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Julien,<br>
<br>
Truly excellent observations about Bangladesh efforts. <br>
<br>
Adding this thought: Thinking of a standard TLUD with metal fuel
chamber, has anyone measured the temperature of the outside wall of
that fuel chamber as the pyrolytic front moves to it, is at it, and
then past that point of measurement?<br>
<br>
This could be done even with a single wall TLUD (no outer cylinder)
or with a large hole in the outer cylinder so that an infrared
thermal sensor could read the temperature on the wall of the fuel
chamber. [But the chamber wall should not be shiny reflective
metal because that messes up the infrared readings --- so use some
high-temp-resistant paint.)<br>
<br>
Who will do this first and then report the results? (please do not
wait for me or others to do it.) <br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
<div class="moz-cite-prefix">On 12/8/2017 10:30 PM, Julien Winter
wrote:<br>
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cite="mid:CALv4xTxwO_9iSkuNowz8YP+uV980oYBzOgwdzXmJ=Av+KcgHYA@mail.gmail.com">
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<div>Hi All;</div>
<div><br>
</div>
<div>Mahbubul Islam and I have tried TLUDs cast as a single
concrete cylinder. You can see photo of a prototype here: <a
href="http://www.biochar-bangladesh.org/"
moz-do-not-send="true">http://www.biochar-bangladesh.org/</a>
on the home page. The concrete is made using Portland cement,
sawdust, sand, and ground biochar. It is not refractory
quality, so the interior of the reactor is lined with clay,
which can be replaced. In another design, there is a
concrete ring above the concrete reactor with a space between
the two created with 12-16 spacers.</div>
<div><br>
</div>
<div>I have also done some experiments with burners, and you can
see a video of that here: <a
href="https://youtu.be/QmnUgj75TF0" moz-do-not-send="true">https://youtu.be/QmnUgj75TF0</a></div>
<div><br>
</div>
<div>We haven't done much work on this type of TLUD in over a
year, because we have concentrated efforts on the metal
reactor cylinder in the Akha Stove.</div>
<div><br>
</div>
<div>What we really needed to develop concrete or ceramic
reactors is research money to pay for gas analysis and
materials. There are many design parameters to adjust, and
without gas measurements, we can't justify and explain our
decisions. In the mean time, we have other things to work on.</div>
<div><br>
</div>
<div>There are a couple of drawbacks in the designs illustrated
above. They are vulnerable to ambient wind, we don't preheat
secondary air, and there are no pilot holes in the reactor
walls. Pilot holes can be made, and protection from wind
could be designed. </div>
<div><br>
</div>
<div>The reactor bodies will be a heat sink. I am not sure how
big an issue that would be, becaue gas flame is a the top of
the stove, and heat in the center of the char above the
'flaming pyrolysis' moves predominantly upwards and not
sideways, because air movement is upwards, and char is a poor
conductor of heat sideways. (I have measured the horizontal
profile of temperature in metal TLUD reactors, and the
temperature only drops in the 1-2 cm near the reactor
sidewalls.).</div>
<div><br>
</div>
<div>For burning pieces of wood more than 1 cm thick, some holes
in the sidewalls of the reactor would provide pilot lights to
prevent accidental shut-down of the reaction. I belive this
is important for thicker pieces of fuel than 5 mm pellets,
because it takes longer to reach pyrolysis temperatures at the
center of thick pieces of fuel. That means that when the
reaction is turned down, char combustion on the surface of
particles becomes important to keep the primary pyrolysis
reaction going. If the char combustion goes out because of
insufficient oxygen, then it is tough to get the reaction
started again if a lot of the partially pyrolyzed wood has
charred surfaces. Some holes in the side walls of the
reactors keeps some embers glowing, so the gas flame stays
lit, and maintains draft. The primary air can be turned-up if
need be. </div>
<div><br>
</div>
<div><br>
</div>
<div>We have to design these stoves with pilot lights so that it
is not that easy for the gas flame to go out accidentally. If
that happened in semi-enclosed cooking spaces, the air would
fill with smoke, and the cook would get angry. We are going
to sell stoves, we need happy cooks.</div>
<div><br>
</div>
<div>I think it is important to work on ceramic and concrete
reactors. I needs a research grant to do it properly.</div>
<div><br>
</div>
<div>(Just a side comment. I have observed that the thicker the
fuel the more primary air is required for the primary
pyrolysis reaction. I believe that this is because of the
time it takes for the center of thick pieces of wood to reach
pyrolysis temperatures. Because the time it takes to
completely char the wood, the heat from flaming pyrosysis is
not sufficient, and heat from char combustion becomes
important. Thus a higher flow rate of primary air is required
for a TLUD loaded with chunks of wood than pellet fuel. As
fuel thickness increases, the yield of biochar decreases.)<br>
</div>
<div><br>
</div>
<div>Cheers,</div>
<div>Julien.</div>
<div><br>
</div>
-- <br>
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<div dir="ltr">Julien Winter<br>
Cobourg, ON, CANADA<br>
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<br>
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