Text 25221, 36 rader
Skriven 2008-12-20 16:49:10 av Robert Bashe (2:2448/44)
  Kommentar till text 25212 av Michiel van der Vlist (2:280/5555)
Ärende: Dust explosions
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Michiel van der Vlist wrote to Robert Bashe on Saturday December 20 2008 at
01:21:

RB>> At any rate, I've never heard of an explosion provoked by metallic
RB>> dusts, although I can't exclude the possibility entirely.

MV> Some metals are ignitable at room temperature. Magnesium and Sodium
MV> come to mind. So I suppose a metallic dust explosion is possible in
MV> principle.

Yes, Roy also pointed out magnesium. As far as sodium is concerned, that's a
bit different since it doesn't oxidize in air: it reacts exothermically with
the humidity in the air (or with water as such) and the reaction produces
hydrogen, which often ignites when it mixes with the oxygen in the air. The
same applies to the other alkali metals (potassium, lithium), all of which are
so soft that you'd have a problem making a finely divided dispersion of them.
Sodium is often used in the lab to dry solvents such as ether by pressing a
block of sodium through a wire die and letting the sodium wire drop into the
solvent.

MV> Metals however are heavy and do not fragment easily. Creating a
MV> sustainable cloud of fine metal dust is not easy in itself. So I would
MV> expect a spontaneous metallic dust explosion to be rare.

I can't think of any examples, but I suppose an iron dust explosion might be
possible at a grinding station. The metal's hard enough to be machines into a
finely divided dust, but I'm not sure the fineness would be adequate to allow
ignition in air (only around 20% oxygen).

I've heard of magnesium fires, but not magnesium explosions, so I don't know if
it's possible to mill the metal fine enough to permit an explosion in air.

Cheers, Bob

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