I hope this is just a really bad accident.

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Le Démerdeur
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Re: I hope this is just a really bad accident.

Post by Le Démerdeur »

I still think it required more than the AN, it needs fuel + a detonation to create the explosion, hard to believe that it would have been stored with the former.

Jimmy Oxley, a chemistry professor at the University of Rhode Island, told ABC News. "200 factories make ammonium nitrate around the world… They are mining all over."

Yet, Oxley, who carried out research into the chemical compound, said that while the ammonium nitrate has been used as an explosive, the compound cannot be solely responsible for the explosion.

"The product itself is not classified as dangerous," said Gilles Choquet, president of AIS service, a training organization in risk prevention in explosive environments. "It is the storage of this product that could generate risks, with the rise in temperatures, which will be all the greater when there is so much product."

The chemical, however, requires a lot of energy to become explosive, and is not, in itself, highly combustible.

"What is certain is that when this product is on its own, it cannot explode," Choquet said. At the moment, it is "hard to say the exact cause for the explosion," he said, and the authorities may never find one.

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Re: I hope this is just a really bad accident.

Post by exile »

But we have been told that there were fireworks going off in the fire immediately prior to the explosion.

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Re: I hope this is just a really bad accident.

Post by exile »

Further information from the UK HSE regarding AN storage and its risks:
https://www.hse.gov.uk/pubns/indg230.pdf

Cleanliness is requested throughout. Avoidance of all spills of oil, grease etc even in small quantities are to be avoided. [Seven years in storage and I could imagine that there might just be a few spills and stains on the warehouse floor. Nothing major, just enough to allow a runaway reaction. ]

A few specific points of possible pertinence:

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. So a fire might be all that is needed to have set this off. Explosions from the nearby fireworks store may just have exacerbated the situation.

Self-confinement of straight ammonium nitrate in large stacks can
increase the risk of a detonation of the whole stack in a fire, so limit
stacks to a maximum of 300 tonnes. I would hazard a guess that it was stored in blocks of much more than that.

Due to the corrosive nature of ammonium nitrate, avoid using galvanised
items such as sheeting, joints and girders. Was the warehouse made of galvanised steel and was the material stacked against the walls? From what I have seen of some of the remains it does look as if it least the main structures of local warehouses were from steel (probably galvanised).

If the warehouse walls were clad in Aluminium then the potential for explosion becomes even higher. (I will say no more publicly on this point.) So if the AN was stacked against a aluminium clad wall we have another potential source for primary ignition.

I think we have enough to suggest that this did not need a major source of fuel to be oxidised. A very small quantity or even none at all might have sufficed.

Le Démerdeur
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Re: I hope this is just a really bad accident.

Post by Le Démerdeur »

I think one of us is missing something, it could be me.

I think we have enough to suggest that this did not need a major source of fuel to be oxidised. A very small quantity or even none at all might have sufficed.


I understand that any quantity of fuel could become oxidised and explosive but if there were none at all there would have been no fire or explosion, the oxidant simply makes the fuel burn much faster than when burnt in air, so fast that its explosive.

Like any fire you need the fuel, oxygen or an oxidising agent and an ignition source.

I dont believe and correct me if I am wrong, that AN will burn itself, so the first element, the fuel is what I am questioning, no shortage of oxygen, the initial fire was burning in air before the explosion and once the AN was in the mix then boom.

The ignition source could be anything, the fireworks or any fire which happens all the time.

If you get aluminium hot enough like any metal it will burn, to do so you need fuel, acetylene or propane and an oxidising agent Oxygen, a typical cutting torch set up, once the metal is red hot and molten you press the trigger and flood it with oxygen and away it goes, you can switch off the acetylene and it will continue burning of the pure oxygen continues to flow.

The aluminium or steel of the building would not explode, it would burn if hot enough and vigorously with the AN, if it were ground to a powder and mixed with the AN then it would make a huge explosion.

So I believe for the explosion to have happened there needed to be a major source of fuel in a form that could be combusted, diesel oil, any powdered combustible material, wood, aluminium, grain.

Something is being hidden or not spoken of.

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Re: I hope this is just a really bad accident.

Post by Le Démerdeur »

Exile.

In your cut n paste you conveniently missed out the sentence preceeding what you posted

Ammonium nitrate has a melting point of 1700C and decomposes
above 2100C. It is not in itself combustible but, as it is an oxidising
agent, it can assist other materials to burn, even if air is excluded.


