[Stoves] Applications of TLUD heat - not for cooking and biochar and terra pretta

[Crispin Pemberton-Pigott]

Dear Michael

>Here in the Marshall Islands one of my longest desires is a better copra
drier fueled by biomass and producing biochar as a by-product.

How about taking a new look at how this might be done. If you need a fairly
large amount of heat for a long time, it is going to be a big advantage to
have a continuously fed process, or one that is batches small enough not to
be much different - let's say 20 kg at a time.

If it was to have a cross draft configuration it would take advantage of the
hot char bed that works so well in the TLUD but it would be possible to make
a char removal section 'after' a vertical fire chamber. If can be side fed,
cross draft, and be a continuous process gasifier.

The gases will be generated in a pyrolysing zone and pass through the char
bed horizontally, the turn up to be burned in a flame chamber. If the last
portion of the fuel path before the fire chamber is thermally connected to
the pyrolysing fuel, it would look a bit more like a water pipe with a
'trap' on it. The fuel could be pushed in through a door from time to time
but the door is closed when running (air control).

If that was an acceptable layout and operating method, what would the size
be?

To answer that we need to know the moisture content and the heat value of
the fuel. Do you have that available? Next we need to know the heat
requirement for making copra. That will give us a burn rate for the gas,
assuming xx% of char produced as a byproduct. 

If the char makes a difference to the fertility of the soil (especially a
bigger difference than using the fuel as mulch or fertiliser or compost)
then more power to you. If not, you can always burn the fuel whole. 

Regards
Crispin