibly the worker sacrificed himself to ignite the leak and avoid to poison 100k people.

4s to the explosion at AZF, that can be the flight time of a debris that hit the ammonitrate there. Other people suggest the air or ground shake ignited the ammonitrate.

Anyway, rocket operators want to get rid of hydrazines, and the production plant was at the wrong place.

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Ammonitrate has already killed more than thousand people over more than a century.
https://en.wikipedia.org/wiki/Ammonium_nitrate_disasters
It would be about time to qualify it legally as an explosive, not as a fertilizer. Then the industry would take the appropriate steps to prevent explosions. Maybe store and transport it as a solution in water rather than a dry powder, if its use is to spread on fields anyway.

Offline wildfyr

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Re: AZF Explosion
« Reply #4 on: June 18, 2018, 10:09:18 AM »
Maybe store and transport it as a solution in water rather than a dry powder, if its use is to spread on fields anyway.

The reason they don't, as always, is cost. The cost of shipping a water slurry is higher than the pure solid.

Offline zenorin

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Re: AZF Explosion
« Reply #5 on: June 18, 2018, 11:06:37 AM »
So the reaction that occurred was a decomposition reaction?

I did some research, and I think this is the reaction:

NH4NO3 = N2O + 2H2O

Am i correct?

Offline Borek

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Re: AZF Explosion
« Reply #6 on: June 18, 2018, 03:31:34 PM »
So the reaction that occurred was a decomposition reaction?

Yes.

Quote
I did some research, and I think this is the reaction:

NH4NO3 = N2O + 2H2O

Am i correct?

No. Hint: one of the most important factors is the stability of N2.
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Offline zenorin

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Re: AZF Explosion
« Reply #7 on: June 18, 2018, 06:02:53 PM »
Hmmm... Is it 2NH4NO3 → 2N2 + O2 + 4H2O?

When the ammonium nitrate decomposes, it releases a large amount of nitrogen gas and oxygen gas, which is the explosion...?

Offline Borek

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Re: AZF Explosion
« Reply #8 on: June 19, 2018, 02:46:15 AM »
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Offline Enthalpy

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Re: AZF Explosion
« Reply #9 on: June 19, 2018, 07:33:36 AM »
Maybe store and transport it as a solution in water rather than a dry powder, if its use is to spread on fields anyway.
The reason they don't, as always, is cost. The cost of shipping a water slurry is higher than the pure solid.
Possibly. The transport of ammonitrate by train earned ~20M€/year just around Toulouse, so doubling the cost over tens of years would be expensive. In rich countries, the indemnity for a life lost in an airliner crash is around 1M€, and the AZF catastrophy killed 31 people. Though, the loss of several chemical plants at Toulouse was more expensive, as were the many people wounded and unable to work. Caution might have saved money in this case - provided that the deciders admit that accidents do happen.

Offline Enthalpy

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Re: AZF Explosion
« Reply #10 on: June 19, 2018, 07:41:27 AM »
I visited a few websites and it said the reaction involved chlorine...
Not chlorine, and neither bleach as I said, but instead sodium dichloroisocyanurate is the prosecutor's explanation - a source of chlorine with the same uses as bleach and often called chlorine
https://en.wikipedia.org/wiki/Sodium_dichloroisocyanurate
https://fr.wikipedia.org/wiki/Dichloroisocyanurate_de_sodium
both NaDCC and ammonitrate were produced on the site, both are dangerous, and they are incompatible. Decently trained workers wouldn't have mixed them, but, well, accidents do happen.

Offline Enthalpy

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Re: AZF Explosion
« Reply #11 on: June 19, 2018, 08:04:34 AM »
The prosecutor's scenario and alternative ones there (not in English)
https://fr.wikipedia.org/wiki/Explosion_de_l%27usine_AZF_de_Toulouse#Hypoth%C3%A8ses_sur_les_causes_de_l%27explosion
https://de.wikipedia.org/wiki/Explosion_in_Toulouse#Thesen_zur_Ungl%C3%BCcksursache

Also a list of observations inconsistent with the prosecutor's scenario, along with alternative ones
http://azf.danieldissy.net/Guiochon/AZF-Toulouse-Houston.htm

The study by physicist Alain Joets, professor at Orsay university and member of the Science Academy
http://azf-enqueteassassinee.typepad.com/files/09.04_Joets-Article_CRAS.pdf
in substance: 12 witnesses at different distances perceived two bangs whose time lag did not vary with the distance but varied with the direction from the chemical plants. From which the author deduces that both bangs propagated in the same medium (not ground and air) hence had two origins, and that the time lag is consistent with a first bang at SNPE's UDMH plant, in distance and position.

Offline zenorin

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Re: AZF Explosion
« Reply #12 on: June 19, 2018, 09:07:44 AM »
Ok, thank you everyone for all of the informative responses. Frankly, I never thought I would get so many answers. I hope you guys/girls will be help me in the future as well :)

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