Also - The risk of fire or explosion is greatly increased if ammonium nitrate is
mixed with combustible or incompatible materials, such as powdered
metals, alkali metals, urea, chromium or copper salts, organic and
carbonaceous materials, sulphur, nitrites, alkalis, acids, chlorates and
reducing agents

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Re: I hope this is just a really bad accident.

Post by Plog »

There was so much damage that as I understand it the jury (almost literally and some say conveniently) is still out on the exact chemistry behind the source of the AZF explosion in 2001.

Given there was about 10 times that amount of AN in Beirut and the explosion happened just a few days ago it might perhaps be a bit early for to be expecting too much detail to be available in the public domain as to what materials were present at the seat of this explosion.

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Re: I hope this is just a really bad accident.

Post by exile »

Le Démerdeur wrote:
Thu Aug 06, 2020 11:22 pm
Exile.

In your cut n paste you conveniently missed out the sentence preceeding what you posted

Ammonium nitrate has a melting point of 1700C and decomposes
above 2100C. It is not in itself combustible but, as it is an oxidising
agent, it can assist other materials to burn, even if air is excluded.
You seem to have increased the temperature ten fold. It melts at 170C and decomposes above 210C
Le Démerdeur wrote:
Thu Aug 06, 2020 11:22 pm
Also - The risk of fire or explosion is greatly increased if ammonium nitrate is
mixed with combustible or incompatible materials, such as powdered
metals, alkali metals, urea, chromium or copper salts, organic and
carbonaceous materials, sulphur, nitrites, alkalis, acids, chlorates and
reducing agents
I left it out simply because we have no information about whether any of these materials were anywhere close. If they were then we have a mechanism. If not, we still don't need them.

Your thinking about AN as an explosive is too simplistic. AN is an oxidising agent therefore all we need is something to oxidise and we could end up with a runaway reaction aka explosion. Indeed in commercial use as an industrial explosive and as used by your next door neighbour terrorist, that is exactly what they do. Diesel, fuel oil and other likely oxidizable materials are added to AN and all you need is a small explosion from a detonator and the whole lot goes off.


The two examples I gave earlier - Texas City and Oppau - show very clearly that AN can behave without the need of the fuel. In the Texas City case (and I think also Oppau) the AN had caked. In the Texas City case a whole hold of the ship had converted to a very solid mass. To break this up, holes were drilled into the AN, dynamite inserted and set off. No material that acted as a fuel for oxidisation used whatsoever. It was simply (as far as I can tell from my limited knowledge of AN decomposition) the shock wave from the dynamite that set off the AN.

So yes AN can explode under the conventional conditions of oxidising agent plus fuel but it can also explode under the wrong conditions without a fuel. It does not happen often but it does happen. Before Texas City I am led to believe that the use of relatively low power explosive to break up AN Cake was the standard. You can almost hear the cockney Michael Caine "You were only supposed to blow the bloody lumps up".

For the Bayreuth explosion to have been activated as convention explosive you would have needed a couple of thousand tonnes of fuel to feed it. That is just not credible and we are looking for other reasons for the AN to explode, perhaps catalysed by traces of organic material (oil spills/grease) or other materials that might be easily oxidised - iron, zinc, aluminium perhaps - hence my comments about the warehouse construction and storage conditions.

Edit: Apologies for my spell checker deciding to put the capital of Lebanon in SW Germany.
Last edited by exile on Fri Aug 07, 2020 9:02 am, edited 1 time in total.

exile
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Re: I hope this is just a really bad accident.

Post by exile »

exile wrote:
Fri Aug 07, 2020 12:41 am
[

Diesel, fuel oil and other likely oxidizable materials are added to AN and all you need is a small explosion from a detonator and the whole lot goes off.
And there perhaps is another clue to the action of AN as an explosive. That small explosion from the detonator does not set fire to the mix. [The days of setting fire to a fuse and running (as loved by MGM and UA) largely go back to the first half of the last century.] It does however set up a shock wave that causes the the mix to detonate. The force of the explosion does depend on AN oxidising the fuel but it is not a burning reaction. It does depend on converting solid (AN) and liquid (fuel) materials to a lot of gas and this gives the explosive force.

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