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I was watching the truly excellent Periodic Table of
and thinking about the oxidation of iron, and iron as
This is not that different than the thermite engine, but is
more practical and safer. Thermite is dangerous
one could make the case that gasoline is even more
dangerous!) but iron less so. I am not confident plain
iron will burn in air - the frustrating trick with steel
wool and O2 gets the iron hot but I am not sure the lump
will burn up once hot. But as seen on the
internet, iron will burn briskly in pure oxygen or even
explosively in LOX.
Could a hopper of pulverized iron, perhaps initially
via induction, burn in unenriched air? And by burn I
like a nice, orderly charcoal fire, not some furious flame
I envision this hopper of iron bits as
the fuel chamber, much like the fuel chamber of the old
Stanley Steamers grandpa used to talk about. A blower
provides lots of air and with it O2, and the iron starts to
burn and emit heat. Once it does you can turn off the
battery and the induction, and once you have steam you
can set off in search of more scrap iron, recharging your
battery on the way.
Here at BUNGCO we were a little skeptical that a strong
breeze would be enough - and plus as we ramped it up it
started kicking the iron bits all over and then out the
holes. You can't have a strong breeze in one end and not
out the other, but when it is carrying glowing bits of iron
oxide some people start to fuss, especially when his
fancy motorcycle is in the way.
We rigged up an oxygen concentrator borrowed from an
emphysematous friend to provide more O2 with less
gusty N2. Of course this taxed the battery even more but
once the steam started chugging along all was forgiven.
[bungston, Apr 18 2015]
Good old iron seems more friendly and predictable than that johnny-come-lately, aluminum. [bungston, Apr 18 2015]
Burning iron for kids
These folks also knew about the combustion properties of steel wool. They are linked because of their practice of conducting experiments naked except for safety goggles. New to me but possibly familiar to others around here. [bungston, Apr 19 2015]
Engineuitys wire+O2 hydrogen+steam generator
[CraigD, Apr 20 2015]
||Might use magnetic fields to suspend the particles and to ignite it ?
||Feeding iron powder into an air jet and then into a combustion chamber might work. But the fuel is going to have to be stored either under dry nitrogen, or as a slurry in oil, otherwise it will oxidise and "clump" into large particles.
||The energy density of the fuel will be low, and the whole system is going to have to run at a fearsome temperature. The fact that the primary combustion product is a non-volatile solid is an additional challenge.
||//Could a hopper of pulverized iron, perhaps initially
heated via induction, burn in unenriched air?
||I think a counter-example is given with grinding. Plenty of
white hot sparks, which extinguish before full oxidation.
What is interesting is that the alloys seem to burn first: the
carbon causes the spark to frizzle (good word, that); the
Manganese causes spears, and so on, as they burn off.
||As an aside: Liquid steel does oxidise, but not explosively.
Most of the time, there will be a covering of slag/scum.
However if the covering is actively removed, by bubbling
Argon gas, you can see the liquid steel directly (around
1650C). What is strange is that it is so hot, I could swear
that it is past white colour, and appears to have no colour
at all in certain patches.
||/Liquid steel does oxidise, but not explosively/
||I wondered about that,given that air or oxygen is
bubbled thru iron in the making of steel. I wonder
if that has to do with surface area - a dense fluid
will not have that much of the volume in contact
with the oxygen at any one time.
||/run at a fearsome temperature/ - This is the part
I wanted to sidestep. If steel wool burns in
oxygen and not in ambient air, there must be
some middle ground where combustion is
sustained but at a moderate pace.
||/grinding/ what is grinding? Like with a
||/energy density low/ OK I am going to try and see
about that. I am sure there are bakers for whom
solving that would be trivial but I am not one.
||//This is the part I wanted to sidestep. //
|| ... thus neglecting the fact that the Carnot efficiency is directly
proportional to the change in temperature of the working fluid.
||//If steel wool burns in oxygen and not in ambient
||Typical steel wool will burn in air, but only if there's a
forced draft. Sufficiently fine steel wool will burn in
still air. A fine iron powder would burn just... fine.
||/Carnot efficiency/ is this proportionality true when
there is a phase change?
||I found loads of different carbons but I have come
up empty for figures showing energy density of
metals to be oxidized.
||// I wondered about that,given that air or oxygen is bubbled
thru iron in the making of steel
||Ah, but the Carbon oxidises first....then the alloys. Pretty
much last to oxidise is Iron. Bessemer, or his underling, was
a brave man.
||Ling, if you were to let the Bessemer process go
would the iron all rust eventually too? Or is it
somehow too hot to oxidize?
||There are some better choices of metal for schemes like
this, such as aluminum or magnesium, and its not
necessary to have a flame, only the reactive metal and
||Something much like this was briefly baked in an
aggressively businessly manner in 2005 by the small
innovation company Engineuity R&D Ltd (see link). They
(chiefly its lead inventor, Ammon Yogev) claimed a good
working prototype of a hydrogen + steam generator
fueled by spools of thin aluminum or magnesium wire in a
cassette that could easily be recycled back into clean
wire, then retracted all mention of the idea almost more
quickly than archive.org could snapshot its webpage.
||bungston, yes the iron would oxidise. I must admit, we never
oxidised a whole heat (batch), but some operators at the
steel plant had a bloody good go at it...