[Stoves] Challenging fuel

[Crispin Pemberton-Pigott]

Dear Marquitusus

 

The fuel looks really good. I agree with Richard that breaking it down to a
certain 'sieve size' might be a good idea but if you want an
almost-no-equipment solution, sieves are fine.

 

I agree with Julien that getting the largest and smallest pieces divided
into two piles is a good start but only after removing the pieces smaller
than 6mm. So there will be two fractions: larger and smaller than 14mm or
so. I have no strong opinion on the divide - test it and see.

 

However my more important point is that the smaller portion of the shells
should be loaded first and put the larger fraction on top. The larger shells
pieces will light more easily and spread the fire more readily across and
into the surface. 

 

One of the consistent complaints about TLUD's from users is that the fire
takes too long to get going. I have been promoting the user of a lighting
cone here on the list but I haven't heard that anyone is using it. When the
fuel pieces are larger, the small burning pieces fall further down into the
fuel bed lighting a larger amount of fuel than would happen with small
pieces. The spaces between small fuel chips prevent the fire spreading
downwards rapidly. In the beginning people usually want a hot fire quickly.
Segregating the fuel by size can assist that spread in the early stage.

 

Later when the whole stove is hot, the small chips will prevent the fire
from accelerating downwards and producing too much gas to burn.

 

For the smallest bits, they can be made into biomass briquettes using leaves
or paper in 'the regular way'. Small hard pieces of shell are perfect for
adding to light biomass briquettes.

 

For lighting, it is still good to use a lighting cone to accelerate the
development of the fire across the top of the fuel. In almost all cases it
reduces emissions (a lot) as well.

 

I have conducted a number of tests with pistachio nut shells which are very
constant in size and shape. Because they are so light ignition is easy but
it is hard to limit the gasification rate due to the small coals dropping
vertically into the spaces. "Flattening" them helps get the bulk density up
to the point where they behave better.

 

Regards
Crispin

 

 

Dear stovers,

I send you a picture of the fuel I'm trying to deal with.
This is the raw fuel as it is normally sold here. They are almond husks.
As you see, it's sizes varies from 1 to 40mm!

Maybe people can tell me how this can affect the TLUD design

  

 

 

 

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