[peppercorn (OP)]

Okay, I know it's difficult enough to get liquid fuels to combust uniformly in most circumstances that a heat engine is used, but as flour mill explosions illustrate, a fine enough (hydrocarbon) dust in perfect circumstances will lead to pretty effective release of energy (explosions are a one-shot supersonic event, whereas combustion is ideally a continuous metered subsonic condition, but still...).

I'm sure this must have been experimented with during the age when coal was king, but I can't find any references to it at present.
Admittedly raw coal (or even coke) would not appear to be a nice fuel because of the ash content, but the alternative of torrefied wood (than can be easily co-fired with coal) could, on the face of it, be a far more manageable fuel and can be pulverised with similar ease as coal.

[Cheese2001]

A Pulsed Detonation Engine could use a fine enough solid for combustion, but PDE's are still in the experimental stage...

http://www.afmc.af.mil/news/story_print.asp?id=123098900 [nofollow]

[Bored chemist]

I guess it's cheating to use pulverized coal in a burner to heat a boiler then use the steam to drive a turbine. Mind you, it might be cheating, but it's very effective.
http://en.wikipedia.org/wiki/Pulverised_fuel_firing

[peppercorn (OP)]

I guess it's cheating to use pulverized coal in a burner to heat a boiler then use the steam to drive a turbine. Mind you, it might be cheating, but it's very effective.
http://en.wikipedia.org/wiki/Pulverised_fuel_firing

[]
Not so much cheating as potentially less efficient.
Also not as compact/lightweight - you couldn't easily put one on a train or a large truck for example. Though I know there were experiments with steam turbine trains (and the TNS community has previously discussed them IIRC).

[peppercorn (OP)]

A Pulsed Detonation Engine could use a fine enough solid for combustion, but PDE's are still in the experimental stage...

I believe they've been at the experimental stage for over half a century []

[syhprum]

When we and the Germans were scrapping 70 years ago they used to send over small aircraft loaded with explosives driven by a pulse jet engine, I dont know if it was petrol or powerded coal as engine life was not an impotant consideration.

[Geezer]

Tell you what; why not convert the coal into a combustible gas like, em er, carbon monoxide, then stick it into a gas turbine. Yes, yes! I'm pretty sure that will work (queue sound of feet running towards patent office).

[peppercorn (OP)]

Tell you what; why not convert the coal into a combustible gas like, em er, carbon monoxide, then stick it into a gas turbine. Yes, yes! I'm pretty sure that will work (queue sound of feet running towards patent office).

Too late []
Källe-gasifier

Trouble is you've already thrown away part of the chemical energy by oxidising to CO.

[peppercorn (OP)]

When we and the Germans were scrapping 70 years ago they used to send over small aircraft loaded with explosives driven by a pulse jet engine, I dont know if it was petrol or powered coal as engine life was not an important consideration.

I think they used Kerosene.

Trouble is you've already thrown away part of the chemical energy by oxidising to CO.

Enthalpy for the combustion of solid carbon to:
carbon monoxide   is  -110.4 kJ/mole.
carbon dioxide      is  -393.7 kJ/mole.

That's potentially 28% of the energy unavailable.