Julien,
Thanks for the photos I did not see them before my first comment.
I believe you best chance is to let the primary and secondary air come
through the same hole through the bottom of the drum.
If the bottom hole is large enough aprox 6 or 8" and you top light it, I
think enough oxygen will get to the top without reacting with the straw, to
give you a clean burn. Also do not use the lid, the rising column of gas/
fire will pull the smoke from the whole surface to the center fire.
With a typical TLUD configuration ( primary combustion burning down through
the fuel bed and secondary air across the top) it is not going to be easy
to get the secondary air at the top of the drum to move across the fuel bed
to mix and react with the gases, because of a lack of draft. If you set a
second or third drum on top. then you may be able to move enough secondary
air across the top in a typical TLUD configuration.
One thing about straw is that it gives up its moisture real fast which
displace the oxygen.
TLUDs handle moist fuel better than bottom lit designs (if there is such a
design) because top lit designs vaporizes the moisture in the fuel a little
at a time as the fire burns down through the fuel bed. When bottom lighting
a fire, the moisture of all the fuel has to dry to the point that it will
burn.
Lanny
----- Original Message -----
From: "Julien Winter" <[email protected]>
To: <[email protected]>
Sent: Tuesday, April 09, 2013 5:03 PM
Subject: [Stoves] The Art of Using Grass Bundles in TLUD Stoves
Lanny Henson Tue Apr 9 12:58:26 MDT 2013 wrote:
Julien,
Have you tried top lighting the 30 gal drum of straw?
Do you have problems maintaining an open, central, air flow, pathway?
Lanny
Lanny;
I did not try top lighting the 30 gal drum with a hollow core in the
bed of straw. That is probably worth trying, but the paint can tests
suggest that it may not work if the reaction is in TLUD mode.
I have not had trouble with the central hole in a bed of straw
collapsing during a burn. Gasified straw maintained its structure,
even though it had lost ca. 80% of its mass.
I think my next move is to bottom light a 30 gal bed of straw
containing multiple vertical holes, to see if I can shorten the path
length for the convection of gases and heat. If I can get that to
work, I will try top lighting it as a TLUD. I like the TLUD process
in theory, because the oxygen is used up in the descending ignition
fire, and not in ashing charcoal, as occurs with bottom lighting.
However, I will not be running any more trials for a week, because we
have rain and possibly snow in the forecast.
I find that a paint can reactor is a fairly good model for a 30 gal
drum reactor. I can easily test equipment designs, fuels and
procedures. I can run several trials in an hour and not use too much
feedstock, and I can run replicates to be sure. I can also run
special photo-ops, such as in the dark. If a paint can trial is a
failure and I have to put it out, I don't have to dispose of much
waste straw. By contrast, a run of the 30 gal reactor can take a
couple of hours, plus, if it goes really badly and I create heaps of
smoke, I could be visited by the city fire brigade. Alas, I am not
working in a farmyard, but in a suburbia. One-upon-a-time, my family
used to collect cows, but not any more.
Thanks to all for the input,
cheers,
Julien.
--
Julien Winter
Cobourg, ON, CANADA
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