[Stoves] ash layer beneath fire

Richard Stanley rstanley at legacyfound.org
Wed Jan 22 12:09:22 CST 2014


Vincent,

We have found that ash can also block infrared emissivity from glowing coals. As the ash spalds off the fuel it has to not accumulate but rather fall cleanly as possible thru the grate. I would advise use of round bars as Crispin but I would suggest you grind any round bars down to result in effectively a series of had cylinders along their length with the flat side up. That way, far less bridging /clogging of the grate/ with ashes takes place. This is important for briquettes made of ordinary ago residues, (ass opposed to char blends) where ash content can be much higher than or solid fuel wood.

Tulabagane,
 
Richard  Stanley
www.legacyfound.org

PS: Are you related to Victoria Akello of the UUWA-J in Mbale Uganda ? She is a dear friend and great trainer if you ever need such for briquettes ! 
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On Jan 22, 2014, at 11:48 AM, Crispin Pemberton-Pigott wrote:

Dear Vincent
 
It will help a little. What would really help your overall fuel consumption however, applies to all stoves of this type which have a flat bottom and no grate.
 
Put a metal grid grate at the bottom, elevated perhaps 10-15mm. That takes up very little vertical space. The grate can be reused if the clay is exchanged, or replaced if it wears out.
 
Try this: Use straight 12mm round bars. The spacing of the bars should be 16mm centre to centre. This is a lot more bar material than one is usually offered and there are good reasons for that. Make it the same diameter as the hole, minus a bit to drop it in easily and either provide a mud/clay ridge around the bottom to elevate it or give it a few short feet.
 
Then use the stoves as normal. What you are looking for is clear evidence of the production of less charcoal. If the char has support from below, it will burn properly instead of smouldering in the accumulated ashes. It can increase the total heat available by as much as 25% in a typical cooking cycle. The gap under the grate provides for an element of preheating of the primary air which increases the completeness of the charcoal combustion.
 
Whether the bottom is made of ash or loose-but-packed clay will make little difference to anything.
 
Regards
Crispin
 
 
Hi.
 
Could anyone help me out with this - would an ash layer beneath a fire in an improved cookstove (as in the sketch attached) help insulate the fire and prevent heat loss into the body of the stove? The layer would be about an inch thick after compression, and is about half an inch below the base of the stove.
 
Thanks,
 
Vincent Okello
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