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

[frank]

Dear Tom,

What is the chemistry of the black 'soot' that seems to form out of air? 
>From what I have seen it appears to be  formed when unburned gases are 
cooled. It does not seem to be the tars that are produced and condensed 
on the side of stacks but of very similar make up when I look at it 
under the microscope.

Thanks
Frank

Thomas Reed wrote:

>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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>>
>>
>>  
>>    
>>
>
>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com