[Stoves] Charcoal burning, secondary flame vs no flame

ajheggie at gmail.com ajheggie at gmail.com
Wed Aug 5 02:49:46 CDT 2015


[Default] On Tue, 4 Aug 2015 08:15:37 -0600 (MDT),"Rebecca A. Vermeer"
<ravermeer at telus.net> wrote:

>THANK YOU, ROBERTO!  THANK YOU, CRISPIN!  THANK YOU, PAUL! - for discussing a topic that is of great concern to me.  
>Not being able to afford a combustion analyser, I have always been worried about the CO level that is produced in wood burning stoves (3-stones, traditional and improved) that become charcoal burning at the end stage of cooking.  I am specifically referring to the traditional way rice is cooked in the Philippines to prevent it from burning at the bottom of the pot.  First, the water is brought to boil at high power; then rice is added and stirred until most of the water is absorbed; and then any remaining unburned wood is removed and the rice, in the covered pot above the stove, continues to cook to perfection the "palangay" way -- i.e., with the heat from the glowing embers of the charcoal remains.  Alternatively, rice and water are brought to boil together and then cooked the "palangay" way. 
>  
>Have you or anyone else taken CO/CO2 measurements under the above described cooking conditions, both indoor and outdoor? 


Rebecca I too have never had access to a combustion analyser and CO
from char burning is a very real danger, killing people in England
despite our general level of education. Wood burning tends to be safer
in that the fumes from incomplete combustion are so acrid that people
are warned of the danger, CO from an oxygen starved fire is odourless.

Your palangay way looks like it is a good candidate for retained heat
cooking.

Even so the method you mention of allowing char embers to burn out and
produce the remaining necessary heat need not necessarily produce a
lot of CO. This is because the conditions for a full CO generator
require the char to be hot and deep so that oxygen first encountering
a hot piece of char will dissociate on the char surface and form CO2,
this CO2 then would only be reduced to CO if it encountered another
bit of hot char in the absence of any other oxygen, this reduction to
CO is also endothermic, so it lowers temperature. Hence if the char
bed is shallow and heat is being radiated from it little CO need form
but some always will.

This is also why there is often a blip of CO at the point one decides
to reload a batch loaded stove with fresh wood and before a flame
catches.




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