Sciencemadness Discussion Board

TCCA fire (CSB)

jackchem2001 - 7-1-2025 at 23:08

The CSB recently uploaded a video about an industrial accident with TCCA. They claim that a small amount of water caused TCCA to decompose violently, eventually causing a fire.
https://youtu.be/sqqIxWlCfd0

I find that claim a bit interesting. If I had to guess the cause of the fire I would say the small amount of water dissolved an alkali impurity/additive in the TCCA formulation and the action of *concentrated* alkali on TCCA (rather than water) formed NCl3 (which has been documented here before). I have never heard of neutral water causing any kind of violent reaction with TCCA but obviously the scale here is much larger than lab scale so perhaps this is what happened.

The CSB didn't express concern at water being used as a fire suppression mechanism with TCCA which seems odd given their claim that the two may violently react when initially brought into contact.

In any case care should be taken with TCCA. Having nitrogen and a chlorinating source in the same molecule is a hazard.

bnull - 8-1-2025 at 05:55

Quote:
If I had to guess the cause of the fire I would say the small amount of water dissolved an alkali impurity/additive in the TCCA formulation and the action of *concentrated* alkali on TCCA (rather than water) formed NCl3 (which has been documented here before). I have never heard of neutral water causing any kind of violent reaction with TCCA but obviously the scale here is much larger than lab scale so perhaps this is what happened.

No, you don't need alkali. Pure water is enough. It goes like this:
  1. Water hydrolyses TCCA to hypochlorous acid and dichloroisocyanuric acid. No news here.
  2. Dichloroisocyanuric acid is easier to hydrolyse than TCCA, so you have more HClO appearing in solution.
  3. The (let's call it) cyanuric ring is attacked by HClO preferably at low pH.
  4. The substances produced by the action of HClO on the cyanuric ring depend on pH. Above pH 4, we have chloramines; below pH 4, it is mainly nitrogen trichloride.
  5. If HClO keeps coming into solution, pH continues to lower.
  6. pH goes below 4 with TCCA, DCCA and HClO in the same place. Result: nitrogen trichloride.
  7. The lower explosive limit for NCl3 is a little below 6%. It doesn't look good when you have TCCA and water in a closed or barely ventilated vessel.


The use of water to extinguish fire is not as odd as it seems. It is essentially a high water-to-TCCA ratio with good ventilation. As long as the water goes somewhere else, there's no risk.

J.-L. Mieloszynski, "Study on the ability of chloroisocyanuric derivatives to generate chloramines, alone or in presence of nitrogen-containing compounds" (in French, from l'Actualité Chimique).

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fx-991ex - 8-1-2025 at 06:48

Do you think storing TCCA in a humid area could trigger an explosion? i hope not because mine is not stored in a very dry place.

jackchem2001 - 8-1-2025 at 14:32

Excellent reply bnull, thanks very much

I'm not sure about storage. I would assume the commercial formulations (the large pucks) present less hazard than powder.

bnull - 9-1-2025 at 15:32

Quote: Originally posted by fx-991ex  
Do you think storing TCCA in a humid area could trigger an explosion? i hope not because mine is not stored in a very dry place.

It depends. Is it getting wet? Is there ventilation enough? Is it powdered, and if so, why the heck would you store powdered TCCA?

Put it in a dry plastic pot with a good lid and some silica gel in the bottom, and put the pot in a higher place. There will be the normal build up of chlorine but that is manageable, just loosen the lid occasionally and close it back again.

Edit: I forgot they also sell granulated TCCA. I prefer the pucks anyway. They're annoying to powder but keep well.

[Edited on 9-1-2025 by bnull]

woelen - 10-1-2025 at 00:25

I myself have TCCA and I must say that it storesd exceptionally well, provided that the container you keep it in is sealed very well. No pressure builds up, no formation of chlorine gas. Apparantly, TCCA is quite stable, as long as it is kept pure and dry.

This is in strong contrast with Ca(OCl)2.xH2O (the normal commercial salt is hydrated). The latter decomposes, even if perfectly dry. There is a slow pressure buildup. The gas is a mix of Cl2 and O2. When it decomposes, it also becomes somewhat humid and this seems to accelerate the decomposition. You MUST release pressure from the container every few weeks, otherwise it may explode if it is tightly sealed.

Na-DCCA also stores quite well. Same as with TCCA, just keep the container perfectly sealed.

fx-991ex - 10-1-2025 at 06:39

Quote: Originally posted by bnull  
Quote: Originally posted by fx-991ex  
Do you think storing TCCA in a humid area could trigger an explosion? i hope not because mine is not stored in a very dry place.

It depends. Is it getting wet? Is there ventilation enough? Is it powdered, and if so, why the heck would you store powdered TCCA?

Put it in a dry plastic pot with a good lid and some silica gel in the bottom, and put the pot in a higher place. There will be the normal build up of chlorine but that is manageable, just loosen the lid occasionally and close it back again.

Edit: I forgot they also sell granulated TCCA. I prefer the pucks anyway. They're annoying to powder but keep well.

[Edited on 9-1-2025 by bnull]


Its in puck form(with some that i broke in pieces to use small ammount) in the original plastic container stored in the back of my cottage in cool and well aerated space(i use it for my rainwater in the summer)
No contact with water, just humidity when snow melt outside.



[Edited on 10-1-2025 by fx-991ex]