RogueRose
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Spontaneous combustion of oil soaked cellulose
I've been amazed to see some large piles of wood chips (from freshly chipped trees) catch fire even though there is a high moisture content,
especially with wet leaves mixed in, and the moisture seems to be higher on the outside of the pile. This happens just from the heat of
decomposition, which is pretty amazing.
I'm trying to figure out if the same thing would happen with things like wood pellets, the stuff that people use in their home furnaces instead of
oil, gas or wood. These pellets can vary in moisture as they need some to keep from faling apart.
I'm wondering what would happen if completely dry sawdust, super fine chips or something like finely shredded paper/cardboard were mixed with oil (mix
of plant oil and also motor oil) and then pressed into pellets.
I would think that the size of the pellet would matter, the larger, the more heat could build up in the center, but does this happen w/o water? Will
the oil decomp the wood?
If a mixture of the oil/cellulose were kept in a tank (not pressed into pellets) would it have the same issues? If this is possible, it could be
pressed/expelled into form as needed right before use.
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TheMrbunGee
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as far as I know the heat comes from bacteria "eating" the organic mater, so moisture is required.
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Metacelsus
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In the case of plant oils, highly unsaturated oils (such as linseed oil) can oxidize in air, and if there is enough area exposed to air, this can
build up enough heat to spontaneously combust. Oil-soaked rags are notorious for starting fires.
However, I don't think compressing it into pellets would work very well. There wouldn't be enough surface area.
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nitro-genes
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Linseed oil was also what I thought about...
Regarding the pile of woodchips catching fire, this is an interesting process indeed known as spontaneous combustion. The "steam" seen coming from
stacks of decomposing matter are usually due to action of thermophillic bateria. Although these bacteria can tolerate very high temperatures up to 100
deg C, it is obviously not enough to reach the ignition point, so at some point a chemical process must take over. I know maize silage can produce
quite large amounts of NOx, so I'm guessing that in some cases (if the bacterial composition is just right so to say), the bacterial decay might
produce a mixture of NOx and other reactive volatiles organics that may self ignite.
somewhat unrelated, though on the topic of self ignitable volatiles...my father used to have the "gas plant" in his garden, on a windless warm summer
evening he would hold a lighter to it producing a miniature fireball, remember how amazing this was to see as a kid. Hehe, chose nitro-genes as a
forum name for a reason.  Wonder if formation of peroxides from the volatiles
might be involved here as well.
https://www.youtube.com/watch?v=pQTZyS7BKV8
https://en.wikipedia.org/wiki/Dictamnus#Volatile_oils
[Edited on 11-9-2018 by nitro-genes]
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Herr Haber
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Linseed oil is also used to treat Mg against moisture in the Pyro craft.
I dont think it can catch fire that easily otherwise it wouldnt be used for that
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Deathunter88
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I did an experiment about this exact issue a few years ago, you can check it out on my blog:
http://davyblog.blogspot.com/2016/08/spontaneous-combustion-...
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TheMrbunGee
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Quote: Originally posted by Herr Haber  | Linseed oil is also used to treat Mg against moisture in the Pyro craft.
I don't think it can catch fire that easily otherwise it wouldn't be used for that |
It does, it oxidizes (and polymerizes), but after it is done - the oil becomes hard and stable. Rags are more of a hazard because of bad heat
conduction, Mg would dissipate heat quickly, and the speed of process increases with temperature. And also much higher temperature is required to
ignite Mg.
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