[Gasification] [Stoves] Stoves using wood and charcoal at the same time

[Thomas Reed]

Dear Crispin and All:

Good comments all around. 

One sin that I have been guilty of, but am fixing, is that "charcoal is 
not carbon". Wood can be looked at as a carbon hydrate, ie

CH1.4O0.6 = C (H2O)0.6 H.2

with increasing temperature driving off successively .1, .2, .5 of the 
H2O. 
Cooking charcoal is made at about 450 C, driving off maybe 0.2 of the 
0.6 waters.  Pyrolysis proceeds approximately

CH1.4O0.6 + heat ==> C H O0.4 + 0.2 H2O

so the wood charcoal still has a significant quantity of "volatiles" and 
H2 to contribute to the "charcoal" fire.  The hydrogen greatly increases 
the combustibility of the pokey CO. 

TOM REED            BE



Crispin Pemberton-Pigott wrote:
> Dear Cornelio
>
> You are on the right track to produce a charcoal flame (almost a pure CO
> flame) with you stove as described with preheated secondary air. It is
> similar to the way coal is burned in a steam engine.  The coal is actually
> gasified to produce high CO gas and this is mixed with preheated air to burn
> in a separate section of the combustor.
>
> Try to leave 50mm between the top of the charcoal and the bottom of the pot
> to give the flame a chance to burn.  Any less and it kills the flame against
> the cold pot raising CO levels rapidly.  And of course CO is a good fuel so
> you don't want to throw it out.
>
> The Maputo Ceramic stove adopts this method and dimensions with considerable
> savings over the traditional metal stove (more than 50% saved).
>
> You can get you 5 litres boiled in 15 minutes by fires working out the
> approximate thermal efficiency of the stove and dividing that into the
> amount of heat you need in the pot in 15 minutes.  This will tell you how
> much heat you need to be obtaining from the fire (at a minimum).
>
> Then you plan a burner that will maintain the efficiency level while burning
> enough fuel to give that required heat. You will get to the solution more
> rapidly this way than to just experiment hither and yon.
>
> Best regards
> Crispin
>
>
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