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

Mon Jun 22 22:43:52 CDT 2015

Crispin,

There are numerous examples of 210 liter barrel TLUD char-makers. One 
document by me (ETHOS a few years ago) showed several.

AIR CONTROL is the key.   There must be sufficient _potential _for 
primary air flow, meaning to have sufficient holes or slots, etc to let 
in the primary air.   But then have a way of controlling the amount of 
air that can get into the space under those holes!!!    It is not 
reliable to expect the fuel to do the control of the air flow (except 
perhaps for the case of industrially processed pellets that have great 
consistency).

My general recommendation is for people to make a TLUD that is known to 
work well (and know its fuel also).   Gain experience.   And only then 
make changes and new designs, with the intention of getting better 
results.   I have observed that some people who launch into a new design 
(and/or new fuel) without much prior experience can be disappointed with 
their results and blame the technology because they lack any prior 
positive experiences for comparison.

I do not discourage people from trying new variations and fuels, but I 
encourage them to understand what has been shown to work rather well.   
THEN go for the improvements and new fuels, etc.

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

On 6/22/2015 5:52 PM, Crispin Pemberton-Pigott wrote:
> 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 <http://www.drtlud.com>
>
>
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