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Beirut Port 2020 Explosion

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Enthalpy:
Hi everyone, thoughts for the victims and relatives.

How do you understand the colour of the smoke cloud over the explosion in Beirut's port on 04 August 2020?

I know NO2 with that colour. A few uncommon metal oxides would resemble but not so closely.
https://www.aljazeera.com/indepth/inpictures/pictures-lebanon-capital-beirut-shaken-massive-explosion-200804162150133.html
https://en.wikipedia.org/wiki/Nitrogen_dioxide

A Lebanese minister claimed 3750t of ammonium nitrate NH4NO3 exploded. Newspaper reported that as an obvious explanation. I doubt.

First, the exploded amount was not in the thousands of tons, not of a single-molecule explosive. The silo tens of metres away resisted.

Second, do you imagine ammonium nitrate producing vast amounts of NO2 in an explosion? Here's a video of 2t ammonium nitrate, apparently without a fuel, "disposed of" the military way. It disperses some dirt and makes no coloured cloud
https://www.youtube.com/watch?v=084GndZlew8 boom at 0:48

Unless someone proposes a better explanation, my present impression is that tens of tons of NO2 deflagrated with a badly mixed fuel.

Here's a crash example of a rocket loaded with NO2-N2O4 (and UDMH, which burnt a good part of the nitrogen oxide)
https://www.youtube.com/watch?v=ycRVAcZC5R4
this resembles better what happened in Beirut. Something like a rocket development gone wrong for internal or external reasons.

wildfyr:
Fuel could be as simple as wood pulp product X (paper, cardboard, whatever)

Enthalpy:
Sure! Flour too, and even dust.

Worse: ammonium nitrate needs a fuel only to start detonate, or something else that detonates, or enough heat. Once the detonation mode has started, pure ammonium nitrate suffices.

But for the red fume? Would you imagine anything else than big amounts of NO2 for that colour? And how could NH4NO3 produce it?

wildfyr:
Thermal decomposition of ammonium nitrate gives all the various small nitrogen gases possible

https://www.researchgate.net/figure/Modes-of-thermal-decomposition-of-AN_tbl1_263578419

I see ammonia, nitric acid, N2O, NO2, NO, plus water, oxygen and N2. Various combinations of these can intercovert as well under heat, pressure, oxygen etc etc. I'd be more surprised if this explosion DIDN'T produce various nitrogen oxides. Especially since there could easily be some metal dust from steel getting heated to a liquid in the initial fire then particle-ized by the explosion.

Enthalpy:
Thanks wildfyr!

Meanwhile I've looked for the damage after similar disasters, and ammonium nitrate isn't quite as destructive as TNT. 300t in Toulouse made as much damage as estimated 30t of TNT. The damage by 2300t of ammonium nitrate at Texas City in 1947 is similar to the destruction in Beirut
https://texashistory.unt.edu/ark:/67531/metapth11736/
https://carynschulenberg.com/2018/04/texas-city-disaster/

I still don't grasp the colour of the plume. In the decomposition of pure ammonium nitrate, Propep finds no NO2 at all. In an expansion from 1kbar or 10kbar to 1atm, the initial concentration of NO2 is about 10-4 only, the final concentration is zero, meaning less than 10-7. Starting at 10bar leaves 2*10-7 and 1.02atm leaves 1.5*10-6.
The molar composition after expansion from 1000bar is:
0.46 H2O
0.29 N2
0.14 O2
0.12 H2O liquid
Zilch, nada, niente -> Everything else, including N2O, NO, NO2

A limit of Propep: it computes equilibria. With 1245K reaction temperature, the hypothesis isn't too bad, but the fraction of ammonium nitrate dispersed before it detonates can undergo more subtle reactions, where the reaction path influences the products.

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