DIY terrorism.

[dennis]

I would think everyone should know that corn flour is explosive.

[tim.....]

Isn't "everything" that burns explosive if you get the particulate size and oxygen mix right.

Of course, they don't necessarily self combust

tim

[Harry Bloomfield]

dennis@home a écrit :

Most (all?) powders will combust, if the particle size and oxygen levels are correct. Ignition source need only be static.

[GB]

Not all. Only those that can be oxidised. So, iron filings will combust (in the right conditions), but not rust (which is iron oxide), no matter how finely you powder it.

However, there are lots of things that you don't normally think of as combustible that can be oxidised in the right conditions. Have there been any flour mill explosions in living memory?

[dennis]

Yes. Here is a couple and some older ones. Tens of people killed too.

[Huge]

Most *organic* powders will combust.

Good luck trying to get talc to combust.

[Tim Streater]

Rust will "burn" if you use fluorine instead of oxygen. Don't think it even needs to be powdered. Fluorine will even burn water, too.

[Huge]

Fluorine is something of a special case, though.

This is an amusing read, about chlorine trifluoride, which will burn sand;

[Huge]

Well, yes, but I kind-of assumed we were talking about combustion in air.

Although my point about organic powders is wrong, since I now recall preparing finely divided iron (in 'A' Level Chemistry) which would spontaneously combust in air.

[Tim Streater]

Ah, you beat me to it :-)

[F]

When in the sixth form many moons ago we were taken to a flour mill in, from memory, Selby where, we were told, there had previously been an explosion. Sort of calmed us all down.

[ARW]

Can rhetorical questions explode?

[Harry Bloomfield]

GB a écrit :

Yup, I seem to remember hearing about one a few months ago.

[Harry Bloomfield]

F a écrit :

That one is closed now I think.

[Martin Brown]

Any kind of fine powder that is flammable.

Yes. One of the nastier dust big industrial explosions I remember from the late 60's was of a milled additive product that was sold as an antioxidant for inclusion in Vulcanised rubber for car tyres.

It came as a big surprise to them when the milling facility was destroyed (not by the first dust explosion that just disturbed the dust from all the beams and rafters but by the secondary dust explosion).

When they rebuilt it there was one sacrificial double skinned tissue paper end wall and as far as possible no exposed horizontal surfaces to collect dust. Much greater attention was paid to cleaning too.

The standard dust explosion demo is a biscuit tin with a night light candle in it, small pile of baking flour and a rubber tube through a hole in the side leading off to a balloon. Open the tap and bang! (don't stand too near and make sure the lid is loose fitting)

[Chris Hogg]

Not quite. I had reason to look into this quite a while ago when working on a project that involved fine powders of coal dust, anthracite and carbon black. Organic dusts are only potentially explosive if the composition of that organic is such so that when heated, it gives off an inflammable gas. Thus dusts of flour, custard powder, rubber dust, soft bituminous coal, instant coffee etc. are potentially explosive when aerated, but dusts of anthracite (almost pure carbon) and carbon black are not.

That was very convenient for me, as it allowed me to use anthracite powder or carbon black in the project without having to take extreme precautions, and bituminous coal wasn't as effective in the application anyway.

[Brian-Gaff]

Lots of things are, flour mills used to go up like torches a lot in the olden days, its this airborne dust. Coal dust is much the same but more so.

They have obviously never watched Myth busters. Brian

[GB]

If you are referring to my question, it wasn't intended to be rhetorical. I just thought that, as the origins of flour mill explosions are better understood, they would be a thing of the past. It's sad that that is not the case, really.

[harry]

I once saw a dust explosion in a laundry. I was right in the middle of it. Fine fibres from laundry activity in this case. The dust was on steam pipes, an explosion flashed round the building in a fraction of a second. The explosion created a "front" of airborn dust particles that was self sustaining.

[ARW]

But you know what thought did.

That is why I thought you were taking the piss and asking a rhetorical question.