[Stoves] "Vom Pyrolysekocher zur terra preta" Workshop 11-12.06. --> Clay TLUDs

[Julien Winter]

Dear Werner;

Good luck with your workshop.  It looks very interesting.

However, I am interested in the picture of the TLUD reactor in your pdf
attachment.  Can you provide details on its construction, and who designed
it?

Clay TLUDs could be very important in communities were imported materials
(i.e., metal) are very expensive.  Clay TLUDs could maintain the
self-sufficiency in cooking that traditional stoves provide.  The method
being used in Haiti (Jon and Flip Anderson) and Bangladesh (Mahbubul Islam)
is to mix clay and organic material (1:1 by volume), where the organic
material is sawdust or rice straw, plus cow dung.  After the stove has been
formed, the interior is polished to seal pores, and may also be lined with
clay slip.  This method is already part of the existing skill-set of some
artisans in Bangladesh.

The organic mater in the clay becomes a pyrolyized "fugitive" creating
porosity, wherever the temperature is high enough.  In any case, organic
makes the stove body a poorer conductor of heat, with a lower heat capacity
than solid clay.  Porosity in the stove body also makes the clay more
tolerant of thermal expansion. Because the stove body doesn't conduct heat
as well as solid clay, the inner wall of the combustion chamber may become
vitrified.

A similar approach was taken by Clayton Bailey (1971) “How to Do Horseclay
Firing Without a Kiln”  with his self-fired clay pottery.  He used 50%
horse manure in his clay body.

What is needed is to know more about the durability of clay TLUDs and the
range of clays from which they can be made.

All the best,
Julien.



-- 
Julien Winter
Cobourg, ON, CANADA
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