[Stoves] ash layer beneath fire

Crispin Pemberton-Pigott crispinpigott at gmail.com
Mon Jan 27 09:45:53 CST 2014


Dear Vincent

 

>The question was prompted by the overall need to stop the heat in the
firebox from reaching the foundation (made of clay) and burning it up.

 

Something you can try is the system used in the StOvs Cooker from Senegal.
When you visited (in the past) the bioenergylists.org website there used to
be a background picture showing a strange stove in a cutaway drawing. I am
not sure if you ever noticed it. That was a StOvs cooker. It is made of thin
concrete with a clay combustion chamber and had to protect the cement
portion at the bottom of the chamber. In order to do that a circular
depression was made with a supporting ring upon which sits a fired clay disk
- something really cheap and easy to make locally for a few cents (or less).

 

The disk sits under the combustion chamber and is free floating, meaning not
held in position with some clay or anything - just sitting there with an
airspace underneath and some form of supports on the side/lip.

 

This is replaceable and creates a hot surface to help burn the char that is
otherwise smothered in the ash. 

 

In Indonesia this disk is often used in improved stoves however they
perforate it and allow air in below the floor which also means having a
cleanout for ash. This provides 'under air' to the char and again helps burn
it reducing fuel consumption. One such stove is the Jolentho Stove which can
have 2 or 3 pots, a chimney and comes in various sizes up to 'huge'. The
disks (if perforated) tend to be quite thick and not of very suitable clay
but that is another story (clay selection).

 

The Jolentho stove is built in with clay. Here are the components which are
supplied to the builder:

 



 

The right hand one has the perforated disk at the bottom of the combustion
chamber. A side-access us constructed in the floor and even has an air
controller. Stick fuel is bed into the right side as viewed from this angle.

 

The point is that having a loose disk of clay is a pretty good way to limit
heat going down. Air under a hot surface is a really good insulator. 

 

Regards

Crispin

 

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