[Stoves] Kearns' comment on control of primary air flow

[Crispin Pemberton-Pigott]

Dear Paul

I am willing to give the 210 litre drum a go with non-woody biomass.

Offhand, if I scale it ‎from something smaller, is there anything you think changes the functions fundamentally?

I am presuming the same general rules apply: wetter fuel means less charcoal, ‎lower temperature means more char, and particle size dominates the air flow.

>From the message below it seems the fuel is being used as the air flow controller more than the hardware. That could be risky if the fuel is not homogeneous. Maybe it is best to plan for complete control of the air.

Thoughts welcome
Crispin

Josh and Biochar folks (and to Stovers because it relates to the TLUD
cookstove),

Josh had a truly excellent and important presentation today as an IBI
Webinar about water treatment with charcoal / biochar.   And TLUD
technology for char making was well recognizied in the presentation.

He was asked about control of primary air in barrel-size TLUD ovens.
He uses barrels with lots of holes in the grate (even using expanded
steel.   His control method was mainly via the careful attention to the
sized of the biomass feedstock.

There are other methods that should help simplify the char making.
Simplest one is to have the barrel over a shallow pit, with one (or a
few) entries as fist-size "notches" in the dirt for entry of the primary
air.   Then, when the reaction is getting to be too much, put some dirt
over most of the notches (be sure to leave some air entry, learn by
experimenting.)

How to know when the reaction (pyrolysis plus the flaring of the gases)
is too much?   Create a visual "gauge" in the side of the chimney (or
upper barrel, in Josh's configuration).   I like to use 1/8th inch (3mm)
holes drilled into the side in a straight vertical line, with spacing of
4 inches (10 cm) between the holes.  Do this all the way to the top of
the chimney.   So 10 holes would be 40 inches or 100 cm.  You can see
the flames flickering inside the chimney.   It could be a 4 hole (16
inch or 40 cm) tall flame. This is nice for being able to see the height
of the flame even if you are away from the unit but can see the holes.
*********
Josh was also asked about use of the heat, but his interest is in the
char.    EITHER the value of the heat or the value of the char might
justify the use of the TLUD.   But when you have use for BOTH, each one
supports the other.   Char of water filtration and heat for
institutional cooking or a bakery, etc can match with the barrel-size
TLUDs.   Or use many household cookstoves to gather the quantity of char
for a village-size water purification installation that Josh has.
Either way can get the benefits of using the heat and getting the char.
**********
About the last question to him:  Scaling up the TLUD technology larger
than 55 gallon (200 liter) barrels has not been very successful.   If
you try it, please report your results (favorable or not).

Paul

--
Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com


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